Extruder motor knocking sound

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Extruder motor knocking sound

Postby mattvl » 2017-Nov-Sat-17-Nov

I just replaced my printrboard on my Metal Plus and my extruder keeps stuttering and making a knocking sound. I tried loosening/tightening all the screws and adjusting the current in Cura, which did nothing. I just tried swapping the motor connectors on the printrboard and when the Z is plugged into the extruder port those motors still work, but when the extruder is plugged into the Z axis port, it gives a constant loud sound without any movement on the drive shaft. Is it time to get a new extruder motor, or is there something else I should try?
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Extruder motor knocking sound

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Re: Extruder motor knocking sound

Postby frankv » 2017-Nov-Sat-21-Nov

I'd start by taking filament,etc out of the extruder and see if it still does it with no filament.

If it still does it, then check the wiring to the motor. Maybe you have a wire broken inside the insulation, so it only makes intermittent contact?
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Sun-15-Nov

I took the filament out, even removed the entire assembly from the driveshaft and it still does it. As far as the wiring goes, I tried jiggling it around at the motor and the board end a bit, but that didn't result in any changes. It's a little odd that when connected to the extruder port it knocks with tiny forward and backward movements, but when connected to the Z axis port it just has a constant whine with no movement. My thought is that there is a disconnect in the wire somewhere, but short of peeling all the insulation off (which seems like it would require me to buy a new motor anyway), is there something else I should check?
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Re: Extruder motor knocking sound

Postby Mooselake » 2017-Nov-Sun-16-Nov

Check for coil resistance. Pick any two wires at random and look for some resistance (relatively low, like single to double digits, google the motor number for a datasheet if you want the factory value). Repeat with one of the wires until you find a coil pair. Then check across the other two wires, which should have approximately the same value.

If you can't find two coils from the wire ends then you have a busted wire, either inside or outside the stepper. For a quick test poke a small hole through the two open wires close to the motor (I usually just use the sharp probe tips) and see if you find some resistance there. If so, it's in the external wiring, otherwise it's probably in the motor.

Steppers are cheap, worst case you can just replace it with the same motor off one of the usual sites (Amazon, eBay, the overseas megamarts, etc).

Kirk
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Mon-23-Nov

So the resistance from the far end of the wires seems to be different by a factor of 4 between the two sides. I checked at the end of the cable extension and I get 3.1 and 3.4 ohms...or milliohms...I can't remember. Anyway, it looks like it's a problem with the extension wire, so does anyone know where to buy extension wires in Canada for a decent price, or do I need to order it for $5 from Printrbot?
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Re: Extruder motor knocking sound

Postby RetireeJay » 2017-Nov-Tue-08-Nov

Five dollars isn't a bad price. But if the defect is in the wires coming out of the motor then replacing the extension won't help. Maybe you can find a ham radio operators or Maker group nearby with the tools, expertise, and materials to find where the bad spot is in the wiring and splice in some new wire to bridge the bad spot. It's really not hard to do if you have a soldering iron, some "hookup wire" and some shrink tubing to insulate after the wire has been spliced.

A very likely location to look for internal breaks in wires is where the wire has been bent back and forth repeatedly at a single point. I highly recommend using cable chain and other techniques to make sure all wire bending is spread out over a long distance, not focused at a point.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Tue-13-Nov

Sorry, it looks like I wrote cable extension in where I meant the stepper motor cable. The resistance is similar across the contact pairs at the end of the stepper motor cable, but there is a large difference at the end of the extension cable. Based on Mooselake's description, my assumption is that it means the extension cable is the one with the break. If so, I need to find a vendor the purchase another extension cable from.
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Re: Extruder motor knocking sound

Postby RetireeJay » 2017-Nov-Tue-13-Nov

Omit the second sentence of my previous reply; everything else I said still applies.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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RetireeJay
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Wed-15-Nov

So continuing with the assumption that it's the motor or the extension cable, where does one buy the stepper motors from that ships to Canada? Getting the cable from Printrbot isn't a problem and I found a Kysan stepper motor that apparently works as a substitute for what came with my printer on Amazon (https://www.amazon.com/Kysan-1124090-NE ... pper+motor), but it doesn't ship to Canada. When I look at other sellers, I believe I found one that does, but the shipping is twice the cost of the motor itself. Any other suggestions for models/vendors that ship to Canada?
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Re: Extruder motor knocking sound

Postby RetireeJay » 2017-Nov-Wed-17-Nov

When I bought new steppers, I got them from https://www.omc-stepperonline.com/ but I have no idea if their shipping to Canada will meet your criteria.

HOWEVER, the electrical guts of a stepper motor are extremely simple. There are two independent, stationary coils. That's all. There are no brushes or any kind or moving electrical contact to fail inside the motor. Stepper motors might eventually fail due to worn-out bearings, but electrical failure is extremely unlikely unless the motor has been overheated to the point of smoking. If I lived next door to you I could almost certainly guarantee to fix your problem by splicing in a repair to the wires going to the motor. Unfortunately, shipping the motor with its wires to me and back would not be cost efficient.

If you live near a big city, try to find a maker's group. Plexus, the Administrator of this forum, lives in Toronto. If you click on "Members" you can get a list of all the forum members. Click twice on the "Location" tab and you'll get a listing of their locations in reverse alphabetical order. It's a little mixed up with websites and so on, but maybe you can find a forum member who lives near you and then try sending them a Private Message.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Wed-21-Nov

Is this an appropriate substitute for the stock Metal Plus extruder stepper motor?

https://spool3d.ca/nema17-stepper-motor-48mm/
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Re: Extruder motor knocking sound

Postby RetireeJay » 2017-Nov-Thu-13-Nov

I think that should work OK.
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
User avatar
RetireeJay
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Sun-15-Nov

I ended up finding a site that was selling the same motor I already have for a decent price with shipping to Canada. I'll let you know if that solves my problem.

Thanks everyone for your help!
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Re: Extruder motor knocking sound

Postby mattvl » 2017-Nov-Tue-20-Nov

At long last, the stepper motor has solved my problem! Thanks again everyone!
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