Group 27 - Ryobi Corner Cat Palm Sander

Figure 1: Assembled Product

Executive Summary

The Ryobi Corner Cat Finish Sander [1] is a slight variation of the typical square or round pad (or palm) sander. The Corner Cat's sanding pad is three-sided, and tapers to a point, allowing it to reach into corners and tight places. When elbow grease isn't enough, this portable sander can remove material at up to 11,000 operations per minute. Made even more versatile by incorporating a hook and loop fastener system, the sander can be fitted with one of several variations of detachable pads designed for scrubbing, finishing, and sanding.

The sander is well-made, using relatively few components (49 components, 23 of which are fasteners), appropriate-length wiring, light-weight materials (mostly ABS plastic) for main shell components, aiding in portability, and heavier machined metal only for high-stress components. All fasteners can be removed/inserted using the same tool (#2 Phillips Screwdriver), and there is no unnecessary variation among fastener types (only two different lengths.) There are no excessively fragile components, and wiring is securely fastened to electric components. Due to the grease chamber, disassembly was a little messy, but it is important that the sander's gear assembly stay lubricated, increasing the lifespan of the device.

Disassembly and assembly were relatively easy, with each being the reverse process of the other. We noted no extraneous parts, and only two components we thought could be combined into one part. No parts were broken or lost, and spring-loaded components were easily recovered after leaving the work area as projectiles. Our dissection group had few suggestions for improvement, including positioning the on/off switch in a more convenient location, and designing a shell that would more easily accommodate operating the sander in a position other than a clothes-iron type grip.

The following documentation includes pre-disassembly assumptions and estimates, detailed disassembly and assembly steps, parts list, and post-disassembly thoughts and conclusions.

This particular model of the Ryobi Corner Cat Finish Sander (model P400) is DC battery-powered, but did not include a battery pack. We were not able to verify the operability of the sander before or after dissection. However, we suspect it is in perfect, or near-perfect working order.

Introduction

The 18 Volt One+ Corner Cat™ Finish Sander by Ryobi utilizes an 18-volt proprietary battery pack to power a small internal motor. The motor turns an slightly off-center bearing paired with an unevenly distributed weight up to 11,000 operations per minute, which causes a vibration-like motion in the sanding pad. Using a hook and loop fastening system, the sanding pad can be fitted with a variety of abrasive materials, and can be used for sanding, grinding, and polishing. Two of the three edges of the Corner Cat™ Finish Sander pad taper to a 60-degree point, rather than the standard square or circular shape of most palm/pad sanders.

This disassembly project is part of the Fall 2007 semester of course MAE 277, instructed by Dr. Kemper Lewis at The State University of New York - University at Buffalo.

MAE 277 Group 27:

Javon Frater - Group Leader, Assembly

Ian Clark - Assembly

Jenna Curry - Disassembly

Ryan Krawchuk - Disassembly

Sara Smith - Data Gathering, Wiki Documentation

Before Disassembly

The Ryobi Corner Cat Finish Sander is used for sanding, grinding, and buffing surfaces, depending on which abrasive pad is being used. The pointed shape of the sanding pad allows the sander to reach into corners.

An 18-volt rechargeable battery pack stores potential energy. When the power switch completes the circuit, the battery releases energy as Direct Current energy, powers the Direct Current motor, which is converted to mechanical energy. The motor quickly rotates a shaft that is connected to the sanding pad. The motion of the sanding pad, equipped with a sheet of an abrasive material (e.g. sand paper), removes surface material from wood, metal, plastic, painted wall, etc. The type of abrasive sheet used with the sander determines how quickly or slowly material is removed.

The product is not operable as a battery was not included.

Pre-disassembly estimated number of components: Approximately 60 total components, including fasteners.

Pre-disassembly estimated types of materials: Approximately 7 types of materials - plastic, nylon, rubber, steel, aluminum, copper, hook and loop adhesive (Velcro).

