Group 16 - DeWalt 4 1/2 in Angle Grinder Gate 3

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View of Dissected Angle Grinder

Contents

Introduction

In this phase of the project our group analyzed the components of our now dissected angle grinder. Before we could begin with this step of the reverse engineering process we first had to assess how our group has changed since Gate 2. We implemented several changes to address our problems at the time but still must address one new issue that has arisen. This analysis of our group can be found under Project Management. The next step we took was forming a catalog of all of the parts in our product, along with a brief description of each. Our group then performed an in-depth analysis of several parts, created solid model assemblies for important system interactions, and considered how an engineer would have gone about designing the motor armature. All of these things can be found under Product Archaeology. Lastly, our group proposed three design revisions that would improve the overall design of the angle grinder. These revisions can be found under the Design Revisions section.

Project Management

Since Gate 2 our group has resolved most of our internal issues using the methods we outlined. The successful changes were as follows:

  • Not knowing how to use the wiki: This problem has been completely resolved as not only has our communication liaison learned how to upload files, make tables, and structure the wiki, but all of the other group members also have a basic functional understanding of the wiki themselves, reducing dependence on the communication liaison for minor edits and changes. In addition to the outlined plan of viewing online tutorials, our communication liaison also demonstrated simple text uploading so that the entire group could better communicate.
  • No out of class meetings: After realizing poor communication had hurt us on Gate 1, our group agreed that we needed to have and attend more extended group meetings. We didn't have any enforcement mechanism, but most of the group members realized that these out of class meetings would be vital to success. Having these meetings have allowed us to make our submissions more uniform, clarify tasks, and discuss our interpretations of the assignments, all of which have benefited our group.
  • An unevenly distributed workload: Our group has done a much better job of distributing the workload for this Gates 2 and 3. Our success has come from two improvements. First, our group no longer relies exclusively on the communication liaison to upload work to the wiki. This allows him to take on more meaningful tasks without needing to format and submit all of the other members' work. Second, our group has divided tasks with a better understanding of the time frame involved for each of them. Rather than just giving each person the same number of tasks in the gate summary, we consider how long a given task will take, which group member is best suited to perform that task, and then will give that member fewer jobs overall to allow them the extra time to perform a task with a higher skill level (ie solid modeling, tables, file upload, etc.).

The only unresolved issue is that one of our group members still does not attend these meetings or else shows up unreasonably late. We have no method of forcing this member to attend and cannot kick him out of the group, so have instead begun to work around his lack of attendance. Our group has tried to avoid giving this member essential tasks and instead the rest of us have taken a greater workload upon ourselves in order to make sure the overall quality of the wiki doesn't suffer on account of the one member. While this solution may not be the fairest for the other group members, it does allow us to still complete the assignments effectively whereas this member would most likely do his tasks incorrectly due to not understanding our group's interpretation of the assignment. While this may not be a direct solution to the attendance problem, it will allow us to mitigate the impact.

Product Archaeology

Component Summary

In this section Our group will document all of the components used in our product. We will include a brief description of the product's function, the material(s) the product was made from, the manufacturing method used, the part number, and an image of the component. All of this information can be found in Table 1 below.

Regarding Manufacturing Methods: In Table 1 our group explains that parts were manufactured using specific methods based on certain evidence that can be gathered from close inspection. We only refer to this evidence in the table, but examples are provided here to clarify what we are referencing.

Table 1a:Examples of marks that indicate specific manufacturing methods
Mark Description Image
Riser Mark Evidence that a part was cast. This mark is the deformation caused where the metal entered the die during casting.
Riser.JPG
Ejector Pin Mark Evidence that a part was injection molded. These are the flat round spots caused by the ejector pins, which are necessary to separate the mold after the part has begun to harden.
Ejector pin.JPG
Gate Evidence that a part was injection molded. This is the risen spot from where plastic was entering the mold during manufacturing.
Gate.JPG
Surface Finish Evidence whether a metal part was machined or cast. A rougher, duller finish is evidence of casting. A brighter, smoother finish is evidence of machining.
Finish.JPG
Parting Line Evidence that injection molding or die casting was used. This is a material line from where the mold was separated.
Parting line.JPG

These descriptions should help in understanding what evidence indicated manufacturing methods for Table 1.

