RC Baja 2: The Search for More Baja
Construction Methods
There are three significant manufacturing methods used in this project, 3d printing, machining, and sheet metal fabrication.
The majority of the parts are 3d printed. 3d printing involves precisely extruding melted plastic into discrete layers that make up the part.
Machining involves removing metal from solid stock with sharp tools attached to precise machines.
Sheet metal fabrication usually has the part cut from sheet stock with a laser or plasma cutter. Sometimes these parts are then bent into their final forms, but bending was not used in this project.
The image to the left shows the drawing tree. It shows all of the different parts and sub-assemblies used to create the car.
Manufacturing Axle Tubes
This video shows the axle tubes being machined to final size. Using a lathe the inner diameter was drilled to 10mm to allow a brass bushing to be pressed in later. The outside diameter was also turned down to 12mm to fit within the differential housing.
3d Printing the Axle Shaft Coupler
This video shows the axle shaft coupler being printed. The printer is using PLA filament which was chosen because of its reliability and ease of use. Prints made with PLA seldom fail and it has good overhang stability. PLA was also chosen because of its rigidity which will help the part clamp down on the axle shaft.
Pressing Axle Bushings
The picture to the right shows using hydraulic press to insert off the shelf brass bushings into the aluminum axle tubes. The axle tube was drilled at a slightly smaller diameter than the bushing to create a interference fit which will hold the bushing without any adhesives or fasteners.
Drilling Holes for Axle Shaft Coupler
In this image the axle shaft coupler is being drilled for a cross pin. It is necessary to do this on the knee mill because it must be centered exactly.
Threading Axle Shaft
The axle shaft is being threaded to mount the nuts that hold the wheels on. This was difficult because the shaft is made of 4140 Steel which is harder than typical steel. The lathe tail stock was used to keep the die perpendicular to the shaft.
Inserting Nuts into a Printed Part
When creating a 3d printed part there are a few ways to created internal threads, tapping, form tapping with a bolt, print the threads, or insert nuts into the print. To insert nuts into a print program the printer to pause at the top of cavity, place the nuts in the part and resume printing. This creates the strongest connection because it is metal on metal, instead of plastic.