Speed oscillation – motors are skipping steps or the Rambo c

[Bahrt]

Hello to all you helpful people in here, who have been a great support to me in my process from being a complete printing noob and now being able to print decently on my Rostock Max V2. I definitely still have a lot to learn and now have a specific printing issue, which I cannot define.

I know that too fast printing speed can reveal different issues. I this case it seems like I struggle with a combination of poor jerk / acceleration / high speed and the printing pattern of the part. I am not sure where I should put my main focus – are the delta motors skipping steps or is the Rambo position control lagging behind…? The thing is though – I can only get successful prints with this particular part if the perimeter printing speed are below 30 mm/s, which I consider as fairly slow.

Part overview -

Part overview

The part dimensions -

The part dimensions

The blobs marked in red circles, in the picture below, are coursed by a fluctuating speed at 70mm/s.
The yellow line layers are printed with 40mm/s.
The blue line layers are printed with 55mm/s.
The red line layers are printed with 70mm/s.
The green line layers are printed with 25mm/s, which eliminate the blobbing completely and gives me a fairly nice wall surface, even for a 0.7 mm nozzle.

I would like you to notice that I have only marked every second ridge, with a red circle - the blobs are distinctly present on every second ridge. This is why I suspect the Rambo controller lagging behind, not doing the delta maths fast enough...?

Speed oscillation

I do increase temperatures when increasing speed. I am sure that the temps are well controlled, as I have success printing other “more smooth” parts, with no ridges, at higher speeds.

The blobs on my print here are definitely coursed by too much material extruded, every time the nozzle does a brief stall. It is clearly both visual and audible.

Have a look at this video sample via external link - https://www.dropbox.com/s/tp4yec4mpd2yx ... 3.mp4?dl=0 (you might actually hear it, if you turn on the sound)

Can anyone recognize this behaviour and come up with some thoughts? The ridges around the part seems to be a challenge… But, why do I already have the speed drop outs at 40mm/s?

Thanks!
Andreas

[bot]

Delta segments per SECOND may be what is at play here. Since it is based on time, not distance, different speeds will have different "resolutions." Either that, or just general "ringing" caused by slack in belts, play in u-joints, and flex in the arms.

[Bahrt]

Thanks a lot, not the answer I was hoping for though… I have to decide where to fit a Smoothieboard or the RADDS/DRV8825 (ARM) equipment, in my upgrades to-do list… Can someone explain me the meaning of having a “low” performance controller fitted in a delta printer? I don’t even see a cost benefit.

Ok, I can try to play with the DELTA_SEGMENTS_PER_SECOND_PRINT repetier firmware setting, but I don’t want to lose quality on that behalf. It is hard enough already to have quality prints, according to this - http://forum.seemecnc.com/viewtopic.php ... 3&start=50

I have to say, I am disappointed…I have just bought a delta printer to, among other things, gain higher print speeds. When a part becomes a little complex the stock Rostock Max V2 is not capable of doing higher print speeds than 30mm/s?!?