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NEMA (extruder) motor rotation indicator (Prusa MK2(S)/MK2.5/MK3/MMU2)

by Petclaud Nov 11, 2017
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I just tried that on my machine (CR10 clone) with a magnet and it doesn't magnetize to it. I'm guessing the motor shaft is made of aluminum :(

yeah. I am one of those whose resulting part stick to the housing. I see I Am not the only one here with this problem. I suggest adding this to the description to save some people time. Thank you for your work, regardless.

Thank you for your message. The description mentions "(make sure to glue the magnet to the 'raised' side)" and I trust this is clear.

I first put the magnet on the bottom (as printed) and then realized that it fit better to attach it to the top, as the raised part gives the spinner a little more clearance. Plus that matches the photos. It might be worth adding that as a comment in the description. Great parts though.

Thx. However I do believe that is already mentioned in the description: "make sure to glue the magnet to the 'raised' side"

Thanks. Sorry I missed that.

Shame with new Prusas is not working, the magnet gets attached off centered

Thank you for reporting. These indicators are downloaded tens of times a day, including the many derivatives even more and this is the first report of this phenomena. Please check again. I trust you have made a version with a 8 mm x 3 mm Neodymium magnet - correct? The hole in the NEMA motor is 8.5 mm, so even off center, it will only be minimal, however the friction should not be so high that the indicator does not turn. I do not know how new your Prusa is, but just FYI: I have received my MMU2 some 3 months ago and all three stepper motors perfectly 'accept' the 8mm indicator.

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An odd question, but... How do these work? I have 3mm diameter by 3mm high neodymium magnets already that stick to my snips, vernier, ruler... VERY well, but I can't get it to attach to the motor spindle on my Prusa MK3 (using a regular NEMA17). The magnet wants to stick to the casing more than the spindle. I have an 8mm extrusion that the magnet sits inside and just a bit proud so it should centralize on the spindle and have support around so it doesn't move, yet enough clearance to spin freely in the hole.. but then the visualiser still won't spin. My only other thought is that the 8mm magnets are actually controlled by the magnetic field caused by the motor actually moving and not the spindle... especially since looking closely the spindle doesn't seem to stick up clear of the housing too much, and if I attach the magnet to the motor alone, it sticks to the edge but does rotate. If I have to order the 8mm magnets then fine, but I'd like to understand why :) Thanks

Hi Nigel, interesting indeed. I happened to have 3 mm neodymium magnets lying around and like you described; these stick immediately to the motor housing - off center of the axle. I do not know what causes this effect, but I do know that an 8 mm stays centered

It must be the magnetic effect from the steppers. No matter how I build the tube to centralise the magnet, it just won't turn. I then offset the magnet so it's right at the edge. And huzzah, it now works. How weird. :)

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Will this work with Anet A8? Prusa motors are different.

I do not have an Anet A8 but if this works would not be so difficult to find out; the motors should have a hole with a diameter of minimum 8,5 mm and the rotor of the motor should have been made from material that you can stick a magnet to. Just check with a magnet and you'll find out. If the rotor end is deeper in the motor than +/- 3 mm you can stack magnets to get sufficient height.

Thank you for this thing! Thumbs up to you!

  • Sent from 3D Geeks: Thingiverse Browser for Android

Unfortunately, the axes of my motors are not magnetic. :(

same here! i printed a rotation indicator, glued a magnet onto it and went to put it on the extruder and it snapped off center. i took it off and grabbed a loose magnet and turns out the spindle in my extruder and x-axis stepper motors are non-magnetic. bummer!

so instead a small bit of 3mm plastic rod from the model bench and a wee bit of sticky blu-tac and i'm entertained again by the whirling.

True, even my indicator is off center as the rod is non-magnetic. We need to find a solution to this issue.

I had to add some tolerance by increasing the 6mm version by 106% in X&Y because the ID came out at 5.65mm due to my [every?] printers expansion of material around holes.

Ok thx. I have printed 2 or 3 times the 6 mm version and the magnet fitted just fine in those prints. As written in the Thing Details; the 6mm version did not really work well in my case, since with rapid extruder movements (extraction and small extrusions) I saw the indicator slipping and hence continued with 8mm versions. I hope it will work for you.

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It's working great thanks. Trying to resolve a problem with uneven extrusion so needed to see what it's doing!

Annndddd everyone has used my idea without credit. : (

Hi, thank you very much for bringing this up. I have remixed several things and always reference the original designers (see my other stuff). In this case, it was really my own idea - at least thought it was up till now :-) - but you are absolutely right that you posted something similar earlier. Credits to you, I immediately changed the description. Searching Thingiverse now I see that Tinkerer already posted a magnetically attachable indicator on July 2013 so also credits to him/her. Maybe there are even more. Anyway, credits to whomever deserves it, I just hope people love it and have fun with it.

Speaking of credit, do you know that Prusa’s YT channel has posted a video including one of your designs?

Damn, I thought I had managed to come up with something before anyone else for once... Anyway, thank you for the edit and how friendly you’ve been, I was worried that things would be hostile. Nice find in regards to tinkerer’s thing, I never found it when I went looking for others. They definetly deserve the credit. Also, your design is definitely the nicest of the three. : )

Thx no probs. Yes saw the Prusa video and was quite surprised actually. Link to the Prusa video is also in the description.

Thanks! Can't wait to try it out. Also seems like something fun to design.

Great idea. I came here from the video Prusa just posted on YT!

Good job, thanks for sharing.

Thx. Feel free to make your own design !