Table 1: Catalog of Angle Grinder Components and Basic Summary
Component Function Material(s) Used Manufacturing Method(s) Used Part Number Number of Times Used Image
Guard Protect user from debris when grinding Steel This part was most likely stamped out of sheetmetal based on the bend marks on the surface, the material, and geometry of the part. The attachment ring was spot welded on. 628580-00 1
Guard.JPG
Clamp Nut Secures grinder attachments Steel This part was most likely die cast because of its simple geometry, but the threads on the inside were then machined to achieve greater precision. 636266-00 1
Head Nut.JPG
Backing Flange Provides support for the gear shaft and delivers torque to the grinder attachment Steel This part was most likely die cast because of its simple geometry and the relatively poor surface finish on it. 633257-00 1
Group 16 Backing Flange.JPG
Helical Gear This part redirects rotational energy from the pinion on the shaft and turns the grinder attachment at a 90 degree angle to the original rotational energy. Steel This part was initially cast based on its simple geometry and relatively poor surface finish. It was then machined at the gear shaft and on the gear side to achieve greater precision at these parts. The gear shaft was machined by turning, while the gears were machined by sawing based on the shape that was achieved. N/A 1
Gearbox Zoom.JPG
Gear Box This component holds the helical gear and secures it while still allowing it to spin freely. Aluminum This component was die cast as it is made of metal and has a riser mark and parting lines. Specific areas were machined based on an increase in shininess and different surface finish. These parts were probably drilled as they are circular and contain threads. 650717 1
Gearbox Profile.JPG
Gear Case Cover This component protects the user from accidentally touching the moving gears and stores grease. Plastic This part was injection molded, as evidenced by the parting line and surface finish, with holes drilled to accept screws. 625414-00 1
Gear case cover.JPG
Pinion This component delivers rotational kinetic energy to the helical gear, which will turn the axis of rotation Steel The general shape of the pinion was forged, based on the material used and lack of any signs of casting. The grooves were then added by turning based on the better surface finish and shininess, as well as axis-symmetry. The hole through the center was drilled in based on the surface finish. 623564 1
Helical Gear.JPG
Housing These components protect the interior components from the environment as well as giving the user safe surfaces to touch the part. Plastic These components were most likely injection molded as they have ejector pin marks and gates. In addition, the material used would make injection molding an efficient process. 623599 (left) 626996 (top right) 626997 (bottom right) 1 each
Housing.JPG
Plastic Switch This component allows the user to signal the electric switch to start carrying electricity. Plastic This component was injection molded based on the material used and the presence of ejector pin marks. 626999-00 1
Switchbar and Switch.JPG
Electrical Switch This component takes the signal from the Plastic Switch and either starts the flow of electricity to all of the electrical components or stops it. Plastic (case), metal (leads), Copper (wires) The plastic part of the electrical switch was injection molded, as evidenced by ejector pin marks. The copper contacts and aluminum leads were probably sawed as they do not have any indication of material manipulation, and appear to be made of stock metals. Machining would also be a simpler process for such small parts. DPX-2110-R 1
Electrical Switch.JPG
Retaining Bracket This component holds the armature in its position and prevents sliding out of or further into the magnet. Steel This part was cut out in the flat and then stamped based on the geometry and material. It is an easily manufactured part. PA6-GF30 1
Beaaring Retainer.JPG
Bearing This part is used at either side of the armature to allow it to spin freely without rubbing the housing or electromagnet. Steel (rings and balls), Rubber (seal) The outer ring and inner ring were both grinded as evidenced by the high shine and smoothness on these surfaces. The balls on the inside of the bearing were also grinded in order to achieve the high precision necessary for the part. The rubber seal was probably stamp cut based on the shape and material. 608 RS 2
Bearing.JPG
Fan Baffle This component directs the flow of air from the fan in order to cool the parts that are most prone to overheating. Plastic This component was injection molded based on the presence of injector pin marks, a parting line, and the material used. 623572-00 1
Fan Baffle.JPG
Armature This component transforms the fluctuating magnetic field caused by the electromagnet into rotational mechanical energy. It also performs the secondary function of cooling the product. Steel (shaft),Copper (wires), Aluminum (coating), Plastic (insulation and fan) The shaft was die cast based on the simple geometry and rough surface finish. The Aluminum coating was rolled based on the sheet-like shape and surface finish. The copper was drawn based on the very long and thin geometry. The plastic insulation was also drawn with the copper. The fan was injection molded based on the presence of ejector pin marks and a gate. 050312-XP 1
Armature.JPG
Electromagnet This component transforms electrical energy into a magnetic field in order to power the armature Aluminum (exterior), Copper (wires), Plastic (insulation) The steel exterior was stamped based on its simple geometry. The copper wires were drawn based on their long length, small, constant cross sectional area, and the material used, and the insulation was drawn with the copper. 051712-XP 1
Electromagnet.jpg
Brushes The brushes allow electricity to flow to different parts of the rotating armature so that even though current is alternating, the armature always has an applied torque in the same direction. Carbon (block), Copper (wire) The carbon block was probably sawed given the material does not lend itself to material manipulation, and sawing would be able to achieve the desired shape. The carbon wires were drawn based on their geometry and material properties. 650916-01 2
Group 16 Brush.JPG
Power Cord This component delivers electrical energy from an outlet to the electrical switch. Copper (wires), Rubber (insulation), Plastic (housing connection) The wires were drawn based on their geometry and the material used. The rubber insulation was drawn with the copper. The plastic housing connection was injection molded because it has ejector pin marks and a gate. 330005-01 1
Power Cord.JPG
Handle This component allows the user to easily maneuver the product. Steel (core), Plastic (grip) The steel core was most likely cut out of bar stock based on the simple geometry of the part, surface finish, and material used. Turning was then used to add the threads on the end. The plastic grip was injection molded based on the presence of a parting line and gate, as well as the material used. 149142-00 1
Handle.JPG
1/8" UNF Torx Screw These components are fasteners that hold various other components in place Steel The general shape of the screw was cold forged, as ingots would be required to add threads. The threads were then added by turning, as evidenced by the surface finish and axis-symmetry. N/A 8
Screws and Nuts.jpg
1/8" UNC Phillip's Screw 12
1/8" Hex Nut The general shape of the nut was forged, as evidenced by the material used and surface finish. A drill was then used to but threads on the inside of the screw, as evidenced by the increased shine and axis-symmetry. 2

Product Analysis

Our group considered seven of the grinder parts in depth, and analyzed the many aspects of these components in order to determine what the intent of the engineers was when they made the design decisions they did. In addition to considering function, form, and the manufacturing methods for each component, we also rated each component's complexity. The scale that we will use throughout this section rates the complexity of the components as follows:

