Repetitive layer defects

dc42

@edgars-batna said in Repetitive layer defects:

@deckingman There it is - I bought a "Random switch-on" relay. Learned something new today.

Zero-crossing turn on is recommended for resistive loads such as heaters. However, heaters have no inrush current, so using a random switch-on SSR (which is the right sort for driving inductive loads) will make very little difference.

Denis

@dc42 Yes, David. You are absolutely right. This is a delta, motors 0.9 degrees, 16 teeth pulley. And I used the height of the layer 0.1, 0.15, 0.2. This is very valuable advice, but since I am not familiar with the delta kinematics, can you explain where the figure 0.8 came from? Some use 0.1618, but I didn't get a good result with such a layer.

dc42

@denis said in Repetitive layer defects:

@dc42 Yes, David. You are absolutely right. This is a delta, motors 0.9 degrees, 16 teeth pulley. And I used the height of the layer 0.1, 0.15, 0.2. This is very valuable advice, but since I am not familiar with the delta kinematics, can you explain where the figure 0.8 came from? Some use 0.1618, but I didn't get a good result with such a layer.

You have 200 steps/mm @ x16 microstepping, so 100/16 = 12.5 full steps/mm. 1mm/12.5 = 0.08mm.

Edgars Batna

I followed some advice from here and got some results to report for reference:

Switching to a zero-crossing from random-crossing SSR did not visibly affect the light flicker issue.
Switching from bang-bang mode to PID at the bed heater did not affect the horizontal banding issue.
I was able to further tune the PID and keep light flicker to a minimum.
The Z axes construction was worse than I expected. I could measure +/-50% variation every Z motor revolution with just a basic electronic caliper. Apparently the Z screw rods were misaligned so just a little rod bend was being exaggerated.
The weight of the bed was high enough to press the Z stepper rotor downwards on high acceleration moves (this obviously depends on its construction), so I added some flange bearings at the bottom.
The Z smooth rods were not really smooth in the Z direction and needed some 800 or more grit sanding.
I remodeled and fitted bigger, bulkier variants of all brackets, couplings, etc on the Z axis.

Now after improving 2 out of 4 Z axes the banding is nearly gone!