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Extruder Stepper Motor Replacement with E3D v6 and MK8
#1
I was doing some research on all of the Da Vinci extruder replacements and have yet to find anyone replace the stepper motor. I actually didn't find any information at all on what model stepper motor was used for the extruder. I had to remove the screws to check it out myself.

Here is the spec sheet for all the motors in the Da Vinci:
ww.nmbtc.com/pdf/motors/17PM-K.pdf

My 1.0 is using the 17PM-K142B for the extruder. I have not been able to find a place to purchase these yet.

I have already purchased an E3D v6 with Bowden extras and a .25mm replacement hot end. I am about to purchase some LM8UU bearings and an MK8 drive gear and possibly some pretty standard bearings like I have seen in the other mods.

My question is should I continue to try and find the 17PM-K142B motor or should I go with the trusty Kysan 1124090 NEMA17?

From what I understand I cannot use the stock motor as the drive gear is attached to the shaft, otherwise I would just use stock and replace the drive gear.

I notice the Kysan is a little heavier then the stock motor. It also is 1.5 Amps as apposed to the 1 Amp stock motor. I'm not well versed in stepper motor compatibility so I was hoping someone would shine some light on what I would need to look for.

Thanks!
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#2
You can use the stock stepper with the mk8 gear you just need to either use a jaw pullers or cut off the stock gear. As far as the new motor goes it is all about what the board can supply for amperage so if you have 1.5 amp motor the board may only be driving it with 1.0 amps which is no bueno...
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#3
Well I did a bit more research and found some info on the stepper driver boards. They are using the 4988ET driver chip that is rated for 1 Amp with no cooling but can go up to 2 Amp with heat sink and/or fan cooling.

I figure 1.5 A should be doable with a heatsink. Do you think there would be any special configuration in firmware or otherwise to accomplish that or will the circuit simply draw more current with the new motor?

I will continue to look into this, but I figured I would pose these questions so the community could benefit from any responses.
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#4
Are there different specs for the MK8 gear to buy for the stock stepper? i.e. diameter, material, etc?

Anyone can link a quality gear?

thanks
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#5
I purchased 1 from an e-bay seller in New Hampshire for $6. Quality seemed fine. I suspect it is just one of the $4 ones from Hong Kong but without the wait. Tight fit on the stock Da Vinci stepper but not too much trouble to put on. The problem comes from using the E3D mod with it. It is set up for an 11mm diameter gear and the Mk 8 is smaller (~7mm) so things aren't lining up. I put the stock gear back on and am working on modifying a design. I also ordered a Mk 7 since it is closer to the Da Vinci gear. Any 5mm center hole gear should work, you just have to make sure your extruder is positioned correctly below it.
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#6
I just completed installing an E3D V6 hot end into my Da Vinci 1.0 with a Bowden Extruder. It's working great. I re-used the extruder stepper from the stock setup.
You can remove the brass drive gear from the motor a couple of ways. If your lucky, a little heat and a vise grip should be adequate. Ideally, a gear puller is the safest way to remove it, can find one from on-line hobby shops. A final resort is cutting the gear off with a dremel.

Extruder wise, I just grabbed one from Thingiverse Bowden Extruder that I liked alot. There is a MK7 and MK8 version of the files in there. I grabbed a MK8 gear off Ebay for $8 or so. The only issue I ran into is that I ended up needing a fan on the extruder for longer prints. I ended up mounting a fan in the top cover that, when closed, blows right on the extruder where I mounted it.

All told, the only things I ended up needing to purchase other than the E3D hot end was a 12V fan for the extruder and a set of Oillite bushings. I would recommend a good set of bushings over Linear Bearings. I have yet to find a set of bearings that aren't noiser than the bushings.

Good luck
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#7
So are the stock bushings sloppy (oversized) or bad quality? Did you replace every bushing in the machine?
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#8
The stock bushings have more tolerance than the lm8 bearings. Mine were incredibly sloppy, but as most know my printer has a boatload of hours. The LM8 bearings are notoriously noisy but the performance difference, both in accuracy and reduced friction, is -imo- worth it. The bearings do "settle down" after a few hours, and the lubricant you use on then makes a difference. (For LM8 a Light oil, such as 3 in 1, is usually recommended over grease. For bushings a grease is better. Jmo.)

Kieth
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#9
I'll be honest, I haven't put any LM8's into use. I bought a bunch and was going to use them, but when I started building up I really disliked the feel and noise of them. As well as the size. I would avoid utilizing them in a fashion where they are fully pressed into holes in a printed part. Due to their size, getting them aligned in part is a bit more tricky than shorter, smaller bushings...plush, bushings can be "adjusted" for misalignment with a drill bit..... Smile If I were to use them in the future, I would design around having more more "open" fit to the bearings.

I've left all the stock bushings in the machine except the on the hot end carriage. There I used Oilite 8mm x 20mm bushings. My machine isn't any nosier than the stock configuration. Printing .2mm layer PLA parts, I'm getting finished parts that are indistinguishable from the parts off the MakerBot Replicator 2 at work with simalar settings.

I'm happy.
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#10
That rough feel and much of the noise in an lm8 will go away once it "breaks in" after a few hours. As for press fit, i somewhat agree, which is why a reamer the holes slightly to allow the bearing to be pushed in and out of the carriage by hand. A smear of silicone before pressing them in holds them in place, yet allows me to replace them if needed.

Honestly, in don't know how many hours or miles an lm8 will go compared to the oilite bushings. I just know the bushings in my printer were so loose they could be rotated in any direction while on the shaft. They were not like that new, and the machine is regularly lubricated with a dynthetic grease containing ptfe.godly the lm8 will give a better service life. On the other hand, I've probably printed more with my machine tab most people will ever print at home...

Kieth
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#11
Has anyone successfully replaced all the bushings on the da vinci with the lm8 bearings? Only asking as my bushings are really worn and i just bought a bunch of the lm8 bearings from amazon.
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#12
I replace mine with cheap LM8s. Been a little over 20 print hours and I can feel grooves starting to wear. As soon as I master PLA printing I plan to replace the lm8s with printed bushings ( http://www.thingiverse.com/thing:13631 ).
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#13
What lubricant did you use on the bushings?
Were they installed so they moved freely with no binding?
I'm concerned as I've just replaced all bearing with lm8s. About to reassemble.
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#14
I suspect there is a bad bearing, incorrect grease, or incorrect bearing orientation involved with the wear you are seeing. Im well over 100 hours of print time since changing to the e3d/lm8 bearing and can detect absolutely no wear. I find it hard to imagine, but am not saying it is impossible, that a properly functioning bearing is going to create more wear than a bushing, particularly when it it easy to feel the bearings slide much easier than the bushings did. I really wouldnt be surprised if one of the balls is stuck in place.


So here goes- If you have LM8 bearings, are you seeing any wear??

In any case, there is noting special about the 8mm rods used in the davinci, so if the need to replace arises I personally wont be concerned...

Kieth
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#15
(01-10-2015, 07:47 AM)The Cure Wrote: What lubricant did you use on the bushings?
Were they installed so they moved freely with no binding?
I'm concerned as I've just replaced all bearing with lm8s. About to reassemble.

Just curious how well the lm8uu are working for you
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