Table 2:Complexity scale for product analysis
Rating Description Example
1 This component is very simple. The function it performs does not involve moving parts, nor is it subjected to significant stresses. The geometry is very simple, and the manufacturing of this part would be straightforward, with only one, simple process used. Copper Wire
2 This component is still simple, but not to the extent that a 1 would be. While it still does not contain any moving parts, this part may be subjected to significant forces, and will therefore require some mechanical analysis. The geometry may have more features, but the manufacturing method is still simple, and will probably only involve one process. Crescent Wrench
3 This component has a moderate level of complexity. This component may or may not contain moving parts, however it must perform a function that required non-trivial engineering decisions, such as what material or shape would maximize part performance. The geometry should not resemble any common shape, and the part was probably made in at least two steps that either applied a specific finish, added features, or brought different materials together. Channel Lock Pliers
4 This component is quite complex. In addition to performing a function that is essential to the overall function of the product, the function of this part must involve energy or signal flows. The geometry of this part is very detailed, as a specific, non-ordinary shape is required to perform the part function. In order to manufacture this part several steps would have to be taken, possibly involving the manufacturing of several sub-parts and then using manufacturing processes to bring these together. Socket Wrench
5 This component is very complex. It exhibits similar qualities to a 4, but to a greater extent. The function involves complex flows of energy (time varying, interacting with each other, etc.) in order to provide an essential function to the overall product function. The geometry of this part is intricate, and has several nuances necessary to achieve the part function. To manufacture this part would involve several steps and materials, as well as previous manipulation of the materials being used. Circuit Breaker

As can be seen in Table 2, the function, form, and manufacturing method were the primary criteria for determining a component's complexity. This was due to the fact that general tasks can be achieved with simple parts, but more advanced tasks inherently required highly specific, complex parts in order to achieve the task. Thus, the desired function (and its relative complexity) was the main driving factor behind how complex the form or manufacturing method for a given part had to be.

In addition to considering how complex each component was, our group also analyzed the interactions our selected parts had with each of their surrounding parts. These interactions ranged from simple tasks such as the housing protecting other parts, to highly complex ones such as an electromagnet creating flux through an armature. The best way to analyze the complexity of an interaction was based on the energy and signal flows between interacting components. The ratings used for interactions are given in Table 3.

Table 3: Complexity of Component Interactions
Rating Description Example
Simple This component interaction involves no flows of energy or signals. The component interaction is purely for aesthetic, protective, or ergonomic reasons. One component's function does not contribute to the other's in any significant way. A rubber seal on a ball bearing
Moderate This component interaction involves the transfer of a simple signal or a basic flow of mechanical or electrical energy. Any energy flows should only involve the direct transfer of energy through simple means (e.g. wires and direct contact that doesn't involve complex mechanisms). One component's function is related to the other's. A light bulb and switch
Complex Interactions of this nature involve the transfer of complex signals or energy transfer through complex means. These energy transfers should require mechanisms for the flow of mechanical energy or the induction of fields and/or current for the flow of electrical energy. One component's function will be directly related to the other's but because of the complex interaction the original input energy may have a different form than the output energy. A Geneva cam and constantly rotating drive disc

Switch

Electrical Switch.JPG

Component Function

  • The main function of the switch is to control current applied to the motor.
  • The switch is located inside the housing hidden from sight.
  • The user interacts with the component via a trigger.

Component Form Component Shape

  • It is 3 dimensional.
  • Rough size is 1.5" X 1.5" X 1.5"
  • Weight is less than a pound
  • Made of plastic case and electrical componets

Relationship Between Shape and function

  • The Exterior snaps together to make assembly easier.
  • It interlocks inside the housing to prevent movement

Material

  • Case is made of plastic, good choice for easy and cheap assembly and manufacture.
  • electric lead is made out of steel (good conductivity)
  • the switch button is covered with a rubber boot to protect sensitive switch
  • button is plastic
  • switch components are copper which is one of the best conductors (inside plastic case)

Asthetic Properties

  • no asthetic properties were chosen for design of this component

Manufacturing Methods

  • The exterior is 2 seperate halves that were injection molded (Plastic) and then snapped together during assembly
  • The switch has conductive metals that contact each other to carry current

GSEE FACTORS

  • Global

The manufacture process must use electricity and even gas. So the manufacture must take place in a developed country where this and skilled labor is easily accessable

  • Societal

The user never sees the switch there fore never interacts with the user. But the user interacts with the switch through the button so it is almost a secondary interaction.

  • Economic

Plastic case was chosen due to cheap cost Interlocking parts makes for faster manufacture.

  • Environmental

Plastic and metal are recyclable. lessens impact part lasts the lifetime of the tool.

Component Complexity

  • According to table 2 this component is a 2 for complexity. it has very little moving parts and provides one function.
  • This is a simple example because electricity flows through it. that is all. almost like a wire.

Electromagnet

Electromagnet.jpg

This component was chosen for analysis because it is one of the primary components for the product’s electric motor. In addition, it has a complex relationship with the armature, which means a lot of consideration had to be given to this part just to make it function properly.

Component Function

  • This component transforms electrical energy into a fluctuating magnetic field which will exert a force on the armature.
  • This component only performs its primary function, generating a magnetic field.
  • The only flow into this part is AC electricity, and the only flow out of it is energy in the form of a changing magnetic field.
  • The component functions inside of the housing, protected from the environment, and translationally constrained by the gear and bearing.

Component Form

Component Shape

  • The Component is primarily cylindrical. It is symmetrical along its center lines. The exterior is axially symmetric, but the interior wire is only symmetric along the horizontal and vertical axes.
  • The exterior of this component is primarily three dimensional, taking the shape of a cylinder. The two interior wire loops are primarily two dimensional. They take the shape of two parallel circles (though they do have some depth due to wire thickness).
  • The component is 2.5x2x3 in, which is roughly 1/4 the length of the entire product, and almost the same cross sectional area of the product’s body.

Relationship Between Shape and Function

  • The exterior of the component is made cylindrical in order to fit in the grinder housing, but the edges are flattened so that the rotational force exerted by the armature on the electromagnet will not turn it.
  • The interior wire loops are in the shapes of parallel circles so that the generated magnetic field will be uniform and straight down in the magnet.
  • The product has almost the same cross sectional area as the entire product because it is press fit into the housing to prevent translational motion.

The component roughly weighs 1 lb.

