Uneven Bed Temperatures
I have a new MK4S. I printed a 9-inch wide by 3-deep box-like object. Jessie PLA, 0.25mm layers with temps at default settings. 215/60: nozzle/bed temps….the “Printed Solid Jessie PLA” default settings. I watched the first several layers lay down and they seemed ok. Checked in an hour later to find the print ends warped. Keep in mind, the print is wide and extends to the edges of the plate by 3-inches deep.
Since I’m new to 3D, I jumped on the chat line…. The advice was to raise bed temp to 70c, and reduce first layer height to 0.15mm. I have not printed a new version with said adjustments, but I decided to check the bed temps at various points with an infrared instrument. I found that nowhere on the bed did it show 60c…the highest point was about 58c. The edges dropped to low high 40s to low 50s, and the right-hand corner, closest to the front was very low 40s. I checked the hot plate with the build plate removed and saw similar numbers. I did let the build plate heat for a while before taking reads…even though the printer actually starts laying down its first layer as soon as the bed reads 60c on the display.
Can anyone comment on Prusa’s Chat-line’s suggestions? I understand raising the bed temp, but I’m not sure I understand the correlation with a first layer height being reduced (I see it would cool faster, is that what you want for the first layer?).
Also, can anyone comment on the bed temperature distribution. Is that patten normal?
Lastly, does anyone have any thoughts on how to avoid the warping beyond Prusa’s suggestions.
Thanks in advance and I look forward to hearing more.
The three main reasons for warping are:
Poor adhesion - the bed must be clean and if necessary brims and mouse ears used to increase the base area of thin parts.
Drafts - ambient air changes, especially if cold, cause local thermal contraction of part of the print creating bending forces. Protect the printer from drafts, perhaps enable a skirt to further protect the print.
Shapes with long extrusion runs aligned, especially if tall - the hardest to fix, common in boxes and trays. careful selection of fill types helps if the volume is large, internal structures aligned to redistribute stresses is another, an enclosure, even a large cardboard box placed over the printer for emergency use can help to maintain temperatures close to softening point to anneal as you print.
Somewhat uneven bed temperatures matter little, the objective is to create a slowly rising curtain of warm air around the print to reduce thermal shock. Skirts and enclosures aim to assist by keeping the warm air close. Bed surface temperature will always be lower if open to the air, when covered by a print heat is retained better.
The default bed temperature is that at which the filament *just* starts to soften, eg 60°C for PLA, you can usually go a few degrees higher but it may impact detail near the bottom of the print.
Cheerio,
RE: Uneven Bed Temperatures
Thank you.
RE: Uneven Bed Temperatures
I forgot to mention that I found the reasoning behind Prusa’s recommendation to lay down a 0.15mm first layer, as opposed to its default 0.2mm. The reasoning, best I could find, is that you want to get the print head a little closer to the bed. So, worst case, you may get a little squishing, if the z-cal is slightly off one way or the other; which closes the gap if, in fact, you are a little too high off the bed. Interesting that Prusa tech didn’t mention the disc helpers (a.k.a mouse ears) as a solution.
I hope this helps.
It sometimes helps with very new or imperfectly cleaned print-sheets, sometimes textured sheets need a little more squish - if it doesn't help, drop back, in any case try dropping back in a few weeks.
Cheerio,
RE: Uneven Bed Temperatures
I have a new MK4S. I printed a 9-inch wide by 3-deep box-like object. Jessie PLA, 0.25mm layers with temps at default settings. 215/60: nozzle/bed temps….the “Printed Solid Jessie PLA” default settings. I watched the first several layers lay down and they seemed ok. Checked in an hour later to find the print ends warped. Keep in mind, the print is wide and extends to the edges of the plate by 3-inches deep.
Since I’m new to 3D, I jumped on the chat line…. The advice was to raise bed temp to 70c, and reduce first layer height to 0.15mm. I have not printed a new version with said adjustments, but I decided to check the bed temps at various points with an infrared instrument. I found that nowhere on the bed did it show 60c…the highest point was about 58c. The edges dropped to low high 40s to low 50s, and the right-hand corner, closest to the front was very low 40s. I checked the hot plate with the build plate removed and saw similar numbers. I did let the build plate heat for a while before taking reads…even though the printer actually starts laying down its first layer as soon as the bed reads 60c on the display.
It sounds like you're experiencing some issues with warping on your print, which is common, especially with larger objects. Here are a few tips to help you improve adhesion and reduce warping:
Bed Temperature: Since your bed is not reaching the desired 60°C, try recalibrating the bed to ensure it can maintain the correct temperature. Consider using a glass or PEI sheet if you're not already, as they can improve adhesion.
First Layer Settings: Lowering the first layer height to 0.15mm is a good idea, as it can enhance adhesion. You might also want to slow down the first layer print speed to give the filament more time to stick.
Brims or Rafts: Adding a brim or raft can help with adhesion and minimize warping, especially for wider prints that extend to the edges.
Cooling: Ensure that your cooling fan is not too aggressive during the first few layers, as this can lead to uneven cooling and warping.
Ambient Temperature: Make sure that your printing environment is free from drafts and temperature fluctuations, as these can contribute to warping.
Try these adjustments, and hopefully, your next print will turn out much better!