Heated Warping

I'm sure you answered this question many times before, but do you have any tips for elimination warping (preferably without using acetone)
I printing in ABS with the extruder temp @215C and the heatbed @100C. I have a mirror coated with kapton, on top of the MK2 heatbed, and wool for insulation underneath.
Despite all this I still get significant warping on the corners of even large prints and the object often unsticks completely mid-print, forcing me to start over.
Is there anything I could do to prevent it from happening?

Where are you measuring the heated bed temp? On top of the glass?

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

My 100k termoresistor is placed just below the mirror. It sticks out a bit so it touches the mirror from below.

I had this problem as well, despite all the info saying 100 to110c is a good temp for the heated bed. I turned my heated bed down to 90c (yes measured accurately confirmed with multiple methods) and my warping went away completely.

"I'm sure you answered this question many times before, but do you have any tips for elimination warping"

Use brim (See Slic3r). It creates a thin island surrounding the print that acts a bit like tape, to hold the edge of the piece(s) in place.

sand the kapton tape on top of your mirror with a sand paper... the prints will stick very firmly!

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Wow, thank you all for the quick responses, yes I did know about the brim option, it did help with smaller objects, but in extreme cases it didn't stop the object from warping. I've never heard of the method of sanding the tape, it seams as it would work. As for the lowering the temperature of the heatbed, i always assumed the higher the temperature the better the adhesion. Anyway it getting late, so I'll try those techniques tomorrow, and letting you know of the results.
Again Thank You for the feedback, and Happy Printing

It's hard to say to what effect do the methods (sanding the kapton tape and changing the heatbed temperatures) work. The parts with the tips seam more warped, but that might perhaps be because I could manage to finish printing the without unsticking. The only reason it was possible to do that is that I paused it mid-print and physically kapton-taped the print to the heatbed, and cut of the exes after printing, I'll attach an image of this print (thingiverse.com). Adding a brim seamed not to help much.

I have heard that some people had success with treating their beds with chemicals such as hair spray, or a mixture of acetone and ABS scraps. Have any of you tried it, and did it work? I want to avoid them as much as possible as my reprap is not i the best ventilated place.

What worked work in the past ? What didn't?
Help would be greatly appreciated. Thank You in advance

I have one of those mirrors on top of a Mk2 heatbed.

Here is my advise after troubleshooting - a lot.

The temperature at the glass is not what it says it is on your computer, even if your thermistor is touching the bottom of it. I measured mine with an electronic contact thermometer designed for that purpose and found that out. I have to set my bed temperature to 140 degrees in order to get the surface of the glass up to 110 degrees. An easy way to figure out if you are having the same problem, if you don't have a contact thermometer, is to simply try setting the temperature to 140 and see if your prints improve. If you are using Ramps 1.4, make sure you have a cooling fan over those yellow fuses near the power inputs or they will not handle operating the bed with that kind of power for any length of time.

Shield your printer from drafts by enclosing it in a box of some kind, and keep the ambient temerature inside the box up around 30 degrees, at least. This will also stop some of your distortion. I sometimes hang a 75 watt heat lamp over the bed during difficult prints. This also takes a load off the beds efforts to keep it hot enough. It can cause the objects to sink a bit though, so I don't use it unattended.

Scrap the Kapton tape - its a waste of your time and unecessary, clean the glass really well and don't spray or add anything to it. The prints will stick quite well to clean, polished glass, if it is at the correct temperature. I have my end of print gcode set to lower the temperature to 80 degrees and before the bed reaches that, you can't pull the prints off the glass. As soon as it gets to about 90 degrees, you can hear the part breaking loose (sounds like ice cubes in warm water), and at 80 degrees the objects slide right off the glass. (can't always lift them off because of vacuum, depending on the shape of the object, but sliding works fine).

Make absolutely certain that your bed is level, and then make absolutely certain that your X axis is level. Check it by putting a small level right on the rods. If the X axis is not level and parallel to the bed, (actually this is caused by the Z axis being uneven side to side), then your hot end will dig into your objects and knock them loose.

Make sure your hotend is at a right angle to the bed, for the same reason above.

Thank You very much for the elaborate answer. Yes I have noticed that the RAMPs board can't handle the bed at high (100C+) temperatures, now I know why. I'll try operating it at higher temperatures and see what happens. Thank You again for sharing you trouble shooting information.

Interesting thread.
I also have trouble with large prints lifting at the corners and warping.
I have been using blue painters tape but the tape lifts with the print.
Have tried glass cleaner but the prints don't stick so will have to try the bed temp a bit higher than 110.
What is the gcode needed to drop the bed temp to 80.

Gregted,
[reprap.org]

Insert "M140 S80" into your ending G-code


In my experience, this is caused by one thing, with an aggravating factor.

Your heated bed may not be hot enough, true. I print @ 90C measured at the corner of my bed, but I'm sure it's much hotter in the center.

The biggest problem is the relatively cold air you're printing in. ABS *loves* heat. It needs an envelope of nice warm (hot if I'm honest) air to not warp. You can achieve this several ways. The cheapest low-tech way I found was to get a kitchen garbage bag and put it over top of the entire machine, poke a hole and feed your filament into it. The heated bed should provide enough heat to warm the pocket of air nicely and reduce warping. Of you can go the DIY heated chamber route if you're going to print a lot of ABS. This can get pricey though.

To give you an idea, I print ABS @ 230C~235C, in a pocket of 40C air on a 90C heated bed. Print directly on Kapton attached to AL bed. First layer @ 200% has nearly no "squash" and adheres like there is no tomorrow. I always need to pry my prints off the bed.

CAVEAT!

If you have a machine printed in PLA don't do this. You might get away with it a couple of times, but eventually your parts may fail. That would be...bad.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Created an account to post:

We got a Prusa i3 and have been struggling to get decent prints in ABS (magma hot end, abs only but I'll challenge that soon). Yesterday I built a rough cardboard enclosure for the build area and have been getting enormously improved adhesion/warping. I did 2 prints in a row and in the second, the y axis suffered a 30~mm shift after 5 layers, which I suspect is due to overheating, as cold starts haven't failed.

Very dilute white wood glue (pva) may also be worth a try.
It doesn't fume much while drying (abs fumes are far worse) and can be reused at least for a few prints. I haven't tried to wrap my printer for better heat retention yet (i think the combination would rock), but the glue has got me from completely useless prints to good enough (most of the time).

/Andreas

I know this is a old thread but to anyone coming from a search engine here how I solved my problem. Spray the build platform with hairspray. Careful when removing the objects after printing not to damage them! I don't use hapton tape anymore as it always came of with the object anyways