3D Printing - "It's all about design and quality output. Not how fast the printer can run."
I hardly believe this myself. I started a new hobby model construction project. I am now working on building large scale model train equipment. I have been posting a little about whimsical model railroading in a few blog posts and the desire started to grow.
The first step is a powered wheel set (truck) for a diesel-electric locomotive. It is made using 3D printed parts. That is the prime reason I am doing it. I want to see if I can, with 3D printing. A proof of concept. Then see if I can make it operate. It will have an electric motor and gearbox.
I don’t think I am going to complete the entire model. The working powered truck is my immediate goal. I may try to sell it once it is done and operating.
I want to use this project as a trial experience. To see if I will really get more involved building with plastic. The size of this powered truck is substantial but the engineering was done by someone other than myself. It’s mostly a print and assemble project. As I said above, it’s going to be my proof that 3D printing is or is not worth the effort in model construction.
This may be enough to get me back to the machine shop and working on my live steam engine. I shall see. That project is mostly mostly a brass and steel construction.
I did some research on the internet about 3D printing in real world (non-hobby) applications. It’s growing rapidly. Some of it for the same reasons Laser Cutting and engraving has grown.
Old school machine shop work is mostly subtractive. Milling removes material with cutting tools that is not part of the desired product. A large variety of cutting tools are required. They get worn out and sometimes break. A large investment in tooling is required.
3D printing is an additive process. No tooling is required. It builds using layers and very complex shapes can be made, especially in areas where cutting tools can never reach.
The real world is combining both processes. Each have a strength and both have weaknesses. But the smart people are using the strengths where they make the most sense.
In this first 3D printed railroad component, I have to admit I am not excited about using 3D printed plastic wheels. The axels are steel and that’s good. But the plastic wheels will probably be far from true and durable.
For a display-only model, plastic wheels may be suitable. For an operating model, they definitely are not. I don’t plan to run this truck except for display. If It is going to be used in an operating engine, the wheels need to be changed to metal.
Here are a couple of early pics. More as the build progresses. Axels, bearings and motor are on order.
|The first parts in ABS||
Wheels and gears in manufacturing.
The parts ordered have arrived so here is the next 3D printing step. I need a way to secure the electric motor on the mounting box. I decided a split bushing would do the trick. But I would have to design it myself. No problem of course.
The photos below show what I have done. I don't take a lot of pains with my pencil sketchs when noodling out a design. It's just for reference for the real drawing in CAD so I will have a reference for all the dimentions.
The split bushing takes up the space between the electric motor housing and the previously made housing box. In the picture I have not forced it all the way "home" as I may need to adjust the position before I do that. I lightly filed the edges to take away any ridges and create a small chamfer so the gap in the picture looks bigger than it really is. The fitup is very secure and tight.
The slot is not square but rather wedge shape with the apex at the center of the circles. Little details are important.
I have run out of ABS black and I had Bronze ABS in the printer, so that is why the new part is bronze. The color is not important and I actually like the contrast. The split ring is 100% fill amd 0.2mm layer height. Three shells wall thickness. The first ring was slightly undersize due to ABS shrinkage. I made measurements, caluculated the undersize amount as a percentage and enlarged the drawing by the same amount. That drawing printed exactly correct.
|My ususal quick dimentional hand sketch||Rendered in RhinoCAD and exported as a .OBJ file|
|First split ring fresh off the 3D printer. The ink mark on the side is to identify it as the first print.||2nd and final split ring in place on the motor housing.|