Disassembly

Table 4.1 - Disassembly Steps

Step #	Description	Tool Used	Difficulty (1=not difficult at all, 5=very difficult)	Image
1	Snap off battery slot cover	Hands	1
2	Remove four black screws from battery slot cover (yellow)	Screwdriver (Phillips)	1
3	Separate two main parts of battery slot cover by snapping yellow pieces from blue piece. Remove two springs	Hands	2
4	Remove the small plastic component that held in the nylon strap from the inside battery slot cover	Hands	1
5	Remove steel rod that held nylon strap	Hands	1
6	Remove five screws from the bottom sander pad	Screwdriver (Phillips)	1
7	Remove sander pad	Hands	1
8	Remove four screws from solid black plastic component beneath sander pad	Screwdriver (Phillips)	1
9	Remove solid black plastic component	Hands	1
10	Remove screws from top body of sander	Phillips bit, wrench	4
11	Separate outer casing into two pieces	Hands	1
12	Remove white flexible plastic fastener from slot near bottom of sander	Hands	1
13	Remove second white plastic fastener from slot near bottom of (other half of) sander near motor	Hands	1
14	Remove anti-theft device from thin slot near the center handle	Hands	1
15	Remove bearing gear assembly	Hands	1
16	Remove screw from small metal component that held yellow plastic switch	Screwdriver (Phillips)	2
17	Remove motor and wiring from slot in outer casing	Hands	1
18	Remove 2 screws from motor	Screwdriver (Phillips)	1

After Disassembly

Table 5.1 - Parts List

Part No.	Part Name	Part Description	No. Req'd	Material	Manufacturing Process	Image	Image (supplemental)
1	Battery Receptacle Cover (outer)	Yellow. Covers battery receptacle when battery pack is not inserted. additional information	1	ABS Plastic	Injection Molded
2	Battery Receptacle Cover (inner)	Blue. Covers battery receptacle when battery pack is not inserted.additional information	1	ABS Plastic	Injection Molded
3	Fasteners	5/8" fillister-head phillips screw. Fastens the two parts of battery receptacle cover.additional information	4	Steel	Extruded and Machined
4	Battery receptacle cover clip	Yellow. Spring-loaded clips - depress to release receptacle cover.additional information	2	ABS Plastic	Injection Molded
5	Spring	1 1/8" x 1/4" Creates tension for battery receptacle cover clips.additional information	2	Steel	Extruded and Shaped
6	Lanyard-rod cover	Yellow. Secures lanyard rod.additional information	1	ABS Plastic	Injection Molded
7	Lanyard Rod	1 1/4" x 1/8" Secures lanyard to battery receptacle cover.additional information	1	Steel	Extruded
8	Lanyard	Black and Silver. Allows sander or battery receptacle cover to be clipped to nail, belt loop, etc.additional information	1	Metal alloy and black nylon	Die Cast and Sewn
9	Sanding Pad	Black - one side is covered with hook portion of hook and loop fasteners. Secures sanding/scrubbing pads to sander.additional information	1	ABS Plastic, foam plastic, nylon	Injection Molded
10	Fasteners	3/8" fillister-head phillips screw. Fastens sanding pad to sanding pad support piece.additional information	5	Steel	Extruded and Machined
11	Sanding Pad Support Piece	Black. Supports sanding pad, provides bulk for rotating shaft and vibration.additional information	1	ABS Plastic	Injection Molded
12	Fasteners	3/8" fillister-head phillips screw. Fastens sanding pad support piece to vibration support pieces.additional information	4	Steel	Extruded and Machined
13	Sander Shell - one of two	Blue and black. Encases sander's internal components, provides grip for human operation.additional information	1	ABS and rubberized plastic	Injection Molded
14	Sander Shell - two of two	Blue and black. Encases sander's internal components, provides grip for human operation.additional information	1	ABS and rubberized plastic	Injection Molded
15	Fasteners	5/8" fillister-head phillips screws. Fastens two parts of sander shell.additional information	10	Steel	Extruded and Machined
16	Vibration support piece (lower)	White. Attaches sanding pad components to body of sander. Shaped to withstand vibration.additional information	1	ABS Plastic	Injection Molded
17	Vibration support piece (upper)	White. Attaches sanding pad components to body of sander. Shaped to withstand vibration.additional information	1	ABS Plastic	Injection Molded
18	Anti-theft device	Alerts retailers of attempted theft.additional information	1	Plastic and iron-containing metal (ref)	Shaped and Formed
19	Power switch tension tab	Places tension on and holds on/off switch in place.additional information	1	Steel	Sheet Metal Forming
20	Fastener	3/8" fillister-head phillips screw. Fastens power switch tension tab to sander case.additional information	1	Steel	Extruded and Machined
21	Power switch (external)	Yellow. User-activated toggle-switch. Controls an internal switch box.additional information	1	ABS Plastic	Injection Molded
22	Bearing and gear assembly	Transfers rotating motion from motor to sanding pad.additional information	1	Composite Metal	Machined
23	Power switch (internal)	Completes a circuit and activates motor.additional information	1	ABS Plastic and steel and/or copper	Injection Molded, Sheet metal forming
24	Battery Contacts	Completes a circuit with battery power pack.additional information	1	Steel and ABS Plastic	Sheet metal forming, Injection Molded
25	Motor Assembly + gear	Provides mechanical energy for movement of sanding pad.additional information	1	Steel and copper wire	Sheet metal forming, machining, extrusion
26	Wires	Transfers electricity between battery pack, power switch, and motor.additional information	3	Copper and plastic	Extrusion

