Ultimaker Chambered!

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destroyer2012 I know my way around here Level: 23 Points: 314
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destroyer2012

Posted Jun 15, 2012 - 8:13 AM  

I decided my ultimaker could be improved by being able to print ABS. So naturally this meant making a heated bed, but recently I went one step further by enclosing the whole thing in a bunch of oven bags, in so making a sort of warm chamber. The chamber temp is not controlled and there's no fan in it, the bags are there just to keep the whole thing warm and help prevent warping.

So underneath that 3mm aluminum sheet there are four 30 ohm power resistors JB welded to the bottom. A 100K thermistor in the middle of the bed provides the temperature readout. The wool towel clipped around the bottom serves as insulation. At the bottom of my UM frame I put a small perfboard with the solid state relays that power the resistors. 120VAC through 120ohms of resistance yields about 1 amp and 120 watts of heating power. That is a bit on the low side so it takes about 20 minutes for the bed to heat up. The slow heating was part of my motivation to make the chamber.

The chamber itself is made of cut up oven bags, taped along outside the walls and on top. The cross bars on the xy gantry keep the top bag from falling down and fouling everything up, which is nice. Also after its been printing for a while hot air travels up and inflates the top bag a bit which further helps prevent it from snagging on stuff.

I had to take off all the PLA stress-bearing parts, including my bowden clamp which was sitting on top of the insulating bag. I imagine i'll have to take off my belt tensioners before too long too, but they don't have to bear as much force as the bowden clamp did.

Still trying to work out the bugs in the filament feed system (my ABS is just slightly too fat but it seems to work most of the time) so I haven't done any enormous prints or tried to compare warping vs non chambered setups. That is what i want to do eventually though.

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futurejames I know my way around here Level: 21 Points: 202
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futurejames

Posted Jun 15, 2012 - 5:05 PM

Very nice!

I thought about doing something similar, but I wanted to put some sort of blower on top to take fumes out and toss them out the window. I have an old kitchen range hood as well as a bathroom ventilator I was going to use for this.

If you print out the Bowden clamps in ABS will this resolve your issue with the claps being made out of PLA?

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destroyer2012 I know my way around here Level: 23 Points: 314
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destroyer2012

Posted Jun 15, 2012 - 11:21 PM

Gotta be careful with the blower though because if it blows too much you end up cooling everything inside the chamber. I guess I have quality ABS because there are almost no (smelly) fumes. It also helps to build at the right temperature, I think if you build too hot then you get more fumes.

Yes I made the clamp out of ABS (luckily before the PLA one broke! Dodged that bullet) but I discovered that the actual clamp part has to be PLA, because PLA is harder so it actually bites into the bowden tube better. Also after trying an ABS clip I was having the bowden tube slide out and that sliding made the tube really slippery right where the clip was. So I had to rough it up with some wire clippers making shallow perpendicular gouges on the bowden tube to maximize the grip. And I am now using a PLA version of the "extreme grip cone" from here

http://www.thingiverse.com/thing:11864

Printing a brand new one would help with the grip too but I've been too busy printing with abs. This filament I have is 3.04mm diameter, so it pretty much just barely fits and the slight compression of the bowden tube given by that clamp is enough to affect the filament friction by a lot. If I had the stock PFA tube it would not fit at all, luckily my 1/8" ID PTFE tube is workable. I've got a 4mm ID tube on order so that should be much better when it actually gets here.

I recently printed this

http://www.thingiverse.com/thing:13395

in ABS with almost no warp (the rounded corners of the objects did cause a bit of warp though, really unnecessary part of that model IMO) and I attribute that success in part to the chamber but mostly to the heated bed.

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alaris2 I know my way around here Level: 30 Points: 519
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alaris2

Posted Jun 16, 2012 - 8:39 AM

given there's no fan on the hotend and you are now chambered... isn't there significant danger of overheating the steppers?

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destroyer2012 I know my way around here Level: 23 Points: 314
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destroyer2012

Posted Jun 16, 2012 - 9:24 AM

What happens if the steppers overheat? this

http://sine.ni.com/ds/app/doc/p/id/ds-311/lang/en

says the steppers have a max operating temp of 40C but I know that I have had steppers run hotter than that even before I did anything with the heated bed. My extruder stepper runs very hot, probably hotter than 40C but I didn't measure it. I don't see what could go wrong? I can understand why stepper drivers overheating would be bad but I can't see how the steppers can be hot enough to affect their electrical characteristics... can they?

