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Heating the build chamber
#1
Has anyone added build chamber heating to their DaVinci? (For non-profit uses of course - Stratasys patent issues)
Based upon the little bit of research I've done, this would seem to be the best solution to ABS warping issues.
Heated beds are needed with ABS to get good adhesion, but heated beds are a catch 22 problem. The more you raise the temperature to improve bed adhesion, the more temperature differential you create between the heated base and top of the part that is in cooler air. If by some means you are able to attain ever increasing adhesion, you are risking breaking the glass because of the stresses building up in the part.

My idea is to use a standard incandescent lamp as a heater, and control it with a PID temperature controller such as this one.

I suspect that heating the build chamber just high enough to eliminate warping would require some experimentation. You probably don't want to heat it anymore than necessary because it would stress the electronic and mechanical parts. However, 50C or so sounds like it would have minimal impact, and I'd think it would go a LONG way in eliminating warpage on large parts. Any advice or experience with this would be appreciated!
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#2
Have you made temperature measurements? Try doing so with the bed set to 105c for 10 to 15 minutes. If you want a heated chamber, you could try to toss a towel on top and measure again. I've not measured, but i can tell you there is a definite difference just closing the opening on top with a towel. You might find you don't need a separate heater at all.

Btw,, if you are using good filament the warping is minimal. May i ask what you are using? My dimensional tolerances, warping, and overall print quality are vastly better with voltivo filament when compared to xyz. There are some ebay suppliers i have tried for 15 bucks for a 1kg spool with shipping, and let me say you get what you pay for.

Kieth
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#3
I have not made air temperature measurements in the upper build chamber area yet, but plan to do so as soon as I get the PID controller and thermocouple. I'll try the towel and will measure how much temperature rise I can get by preheating with just the bed alone. Good idea.
I've used the XYZ filament of course, and have also used some Honeycomb. The only difference I noticed is that the Honeycomb seemed to have a little less smell. I didn't run a side-side comparison with the same part and settings to check for differences in warpage. I need to do that too.
My assumption is that all ABS contracts when it cools, and that the need to minimize temperature gradients across the part always exists.
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#4
All abs does contract; abs by design shrinks. The original purpose of abs was for moulds where the shrinkage helped the part release quicker and subsequently allowed for faster part production.

The davinci was designed, for some reason, around abs. Pla was an afterthought that to the best of my knowledge xyz has still not perfected. (There are a few mods you can do to print in pla...)

Generally, in me experience, the shrinkage iss is not top to bottom. Instead, it is along the x and y axis on big prints. I have found the better the adhesion to the bed the leads problems with shrinkage. I almost exclusively use acetone/abs. Let me describe:

1) print a 20x20 test cube in the color of what you intend to print. A solid full cube works best, but if you don't want to print a cube you can use scraps, old support , etc - i just find a cube works best especially when it comes to consistency.
2) allow the bed to completely cool.
3) thoroughly clean bed. Use water first to get all of the old glue if that is what you are using. Then I pour a bit of acetone on about 1/4 of a paper towel and use that to get the bed absolutely clean and oil free.
4) put about 1/2 teaspoon of acetone in the center of the bed. Immediately start rubbing your test cube (step 1) in the acetone and over the expected print area you plan to use. Keep rubbing until you notice the chive beginning to get a little more difficult to slide around. Immediately take the cube off the bed. If there are any large puddles of acetone put the cube on them and run just for s seconds or so then remove the cube.
5) allow any remaining acetone to dry.
6) print.

For what it's worth, i have yet to have a single print fail using the acetone /abs. With glue my success rate was about 80 percent. With pain glass it was about 60 percent. So, give it a shot- the bed cleans well with a bit of acetone, and if you are printing the same color again you can start (one the bed cools ) right on step 4 without and cleaning.

Kieth
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#5
(I'm on my phone, I'll fix the spelling mistakes later, hope you can understand what i meant. Lol)

Kieth
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#6
I've read about people using acetone-abs slurry. I haven't tried it yet, because I recently put a sheet of 8"x8" Kapton on the bed. I haven't printed any large parts on the Kapton yet, but I expect the same problem.

That is my main problem - large parts (anything over 4 inches in width or depth).
I can sometimes print parts this big if I keep the parts thin in height or use very low infill and thin shells.

There seems to be many reports that heating the build chamber helps tremendously with larger and more solid parts.
Google "Heated build chamber" for some interesting reading.
Unfortunately nobody (except Stratasys) sells a machine off the shelf with this feature since Stratasys holds a patent on the idea. They also hold patents on things that are commonly used by hobbist printers such as acetone vapor smoothing of ABS and supports made from soluble material (which I presume includes common filaments like HIPS and PVA)
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