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Extruder Gear Grinding

Posted by Yamster 
Extruder Gear Grinding
September 10, 2013 05:47PM

I've started using a new extruder - one of the Greg's Wade extruder variations - on my printer a couple of days ago. So, this is the second set of extruder I've used/am using.

The first one was made by someone else using ABS. I printed this new one myself, used ABS on the motor mount - in case the motor got too hot - and also used ABS for the small gear. The big gear is printed with PLA, and my thought was that since gears will wear out, I would make one of them with a softer material (ABS) so that one would wear out while the other one stays sharp. Then I would only have to reprint this small gear piece very now and then and replace.

Anyway, after only a couple of days of use, I already see some "dust" around the extruder gears. I believe it came out of the ABS gear. I had a similar experience with my previous extruder which was all ABS.

I'm just wondering, is this common to have small/fine dust like this, which comes from grinding of the extruder gears? Or is it an indication of poor fit of my gears, some misalignment, or things being tighten too much, or something like that?

Would this dust problem go away if I use PLA for both small and big gears?

Thank you!
Re: Extruder Gear Grinding
September 10, 2013 10:05PM
My ABS extruder gear teeth are slowly disappearing and they are both ABS. The small gear's teeth are going faster than the big ones. That makes sense though doesn't it, there are more teeth on the big one. Little one turns more.

I've had it confirmed by three sources in #reprap that PLA gears hold up longer.

I would imagine the smoothness of your prints figures into how much dust is made at first.
Re: Extruder Gear Grinding
September 10, 2013 10:58PM
PLA gears will hold up much longer. It's normal to see dust from ABS gears after a relatively short time.

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Re: Extruder Gear Grinding
September 11, 2013 01:10AM
I've been using ABS gears for quite some time now with no signs of degredation. If I used an ABS small gear with a PLA large gear I would expect the small gear to wear out more quickly since PLA is more rigid than ABS. The only reason I'm using ABS is because I'm concerned that the heat from the extruder motor would soften/melt PLA. With ABS for both gears, I haven't had one wear out yet.
Re: Extruder Gear Grinding
September 11, 2013 07:04AM
ABS gears need lithium grease. Without it they last no time at all. With it they last a very long time.

The small gear wears out faster because its teeth come round more often so are used more.

Re: Extruder Gear Grinding
September 11, 2013 08:49AM
no problems with my gears, got it in kit(all abs), forn now about 200-300 working hours, they are like new smiling smiley

no grease.

but good to know, il print me a set of pla gears if they are needed grinning smiley
Re: Extruder Gear Grinding
September 11, 2013 09:21AM
So, the lesson learned here is:

1. It is common for ABS gears to produce dust from grinding
2. I should lubricate the ABS gears with lithium grease to make it last longer

As I said, one of my gears (smaller one) is made of ABS and the other one is made of PLA. Would lithium grease have any negative/undesired effect on PLA?
Re: Extruder Gear Grinding
October 01, 2013 07:02AM
You should probably not use different plastics for the two gears. Print another set out of a single plastic to have some spares around in case of failure.

Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.
Re: Extruder Gear Grinding
October 01, 2013 08:15AM
how many kg of plastic should last abs gear set?

i have now printed 2-3 kilos and gears are still like new...
Re: Extruder Gear Grinding
October 01, 2013 02:04PM
I have printed about 13-15 kilograms with my current extruder, and it has ABS gears. There is no noticeable wear. I use CRC lithium-molybdenum grease.
Re: Extruder Gear Grinding
October 02, 2013 11:21PM
DeuxVis Wrote:
> You should probably not use different plastics for
> the two gears.

Hmm... May I ask you why?
Re: Extruder Gear Grinding
October 03, 2013 10:44PM
Just my 2 cents
Gear wear can be down to all manner of things > misalignment, mesh between gears, accuracy of individual teeth, ovality of gear wheels etc etc.

Of course our main aim is meshing of gears to reduce backlash ( on filament retraction). When gears are new its normal there will be a bit of wear for a while as they "wear in" to each other. I purposely print black gears so i can see the wear patterns ( wear area turns grayish)
After a few hours printing and im happy with the mesh and alignment i just add a couple of drops of vegetable/ cooking oil. Seems to work

I'm quite interested in the combination of both materials. I think given the choice i'd go with PLA stepper side and ABS larger extruder gear wheel.
Cant really justify other than having the stepper gear rigid, as the driving source "feels" more suitable

Good luck

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