Stepper Motor Repair - Shaft Replacement
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- Опубліковано 18 жов 2024
- In the middle of cutting a customer order on our CNC Plasma table, our stepper motor broke! This was on a weekend for Monday delivery, so the only choices were, tell the customer there would be a delay, or see if we can fix it.
Well.....since we are a machine shop, we chose to try and fix it.
Thanks for taking the time to make this video. Some years ago I converted a Sieg X1 to CNC using NEMA 24 motors, but there have been loads of times I've wished I still had the option to move things manually (for little jobs like when you put a flat on the shaft). Thus I'd like to add the handles on the back end of the motors... and thanks to your video I now know how I'm going to do it. 🙂
Thanks for watching. Glad I could help!
I hope you bought some spare motors so you wouldn't have to go through this again. That's a lot of work for a $35 motor. If they cost more than that, you're being ripped off in the name of branding. Did you ever figure out why it sheered off? Judging from the size of the motor and that it's a plasma table, I can't imagine the motors being under enough load to sheer the shaft.
I appreciated the video. It provided a lot of insight into stepper motors. Thanks for taking the time to make this video. If you're not using Tap Magic as your cutting oil, you're using the wrong oil. :-)
Thanks for the comments! The actual cause of the shear wasn't due to "shear forces" (in an engineering context). I purchased this table used and did give it a good once over, but I guess I missed one part. that motor was at a slight angle in the horizontal plane. Barely noticeable, but that meant the shaft was constantly traveling a slight eccentric path and over the years the stress just added up.
Think of breaking a metal coat hanger by repeatedly bending it back and forth, but instead of over a minute, very, very tiny forces over a very, very long time.
Sadly, these are quite high inch-pound motors and are significantly more than $35. The only real reason I repaired this one was that I had a custom order to get out and a new motor would take a few days to get to me (I live in the middle of nowhere).
Well, that and I own a machine shop, I'm a geek, and it was a challenge for me :)
Oh, I forgot, I go through tap magic by the gallons :D
@@MountainLaurelMetalworks More than 26.5 inch-lb? If so, where doi you get them?
sorry, my mistake, my brain was running in oz/in vs. in/lb. they are the 26in/lb. But all I could find for the $35 range were about half that. If you have a source for the 26in/lb at $35, would you mind posting it. I'll grab a few spares at that price.
Heck, I'm prob building a new, much larger table, in the near future and if they have these at $35, it will save me a lot of money on my next ones as they will need to be much larger (very heavy gantry on the next table).
Thanks for this great video! Something like this is what few people would appreciate, but those that do, will REALLY appreciate the detail (myself included!) Your timing on this video is great for me because I am trying to transfer the shaft from one motor into another. I have been able to disassemble the motor completely, but I can't get the shaft to slide out of the rotor. It is either extremely tightly press fit in there and/or has some sort of adhesive that is making it more difficult. In your video, there appears to be brown residue on the shaft, which I'm guessing is an adhesive.
Do you know how much force you had to apply using your arbor press? I only have a manually operated arbor press, and I believe the most force I can apply is around 0.5 Tons (according to its spec). So I'm wondering if I simply don't have the right tool, if I need to try harder, or if there is a particular solvent that might work well to dissolve some of the adhesive first...
I was actually surprised that mine did not have an adhesive, however, I would not be surprised if there was an adhesive such as 'red Loctite' or some other form of permanent thread locker. With .5 Tons, you should have enough force to move the shaft if it was not fixed with some form of adhesive.
If a permanent thread locker was used, it may require heating to permit the shaft to be pressed out. If you have access to a heat gun, that may be a good way to go. It doesn't take a lot of heat to make these adhesives release. However, understand that if exposed to sufficient temperatures, magnets can permanently lose their magnetic ability. Loctite Red (permanent) requires 500°F (250°C) to release. This could be past the point where the arbor becomes de-magnetized.
Be aware, the permanent magnets on the arbor may be kept in location by your shaft. I highly suggest wrapping them with something such as duct tape before pressing out the shaft to retain the orientation.
Taking all this into account, the risk of damaging the motor was worth it since the shaft sheared on mine and without a new shaft the motor was useless anyway.
I hope that helps and I would love to hear how yours ends up, a video would be great and I'd definitely watch it!
@@MountainLaurelMetalworks Woohoo thank you!!! It worked! I'm not sure if it's because I dunked the rotor+shaft in a beaker full of acetone for 10-15 minutes, or your last comment gave me more confidence to try harder with the arbor press, but I managed to separate the shaft from the rotor! I kept letting go and pushing the arbor press lever with my hands to simulate some sort of hammer action...it eventually wiggled free! I did see some sticky residue in the process, but not sure if it was adhesive originally on the shaft or originally on the outside of the rotor. These are StepperOnline motors for anyone that comes by this thread in the future.
For my second motor, I did not use any acetone...for some reason it just happened to be easier to push through. Maybe because the rotor was shorter in length, there was less friction to overcome, not sure.
I was hesitant to use acetone because it looks like the outside of the rotor may have some sort of glue to hold the magnets in place, but thankfully the the 10-15 minutes it was sitting didn't appear to cause visible harm. (again, not sure if it helped, either).
I skipped using a heat gun for the reasons you mentioned, because I need the rotor on at least one of the motors to work.
I have successfully removed a long shaft from a long motor and transferred it into a short motor, thereby giving a short motor a long shaft!
Thanks again!
That is awesome! I'm glad it worked for you! I love it when I can repair or modify instead of replace.
I would like to have seen the repaired motor actually running or being turned by hand.
That's cool!
any value in freezing the shaft rather than pressing it in?
In this use case, not really. There are 2 reasons. First, pressing creates a different type of fit where it burnishes the surfaces during the pressing operation. This is sufficient for the use case in this situation as the forces are relatively low.
Cooling the material has differing impacts, largely influenced by the diameter, in this small of a diameter, the influence of cooling, even with liquid nitrogen, would only provide a reduction in diameter in the tenths (less than a thousandth of an inch). So a press fit actually provides a more secure fit.
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