MasterCAM/CNC Machining Project
Please consult with your Project Outline on D2L to
see what exactly you will be getting in your parts kit.
Note: Parts may be substituted, depending on what's in the Mech office supply cabinet
1/4" dia. X 12" wooden dowel = 6g
3-3/4" long when stretched out
wire is 0.035" dia.
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"x1/4" thick (nominal)
#6-32 x 3.4" long machine screw with nuts 2.4g
Sheet of 8.5 x 11" white paper
Constant Force Spring
5 lbf - weight = 36g
5/8" wide, 1.13" OD
McMaster- Carr #9293k337
Small DC electric motor (previous year)
motor dia. = 0.730x0.950"
motor body length (not including shaft) = 1.360"
shaft dia. = 0.081"
shaft length from motor = 0.385"
Specs: no load 10,000rpm @ 12V
no load: 100mA and 1.2W
stall (0rpm): 3.6A and 43W
Torque at stall = 0.02Nm
(you must make your own MDF or rapid prototyped pinion gear)
Power must be applied to the two "sockets",
so allow space for wires as shown below:
SolidWorks Part file of the motor
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. If you want a press fit, machine a hole 0.002" smaller, if you want a loose fit, machine a hole 0.002" larger. Keep in mind, the dowel's dia. changes with temperature and humidity.
Remember, small holes can be filed (or sanded) larger. You can't make a big hole smaller!
Mounting the Motor
The motor can be press fit into the body.
Machine a hole in your car body for a press fit.
Close-up of motor mount.
Designing Gear Trains
Devin's Rubber Band Car