Warpage and how to prevent it

[Iain]

My first attempt at a 3D printed car for the most part came out as expected.  However, the bottom was quite warped, and even the body shell was, as well,  In the case of the body, the pressure caused the sides to bow out some, but I figured gluing in the bottom would be enough to address that.  However, the bottom was so curved that I could not get glue to hold straight.  I redesigned the car so the bottom is now fixed to te body and the roof is now separate.  The roof has a bit more structure, so it's not warped near as much, but it still is warped a little bit.  More importantly, the body is still warped, and now the end platforms point slightly up.

A caveat here to any prevention is that I do not have my own printer.  I live in a small apartment and don't have a space for one.  I have been farming out my prints to a commercial provider, and it is quite expensive especially considering my disappointing results.

So, what can I do, from the design side, to prevent or at least mitigate warpage?

[Sumner]

I've only made 2 shells...





... the snowplow and tender above and here....

https://1fatgmc.com/RailRoad/Snow%20Plow/Snow%20Plow-Index.html

I put supports I made inside of both and they were easy to remove (see the attachment).

Are you printing in resin or filament.  If resin which one.  I use Siraya Tech Build and love it for the detail, strength and somewhat flexible if you don't cure it too long.

Sumner

[GGNInNScale]

Here's what I do:
Use a hairdryer, or a heat gun on low setting,  to heat the area of concern.  Then, hold it in place a little further "in" or "out" than needed until it cools, it will relax a little, but will be closer to the final form.  Repeat if needed.
The second thought is to add braces as the above reply noted.  Also, adding extra supports when printing may help.

[u18b]

I'm hoping Aaron @chessie system fan  will chime in with examples.

He's dealt with this a long time.

[Philip H]

I read your headline as help with war page. Need more coffee.

[chessie system fan]

You have multiple issues happening all at once. 

1. With the roof on, there is nowhere for the resin to flow inside, which leads to the sides bowing outwards to relieve the pressure.

2.  Was the car cured with a wash and cure machine?  Or just left in the sun for a little while? Uneven curing can cause parts to warp.  The constant UV light and the lazy susan of the wash and cure machines help with this.

3. Unequal part thickness.  I have found that parts with thick walls should be separate from parts with thin walls.  They will have different shrinkage amounts, which leads to warpage.

4.  This one is a recent theory.  I still have problems with car underframes.  Sometimes.  When they are printed mostly vertically, they tend to do better than just printed flat.  I am beginning to think that removing the flat print from the build tray causes warpage because you have to use a spatula and pry and peal the print off the tray.  Sometimes, it's not possible too print something vertical.  So in the future, I plan to print some underframes flat but have the supports be much higher than needed just to give the print some "springiness"; the supports will flex and not the underframe. 

5. Even with all of that, car bodies can sometimes warp on the printer and have wavy sides.  The only way to get around that is to design interior supports integral to the car.  I like to use a diagonal grid pattern. However, I have to be careful because thick interior supports can create noticeable print artifacts because now the FEP ripples harder.

I hope that helps!

[Jesse6669]

My first attempt at a 3D printed car for the most part came out as expected.  However, the bottom was quite warped, and even the body shell was, as well, 

What resin are you they using..??
I probably would look for another service bureau, maybe one who has more experience with model trains? 

[Iain]

Just want to remind that I do not have a printer and have been using a commercial service, so many of the suggestions are outside the bounds of my control. 

[chessie system fan]

6. Find someone who knows what they're doing.   


Send me a pm.