under-extrusion

Troubleshooting for the mechanical elements of the RigidBot

under-extrusion

Postby jkister » 11 Oct 2014, 21:26

I am having issues with my rigidbot not making a solid surface - has small missing gaps of plastic in random places.

Right on the first layer of a print, i can see gaps in the base which correlate to seeing the filament "bounce" up/down from the extruder.

I adjusted the E-pot in every way conceivable and can't fix this problem. I've tried printing at 200, 205, and 210c. I've disassembled the extruder/hot-end, cleaned it all out and re-assembled. I'm currently printing at 80mm/s (but have bottom layer set to 20mm/s in cura).

I disconnected the e-stepper from the hot-end, put in filament, and brought the hot-end up to 205c. i adjusted the e-pot until the motor was pushing the filament reliably. Then I powered down, reconnected the stepper to the hot-end and ran a test print through. I had to increase the e-pot for the extruder to push the filament at all, but still saw random "bounces". So I increased the pot 1/8 (ccw) and tried again -- saw the "bounce", increased 1/8, saw the "bounce", ... all the way until the e-pot maximum.

I also ran the extrusion test (marking 150mm and telling the printer to extrude 100mm). The printer did extrude 98mm twice in a row. That seems fine to me, so i didn't adjust the firmware. I do wonder if i try to push 1000mm if i'll see the issue, but I don't think that'd be a valid test anyway.

is the e-pot more sensitive than i'm giving it credit for ? should i be moving in 1/16 turns instead of 1/8 ? everything i read online refers to 1/4 so i would imagine 1/8 is fine. is there a better way to check the e-pot than running a test print through and just watching for errors ?

Not sure what to do or what to check. Suggestions?
jkister
 
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Joined: 03 Oct 2014, 01:49

Re: under-extrusion

Postby Kzkid50 » 12 Oct 2014, 12:56

I have had similar issues with my Rigidbot big. The issue for me was related to the motor missing steps. (Sometings you hear the motor click) This usually showed on the first layer of the Skirt or Raft. It looked like a set of dots connected by lines, each dot was the proper extrustion and the line was the missed step. I was able to correct the issue by raising the extrutder temp to 240 (I am using ABS) and turning the fan on the extruder to 60%.
I did PID tune my extruder and that helped a lot on this issue as well.

I hope this helps.
Kzkid50
 
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Joined: 25 Jul 2014, 22:57

Re: under-extrusion

Postby starkist70 » 15 Oct 2014, 03:17

I had a similar problem and the nozzle was slightly damaged from dragging it across the bed during calibration. Used a very small drill bit, #78 to make it round again. Probably made the hole bigger because I'm running 80% extrusion. Bed on mine has a slight warp and is higher in the center than the corners which added to the problem. Hope that helps.
starkist70
 
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Re: under-extrusion

Postby Scatterplot » 15 Oct 2014, 22:26

Just FYI, a #78 drill bit is 0.016", or 0.4064 mm (16% larger than standard). I'd guess you went slightly above that since it's easy to wiggle bits around some when drilling, but you're otherwise very close!
Scatterplot
 
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Re: under-extrusion

Postby jkister » 17 Oct 2014, 09:09

thanks for the replies. i did drag my nozzle on the bed as well; i wonder if that's my issue. I've tried everything imaginable (including raising the hot-end to 240 for PLA and turning down the fan) and still get the issues.

I just opened a ticket with IAP to see if i can purchase a new nozzle. in the interim, any ideas on how to drill out the existing nozzle to get a closer 0.4mm opening?
jkister
 
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Re: under-extrusion

Postby DrMerlin » 17 Oct 2014, 18:46

This thread on replacement nozzles may be some interest to you: viewtopic.php?f=3&t=461

No answers yet.
DrMerlin
 
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Re: under-extrusion

Postby jkister » 17 Oct 2014, 19:41

DrMerlin wrote:This thread on replacement nozzles may be some interest to you: viewtopic.php?f=3&t=461


Great idea. Since IAP doesnt respond to tickets quickly, I just pulled the trigger on http://www.ebay.com/itm/251406134779 -- for $3 shipped i wont feel bad if it's not right.
jkister
 
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