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Printing Slotcar Bodies

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  • Printing Slotcar Bodies

    I have owned a Creality Ender 3 Pro filament printer since January 2020, and been keeping it very busy since then. Much of what I have been printing is slotcar related. Almost everything I print now is in either PETG (Polyethylene Terephthalate - Glycol modified) or TPU (ThermoPlastic Urethane).

    Up until now I have not attempted to print any slotcar bodies. That changed a couple of days ago when I tried printing a 1/32nd Porsche 917 slotcar body in PETG. I obtained the STL file from the Cults3D.com website. It cost me US$13.65.

    https://cults3d.com/en/3d-model/game...table-body-car

    I didn't expect my first attempt would be successful, and I wasn't disappointed. I had three major issues. One, the support structure was very difficult to remove. I ended up breaking the model. And that relates to the second issue -- the body was too thin. Only about 0.050 inches (1.27mm) thick. Even if I had been able to remove the support structure without damage, the body was too thin and light for use in a slotcar. The whole body only weighed 9 grams.

    The third issue was the top of the cockpit did not print successfully. That, I suspect, is more a matter of my print setup. Fine tuning required.

    I contacted the author of the print file, and he has sent me a revised file -- no extra charge. Props to him for customer service. I'll be attempting to run that print later today. I'll try a different support scheme from the Cura slicer toolset, and maybe tweak the print settings. Probably install a new nozzle on the extruder and definitely re-level the bed.

    I expect I'll be on a learning curve for a while here. It'll be time-consuming, given it takes about 16 hours to run that print file. The good news is I've seen some pretty smooth surfaces in the areas where the printing went well. Getting to a finished body may not be as arduous as I have feared.

    The whole point of printing my own bodies is driven by three factors. One, it is cheaper than buying them, given that I have a 3D printer already. The cost of the filament is piddling. Buying a body ready-made can typically cost US$20 to US$30. And while buying the print files is not free, it is typically cheaper, and only a one-time expense. I can print any number of bodies once I've made that investment.

    The second factor is, surprisingly, there are more options available in terms of bodies. Credit the many authors out there creating new ones all the time. Quality varies a lot, but there is a thriving cottage industry growing up around the demand for unique body offerings. The Cults3D.com website seems to host a lot of good ones.

    The third and final factor is printing my own means I have control of the print dimensions. I can reference the actual prototype dimensions and make sure my model is exactly to scale. Or, if I need to, tweak the dimensions slightly for practical purposes.

    Don't diss me on this. Slotcar bodies have been tweaked since Day One. In HO particularly bodies have been massively distorted to stretch them over the existing chassis. Never mind the vacuum-formed wing car bodies in 1/24th. It is not my intention to egregiously distort my bodies, but I do intend to create bodies for cars that will be competitive in IHSR classes, specifically at the width limits.

    So the adventure begins. Let's see what develops...


    Last edited by HO RacePro; March 15, 2022, 08:12 AM.
    Ed Bianchi
    York Pennsylvania USA

  • #2
    Back in the fall of 2020 I was set to buy both a regular 3D printer and a resin printer. The first was to be used for all sorts of track stuff, and the resin printer for higher quality car bodies. At the time I was primarily interested in building a field of World of Outlaws sprint car replicas. I got distracted trying to figure out what chassis and running gear to use and never did get into 3D printing. While I agree with the factors you cite that make 3DP an ideal option, for the limited needs I can foresee personally, I'm now inclined to let someone else go through the learning process regarding design and printing and buy from them. Yes, this still means I have to rely on someone else making what I want, but as my car collection approaches overflow proportions in my mancave I need to be more selective anyway.

    If and when I get back to building sprint cars, since they all have the same sheet metal body shape I can replicate that either using print paper stock (NYMODIFIEDS style) or using sheet styrene. Having some cast or 3DP gas tanks would be nice though.

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    • #3
      Ed, compare notes with IHSR member Rick Gondeck. He's printing some nice 1/32 scale bodies.

      Comment


      • #4
        I print all my bodyshells between 0.9mm - 1mm thick but that's resin printing.

        If I were to print bodyshells on my Prusa they'd be 100% infill, 0.25mm nozzle and 150% extrusion width.

        From memory as I haven't FDM printed a bodyshell for 18 months I think I had support density at 10%
        Kevan - Isle of Man
        Life is like a box of Slot cars...🚓🚗🚚🚜

        Comment


        • #5
          I've got a lot to report, so let's get to it...

