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jbebel

Part for hot car needs ABS, but ABS warps

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TL;DR: How do I get ABS to stop warping for this box using an Ultimaker 3 (or 2+)?

or XY problem version: How do I best print this box in a way that can withstand the heat of a car?
Model

Photos of results

 

Background:

I made a circuit to live in my car, and I designed a box to hold it. The box stl files are here with the primary bottom shell in BShell.stl and the top in TShell.stl.

 

After some experimentation, I got this box to print reliably with PLA. Things I found to help included printing the shells one at a time, putting a layer of glue on the glass plate, using a front cover, and pre-heating the build plate. I also got less warping with a 0.2 layer height, but preferred the smoothness of 0.1, and was able to get a good result with it.

 

Unfortunately, with my car parked in the sun, my PLA box got soft and deformed.

 

I set out to try ABS. On my first attempt, I used the same techniques that worked well for PLA, but the part warped very quickly after I started and delaminated completely from the glue layer. Good thing I was watching since it would have damaged the print core if it kept going.

 

Next I tried using an adhesion sheet. This gave me a really nice first layer, but after a while, it still lifted on the back right corner and created a bit of a mess.

 

I made one more attempt and used 0.2mm layer height, since that helped me before. This time it didn't make a big mess, but I still got some lift on the same corner which made for some  strange  results.

 

From what I've read, I'm doing all the right things to help ABS to not warp, I think this box is just a challenge because of the large flat bottom surface. Are there any additional things that would help? Certain tweaks to the settings, like bed temp, that might help this case? Other materials on the plate that might keep it from lifting? I'm a bit limited in chemicals I can use since I'm in a restricted space, and new chemicals require a whole process to be approved for safety, which makes trying new things hard. Would a higher quality ABS work better? Is Ultimaker brand ABS high quality?

 

Alternatively, is there some other technique I could use, like a different material? Perhaps CPE? It seems like it's more temperature resistant than PLA. Perhaps it would be sufficient. Is it easier to print without warping?

 

Thanks very much for any tips.

Edited by jbebel
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Hi and welcome to the community!

 

ABS is hard to print and you will always fight more less with warping, but you should get an acceptable result. It depends also on the brand of material you use and the UM ABS should show less warping, but I haven't tried it myself.

 

I have good experiences with the adhesion sheets. Printing with ASA (like ABS) was very good with these sheets. Additionally it is a must to close the front and maybe also the top of your printer. You want to have it "warm" in your printer that the material cools slowly. Also a higher bed temperature will help in addition to a perfectly leveled bed.

 

A lot of people use ABS slurry (ABS + acetone) for adhesion and this should work great. Just keep in mind and take care to use the same color of ABS, because you will see it on the bottom of your part.

 

You can also use CPE, CPE+ or Colorfabb XT or HT, they all have a higher glass temperature and CPE+ and HT are even higher. They should have less warping compared with ABS, but they have other difficulties like terrible surface quality. (At least in my test I couldn't get good results) But if the box is hidden in the car, then you can give it a try.

 

 

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I have very carefully manually leveled the bed, and the first layer has looked very good as long as I pre-heat the bed. The standard pre-heat cycle doesn't seem to be long enough to get it up to temp.

 

I've used a front cover (which I mentioned) but not a top cover. Is there a standard practice for how to do this without getting in the way of the tubes and cords?

 

As for the ABS slurry, I don't know if acetone is on the list of allowed chemicals in our facility currently, but I could attempt to get it added if the ABS juice is likely to provide better results than an adhesion sheet. Are any of the tapes like Kapton any better than the Ultimaker adhesion sheets, or are they basically the same?

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Cover the top.  Just use an open box that is bigger in the back of the printer such that the bowden and cables have a gap back there.

 

For example if you have a UM2 or UM3 then those boxes that contain photocopy paper or printer paper are perfect.  No tape needed.  No cutting.  Just flip it over and put it on top of the printer.  There will be a large gap at the back of the printer where the bowden and cables come in but that will be enough to get the air temp from 20C to 35C and that's enough to make a huge improvement in layer adhesion and that's enough to get the bed up to 110C.  In addition of course cover the front of the printer with saran wrap or 2 gallon zip locks or similar.

 

ABS gets soft at about 99C and having the bed at 110C versus 100C makes a huge difference.  Having the bottom layer of ABS at 105C to 110C makes it act like putty instead of plastic and when those warping forces come a long the bottom few layers will stretch just enough to spread those powerful forces onto more area and spread out the load so the part stays stuck to the glass.

 

Also it helps if all outer corners of the part are rounded so the forces are spread out more.  Sharp corners mean almost all the force is on one tiny spot on the corner of the part.  Brim helps a lot also.  Use at least 10 passes of brim.

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Instead of ABS, maybe you could try PET (ICE) or NGEN (colorFabb), or something similar?

 

I also had PLA parts warping in a hot car, even in moderate spring weather. This starts as soon as the interior reaches ca. 50°C, which can be very soon.

 

But warping did not happen with PET or colorFabb NGEN, at least not in our European summers (and we had an unusually hot one this year).

 

PET and NGEN stick very nicely to the bed, if heated enough to ca. 90°C. Depending on the model, glue may or may not be necessary; I usually print without.

 

Edit: added benefit: PET and NGEN almost don't smell, compared to the horrible ABS fumes.

Edited by geert_2

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Be careful about enclosing it too much---you still want your printer to be able to breathe. I've seen a couple of cases where if you fully seal the printer off too close (garbage bag, or foam with no openings), the sliding blocks get just soft enough that your printhead shaft won't be able to fit securely anymore. They're just plastic. The printer needs some ability to breathe/keep from overheating.

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We have seen a fair bit of warping in ABS printing electronic enclosures too. Guess that type of geometry is prone to shrinkage.

 

Setting the bed to 130°C seems to be the best so far.

Of course the basic stuff like cleaning plate and apply adhesion every print and proper levelling must be taken seriously.

Our printer is fully enclosed, but breathable.

 

Its so different from printing PLA, I've done about 3 rolls of PLA in a row now without even cleaning the bed nor any extra adhesion.

No issues at all warping or comin loose. Still easy to get out once cooled down.

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