Materials the Component is Made From

  • The exterior of the component is made of steel. The wire loops are made of copper, and insulated in plastic.
  • Steel is chosen for the exterior because sheet metals would be ideal to provide strength while still being cheap. Copper and plastic were NOT chosen primarily for manufacturing purposes.
  • Copper and plastic were chosen because their properties are essential to the proper functioning of this component. Copper was chosen for wires because of its high conductivity, which was essential to the functioning of the electromagnet without overheating or wasting power. Plastic was chosen for the necessary function of insulating the wires. If they had not been insulated, the entire magnet exterior would carry current, significantly reducing the effectiveness of the magnet.
  • Steel was chosen because of societal factors affecting this product. The angle grinder as a whole is a hand held tool, so using a strong metal was essential to making the product last for extended periods of time. Also as previously mentioned, using a metal would be ideal because it would keep production and initial cost down, which is an economic factor.

The necessity of using insulated copper wires was a global issue, as a skilled workers were needed to manufacture the raw materials and then assemble them in the exterior.

Aesthetic Properties of Component

  • This component has no aesthetic purpose because it is inside of the product and should not be seen by the consumer during normal operation.
  • The component is grey, brown, and green because those are the natural colors of the materials, and no aesthetics were considered. The plastic may have been made green to identify the type/quality of insulator used.
  • The surface finish is rough on the steel just because a good surface finish was not necessary for this component’s function and it has no aesthetic purpose. The wires and plastic are unfinished as well for the same reasons.

Manufacturing Methods

  • The steel exterior is stamped and then stacked to make a cylindrical case. The copper was probably drawn, as this is the most common method of making wire. The plastic would have been drawn along with the copper.
  • The aforementioned need for a metal to provide support made die casting a good manufacturing method for the exterior. The use of drawing was not really affected by the choice of copper and plastic, though these materials did make drawing a viable process.
  • The desired shape of the exterior had no impact on the manufacturing method chosen, given the desired shape was already feasible. The desired shape of the wires (very long, very thin) made drawing the ideal method for manufacture.
  • Global Factors: The need for technologies to die cast the steel exterior meant that the part would have to be manufactured in a somewhat developed country just to use the power and water infrastructure.
  • Societal Factors: This part does not interact with the user during normal use, nor is it expected to fail over the life of the product. Therefore, the manufacturing methods were not significantly impacted by societal factors.
  • Environmental Factors: The part is made entirely of recyclable materials, which allows it to be easily disposed of at the end of the part’s life. The part should last for the life of the product without being serviced, which means it will not have a detrimental impact on the environment during the product’s working life. There is no material flow for this product, and the only pollution is therefore the indirect pollution from making the electricity to power this part.
  • Economic Factors: Steel is cheaper than aluminum and easy to work with, provides aforementioned advantages to the consumer. This product would be quite expensive to assemble because interlocking the wires and exterior would require human assembly. However, this is a necessary cost in order to manufacture the product properly, and cannot be avoided without even more expensive machinery.

Component Complexity

  • Using the scale in Table 2, this component would be a 5 in terms of complexity. The function it provides is to turn AC current into a fluctuating magnetic field to power the armature. In addition, the geometry of this part has to combine a shape made to fit the general product AND support circular wire coils. The assembly of this part would have included manually looping the insulated wire around the interior, which had to be done in addition to manufacturing the original components.
  • The interactions of this component with respective parts vary from simple to complex.
    • The interaction with the housing is simple because the housing only secures the part, which doesn’t have any real interaction with this part’s function.
    • The interaction with the electrical switch is moderate because electrical energy is flowing through the connecting wires to the electromagnet.
    • The interaction with the armature is complex because the magnet is using electrical energy to generate a magnetic field so that the armature can then change that energy into kinetic energy.

Power Cord

Power Cord.JPG

The power cord is the only means by which energy enters this system, making it essential to the functions of most other components. Also, the power cord was influenced significantly by the four factors during design, making it a good part for analysis.

Component Function

  • This component’s primary function is to connect the grinder to electric current source and to act as the pathway for the electricity flow.
  • The only flow for this component is the electric current from the outlet into the product to perform its task.
  • The power cord is external to the product, and must therefore be exposed to weather and the environment. It is capable of holding up in most working environments, but may be damaged by accidents.

Component Form

  • It is cylindrical shaped. It has an axis of symmetry through its core. The flexibility of the cord in all possible directions is helped by the shape of cord.
  • The power cord is primarily one dimensional, as it's length is significantly larger than any of its other dimensions. In addition, length is the only dimension that matters for allowing the user to work further away from an outlet.
  • The component dimensions are 8 ft. in length, with the diameter about .32 inch
  • The component is designed to be long and thin so that power can be carried to the product over a significant distance without the cord being in the way of many things.
  • The component roughly weighs around 1 lb.
  • This power cord is made out of copper and rubber.
  • These materials were selected for their properties: copper is an excellent conductor, and rubber is a flexible yet durable insulator.
  • This component needs both insulative and conductive materials in order to perform its function.
  • Global factor: The power cord is designed to be a component that is easily removed. This allows it to be taken off and replaced by a cord with an inverter for sale in European marketplaces.
  • Societal:The rubber insulation not only enhances the cord's performance, but also makes it safer for the operator to use.
  • Economic: Economic factors did not really impact the power cord, as the dimensions and materials were detrmined primarily by functional necessities.
  • Environmental: The power cord was made out of recyclable materials, which means it will have minimal environmental impact at the end of its life.
  • Aesthetic for this component: solid black in color, also smooth. Both of these factors make the power cord more visually appealing.
  • The cord is a component the user will interact with often, which makes the aesthetic appeal a necessity.
  • The coloration is purely for aesthetic purposes as a black wire will not provide any function.
  • The surface finish on this component is smooth for aesthetic purposes.