Additional Parts Information

Table 5.2 - Parts Details

Part No.	Part Name	Why is the part made of this material?	Why does the part look the way it does?	Additional Images (if applicable)
1	Battery Receptacle Cover (outer)	Lightweight, durable, inexpensive	Yellow color is consistent with Ryobi's yellow/blue color scheme.
2	Battery Receptacle Cover (inner)	Lightweight, durable, inexpensive	Blue color is consistent with Ryobi's yellow/blue color scheme.
3	Fasteners	Strength, rigidity	Painted black for aesthetics and corrosion resistance.
4	Battery receptacle cover clip	Lightweight, durable, inexpensive	Yellow color is consistent with Ryobi's yellow/blue color scheme.
5	Spring	Flexible, durable	Standard spring steel color.
6	Lanyard-rod cover	Lightweight, durable, inexpensive	Yellow color is consistent with Ryobi's yellow/blue color scheme.
7	Lanyard Rod	Strength, rigidity	Chrome-plated for corrosion resistance.
8	Lanyard	Durable, lightweight	Standard black woven nylon, chrome-plated clip for corrosion resistance and aesthetics.
9	Sanding Pad	Lightweight, durable, inexpensive. Hook and loop fastening system allows for secure fit of abrasive pads, yet easy, fast, and tool-less switching of abrasive pads.	Triangular shape allows the tool to reach into corners.
10	Fasteners	Strength, rigidity	Painted black for aesthetics and corrosion resistance.
11	Sanding Pad Support Piece	Lightweight, durable, inexpensive	Interlocks with sanding pad, color is likely inexpensive (internal part).
12	Fasteners	Strength, rigidity	Painted black for aesthetics and corrosion resistance.
13	Sander Shell - one of two	Lightweight, durable, inexpensive. Rubberized grips provide a non-slip surface.	Blue color is consistent with Ryobi's yellow/blue color scheme. Shape is ergonomically-designed while accommodating internal components.
14	Sander Shell - two of two	Lightweight, durable, inexpensive. Rubberized grips provide a non-slip surface.	Blue color is consistent with Ryobi's yellow/blue color scheme. Shape is ergonomically-designed while accommodating internal components.
15	Fasteners	Strength, rigidity	Painted black for aesthetics and corrosion resistance.
16	Vibration support piece (lower)	Lightweight, durable, flexible	Thin columns of ABS plastic absorb shock of vibrating motion.
17	Vibration support piece (upper)	Lightweight, durable, flexible	Thin columns of ABS plastic absorb shock of vibrating motion.
18	Anti-theft device	Inexpensive, fits into small spaces, can be magnetized.	Standard acousto-magnetic anti-theft tag [2]
19	Power switch tension tab	Flexibility, rigidity	Bent at a 90-degree angle to fit flush against case while providing tension to external power switch.
20	Fastener	Strength, rigidity	Painted black for aesthetics and corrosion resistance.
21	Power switch (external)	Lightweight, durable, inexpensive	Yellow color is consistent with Ryobi's yellow/blue color scheme. Symmetric shape makes powering the unit on and off with equal ease.
22	Bearing and gear assembly	Strength and durability over many thousands of revolutions, heat resistance.	Symmetric rotary bearings allow for non-vibrating motion inside the case, while slightly off-center external bearing and asymmetric weight cause a rotational-vibrating motion. Note: did not dissect to base components in order to avoid permanent damage to component.
23	Power switch (internal)	Light-weight, non-conductive	Takes little space inside sander case, positioned in such a way that toggle switch is activated by user depressing external power switch. Note: did not dissect to base components in order to avoid permanent damage to component.
24	Battery Contacts	Durable, conductive, flexible	Two contacts in order to complete an electrical circuit. Contact material must be flexible enough to allow insertion of battery pack while remaining rigid enough to prevent battery pack from falling out during use.
25	Motor Assembly + gear	Strength, durability, conductivity	Motor case must be small enough to fit into sander case. Electricity is transmitted through copper wires to create a magnetic field that causes the steel rod and gear to rotate. Note: did not dissect to base components in order to avoid permanent damage to component.
26	Wires	Conductivity, flexibility, durability	Length of wires is appropriate to distance between internal components. Red and black wires are positive and negative, respectively (for correct assembly during manufacturing process.)

