MasterCAM/CNC Machining Project
Please consult with your Project Outline on Blackboard to
see what exactly you will be getting in your parts kit.
Pens - Grand & Toy "RoundEdge" #99011
hex portion is approx. 4" long
distance across the flats on the hex portion is 0.305"
pens can be turned down to 0.290" dia.
Paper Clips - Grand & Toy #99526
3-3/4" long when stretched out
wire is 0.035" dia.
Rubber Bands - size #64 Grand & Toy #99011
about 3" when not stretched
will safely stretch to 12"
K= 1/2 lbf/inch or K= 0.8 N/cm
coefficient of friction on tile floor about u=0.9
Wax birthday cake candle
approx. 2-1/4" long
Medium Density Fiber (MDF) board
(MDF is a wood pulp product)
Boards - 7"x4"x3/16" thick (nominal)
#8-1/2" long sheet metal pan head screws, Canadian Tire #61-6705-2
Sheet of 8.5 x 11" white paper
Small DC electric motor
motor dia. = 1.105"
motor body length (not including shaft) = 1.175"
shaft dia. = 0.078"
shaft length from motor = 0.400"
specs: 2500rpm with no load
0.3W with no load
3.57W at motor stall
(you must make your own MDF pinion gear)
Motor shaft bushing
This presses on to the DC motor shaft, allows you to mount your MDF gear
with a 0.160" dia. hole in the middle
overall length = 0.275"
length of bushing = 0.25"
dia. of bushing = 0.165"
NOTE: MACHINE A 0.160" HOLE INTO YOUR PINION GEAR
FOR PRESS FIT WITH THE BUSHING
1 - twin AA battery case with switch
Fitting Parts Together
The milling machines you will be using are accurate to within a few
thousanths of an inch.
Generally, if you need a 0.250" dia. shaft to rotate in a 0.250" hole, draw a 0.250" hole in AutoCAD,
bring the drawing into MasterCAM, generate G-code and the machine will cut an exactly 0.250" hole.
Remember, small holes can be filed (or sanded) larger. You can't make a big hole smaller!
If you are using the pens for shafts the following fits may be
These are measured across the flats of the hex.
Again, the pens can be turned down the a 0.250" dia. if you need.
Mounting the Motor
The motor can be press fit into the mono-rail car body.
Machine a 1.100" dia. hole in your car body for a press fit.
Close-up of motor mount.
Designing Gear Trains
Devin's Rubber Band Car