          As expected my first attempts at printing a body did not go well. First, the body printed out too thin -- only about 0.050 inches (1.27mm) thick. The top of the cockpit failed to print fully. And the support structure was very, very difficult to remove without doing further damage to the body. Observe...

          Click image for larger version  Name:	IMG_3489.jpg Views:	0 Size:	287.3 KB ID:	154368 Click image for larger version  Name:	IMG_3491.jpg Views:	0 Size:	241.5 KB ID:	154366 Click image for larger version  Name:	IMG_3492.jpg Views:	0 Size:	277.5 KB ID:	154365

          I messaged the author of the STL file I had purchased, and he sent me a revised model with, supposedly, thicker walls. Trouble was, when I printed from the new file the walls were no thicker.

          On this second attempt I tried a different option in Cura's toolkit of support structures -- what they call a 'tree'. The support structure 'grows' in three dimensions, providing support only where needed. Makes for a very strange structure. It reminds me a bit of stuff the 1960's artist Peter Max used to create, except lacking his psychedelic colors...

          Click image for larger version  Name:	IMG_3493.jpg Views:	0 Size:	341.2 KB ID:	154373 Click image for larger version  Name:	IMG_3494.jpg Views:	0 Size:	334.3 KB ID:	154369 Click image for larger version  Name:	IMG_3495.jpg Views:	0 Size:	320.4 KB ID:	154375

          The thin sidewalls of the body were not supported by the 'tree' until too late. They wobbled under the stress of printing. Another print failure.

          I still wanted a thicker body shell so I tried a cute little trick. And it did work!

          Working in Cura, I duplicated the body shell and then shrank it 2mm in width, 2mm in length and 1mm in height. I centered this smaller, second shell inside the first. Cura complained about that, but was still able to successfully slice this merged model. Dig...

          Click image for larger version  Name:	Double Shell.jpg Views:	0 Size:	1.51 MB ID:	154376

          And huzzah! It printed!

          Click image for larger version  Name:	IMG_3496.jpg Views:	0 Size:	280.1 KB ID:	154371 Click image for larger version  Name:	IMG_3497.jpg Views:	0 Size:	282.2 KB ID:	154367 Click image for larger version  Name:	IMG_3498.jpg Views:	0 Size:	392.0 KB ID:	154372 Click image for larger version  Name:	IMG_3500.jpg Views:	0 Size:	267.8 KB ID:	154370

          I was able to remove the 'tree' by hand. Except in doing so I cracked one of the body's sidewalls. I flooded the crack with superglue and closed it up again.

          The print is definitely thicker and less fragile. The sidewalls are about 0.080 inches (2mm) thick. The body weighs about 20 grams. I intend to reinforce the sidewalls, but I haven't quite figured out how best to do that.

          There is obviously a lot of work required to clean up and finish the body, but I'm really happy with the progress I made in three tries. I'm tickled that my nested body hack worked. And pleased that it did not cause any issues with the exterior of the body.

          I'll probably print another body so I have one without a damaged sidewall. I may try to add some features to reinforce those sidewalls. Creating those may be tricky.

          But hey, I've got my tricks!
          Attached Files
          Last edited by HO RacePro; March 16, 2022, 09:42 AM.
          Ed Bianchi
          York Pennsylvania USA

          Comment


          • #6
            I've had a couple of files from that dude, one of which was half hollow which was a pain as my customer wanted about 10 of them. I ended up doing what you did but in 0.1mm increments so there were about 10 copy/pastes all scaled down a little...then a boolean join in Netfabb made it a single object.

            I've also done the same thing to create a window buck with a solid base for a Sunbeam Tiger using the window file. I think Paul (Chappyman) does this also.
            Kevan - Isle of Man
            Life is like a box of Slot cars...🚓🚗🚚🚜

            Comment


            • #7
              It'd be nice if the guys making these models actually printed them to confirm that they work on FDM or resin. I think most of them aren't doing any printing at all, and don't know the first thing about how to make sure they print well.

              Comment


              • Kevan
                Kevan commented
                Editing a comment
                I'd go further and say they don't even make the files, more like they pay someone on Fiverr

              • MrFlippant
                MrFlippant commented
                Editing a comment
                LOL, too right! Like the 3D Printables Shop... it has a TON of files, but I'm 0 for 2 on them being printable without glaring issues. I applaud you guys for what you are doing to make stuff work, but I'm not about to do the work I already paid someone to do. The latest one, the Dauphine for Mike, I'll be asking for a refund if he can't make it printable, 'cus I'm not.