Manufacturing Methods

  • There are two insulated wires inside the rubber insulation. This is done by using the method of drawing.
  • The evidence to support this is the geometry of the wire: it is long and thin, as well as being made of ductile materials.
  • The material choice was primarily made based on the necessary functions of the materials. Drawing was the best option for these given materials.
  • The cylindrical shaped helped this manufacturing method, as the cross-sectional area is constant throughout the component.

Four Factors:

  • Global Factors: This product can be made with relatively simple manufacturing processes, which means it can be made in a variety of areas.
  • Societal: the rubbers is the non-conductor element, since user interact with that a lot. it is safe for them to work with something durable and non conductor.
  • Environmental: This component is made entirely of recyclable materials and has no necessary service, which means it will have no environmental impact over its life.
  • Economic: The rubber and copper are inexpensive materials, and drawing was chosen because it is a relatively inexpensive process for wire production.

Component Complexity

  • This component has a complexity of 2 because it contains some energy flow, but does not have a very complicated geometry or manufacturing process. Moreover, this component only provides one function to the overall product.
  • The power cord only interacts with the electrical switch. This component has an interaction complexity of moderate because there is energy flow between the two components, but they do not interact with each other in complicated ways.

Gear Box

Gearbox Profile.JPG

The gearbox is an important component in the angle grinder. The gearbox is used do hold, align, and protect the gears, making the shape of the gearbox fairly complex in order to achieve these basic functions. In addition to these basic functions, various manufacturing processes are used to make the gearbox.

Component Function

  • The main function of the gearbox is to hold and align the gears.
  • In addition to holding the gears, the gearbox also protects the gears from getting damaged and protects the user from the spinning gears.
  • There are no flows associated with the gear box.
  • The gearbox is located at the end of the angle grinder that has the grinding wheel. It is exposed to the environment and the debris created when grinding.

Component Form

  • The gearbox has two primary shapes. The part that holds the gears is cylindrical and has been hollowed out to hold the gears. This cylindrical section is connected on its side to a square with rounded edges.
  • The gearbox is not symmetrical on the outside, but the hollowed out section that holds the gears is symmetrical.
  • The gearbox is three dimensional.
  • The gearbox is 3.5 inches long, 3 inches wide, and 3 inches tall.
  • The gearbox has a non-symmetrical shape because it is holds the gears perpendicular to the axis of the rest of the angle grinder. The hollowed out section must be cylindrical to hold the gears. The square shape with rounded edges connected the gearbox to the rest of the angle grinder.
  • The gearbox weighs roughly 1 lb.
  • The gearbox is made of aluminum.
  • Aluminum is cheap to manufacture and can be die cast.
  • The gearbox is made from aluminum because it needs to be strong and lightweight.
  • Global, societal, economic and environmental factors influenced the decision to make the gearbox out of aluminum.
Global:
  • Aluminum is widely available.
Societal:
  • Aluminum is a strong and lightweight material.
Economic:
  • Aluminum is relatively cheap compared to other metals.
Environmental:
  • A aluminum gearbox will last a long time and will rarely need replacing.
  • Although the gearbox is visible from the outside, it has little aesthetic purpose. To give to gearbox a more appealing look there is a plastic cover on top of it.
  • The gearbox is silver because that is the natural color of aluminum.
  • The gearbox does not have a general surface finish. It is machined in the hollowed out section used to hold the gears, the hole where the drive shaft is inserted, and the threaded holes for screws. These areas are machined to achieve greater precision.

Manufacturing Methods

  • The gearbox was manufactured using die casting and then select areas were machined.
  • Evidence supporting that the gearbox was die cast are riser marks and parting lines. Evidence supporting that select areas were machined are that these areas are shinier and there are small rings.
  • The gearbox could be die cast because it is made of aluminum.
  • The complex shape of the gearbox made it easier and cheaper to use die casting and then machining for the selected areas.
  • Global, societal, economic, and environmental factors influenced the decision to die cast the gearbox.
Global:
  • Skilled labor is not needed for die casting.
Societal:
  • Safety concerns-The gearbox is strong because it is cast made from die cast aluminum.
Economic:
  • There is a high initial cost for creating the mold for die casting, especially for such a complex design, but the mold can be reused so die casting is cheaper for producing many gearboxes, especially because this gearbox is used on other models of DeWalt angle grinders.
Environmental:
  • After the gearbox is manufactured, it does not consume energy and create any pollution.
  • The gearbox is strong and is made to last so it will rarely need to be replaced

Component Complexity

  • The complexity of the gearbox is a 3. This is because the design of the gearbox needs to be complex to properly perform its desired functions.
  • The function of the gearbox is not that complex so component function does not impact the complexity of the gearbox very much.
  • Component form causes the gearbox to be complex. The shape of the gearbox is complex because the gears are perpendicular to the axis of the rest of the angle grinder. To achieve this, the gearbox is fairly complex.
  • The manufacturing methods add some complexity to the gearbox. The die casting allows the gearbox to receive the complex shape needed from component form. The machined areas make the gearbox even more complex because they reduce the tolerances.
  • The interactions of the gearbox are simple because there are no flows.

Helical Gear

Gearbox Zoom.JPG

The helical gears are important components in the angle grinder. They are used to transfer rotational mechanical energy from the drive shaft to the head. The helical gears are located inside the gearbox and are separated by ball bearings. To make these components, various manufacturing methods are used.

Component Function

  • The helical gears take the rotational mechanical energy from the drive shaft, turns it 90 degrees, and brings it to the head where it can be used to grind materials.
  • The gears only perform one main function.
  • The flow into and out of the helical gears is rotational mechanical energy.
  • The helical gears and ball bearings are located inside the gearbox where they are protected from the environment.

