Group 26 - Craftsman 1/2 in Impact Wrench - Gate 1

Product Development

Craftsman brand tools have been popular to society ever since they have emerged. In the early 1930’s the company featured its first line of power tools and become recognized for aiding in the construction industry. The reputable tool line has been ranked top contender in terms of quality and gained the slogan “Americas Most Trusted Brand.” Craftsman has two types of tool lines each marketed towards a different group of consumers. The standard products are sold at Sears and True Value Hardware meant for homeowners or hobbyists. The professional and Industrial line is a big jump in price and quality. Our 1/2” impact drive was developed during the industrial bomb in the United States. Larger metal infrastructure buildings were constructed with lag bolts and nuts at multiple joint locations. The tool made it very easy to torque lagging hardware down to a specific ft-lb range. Smaller models emerged in automobile repair shops that were equipped with pneumatic air supply systems. This gave mechanics the ability to repair cars and trucks in a timely fashion for customers. Our Impact wrench was purchased at sears for $38.99, a competitive price for homeowners and automobile enthusiasts. The only drawback to this tool is that it requires a suitable air compressor to operate. These portable units take up space and are very loud. Our project dissection group will be reverse engineering the craftsman impact gun to take a closer look at its internal mechanical systems.

Usage

• This product is used for removing and applying bolts and lug nuts at a high torque range.
• You can apply any metric or standard 1/2" socket to the wrench.
• It is to be used in both a professional and home environment.
• Requires an air compressor source to flow 5.2 CFM of air at a maximum of 90 PSI.

Power source

The pneumatic impact wrench is operates off a compressed air source. To generate compressed gas a compressor needs to be used that runs off any standard 110 volt electrical plug. From an energy prospective, the wrench runs on both compressed gas and electrical energy. The energy that is taken from the air is converted to mechanical energy to turn the hammer in the impact wrench which is what turns the socket. The electrical energy that is inputted to the air compressor is then transformed into compressed air and stored in the compressor. The compressed air is then used to turn the metal fins which are connected to a shaft which is the air converting to mechanical energy and unscrewing the bolt.

Disassembly Process

The craftsman ½” impact wrench is a pneumatic tool that is used vastly throughout society. Its main operating purpose is to remove and tighten nuts and bolts in a quick and precise manor. At first glance, the impact gun looks quite simple in nature. Its exterior is made of a hardened plastic with a stainless steel frame encasement. Inside this encasement is where all mechanical parts lie that enable the gun to carry out its main purpose of development. As a group we will be reverse engineering this product to take a closer look at the intricate mechanical and pneumatic systems that lie within the craftsman impact wrench.

Tools Needed

• Allen head screw set- used for the removal of Allen hex head bolts
• Push Pin dowel- needed to remove push pin dowels out of slots
• Small hammer- to break open outer plastic impact gun shell
• Screw driver set- remove all small set screws and trigger assembly
• Needle nose pliers- needed to remove small pressure springs and valve stems.
• Angle grinder W/ cutting wheel- may be used to cut open composite plastic frame.

Subsystem Dissection

The impact wrench we are dissecting is pneumatic so we do not expect to find any electrical components in the system. However, because it is air powered there are likely to be several valves, O-rings, gaskets, and pressure vessels contained within the tool. To start the dis assembly process we must first remove the rear backing plate from the impact gun. This is done by unscrewing four hex head bolts. A small flat head screw driver will be needed to break open the rear main seal of the backing plate. One this is complete all mechanical and pneumatic components will be visible. A push pin and hammer are then needed to push the dowel holding in the tool engagement trigger. On the bottom of the handle there is an air inlet bushing that connects the impact gun to its air supply. An SI 6 point wrench will be used to disconnect this air fitting. On the front of the tool there is a small Allen key bolt that holds on the metal hammer case. When this is cracked we will be able to see the anvil and hammer cage impact system. Now that all the exterior parts of the impact gun are taken off. We can now start to dissect the interior mechanical components and parts. To ensure no parts are lost or misplaced, each will be documented and categorized. A picture of every part will be taken along with a description of its characteristics and purpose.

