Haunted Delta

Okay so I have tried just about everything with my printer, I custom built it myself and am having a problem that I cannot solve
It's a rather large delta printer, about a meter tall, it's using 0.9 degree stepper motors with a makerbase mks sbase smoothieware comparable board that uses built in drv8825 stepper drivers, but this problem was also happening when I was running a ramps board.
The problem is it seems to be missing steps, it will drop in the z axis hit the part its printing and cause a stringy mess, I have built a delta before this and never had this issue, I thought it was the ramps board so I swapped it to the new one, I added a screen to print without a laptop,I swapped out me of the motors that looked like it was damaged and still the same, sometimes it does this 10 minutes into a print and sometimes 10 hours, I've read online that the drv8825 can have problems with not being able to stay accurate at low current so I increased the current to the motors and still nothing, the machine moves very well, I'm using extrusion with v wheels for the linear motion and the. Are all smooth, I don't think it's anything mechanical, the motors get warn but never above 50-60 degrees c, maybe someone can help because I'm out of ideas

Is the fact that the printobject is being hit the reason for missing steps and messing the flow at the wrong positions, or is that the result ?

Did you check, being a Delta, that your horizontal curve parameters are well calibrated ? This will likely hit the object when false, but only when movement is in the not calibrated path.
And also important.. does the arm gently moves over the vertical pilars ? Depending on your construction, the bearings or the distance between the parallell arms can be off.
Finally, if you use timing belts (I do) they can be to loose.


I had missing steps some time on my cartesian.... while diagnosing I resumed printing with a lift of the nozzle when moving more than a few mm. This made it not hitting anything :-)
Also, after each layer ... I home x. (This is against all advise, as home is less accurate than normal positioning, but my home is very accurate. This will limit missed steps to one layer only, which is nota disaster. FDM is reasonable forgiving in Z direction.
I liked that so much for fragile objects that I kept that setting. Try that and se if the problems disappear ? Than you know it is the horizontal pane problem.

Best I can think off.

Thomas

Edited 1 time(s). Last edit at 01/26/2017 02:16AM by Replace.

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www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)

Thanks for the advice, I have the movement quite well tuned, I didn't think about homing after each layer, I will try that, is there an easy way to do it or would I have to manually add it into the G code, trying to describe what happens is a little difficult, it seems to happen when it's doing the perimeter, it goes wide and drops in Z height, then when it comes back around it hits the parts causing it to grind on it and miss steps, and it just goes to shit from there

Oh and the belts are quite tight, and I'm using t2. 5 belts so they won't slip, I've also tried adding lock tight to the pulley grub screws, and the arms move very smoothly, I've plated around with the Concentric nuts to get them very smooth so I don't think that's the issue either

I use Slic3r, which supports the 'After Layer Custom Gcode'

I put this in:

G91;
G1 Z1 F2000;
G28 X0;
G1 Z-1 F2000;
G90;

So this code is inserted at every layer after the previous is finished

I have no idea if other slicers support this.

suc6

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www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)

You said your using the DRV8825 chips, and there is a known issue with those at some speeds. See the following article, it might shine some light into your issue.

DRV8825 missing microsteps

Thanks, I already read that article and a couple others talking about the drv8825 but I put in a Ramps board with A4988 drivers in it and still the same, I'm beginning to think one of the belts is the issue since when I got them I could only get in a maximum of 5 meter lengths, and one of them was a different colour than the rest, and that is the axis that it seems to be happening in, there is some dark residue on that belt so I'm guessing it is either wearing on the pulley and causing it to slip,, so I will try change out the belt and see, but I now know it is something mechanical