Shake Table Design

Design Brief

Design and built a shake table for ME 491 design competition that can provide a platform that is shaking at 2 cycles per second with a ½ inch peak-to-peak motion. The prototype is to be finished by Oct 24, 2011 and cost less than $50.

Make a Plan : A simple chart showing timelines and resources

Developing product design specifications (PDS)Criteria Requirements

Performance 2 cycles per second +/- 5%½ inch peak to peak +/- 5%Uses wall transformer (<10 watts)Motion profile: sinusoidal (desired)

Environment IndoorsLife in service 100 hoursQuantity 1Shelf life N/ACost of production per part (material and labor) $50Size and Shape Clear moving platform 6 by 6 with

pattern of ¼ inch holes.< 1x1x1 feet envelopeDesired: more compact

Weight < 10 lbs - desired < 5lbMaintenance NoneInstallation N/AErgonomics N/ASafety No pinching points, No sharp

corners, stable with a 1 lb weight on top, input power < 10 W,Enclosed moving parts desired.

Materials None (no constraints)Manufacturing facilities None (subject to $50)Shipping N/APackaging N/AAesthetics N/A

Quality and Reliability Must withstand overloading (not dropping) side loading running at higher speeds

Applicable codes and standards N/ATesting Life testing at nominal load

withstand overload test w/o damagewithstand side load test w/o damagewithstand higher speeds

Company constraints and procedures N/ADocumentation (processes) None neededLegal (Related patents) N/ATimelines Finished by Oct 24Disposal N/AOther (Noise) No loud or high frequency noise

External Search

Existing products and technologies Hydraulic actuators Pneumatic actuators Solenoids Linear motors Geneva mechanism Four-bar linkages Cams

Internal Search

Several vastly different designs were suggested. The following design was selected as the most workable concept.

Further simplification of the concept lead to the final selected concept below

Detail Design

Motor selection : based on power and frequency of motion Voltage selection: Based on frequency of motion Materials: based on weight, ability to machine easily, and cost Overall dimensions: bases on space allowance, weight Cam design: Based on motion amplitude, motion characteristics, life of

device Bearing selection: Noise level, maintenance, life, cost

Prototyping

Mass Production Scheme: Build all parts, assemble later (interchangeability) Requires an assembly plan first Requires precision machines and workmanship Requires adherence to all tolerances May not work at the end …. Requiring reworks

Prototype Fabrication Scheme: Fit-and-Build as you go Requires a more elaborate fit-and-build plan Requires less precision machines Requires less precision tolerances Usually works at the end

Fit-and Build Plan

There are 3 sub-assemblies - these can be built separately:

Frame assemblyo Base plate (1)o Side plates (2)o Top plate (1)o Bearing (1)o Screws (8)

Motor assemblyo Motoro Motor bracketo Camo Screws

Slider bar assemblyo Slider baro Follower plateo Platform plateo Screwso Spring

Procedure to build and assemble the frame sub-assembly

1. Make the two side plates from a single plate. a. Make a cleaning cut on top using a millb. Without changing the set up make the cut in the bottom.c. Make a cut in the middle to divide into two plates.d. Make fastener holes where the plate screws to the base plate. They do not need to

be precisely located.e. Place one side plate against the base plate and transfer the hole pattern by marking

with a marker.f. Drill and tap for the screws being used. Be careful not to break the taps in the

hole. Ask someone with experience to show you.g. Screw the side plate h. Do the same procedure with the side plate. They do not need to align precisely

but the two should have the same level height above the base plate.i. Make 4 holes in the top plate and 4 tapped holes on top of the side plates.j. Assemble with screws.k. Disassemble the top plate and make drill and ream a hole in the center of the top

plate for a slight pressfit to the brass bearing.l. To pressfit the bearing we can cool down the bearing if it is too tight. However,

do not pressfit the bearing yet. We need it to check the fit with the slider bar.

Base Plate – no machining required (except for fasteners)

Cut both plates at the same time. Cut a 110 by 100 piece, machine and cut into two.

Top Plate – use ¾ inch drill for the bearing fit

2. Motor Assemblya. Attach the bracket to the motor. Make sure the bracket is square enough so the

spindle of the motor comes out parallel to the base plate.b. Machine the cam. The cam profile needs to be programmed on CNC. The cam

should have a hub long enough for two set screws. The hole that fits the motor shaft should be a sliding fit. Make radial cross holes in the hub and tap for set screws.

c. Attach the motor shaft to cam and tighten set screws.

3. Slider bar Assemblya. Cut the slider bar to the designed length (no precision necessary)b. Reduce the two ends of the bar slightly (about 1 mm) and leave 1 inch of length

unreduced where the sliding action happens with the bearing.c. Clean the 1-inch sliding length (very tiny cut)d. Check the fit against the bearing bore for a sliding fit. use some oil.e. If the fit is too tight use some sand paper to reduce it slightly until the fit is good.f. Make the top and bottom plates and attach to the end of slider bar using screws

through radial holes in the slider bar and hubs of top and bottom plates.