Group Roles

Group Member	Title	Description	Contact Information
Andrew Conti	Project manager	will be responsible for keeping in contact with the group to set up meeting times, also to make sure everyone is doing their fair share to help the group get the job done.	aeconti@buffalo.edu
Mike Motsko	Technical Expert	will be responsible for most of the dissection process and knowing how to reassemble the project; should have a very in-depth knowledge of how the product works as a whole	mamotsko@buffalo.edu
Garret Konecke	Editor	will be responsible for going over everyone’s parts to make sure they are all grammatically and technically accurate, also is in charge of all wiki editing and making sure all the parts flow together	gdkonecke@buffalo.edu
Mark Ho	Documenter	responsible for documenting all of the steps of the process and taking pictures when needed so it is very clear what the step by step process was	jianhaoh@buffalo.edu
Peter Hwang	Communication Liaison	responsible for making sure there is an easy way to get in contact with everyone in the group so everyone can stay in contact especially when the group is not scheduled for a meeting	peterhwa@biffalo.edu

Strengths and Weaknesses

Name	Strengths	Weaknesses
Andrew Conti
Mike Motsko
Garrett Konecke
Mark Ho
Peter Hwang

Group Conflict

• Majority rules, any conflicts will be voted on as a group to decide what is the best route to take
• If a solution is not found through a group vote the project manager will have the last say
• Everyone has agreed to be open to comments and everyone is entitled to bring up and concerns they may have

Timeline

Section	Task	Start Date	Due Date
Gate 1: Project planning	Background of pneumatic wrech and intial assesment of disection work proposal management proposal	9/30/2012	10/8/2012
Gate 2: Product Disection	Disection of product; detailed information about components and how the wrech was manufactured subit cause for corrective reaction	10/09/2012	10/26/2012
Gate 3: Product Analysis	Analyze information and components submit cause for corrective action	10/29/2012	11/16/2012
Gate 4: Product Explanation	Review all information found from disection and analysis to come to large conclution about the design Submit cause for corrective action	11/19/2012	11/30/2012
Gate 5: Delivery	Document all findings and prepare for final review of project	12/3/2012	12/14/2012

Subsystem Complexity

The Craftsman impact gun is comprised of three mechanical operating systems. This includes the rotating assembly, impact system and air supply regulation system. The integral of these components interact in a precise and complex order. Each system is composed of numerous parts and extremely close tolerances to carry out the impact guns functionality.

Pneumatic Air Supply

The Craftsman Impact gun operates of a pneumatic air supply system which uses pressurized gas to drive mechanical motion. Pneumatic systems are widely used in our society especially in industrial sectors. This is mainly because there is an unlimited supply of air in the atmosphere to produce compressed gas and transmit energy. Pneumatic tools are extremely durable and very reliable when maintained properly. Set aside from that, there are no risk factors for overloading or over heating components. There are two ways the impact gun can be attached to an air compressor, either hard piped or through an air hose. Hard piped air systems are mainly used in mechanical and industrial shops where multiple pneumatic tools need to operate. These systems consist of a large air supply, stop valve, filter, regulator and lubricator. A hard piped air supply has greater tool performance because the gas is filtered, lubricated and maintained at constant pressure. For small home owner applications an air compressor needs to be purchased to satisfy the impact guns 5.2 SCFM consumption at 90PSI. It is also recommended that a 3/8 inch ID hose no longer than 25ft be used because it will cause a pressure drop impeding on tool performance.

Pneumatic System

The impact gun is connected to an air supply hose via a quick connect coupler located on the handle. Once it is pressurized, air is fed through an exhaust deflector and throttle valve to the power the regulator. The power regulator is an adjustable switch than can be rotated until the desired output is achieved. The center is neutral, left is reverse and right is forward. The further you go in each direction more torque will be achieved.

Rotating Assembly

Once the power regulator is pressurized, air is fed into the trigger mechanism. The trigger assembly allows the operator to control the air flow of the impact gun. This is simply done by pressing firm on the trigger and releasing to cease operation. When the tool is armed, pressurized gas is charged in the rotating cylinder. This translates into mechanical energy by spinning the rotatory blade in a desired direction of operation.

Impact/Anvil System

The impact/anvil system is last to be charged. It is to be noted that this system only engages when there is a resulting force on the impact gun. If the gun is held in the air freely with no load, it will spin at a very high RPM. The impact system :only works when a bolt needs to torqued down or taken off. This quick succession of force is key in removing stubborn hardware without breaking them. As pressurized gas moves through the rotary blade it passes into the hammer cage. :Enclosed is a cam that pounds into the impact anvil as air flows around it. All excess exhaust air is directed down the handles and out the sound muffled port.

Number of Components

Our product dissection group estimates there are 35-55 moving and non-moving parts contained in the impact wrench. Each system works together with precise accuracy and timing to perform a simple linear oscillating movement. Based upon our research it is presumed that the impact wrench has a pneumatic, rotational, and impact system that can be categorized below.