Can you explain what exactly the danger is?

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futurejames I know my way around here Level: 21 Points: 202
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futurejames

Posted Jun 16, 2012 - 6:36 PM

Ok I see, so the trick is how to vent it without just taking all the heat out.

I don't know if I had good or bad ABS. I do know that I really dislike the smell, and it could be a possible migraine trigger for me (had them after both times). Venting would be much better. I guess a second alternative would be printing in the garage -- no winter printing ABS though.

I'm not sure if the steppers getting really hot is hazardous or not. But maybe there would be a setup where you could have them cooled and/or isolated from the rest of the chamber?

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alaris2 I know my way around here Level: 30 Points: 519
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alaris2

Posted Jun 17, 2012 - 12:47 PM

I get a migraine from the PLA fumes too if the temp is too high. I'm not convinced either plastic is totally safe (despite what is sometimes said) so print with the window open.

as far as steppers overheating - I believe the main problems are delamination of the coil wires (which will lead to shorts) and with extreme overheat, locking of the parts due to thermal expansion. I suspect the torque curves will degrade in some way with excessive heat but I'm not an expert on this.

I have seen inside a stepper that failed due to delamination of the wires - they're covered in a sort of varnish which just melts if the temp gets too high. it was quite a mess inside.

usually of course it's the stepper drivers that overheat and that's the more understood issue.

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destroyer2012 I know my way around here Level: 23 Points: 314
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destroyer2012

Posted Jun 18, 2012 - 8:46 AM

So how hot do they have to get for the insulation on the coil wires to melt? I can't imagine my steppers are getting hotter than 100C but probably around there, which is likely not good :/.

I've been suspecting this for a while but any ideas on how to tune the stepper drivers so the motors don't run as hot? I will move the motors outside the chamber but like I said even before the chamber they got pretty hot and I seem to remember other people saying the motors only got to about a lukewarm temp.. So I gotta be missing something here, right? How hot does your extruder motor get after like an hour-long print?

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alaris2 I know my way around here Level: 30 Points: 519
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alaris2

Posted Jun 18, 2012 - 3:05 PM

I have a thermal camera so can take some proper measurements if you really want, but at a rough guess I'd say the extruder motors are getting to just under 60C if I give them a really good work out (lots of retraction and 100mm/s build). X and Y are considerably cooler, 40-50C would be my guess.

100C sounds bad.

spec. for typical coil potting varnish is 105C max with an assumed 40C max ambient temperature (..is this where you saw the 40C maybe?)

set the build speed really slow would be the best way to reduce heat - or modify the box - drill some holes and mount a fan on the inside next the motor and then enclose the motor from the rest of the chamber.

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jeremy 3D printing enthusiast Level: 19 Points: 143
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jeremy

Posted Jun 18, 2012 - 5:58 PM

Regarding ventilation: I was thinking of closing off my ultimaker to get a heated chamber as well. However, I think the ideal setup would be to have some sort of fan that recirculates the hot air inside the enclosed chamber. When the build is finished, you'd flip a valve or something to vent all the air outside (I was thinking of using my dryer vent). This would prevent wasted wasted energy from constantly heating air and blowing it outside, and at the same time the airflow would prevent heat from building up in the stepper motors.

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destroyer2012 I know my way around here Level: 23 Points: 314
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destroyer2012

Posted Jun 18, 2012 - 7:11 PM

Maybe my driver pots are turned too high.. Well in any case I can tell you that running your steppers really hot for a short period (an hour or so) doesn't seem to have any affect. My steppers survived being at 80C for several hours and seem to work fine after. WHat I'll do though is turn the pots down and flip the steppers to the outside of the UM wooden box (with drive shaft pointing inwards and engaging the short belts). That should get them out of the hot chamber and turning the pots down should help them stay cool. I don't want to put a fan on them because I don't think it should be necessary... lots of people run mendels with no fans on their steppers and I haven't heard of a single failure.

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