Component Form

  • The general shape of the helical gear is cylindrical. The ball bearings inside are also cylindrical, while the balls inside the bearings are spherical.
  • The helical gears and ball bearings are axially symmetric.
  • The helical gears are three dimensional.
  • The smaller gear has a diameter of 1 inch while the larger gear has a diameter of 1.75 inches. The shaft that connects the gears is 2.25 inches long and has a diameter of 0.625 inches.
  • The gears must be cylindrical so they can rotate and move the rotational mechanical energy.
  • The total weight of the gears and ball bearings is less than 1 lb.
  • The gears and ball bearings are made of steel. The ball bearings have a rubber seal.
  • Steel was chosen because it is cheap to manufacture.
  • Steel is strong and lightweight. The gears need to be strong so they can withstand the heavy forces that act on them.
  • Global, Societal, Economic, and environmental factors influenced the decision to use steel.
Global:
  • Steel is widely available.
Societal:
  • Steel is a strong material.
Economic:
  • Steel is relatively cheap.
Environmental:
  • The steel gears are strong so they won’t need to be replaced.
  • The helical gears have no aesthetic purpose.
  • The gears are a silver-gold color, because that is the natural color of steel.
  • The gears and the ball bearings are both machined for functional reasons. This is to achieve greater precision.

Manufacturing Methods

  • The helical gears were cast and then machined to achieve greater precision. The bearings were also and then machined. The balls inside the bearings were cut from steel wire and then machined to get rid of the rough edges.
  • The helical gears have lines showing that they were machined.
  • The cylindrical shape of the gears made it easiest to cast and then machine them.
  • Global, societal, economic, and environmental factors influenced the manufacturing decision.
Global:
  • Steel is widely available.
Social:
  • The gears need to be strong and have tight tolerances to function without failure.
Economic:
  • Steel is relatively cheap.
Environmental:
  • The gears need to be precise to efficiently transfer rotational mechanical energy. If energy is rotational mechanical energy is lost, more electrical energy will be needed.

Component Complexity

  • The complexity of the helical gears is a 4. The gears need to be very precise and were engineered to achieve the highest efficiency possible because the transfer rotational mechanical energy.
  • The function and form of the gears had some impact on the complexity. The manufacturing process had the largest influence on complexity because the gears needed to be machined to perfection.
  • The interactions of the helical gears are complex. The grooves in the gears match up with the grooves in the drive shaft to transfer rotational mechanical energy to the gears. The rotational mechanical energy is then transferred through the gears and bearings to the head.

Housing

Housing.JPG

The housing is an essential part of the angle grinder for the protection it provides to both the other parts, and the user. Its function is not directly tied to the overall function of the product, but it is a necessity to allow the other components to do their tasks in a safe manner. For these reasons we chose to analyze the housing.

Component Function

  • The primary function of this component is to protect the inner subsystems.
  • This component also protects the user, who may otherwise accidentally put their fingers on a moving part such as the armature, or an electrical one such as the electromagnet. It also supports the components in their necessary locations relative to one another.
  • There isn't any flow other then human interaction with the product while working.
  • This is the exterior body of the component, and its working environment will include weather, external loading, and possible exposure to debris from the grinder.

Component Form

  • The general shape of this product is cylindrical, though it does bulge slightly at the end to accept the gear box.
  • This product has axis-symmetry and plane symmetry along its vertical and horizontal centerlines. These symmetries are only for the functional purpose of accepting the other components that go in the housing.
  • It is primarily three dimensional figure.
  • It is about 7.75 in x 2.5 in x 3 in
  • The shape of this product is associated with the shape of the inner parts. its function is to protect the inner parts , which are arranged in the way to function the system.
  • The component roughly weigh around 1.5 lb.
  • This component is made out of plastic.
  • The manufacturing decision did impact this because the plastics are much easier to mold into different shapes. A relatively complex geometry could be achieved at a low cost by using plastic.
  • Material properties were not the primary concern when choosing the material, though they were still factors. Properties such as strength and durability were important, but they weren't the main factors, or else a tougher material such as steel would have been used.

Four Factors:

  • Global Factors: The housing was not heavily influenced by global factors, as the user does not regularly adjust any parts of the housing.
  • Societal : The housing was made lightweight and durable in order to help the user use the product for extended periods of time.
  • Economic :The housing was made out of plastic in order to keep the overall cost down relative to most metals.
  • Environmental: The housing was made out of recyclable plastic, so it should not have a significant environmental impact.
  • Aesthetics is an important factor for this component, as the user will see this component every time they use the product. It is therefore made bright yellow with smooth curves to make it more visually appealing.
  • It does has aesthetic purpose because it is an outward part and people always interact with it. Making this component look good will therefore increase sales.
  • The housing is made yellow because it is one of DeWalt's primary colors, and therefore helps build brand loyalty.
  • The surface finishing is smooth.
  • This has both functional and aesthetic reasons. This has aesthetic and functional reasons, as smoothness makes the product look nicer, but also makes it more comfortable for the user to use.

Manufacturing Methods

  • This component is made using injection molding, as evidenced by ejector pin marks and a gate on each individual part.
  • The rather than the material choice impacting the manufacturing method, the manufacturing method (injection molding is efficient for large product runs) impacted the material choice (it was therefore made of plastic).
  • The shape was impacted by the method, as there is a slight draft and channels to aid in the manufacturing process.

Four Factors:

  • Global: Using injection molding necessitated that the product be made in a region with a good power grid and readily available resources.
  • Economic: Using injection molding has a high start-up cost, but makes long production runs cheap, as the only major cost is material.
  • Environmental: This component is entirely recyclable, and does not require any materials for servicing over its life. It therefore should not have a significant environmental impact.
  • Societal: Manufacturing this product should not be very dangerous, as it is mostly done by machines. It can therefore be done in most places without worrying about regulations.

Component Complexity

  • This component has a complexity of a 2. This is because the product does not perform any complicated functions or move in any way, but it does have a complex interior geometry.
  • This is simple on the complexity of component interactions. There are no flows of any energy between this component and any of the components it supports. The function of this component aids those of the others indirectly through protection, but the component interactions are still simple.

