printing design and process time
as I like to say, "3D printing is just pressing a button...too bad it takes a hundred hours to make the button". Enough with the bad jokes, but really the truth is...it all depends. To design in 3D is a skill set that has to be learned, practiced, and then used enough that you get proficient at it. Fortunately I do this for a living and have been 3D modeling for 30 years, so I am really good at it. The time consuming part for me is getting good data to model from. For this project I purchased as many of the original Lima drawings as I could, which makes it easier (not easy though). Once the design is done then you have to export the file as an STL, then import it into what is called a Slicer software. The part then get orientated for best printing and what are called “supports” attached where they may be either an “island” or a weak area. After all that you then can just push the button. However after you “push the button” and get your print you have to check it to see what printed good an what did not.
Print times depend on how tall the print is, but a good example is that one truck takes 2hr-30min to print. I don’t care how fast it prints, I care how good it prints. Normally I will set up the part for printing and load it into the printer either at night before bed, or in the morning before going to work. I actually slow my printer “lift speed” way down to reduce the printing stress on the part, it reduces failed prints or distorted prints.
If the print does not look good you have to decide if it was just a weird print fail, sometimes happens, or if the part needs to be orientated different, or if you need to adjust your details to show better. Part orientation errors get better with experience because I can pretty much guess what will work or the best way to orientate the part. Same with print details, once you learn your printer and know what things will work and what won’t I do not have as many reprints as I did. An example would be rivet and bolt head sizes, or board gaps.
Some details actually need to be oversized a little because they will get a little smaller in the print process, or bigger depending on how you look at it. An example of this is a seam or a board gap. To get the line not to fill in you have to make it bigger than you want the finished part. For the seam on the sand dome cap I actually made the gap 0.008”, which looks big on the digital file but due to pixel size of the printer it looks like a fine line.
I have a few hundred hours in this Shay so far of just 3D model and testing, not to mention field trips, phone calls and internet search time. I have printed this shay 3 times so far to test the drive, 6 times to test and modify the trucks. Those “body” parts are all the early test parts and I have made detail adjustments or corrections already to the 3D model. The frame you see is actually a test frame printed on an FDM printer, the actual frame will be a brass skeleton with resin printed overlays.
It sounds daunting, but most of it is very exciting. The drive line is the most frustrating part because the availability of parts is just not what it once was.