            • #8
              Aw, Mr. Flippant, don't be too rough on the file authors. I'm happy they have been able to accurately model complex profiles that I can tweak as needed. Without their work I'd have no hope of producing my own bodies.

              It is still early days for the downloadable print file market. Lots of amateurs, no big established players. No standards. One day it will be parceled up by large corporate concerns. There'll be Apple, Amazon and eBay equivalents dominating the market, leaving a ragged bunch of independents and hobbyists to scramble for the crumbs. Just you wait and see.

              Once it is discovered that real money can be made that progression is inevitable.

              Right now I am printing another body -- this one with supports and gussets that I created in CAD, turned into STL files, and added to the model in Cura. Designing those gussets was the CAD/Cura equivalent of cut-and-try. After about three design iterations I was happy enough with my revisions to run a print. It'll take close to 20 hours to run, so it will be a while before I can report back on it.

              I'm finding the positioning and scaling tools in Cura are really very useful. Lots of ways to position and adjust things before you get down to slicing. And lots of ways to examine your model to make sure it looks the way you want it to.

              I spent some time with my first successful print learning how to clean it up. Tools I used include an X-Acto knife, nippers and a de-burring tool. It just takes a lot of fussing. Next I have to fill and smooth the exterior. More labor-intensive fussing. Of course I will report back (and whine) about that business.

              Last edited by HO RacePro; March 16, 2022, 01:35 PM.
              Ed Bianchi
              York Pennsylvania USA

              Comment


              • #9
                This is why there is an entire forum on 3DP....HRW was a leader.
                Come Race at The Trace!
                Timberline Trace International Raceway - SW of Mpls, MN
                https://cults3d.com/en/users/chappyman662/creations

                Comment


                • Kevan
                  Kevan commented
                  Editing a comment
                  Correct, some forums (one in particular) had to be dragged kicking & screaming into 2022

              • #10
                My second successful body has finished printing. I have cleaned it up -- mostly. It's not ready for filling and painting yet.

                I have started my third print. That may be it for now, although I might do a fourth print just so I have one to screw up. I want to have three good bodies to turn into slotcars. Each will get its own gear ratio, to give me some latitude when racing this class at different tracks.

                The gussets I added to reinforce the sidewalls have turned out well. Give some credit to the visualization tools in Cura. They helped me immensely in getting the shape of the gussets right and positioning them properly.

                What I have learned so far is that even a good purchased body STL file can only be relied on to give you the external geometry of a car. Everything underneath that geometry needs to be looked at critically and tweaked as necessary. Even the computer-generated support structures may need to be revised or supplemented. Printing bodies is actually not that difficult, but you do need to develop an adequate toolkit if you are going to be successful.

                So, at this point I am halfway up the mountain. Next comes filling, smoothing and painting. Yet another set of challenges.

                Stepping back one -- why did I post this thread on the 1/32nd forum instead of the 3D print forum? Actually, I suppose that was a simple oversight. But now reconsidering, maybe this is the best place for it. The saga I am relating here is more aimed toward folks who, like me, have been sitting on the fence. Perhaps my experiences will inspire some folks to try it for themselves.
                Last edited by HO RacePro; March 17, 2022, 08:30 AM.
                Ed Bianchi
                York Pennsylvania USA

                Comment


                • Bal r 14
                  Bal r 14 commented
                  Editing a comment
                  I really appreciate what you are doing and your willingness to share the details. I have thought about buying 3D printers on a number of occasions, but have not yet worked up the enthusiasm to do it.

                • HO RacePro
                  HO RacePro commented
                  Editing a comment
                  Capable filament printers are getting very cheap. There are folks offering new Creality Ender 3 Pro's -- the printer I use -- for US$200. Heck, the reason I bought my machine was I realized I had burned so many personal man-hours considering purchasing one that, if I paid myself my own hourly rate, I'd already cost myself far more than the price of a machine.

                  'Course personal hourly rates vary. Keep a printer in mind if a significant other asks you, "What do you want for your birthday/Christmas/anniversary?"

                  Do you like that idea of personal hourly rates? Pick one. It helps a lot in making some decisions.
                  Last edited by HO RacePro; March 17, 2022, 01:33 PM.
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