Suggested Improvements:

Figure 5.1: CAD representation of main components

• Position on/off switch closer to the handle. Though the on/off switch may be placed far from the handle to prevent accidental activation of the sander, it would be more convenient to position the switch in a place more easily reached by the user (this may also make it easier to quickly power off the unit.)
• The sanding pad and sanding pad support piece can be combined into one part. When assembled, the two pieces fit security together (see figure 5.2).
  

  

  Figure 5.2: Assembled parts 9 and 11
• The case could be smaller. There seems to be a lot of unused space inside the unit.
• The screws set in deep, narrow holes in the case are hard to reach without a long and thin enough screwdriver. Shallower, wider holes would make disassembly easier (although we recognize that the manufacturer may not encourage disassembly of their products.)
• The case could be redesigned to be more easily used with different grips. With the current design, the sander seems limited to a clothes-iron type grip.
  

  

  Figure 6.1: Assembly Step 9

Assembly

Table 6.1 - Assembly Steps

Step No.	Procedure	Tool Used	Difficulty (1=not difficult at all, 5=very difficult)
1	Insert motor and wiring into slot in outer casing.	Hands	1
2	Insert switch assembly	Hands	1
3	Insert power switch tension tab and fastener	Screwdriver (phillips)	1
4	Insert ball bearing gear assembly.	Hands	1
5	Insert anti-theft device sticker in thin slot near the center handle away from motor.	Hands	1
6	Insert one white vibration support piece into slot at near bottom of sander.	Hands	1
7	Insert second white vibration support piece into slot on bottom of sander near motor.	Hands	1
8	Assemble two halves of outer casing.	Hands	1
9	Insert screws into outer casing. (see Figure 6.1)	Screwdriver (phillips)	1
10	Insert black sanding pad support piece.	Hands	1
11	Insert four screws into black sanding pad support piece.	Screwdriver (phillips)	1
12	Attach sanding pad to sanding pad support piece.	Hands	1
13	Insert five screws into the bottom of sanding pad.	Screwdriver (phillips)	1
14	Insert nylon strap into yellow half of battery receptacle cover.	Hands	1
15	Insert steel lanyard rod.	Hands	1
16	Insert two springs into blue half of battery receptacle cover.	Hands	3
17	Insert two yellow battery receptacle cover clips	Screwdriver (phillips)	3
18	Assemble blue and yellow halves of battery receptacle cover	Screwdriver (phillips)	1
19	Insert four screws into battery receptacle cover.	Screwdriver (phillips)	1
20	Attach battery receptacle cover to main sander component.	Hands	1

After Assembly

• The product operates by transferring DC power from the battery through the metal contact prongs in sander's battery receptacle. The electric current then travels through wires to a switch approximately 7 inches away, which contains a toggle switch that turns the device on and off. The toggle switch is pressed by an indentation on the user-operated yellow external power switch. The electric current then travels another 5 inches to the motor which turns an attached gear. This gear proceeds to turn another gear in a grease-filled compartment. This second gear is attached to a rod which spins on ball bearings. A slightly off-center bearing (see Figure 7.1)
  

  

  Figure 7.1: Off-center bearing
  , combined with a weight attached to one side of the rod causes the rod to spin off balance and vibrate up to 11,000 operations per minute. This vibration is transferred to the sanding pad to perform the desired task.

• The product did not include a battery pack, so it is not clear whether the product works (although we suspect it worked both before and after disassembly.)

• For designing and testing the product, basic models for torque, like τ = rF sinθ, could be used as well as basic circuit equations. The vibration however, would require a relatively complex and precise model. Analyses would be necessary to determine the stresses on various parts due to the vibration. It would also be necessary to analyze the reaction of the fasteners since they tend to be loosened by vibration - this would help determine appropriate materials, and in the case of fasteners, whether any adhesive is necessary to keep them in place.

• The assembly and disassembly processes were straightforward and took place without any great degree of difficulty. Disassembly and assembly were the reverse of one another and used the same tools: a 6-inch #2 phillips screwdriver. All steps involved unscrewing fasteners or removing pieces by hand. The device had no complicated internal assemblies. We were able to be completely reassembled the sander - there were no broken components.
  

  

  Figure 7.2: Fully-Disassembled Product

References

[1] Ryobi Tools. (18). 18 Volt one+ Corner Cat™ Finish Sander. Retrieved December 4, 2007, from Ryobi Tools Web site: http://www.ryobitools.com/products

[2] How Stuff Works. (2007). Anti-shoplifting devices. Retrieved December 4, 2007, from How Stuff Works Web site: http://electronics.howstuffworks.com/anti-shoplifting-device5.htm

[3] Wikimedia. (30). Help: introduction. Retrieved December 4, 2007, from Wikimedia Web site: http://meta.wikimedia.org/wiki/help