Help with Extruder issue

Hi Guys

started having an extruder issue the past couple of days.

I Started using the I3EXT extruder (uses a MK7 gear) with Zapp SY42STH47-1684A

i dont think its related to using this extruder more that this extruder just takes a bit more torque then gregs extruder.

Iv always had issues on and off with extruders but always put it down to the hobbed bolt.

Problem im having is on a lengthy extrude

my test example of 60mm/sec for 50mm (from printrun running PLA at 190C and also 200C)

after a while i will get the motor clicking as if there is not enough torque to turn the gear.

iv checked and test my pololus . I have tried at 0.4V, 0.5V even 0.6V same issue is there.
Even tried changing the pololu over and same problem.

any ideas?

my next test is to try another stepper motor tommrow

Do you have a fan pointed at the pololu?

What driver?

Edited 1 time(s). Last edit at 05/08/2013 03:28PM by akhlut.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

what hotend are you using?

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Not sure on the pololu driver number its round half a year old

Hotend is currently e3d v4 ( yes I have fan running)

I'll try and get a video tonight showing the problem

What size filament and nozzle?

How easy is the filament to push through by hand? Maybe this is a temp issue. Have you autotuned the hotend?

Are you cooling the pololus? That might help. Your pololu is probably the standard A4988 driver (green pcb). It may not be able to provide the full amount of current to your stepper (0.67 Vref). If all else fails you may want to get a pololu black or a DRV8825 based driver.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

I think something strange is going on.

Like i said this problem has only happened past few days.

Iv taken the hotend out of extruder and tried to push by hand.

Very hard.

Also tried with J-Head i got same problem :|

iv checked and im using temp table 1 which is correct.

any know of a video showing how easy it should be to push PLA through a hotend ?

Video of me pushing PLA let me know if you guys think this is normal

http://youtu.be/ZcDpW21xK74

Have you checked your thermistor wiring lately?

---

- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

that nozzle and hot end appear from the video to be working ok. if there are issues during a print run i would check that the flow rate is not set too high, and that the extruder holes are large enough for feedstock to go thru easily. are you using a wades or a gregs extruder type, and is there any indication that something is catching the feedstock before or after the hobbled bolt. also is your bolt completely clean of any debree?

there is also the applying pressure to the feedstock. it seems to be a bit of an art, as too little pressure causese slipping, and too much causes plastic feedstock to change shape and it will then be next to impossible to push thru as it is rectangle and needs to go thru a square hole.

what layer hieght are you printing at. if greater than 0.2mm i think the expecation of over 60mm/s feedrate is to much for the required flow rate.

Just and update it think i may have solved the problem

Just stripped extruder down and tried turning the large cog freehand and noticed it would bind at some point.

Stripped down the M5 rod which the I3EXT uses and looks like the grub screw of the Mk7 gear had ripped the m5 rod apart. also the M5 rod felt slightly bent.

Luckily i thought using M5 rod was a bit silly so i had already orderd some M5 Hex bolts to replace.

Replaced with the Hex bolt (though not put a flat on yet which can onnly help in the future)

and i can now get a constant extrusion at 90mm/sec for 50mm without s skip

I think the whole heat problem was just me going off my head not thinking strait.

ill try printing a long print tomorrow and see how we go

thanks guys

Just wanted to reopened this problem as its killing me

it looks like the stepper motor is overheating due to so much torque needed to turn the gear on the M5 rod.

iv got a pololu black driver on the way to test that out.

what should i set the V ref to? im currently running at 0.4v on my current old pololu driver.