Makerbot rep2 irregular extrusion amount

rover · 2017-09-27T04:37:09.000Z

(EDIT: pressed publish too early and couldn’t edit to finish the descriptio of my problem.)

I’m trying to fix a Makerbot rep2 with 2000 hours on it but I have never come across something like this before. It seems to be extruding filament in a semi-regular pattern, by which I mean it extrudes for about 10seconds and then doesn’t for a few seconds before extruding, but not an exact repitition. You can see the effect in the picture below, this creates a textured pattern which is interesting but now how it is supposed to be. This can also be seen in the beginning of the raft as it extrudes and then pauses extrusion but keeps moving. I have verified this by loading filament and watching the back of the shaft of the extruder motor pause and then resume.

Is the stepper dying? My understanding of steppers is they work or don’t work, not that they stagger on. Or is this something completely different?
I have also tried several different rolls of filament from different manufacturers and checked for consistency in diameter.

Thanks!

img_20170926_183458.jpg1836×3264 1.56 MB

Sharon · 2017-09-27T11:38:36.000Z

Have you taken apart the extruder and taken a look at the knurled feed wheel? It can get clogged with filament dust and prevent “grabbing” the filament. An old toothbrush and some isopropyl alcohol can sort that out quickly.

S.

Joe9099 · 2017-09-27T12:00:53.000Z

I also check the diameter of the filament, just cut a length off say a meter and check the dia along its length, if you cant measure it, then run fingers along and see if there are any small bumps. Make sure build plate flat and compley clean. Also, just run extruder like feeding new filament, see if it extrudes fine.

SantiRivera · 2017-09-27T12:04:32.000Z

I also never have seen something like this. Did you ever changed extruders and hot ends? May be some kind of intermitent clogging until pressure inside hotend becomes enough to unclog.

360alaska · 2017-09-27T12:19:22.000Z

1. Are you still running a delrin plunger? Get the upgrade kit…

2. If you have the upgrade, Can you disassemble the extruder and clean it with compressed air? Also, Inspect the gear.

3. If all else fails you might have a bad “Botstep.”

Joseph_1 · 2017-09-27T12:51:46.000Z

Obviously the problem is your feed system. Either the toothed gear is stripped in parts and needs to be replaced, the motor isn’t connected well, or there’s something wrong with the stepper motor on the feed system. The feed system is fairly simple, so there’s not much to check.

rover · 2017-09-27T13:39:21.000Z

I updated the OP to what it should have been, hopefully this helps clarify some questions.

I replaced the nozzle just to eliminate a variably(nothing changed). I took apart the extruder head yesterday and didn’t see any damage to the toothed wheel, but I can check again just in case. The printer has been working fine for months and basically nothing has changed until prints started to fail mysteriously.

If the motor shaft can be seen to stop turning it must be an issue with the motor or the signal/power it is getting is being messed with somewhere along the way.

rover · 2017-09-27T13:41:02.000Z

It is upgraded. I had it apart yesterday and everything seemed pretty clean.

What does a bad Botstep mean? is there a way to test or fix it?

360alaska · 2017-09-27T13:47:39.000Z

See here:

https://www.fargo3dprinting.com/products/makerbot-botstep17-rev-e/

makkacom · 2017-09-27T13:51:34.000Z

Probably it’s a problem with the heating process, try to replace the heater cartridge.

ChininisDesign · 2017-09-27T17:37:39.000Z

Check to see if the toothed gear is loose on it’s shaft. There is a Allen nut to hold it but I had one work it’s way loose and slip on the shaft - enough to do something like what you show but still sort of work too.

Henry_Jolly · 2017-09-27T19:27:30.000Z

Ok, here is what I have discovered and fixed on my CTC printer about this issue. First if you incorrectly level the printer by putting the printhead too close to the glass you will get this issue also. But second it is more then likely the filament is not lining up with the hole for the extruder after passing the extruder gear. If it Is not perfectly lined up you will hear clicking as the printer attempts to force the filament into the offset hole. There are thingys for rebuilding the extruder that will line the holes up. I don’t remember what the numbers where, but look for the parts that allow the use of flexible filaments and you should be fine.

SHoutzager · 2017-09-28T16:57:18.000Z

Level the bed again. Unleveled bed has caused funky things like this for me.

rover · 2017-09-28T20:19:05.000Z

Thank you for all the suggestions! Here the things that I have tried with no change to the regular variation in extrusion:

Slicers: Makerbot and Simplify3D

Drive Gear: removed and inspected, no sign of wear and set screw was tight

Botstep: switched cards around from working axis with no change

Nozzle: switched to brand new one with no change

Bed: leveled repeatedly, tried printing in different places on the bed and different orientations

Filament: 4 different rolls and checked diameter with calipers at several locations

Hotend: Is heating up and no components are loose

So basically everything is working but the extrusion pauses during the print at regular points as seen in the photos on my first post. These machines aren’t that complicated so I don’t know what else to check

DROP · 2017-09-28T22:14:14.000Z

Hi, Have you tried increasing the pressure with the screw that changes how hard the drive gear is pressed into the filament? if you have the oldest version of the extruder from Makerbot, it includes a screw at the top and right of the extruder, that increase o decrease the pressure

shahramrobotics · 2017-10-10T12:42:56.000Z

Have you used another power supply?