Handle

Handle.JPG

We chose to analyze this component because it is one of the parts the user has the greatest interaction with. While it is not highly complex and has no energy or material flows, the handle is essential to using an angle grinder, even though it doesn’t contribute to the function in the way most other parts do.

Component Function This component allows the user to maneuver the angle grinder and apply manual force without placing their hand on or near any moving or heated parts. This is the only function the handle performs, and there are no flows associated with it. The component’s environment is exterior to the angle grinder, and it is constantly loaded with forces by the user. It should not be subjected to high heat transfer during normal use.

Component Form

  • The Product is primarily cylindrical. It is symmetrical along its center lines and axis. This component is primarily three dimensional, as the length, width, and depth are all essential to giving the user a good grip.
  • This component is 7 inches long and 2 inches in diameter.
  • The component takes the shape and dimensions it does to make it roughly the same dimensions of a human hand that is gripping something. The dimensions are intended to make the grip comfortable, while still giving the user enough material to apply force when they need to.
  • The component weighs 0.44 lb.
  • The component is made from plastic and steel.
  • Steel was chosen because it is a very strong and durable material that the user should not break during normal use. This allows the handle to best perform its function. The plastic is also used for functional reasons, as it gives a better grip than most metals and is also comfortable because of its elasticity. Manufacturing methods probably did not directly affect the material chosen, though the fact that steel and plastic had the aforementioned functional properties AND were easy to manufacture did confirm the material choice.

Four Factors:

  • Global Factors: The plastic exterior of this part was chosen to prevent corrosion of the steel in very wet working environments.
  • Societal: This part was designed to be ergonomic and allow the user to comfortably use the overall product for extended periods of time.
  • Economic: This handle was designed to work in all DeWalt angle grinders, which reduces the production cost for all models.
  • Environmental: This part has no energy or material flow, meaning it will have no environmental impact over its working life.

The product is black purely for aesthetic purposes. This is not the natural color of the plastic, and it does not aid the functional purpose of the product, but making it black does provide a nice contrast with the overall yellow of the angle grinder. This product has a rough surface finish because it does not need a fine finish to perform its function, and the rubber will probably deform somewhat during use anyway.

Manufacturing Methods

  • The steel core was most likely done by die casting based on the simple geometry of the part, surface finish, and material used. The threads on the end are done by turning based on the increased shininess of the threads, greater precision, and axis-symmetry. The plastic grip was injection molded based on the material used, parting line, and presence of a gate on the end.
  • The choice to use steel and rubber respectively made die casting and injection molding ideal processes, as they would allow the manufacturer to reuse the die and molds and make very large production runs.
  • The shape probably did not impact the manufacturing methods other than to allow turning for the threads on the end.

Four Factors:

  • Global Factors: Die casting and injection molding would require automated factories and a somewhat skilled workforce as well as a reliable power infrastructure. This would limit the countries the part could be made in.
  • Societal Factors: Making this part would not represent a major safety hazard as machines would be doing most of the work. This would allow the part to be made in most developed countries.
  • Economic Factors: The two processes used for this part would have a high start-up cost, but the actual production runs would provide rapid production rates at relatively low costs (primarily material).
  • Environmental Factors: This product is made entirely from recyclable materials. The only impact it will have over its life-cycle is the energy used during manufacturing.

Component Complexity This component would be a 2 in terms of complexity because it does involve two materials to achieve its function, but it has no flows or moving parts. It is only subjected to torsional and linear forces at one point at a time. In addition, the geometry of this part is relatively simple, and the manufacturing would have been straightforward (casting and injection molding).

The only component this part interacts with is the gearbox. This interaction is simple, as there is no energy or material flow between the two. One just supports the other and neither component's function is essential to the function of the other.

Solid Modeled Assembly

The following solid models show the guard, guard clamp, and gear box. In addition, an assembly drawing is provided below. We chose these parts because they are components the user will interact with during use of the product. Unlike some of the components that are press fits or shrink fits, these components can all be easily removed for maintenance or adjustment, but must then be reassembled by the user. This drawing therefore shows how these parts should mate and go together. We chose Solid Works as our CAD package because it would allow us to easily build these models and allow multiple models to interact with each other.

Guard
Guard Clamp
Gear Box
Assembly

Engineering Analysis of Motor

Current carrying loop.gif

When initially designing the motor for this angle grinder the engineers would want to achieve some internal torque, which could then be translated into the torque at the grinder head by accounting for changes in radius, friction, etc. Once this internal torque was decided on, the engineer could then determine how many loops of wire would be necessary for any loop geometry, essentially calculating the size of the armature for a given number of loops or, more likely, the number of wire loops for a given geometry.

Assumptions

In order to perform this analysis, there are certain assumptions that would simplify the otherwise complex math required to determine the relationship between the number of wire loops and geometry of the armature.

  • The magnetic field is constant and will not vary with time or the armature geometry.
  • The effective current is equal to IRMS
  • All wire loops have the same area normal to the magnetic field
  • The resistance of the wire coil does not vary with changes to geometry or the number of loops.
  • A rectangle will be the ideal shape for the coil as it will have a high area for flux, but will not sweep out as large of a volume when spinning as a circle of equal area.

Governing Equations

[1] ∫B*dA=ϕ

[2] T=I*ϕ

[3] V=I*R

[4] IRMS=Imax/√2

[5] Arectangle=2L*r where r is the radius of the spinning coil and L is its length.

Calculations

  • For a given resistance of the coil and a given maximum voltage (about 120V in the US) there will be a maximum current of R/V (Eq. [3]) which can be quickly determined. Now accounting for the fluctuations in current from an AC outlet, the effective current will be IRMS, which will equal Imax/√2 (Eq. [4]).
  • Combining Eq. [1] with Eq. [5],

ϕ=∫B*dA=B*2L*r*sin(θ) where θ is the angle between the area normal vector and the magnetic field (see Figure 1). Because many wire loops and brushes will be used for the overall motor, at any given time it is safe to approximate the sin of the angle between the normal vector and magnetic field as 1.

