Before (Left) and after (Right) setting the bed to use PID and calibrating it.
Layers are set to 0.1mm on a MakerGear M2.
The placement of the bed thermistor on the MakerGear M2 is not optimal. it is at the edge of the platform, so it will be much colder than the center. Because it is so far away from the point that heats up the fastest, it cannot keep the temperature stable. As the bed heats up and cools down, so does it expand and contract. Using PID on the bed helps lower this effect. The result: the layers are now much more consistent and smooth.
@Kevin_Danger_Powers PID is the most common feedback controller scheme. Stands for “proportional, integral, derivative” for the ways it interprets the measured variable (temperature) and adjusts output (heater power) to compensate.
In this context, PID provides smoothly-varying power output, whereas the alternative “bang-bang” just turns the heater 100% on and off when the temp is too low or too high. Bang-bang control can put ripples into the print due to either heatbed flex, or voltage sag at the PSU causing the extruder heater to lose power and briefly drop the hot end temp.
@Stephanie_A So does this mean your imperial screws are not the issue?
I haven’t tested yet. I changed my layer height to be full-step multiples of the leadscrew. Even after I did that, the print results were the same.
Switching to PID made a bigger impact than switching the layer heights.
I’ll see if I can do another print with the old layer heights to compare, but I’m getting closer to the limits of the accuracy/repeatability of the machine.
There is still something happening that is affecting the quality. Maybe bearing slop, maybe something else.
The exact same filament, with the same extruder and hotend type on the Lulzbot mini gives me better quality.
Gotcha. Personally, I’ve always suspected the big visible flaws with imperial lead screws were more likely to be caused by stepper microstep ripple combined with non-fullstep-multiple layer heights. Metric screws are just a lot more likely to hit fullstep-multiple layer heights on accident, so people could switch from imperial to metric and see their Z ripple disappear… even if the problem didn’t have anything to do with rounding errors like usually claimed.
I would hope metric vs imperial would not matter as long as the tolerances are the same and there is no mixing of metric and imperial in the leadscrew related areas.
I want to replace the entire bed eventually. It has a 4mm thick aluminum plate with a 4mm thick glass plate on top.
With glass being nearly the same weight per volume as glass, I’d be better off buying a 6mm thick piece of MIC6. It would warp less and carry the heat better.
I typically run M6x1 leadscrews at home, with 400 step motors. They do quite well.
That 4mm thick aluminum should spread the heat evenly, I think.
@NathanielStenzel Depends on the heater power. Not too hard to believe that 200w pumped into the bottom of a 200x200mm aluminum plate can make it flex by 0.01mm in the middle because the bottom is warmer than the top. That’s all it takes.
I myself expect the bed to warp anyways. I am cursed. ha ha ha at least the heat should be even though.