Pneumatic system

1. Quick connect air fitting
2. Exhaust outlet/muffler
3. Throttle valve spring
4. Pressure regulator
5. Power control toggle
6. Trigger switch

Rotating Assembly

1. Reverse/forward valve
2. Washers and bearings
3. Rotational cylinder
4. Air tight rear gasket
5. Rotor and blade assembly

Impact System

1. Hammer Cage
2. Cam hammer
3. Impact anvil
4. Bushings
5. Air tight front seal
6. Metal front end Case




External Materials

The Craftsman impact guns external profile is quite basic and very user friendly. Most of the external frame work is made of black plastic with red accents on the trigger handle. This is presumed to be a high strength plastic composite that can with stand strong internal and external forces. Making the impact gun out of a plastic composite gives it light weight features and also cuts down on production costs. Both the trigger and pressure regulator control switch are made of plastic as well. The power regulator switch is clearly marked with reverse and forward direction of rotation arrows. The user only needs to remember one rule of thumb, “Left loose and right tight.” On both sides of the external body, Craftsman embedded their company trademark logo. The front hammer case is made of stainless steel with a brushed finish. This gives the impact gun a sleek and modern design. On the very front lies the ½” drive where most impact sockets and extensions attach to. Its shape is square with a C clip on the end to hold attachments in place from falling off. The hammer case and impact drive are both made of metal but are two different colors. We concluded that the ½” drive must be a high strength metal composite to endure the extreme operational forces.

User Interaction

Safe Operation

The Craftsman Impact gun is a very simple to tool to use once you understand its mechanics and possible safety risks. There are two switches located on the front and rear that control tool engagement. The trigger located on the front handle controls the air valve. Squeezing the trigger allows air to pass through the impact gun and will cease when let go. The toggle switch on the rear The tool operates off a high pressure gas system that converts compressed air to mechanical energy. Since a high pressure air hose is attached the user needs to be aware not puncture the supply line. Maximum operation is suggested not to exceed 90 PSI at 5.2 SCFM. While using the Impact wrench always use two hands since it out puts a large amount of rotational force. In some working conditions, rust may exist on stubborn bolts. Eye wear should be worn to prevent any small pieces of metal from endangering the user. During tool operation ear protection may be necessary from noisy working environments.

Tool Maintenance

The impact wrench requires some maintenance steps to prevent shortening tool life. There are many moving parts like pistons, springs bearings and rotors that are under large forces of pressure. These parts rotate at a free speed of 7400 RPM with no load and at 400 ft-lbs loaded. Friction will be the main reason for tool failure if not properly maintained. The impact wrench must always be lubricated with tool oil or high grade turbine oil containing moisture absorbent, rust inhibitors, metal wetting agents and EP additive. This can be done by disconnecting the gun from the air supply. Removing the Allen head screw and squeezing 1 oz. of oil through the port hole. Craftsman’s engineers recommend using an in-line filter-regulator-lubricator to increase to life span as well. It is essential after ever use that the tool be stored in a clean and dry environment.

Alternatives

Since one of the main applications of the impact wrench is removing and tightening lug nuts on automobiles, a tire iron could be considered an alternative tool. A tire iron, which typically consist of two crossed bars with a socket at each of the four ends, uses the force of leverage and human strength to deliver enough power to turn extremely tight lug nuts. Because it is man-powered it does not require an air compressor like the impact wrench thus it is much more portable and cost a fraction of the price of an impact wrench and compressor. However, an impact wrench can generate a greater amount of torque than the average individual with a tire iron and also creates pulsations that help loosen the lugs making it a quicker and more powerful option.

	Product Name	Price	Performance	Advantages	Disadvantages
	Cobalt 18v 1/2in cordless impact wrench	$279.00	1900rpm 300ft-lb	Runs on a battery instead of compressed air making it more portable Do not have to buy an air compressor if you do not already have one	The battery takes a minimum of 1.5 hours to charge to one hundred percent power Much lower rpm than pneumatic wrench Much more expensive
	DEWALT 7.5-Amp 1/2-in Corded Impact Wrench	$179.00	2100 rpm 345 ft.lb	Runs off electrical power and is simply just plugged into a wall outlet, so you do not have to have an air compressor to run it and there is no worry about charging a battery	Corded so you will always have to be dragging a cord behind you or possibly need to use a extension cord to reach your work area Runs at a lower rpm of 2100
	Ken Tool Tire Iron	$15.00	man-powered	Simple in that it is made from basic physics in giving yourself enough leverage so you can with your own power break free your lug nuts Compact you can keep it in your car at all times stored away for your convenience	You need to have a good amount of man power to break the nuts free and to reapply them at the correct pressure Not as fast as simply pressing a button and having a power drill loosen it for you