  • Using Eq. [2], T=I*ϕ=B*2L*r*Imax/√2

Given that each loop will contribute the same amount of torque, the torque will actually be T= B*2L*r*N*Imax/√2 where N is the number of wire loops in the coil.

  • Finally, rearranging this equation for the number of wire loops will yield

N=(T*√2)/(B*2L*r*Imax)

Solution Check

This solution makes sense as extra wire loops are required to increase torque in the motor, and the value of N will increase with increases in desired torque, and decrease with increases in the magnetic field, radius, length, (all increases in magnetic flux) and current. The solution is therefore reasonable.

Interpretation of Solution

This solution would allow an engineer to decide how many wire loops need to be used in the motor armature. In addition, if magnetic field, desired torque, and maximum current are all known, as they were assumed to be, this equation is then a direct relationship between the radius and length of any given wire loop and the number of loops required, which will allow the engineer to fully design the armature. This analysis could be done numerically, but creating a computer program that could process the combinations of each variable and then analyze for other desirable characteristics (i.e. material used, max speed) would allow the engineer to decide on the dimensions of the armature coil with consideration of design requirements. We would therefore recommend using this equation as the basis for a computer analysis.

This result is most sensitive to the assumptions that the wire coil has a constant resistance (this will actually vary as the length of wire in the coil increases) and that the magnetic field is constant (if an electromagnet is used, the field will fluctuate). The fluctuating magnetic field can be accounted for by multiplying the max magnetic field by the square root of 2 (this will yield BRMS). If the increases in resistance are non-negligible, the equation can be modified by adjusting the calculation of Imax (V/R) to account for variable resistance. Moreover, this Imax could be expressed in terms of wire length, which would allow this formula to still be used to solve for the necessary number of turns in the coil.

Design Revisions

Guard

To make adjustment and user interaction improvements to the guard. The proposed design of a cam pin will replace the philips head screw and bolt. This will make adjustment faster and easier. And also will be able to adjust without tools.

GSEE Factors

  • Global

The similar design and materials will make the global impact be less.

  • Societal

The adjustment method is more intuitive and is easier for the user to perform and use.

  • Economic

will cost slightly more than previous design(almost negligable)

  • Environmental

No new environmental impacts

Battery

Standard DeWalt battery pack

In order to improve the overall functionality of this grinder we are removing the power cord as the supply of electricity, and replacing it with the use of the Dewalt standard battery pack which will plug in at the bottom. This change will solve the restrictions imposed on the user by the power cord. The power corded grinder can be used only within the length of the wire from power outlet. Now, after updating it to the battery, there will no longer be any restriction on the range of product use. The bottom of the housing and electrical switch will have to be modified slightly in order to accept the battery pack. The product will be longer and a little heavier than what it was before, so we are moving the switch down to balance the product during use. We will also be adjusting the electromagnet to work with Direct Current because we will now have the battery power instead of alternating current. The batteries are rechargeable and charging the batteries is simple: DeWalt already runs a large product family off of these battery packs. The necessary modifications will therefore be minimal, while the increased benefits for the user will be substantial.

Factors The new battery pack design will benefit the consumer in terms of global and societal factors, but the negative impact on economic and environmental factors must still be considered.

Global

  • The battery pack will always provide the same energy source to the product. While chargers may need to account for different voltages in the country of sale, the same grinder can be sold worldwide.

Societal

  • The battery pack will increase the product's range of use and allow the consumer to use it in all working environments.
  • The battery pack will also reduce the risk of tripping, or knocking things over with a cord.

Economic

  • The battery will cost more to make than the power cord because it includes materials that are significantly more expensive than the copper and rubber used for the cord.

Environmental

  • The battery will have a greater impact on the environment because unlike the power cord, which is made of recyclable materials, the acids and metals in the battery are non-recyclable, and must be disposed of.

Trigger Switch

Angle Grinder revisions.jpg

We will change the power switch to a trigger switch. This will improve the performance and safety because it will allow the user to control the speed of the angle grinder, rather than simply having it on or off. To do this, the trigger will be located on the bottom side of the angle grinder, 3.25 inches below the top of current location of the power switch. This will make it easy to operate with the index finger. The plastic housing will have to be adjusted to accommodate the trigger design. The trigger and the plastic around it will be ergonomically designed to ensure that the user's hand is comfortable when using the angle grinder. Instead of sending an on/off signal, the trigger switch will send a signal that tells how much electrical energy is needed for the speed that the user is asking for. This new trigger switch design will make the angle grinder more user friendly.

Factors

The new trigger switch design will address both global and societal factors.

Global
  • The trigger switch will make the angle grinder more intuitive. When using a trigger, users will know that the angle grinder is off when they are on pushing on it. With a power switch, either position could mean on or off. This means that the power switch could accidentally be switched on when the angle grinder is not plugged in.
Societal
  • The trigger switch will make it easier for both left and right handed people to use because the location of the power switch favors right handed people.
  • The trigger switch will make it safer to operate an angle grinder for two reasons. First, the trigger's location will be farther from the spinning head than the power switch. Second, the trigger will allow the user to stop the angle grinder faster than the power switch does. If something goes wrong and the user lets go of the angle grinder, the trigger will stop the angle grinder it leaves the users hands, whereas the power switch leaves it running.
  • The trigger and the housing around it will be ergonomically designed, making it more comfortable for the user to operate.

References

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html

http://www.uni-regensburg.de/Fakultaeten/phil_Fak_I/Philosophie/Wissenschaftsgeschichte/Termine/E-Maschinen-Lexikon/Chronologie.htm

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