I am printing a large flat print, approximately 8" x 4" x 1/8". It has good adhesion when printing and lays flat when finished. I allow the print to cool slowly but the center of the print bows upward 1/16"-1/8". It bows in both directions but more noticeably in the longer direction. The corners are not curling up this is the center of the print lifting.

I started printing at 25% infill but have tried 100%. 100% bows less but still bows. This does not happen with PLA or PETG. 100% fill was printed with no fan. 25% printed with no fan for first layers and fan at 40% after.

Is there anything I can do to stop this from happening?

Printer: Lulzbot TAZ 5 w/ 0.5mm hotend in sealed enclosure. Heated bed at 115C, extruer at 240C. Environmental temperatures are 30-37C depending on the stage of the print. Hotter as it continues.

Follow Up Questions:

What is the ideal environmental printing temperature for ABS? If a part were reheated could an existing arch be corrected?

Update: Build Plate Thermal Images w/plate set @ 115C

Center Plate Front Corner

  • $\begingroup$ Sorry it took me a bit to get back to your question, but that's very odd that the part is bowing in the middle. My immediate thought is that there is a cold spot in your HBP, which would mean replacing the build plate. But, I would certainly leave that as a last resort. Another thought is the HBP is bowed itself, so try indicating across the BP with your nozzle to check flatness. Otherwise, are you sure you have good quality filament? You will typically see more bizarre issues with bad quality filament. $\endgroup$ – tbm0115 Oct 31 '16 at 19:05
  • $\begingroup$ From my experience with ABS, your HBP makes sense if you're in a somewhat colder climate. Your extruder temp is okay, a bit high for my own liking, so you might encounter extra ooze/clogging in your prints. Your environment seems pretty hot if it's outside of your build space, are you meaning the build environment or room environment temperature? And, theoretically you could mold the part back into shape, but it may more hassle than is worth. If it's a small bend, you may even be able to use Acetone to soften the part enough to re-shape it. $\endgroup$ – tbm0115 Oct 31 '16 at 19:09
  • $\begingroup$ @tbm0115 It could definitely be the heating on the print bed. I don't know how consistent they typically are but I have added an image to my question to show the inconsistency of mine. I don't think the plate is bent because other materials print perfectly flat and the bent parts placed back on the surface appear bent. $\endgroup$ – jmb2341 Nov 1 '16 at 17:44
  • $\begingroup$ In terms of filament quality I think I am using decent filament. I've used Mitus ABS and IC3D ABS with the same result. The temperature is measured at one point in the build environment. I've made a Plexi box to enclose my TAZ 5. $\endgroup$ – jmb2341 Nov 1 '16 at 17:55
  • $\begingroup$ The images are great! At first glance it seems that you have some dead coils in your HBP. However, it doesn't quite make sense because I think most HBP coils start in the center. So, you would think if the center was dead, the rest of it would too. I might recommend reaching out to @RyanCarlyle on this one. I'll keep poking around for better alternatives, but at this point I think you might be looking at replacing your HBP. $\endgroup$ – tbm0115 Nov 2 '16 at 14:46

Short Answer: Make the environment temperature is a bit warmer to offset the cooling rate.

Long Answer

All materials shrink as they cool, but some materials shrink at a much higher rate than others. This is primarily driven by temperature coefficients and thermal conductivity of the individual materials. There are calculators available online that you can get more involved with discovering how this works mathematically.

However, in layman's terms, the temperature between your build plate and the first layers of plastic are so drastically different, that at a certain point the plastic becomes under tension as it shrinks faster/more than the build plate. Over time, since the surface tension between the part and the build plate is no longer in the way, the corner can continue to shrink.

Here are some options:

  • Ensure your build plate temperatures are correct acceptable. I've had success with 112C in NW United States. Increasing the temperature will be an attempt to bridge the gap between BP temps and plastic temps during the final cool-down.
  • Search for ways to "anchor" the part to the build plate. There are lots of resources on the internet on how to do this, so I'll spare you the list.
  • Increase your environment temperature. I highly suggest this because it can help reduce other errors you might encounter throughout the printing process, such as de-lamination, warping, brittleness, etc. I'm not recommending placing a space heater next to your printer (really, don't do that!), but perhaps even a space heater in the room can help regulate the environment temperature a bit better.
  • Consider other environment variables. Consider things like "Is my printer next to a window?", "Do I live in a particularly cold environment in general?", or even "Am I baking cookies in the next room?". A lot of these seemingly meaningless variables play an important role in ensuring quality prints.

(I know there's more, so I'll add onto this answer a bit more as I remember them)

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    $\begingroup$ Are you sure you read the question correctly? As I read it, it is about the print warping after it has completed (and the bed is cooling down), while your answer seems to be about how to combat warping during a print. $\endgroup$ – Tom van der Zanden Oct 28 '16 at 6:37
  • $\begingroup$ I think you misread my answer or I didn't write correctly. However, it's directed at post-print warping. $\endgroup$ – tbm0115 Oct 28 '16 at 14:03
  • $\begingroup$ @tbm0115 Thanks for the response but most of your suggestions are addressed in my original post. The corners are not lifting during or after printing it is the center of the print. The print appears anchored to the heated bed set at 115C while printing but bends as the finished print cools. The printer is in an enclosure that maintains a relatively warm environment during printing and cool down. The print is allowed to cool on/with the bed further slowing the cooldown process. $\endgroup$ – jmb2341 Oct 29 '16 at 20:50

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