Experimenting with build supports

[bbussey]

Now that I’ve starting printing various parts, I see that there are certain quirks to overcome. I went through a similar period with Shapeways parts, experimenting to find the best orientations and design methods to get the best results. Fortunately not as many hoops need to be jumped through with the 3D printing at home. But I’ve encountered some minor issues and have come up with solutions to overcome them.

One of the issues I’ve encountered is curling at the corners of parts and warping of details toward the ends of a model in some circumstances. I’ve also discovered that the detail on the flat face of the model that faces the build plate is “soft” on detail and not perfectly flat. I love the auto creation of supports in Chitubox, and the ability to fine tune the supports afterward. But even with insuring there were supports at every corner, I’m getting some distortion – in particular on the ATSF #91-110 RPO bodyshells I’m attempting to print.



This was the second attempt, with the model orientation both vertical and horizontal to see the results, both secured with adequate supports. It’s not as evident in this photo, but both orientations have some distortion issues in different areas. On the vertical, the corner fluting is skewed and the A-end facing the plate is soft on detail. On the horizontal, the side fluting starts curving up slightly about a half inch from the ends.

The vertical was the easiest to address. First, I removed the A-end and printed it as a separate part. That corrected the soft detail issue. Next, I went with a membrane support around the entire perimeter of the ends, 1mm high and .2mm thick. I then extended 5mm further with an 8% outward draft. That matched the total 6mm that Chitubox recommends. I then added the 1mm base with a 30% inner draft again to match Chitubox. Then I created the sliced file directly without doing the support prep. I also added membranes across the stirrup cutouts so that the corner fluted extensions would have full support. I ran the file overnight and I’m very pleased with the initial results.



This is after the initial isopropyl wash. All the detail is present and not distorted. The only addition needed is a support spine for the end, as the straight membrane wasn’t sturdy enough to keep the part rigid during the rendering of the upper half.



The method worked for the trailer floors that also were in the build job. They rendered perfectly.





Passing along my findings so that others can experiment.

[Chris333]

I still have never used auto supports, but those new supports you make up are very similar to a bunch of 3D stuff I got from Toma Model Works in Japan. I like them and will have to give it a try soon.

I don't just make sure there are supports in the corners. I make sure they are clustered up heavy in the corners. It all as to do with the FEP tension. The FEP is the next big problem they need to invent a solution for.

[John]

Are you using Chitubox Pro?

[bbussey]

I’ll keep that in mind regarding the FEP tension. These prints look perfect from what I can see. I did a quickie wash this morning before leaving. I’ll clean more thoroughly this evening when I get home and confirm everything is good.

Using Chitubox free. So far, it’s doing everything I require. Someone in one of the FB 3D-print groups recommended Lychee Pro.

[John]

I’ll keep that in mind regarding the FEP tension. These prints look perfect from what I can see. I did a quickie wash this morning before leaving. I’ll clean more thoroughly this evening when I get home and confirm everything is good.

Using Chitubox free. So far, it’s doing everything I require. Someone in one of the FB 3D-print groups recommended Lychee Pro.

I tried Lychee -- it's OK .. but I went back to Chitu free .. its a bit simpler imo to work

[chessie system fan]

I'm excited to see you finally enter this world, Bryan.  Now do that Hooker tank car!  A CBQ Transco boxcar and that NYC canstock car were on my long-term design to-do list.  I think I'll scratch them off my list now.  They look great. 

Those RPO's look great too, but I want you to stick one in a drawer and forget about it for a few weeks and see what happens.  There's a good chance it will turn into a banana.  I've been mostly designing and printing passenger cars lately and each one warps after a while and I haven't completely figured out why.  Right now I'm conducting some long-term tests. 

How thick is the body? And how thin is the area around the windows?  For my first ones, I did 0.5mm around the windows and 1.5 for the main walls but that warped over time.  A baggage car with 1.5mm sides has fared much better.

[bbussey]

Aaron, I’ve started reworking the acid tank to see if the body can be printed with stepping not obvious. I will experiment with various angles to see how inconspicuous I can get the stepping. It would be cool to be able to 3D print the entire tank and frame, and eliminate the tank and dome wrappers and the bottom plate from the etchings.

Also reworking the DL&W wood caboose. Definitely better the way I have it now than the original design, with a fully 3D printed cupola except for the etched side window frames. Also reworked the floor/underframe and it’s much better.

[bbussey]

The wall thickness of the RPO is .040”. The ABS-like resin arrived today, going to start playing with that after the AnyCubic gray runs out.

My first Mt Vernon circus flat was printed months ago. It started going banana-boat but stayed straight after I Goo’d the body to the diecast frame.

[chessie system fan]

I'll try thicker.  What about the thickness around the windows?

[Erock482]

What version of chitubox are you running? I have not seen this style of support before and I'd like to give it a go. is it available on the free version?

[bbussey]

I'll try thicker.  What about the thickness around the windows?

I have cutouts for .015” clear styrene so it has to be .025”.

[bbussey]

What version of chitubox are you running? I have not seen this style of support before and I'd like to give it a go. is it available on the free version?

No, I built it in SolidWorks. It’s easy enough to add the membrane, draft and base in whatever cad program you are using.

[bbussey]

No distortion btw in this revision. The A ends are reprinting now. I’m going to remove the membrane before curing, which I did on the trailer underbodies.

[timwatson]

I'm really digging this method of printing large cars @bbussey . I am assuming the bottom support that spans the car body just "snaps" off cleanly or is there a bit of sanding involved?

No distortion btw in this revision. The A ends are reprinting now. I’m going to remove the membrane before curing, which I did on the trailer underbodies.

[bbussey]

I use an X-Acto #1 blade to insure nothing snaps off that I want to keep, but the knife goes through like butter.