I bought a bunch of used steppers from Mosaic Manufacturing (they changed their product line). It seemed like a really good deal…
The stepper motors came with extruder gears loctited onto their shafts. The guy that I bought them from swore that they had been able to get the gears off with a little heat and pressure. I didn’t ask him if the stepper motors actually worked after they applied that heat and pressure…
From what I’ve read, the amount of heat that I’d have to apply to loosen the loctite would damage the stepper motors.
Home Depot sells a plumbing pulley puller, and after getting the set screws out I managed to get the extruder gear off of one stepper motor. However on most the of the stepper motors the extruder gear is shoved so far up the shaft that there isn’t clearance to get that pulley puller on them - most of them have less than 1/8" clearance, and a lot of them have 1/16" or less clearance. Plus after removing only a few loctited in set screws the allen key that I was using was stripped.
I bought a nut splitter and tried to use that because I read that some guys have been able to get the pulleys off that way, without wrecking the motor. Those guys must be a lot stronger than I am, or they must be using a vice to hold the tool, and a pipe on the wrench to increase their leverage. I don’t have a vice where I am located, but I’ll be able to try this on the weekend.
Has anyone here successfully gotten loctited extruder gears off of stepper motors without wrecking the stepper motor? How did you do it?
Use a cut open aluminum can with a slit cut in it for a heat shield. Slide that behind the gear, then you can hit it with a torch. It shouldn’t need that much heat to soften the loctite. You can also try to see if you can get a bolt or something like that on the bottom of the shaft, then use a socket and hammer to push the gear down toward the stepper to break the glue free, then you should be able to pull it off. That’s just a guess though, without having it in hand.
> Use a cut open aluminum can with a slit cut in it for a heat shield.
> Slide that behind the gear, then you can hit it with a torch.
Even using a heat shield to protect the body of the motor from direct heat, the shaft will transfer the heat to the rest of the stepper motor. Have you tried the above?
> use a socket and hammer
I’ve seen this suggestion elsewhere on the internet. And I saw the response of someone that tried it. It is a good way to damage a stepper motor. Even if you directly applying the force only to the shaft, it turns out that hitting a stepper motor shaft with a hammer results in a lot of vibrations that get transmitted to the internal workings of the stepper motor.
One other thought is a complete disassembly of the stepper motor to get better access to the shaft similar to the approaches others have used to replace the shaft with an integral leadscrew.
I don’t know that anyone will have an answer that is guaranteed to work on all of the motors. Some of the variability will in the type of loctite that was used as well as what you’ve already pointed out (gear location). I think you’re just going to have to try one or more of the methods and it looks like you have some spares (3 spares if you’re building the MPCNC or 2 spares if you are building the MPCNC with an extruder).
> One other thought is a complete disassembly of the stepper motor
I’ve looked into this, and I’ve seen multiple articles discussing how this results in a stepper motor with a lot lower torque after you manage to put it back together.
I am going to give the nut splitter another try on the weekend, with a vice and a big pipe on the wrench to give me some leverage. I should have researched getting those gears off before I bought the motors, but I took the guy selling them at his word.
I ran into something similar on a larger servo. I drilled three holes 120° apart in a piece of pipe and tapped them for 10/24 screws. I was able to tighten it to the gears, and grab it with a puller, instead of the back of the gear. If your not trying to use the gear again, you should be good.
It might be more trouble than it’s worth. I only did that, because I had stuff laying around, verses ordering something.
Oh, I cut a groove in the pull to help the threads grab.
After reading about the right intensity of vibrations damaging stepper motors, I’m reluctant to try cutting/grinding the gears off. I’m going to try the nut splitter again once I have a vice that will hold the tool steady.
Shield the motor from heat, then use the blowtorch to heat the pulley.
You won’t ruin your motor if you don’t heat the sh*t out of your pulley for hours like a moron, just heat it 6-8 seconds and you should not have any problem whatsoever.
The heat won’t have enough time to go deep inside the motor, plus those things can withstand a lot of thermal abuse, they don’t break that easily. Once the pulley is out, just cool the shaft using a wet tissue, to further limit heat exposure. Easy.
Don’t be so afraid of doing it, steppers are pretty resistant. This is really no rocket science, no need to overthink here.
Otherwise, if you’re really that scared of heat, the “right” solution would be to use a bearing extractor, which is generally what I do whenever I cannot get a pulley out.
“When heated above 176° Fahrenheit (80° Celsius), magnets will quickly lose their magnetic properties.”
and
“An air-only torch will burn at around 1,995 °C”
I think I’ll avoid applying a blowtorch to my stepper motors, even if only for 6-8 seconds. That metal shaft will quickly conduct heat into the stepper motor.
There isn’t enough clearance for an automotive pulley puller. There isn’t even enough clearance on most of the motors that I have for a plumping puller (same idea as a pulley puller, but smaller).
I get the feeling that some of the suggestions here are from guys that want to be helpful, but haven’t actually tried what they are suggesting. I was hoping for “this is how I did it, and I didn’t wreck my stepper motors or reduce their torque.”
I tried it before I had the bearing remover tool and done it several times. It works fine.
You are overthinking the thing way, wayyyyy too much. If you don’t trust me, just make this easy test: take a M5 screw in your hand, heat one end of it with a blowtorch for 8 seconds. The side where your blowtorch heats will be super hot, but the other side where you are holding it with your hand will barely get warm. Steel is a poor heat conductor. My guess is that it would take you at least 1-2 minutes of continuous heat on the shaft to really damage your magnets.
I do this litterally every day to embed nuts in my 3D prints: I take a screw, put a nut on it, heat the nut until it gets red hot and then press it into the 3D print. I do this by hand, without gloves, and I never got burned, ever.
Plus I deal everyday with BLDC motors and stepper motors, I think I kinda know what I’m talking about when it comes to these things.
Please don’t assume we don’t know what we are talking about just because it isn’t the solution you were hoping for
But if you wish to make your life complicated, then by all means, carry on!
Well I don’t know what kind of pulleys, motor or puller you have, but it surely should work.
I’ll try to remember to take a picture tonight so I can show you how to do it if you want. My bearing puller is gigantic and it is a pain to set up and to use, but I managed to pull out the pulleys with it (they were totally seized in placed, the set screws were stuck in and impossible to remove with the blowtorch technique).
You’ll need to use a 4mm screw to place between the puller main shaft and the motor shaft (because the puller shaft is usually way bigger than the motor shaft).
If you’re afraid of using a torch, then use a high power soldering iron on it’s highest setting to apply the heat just to the pulley. By the time the shaft starts to get hot, the loctite will already be melted.
The soldering iron will take a while to heat up the pulley vs a torch, but it works.
This is assuming red loctite was used. If it’s green, then you might as well pull out the dremel with the cut-off tool and start slicing and dicing the pulley.
Interesting. I knew green was wicking as it’s used to glue pinion gears onto shafts on RC cars. I thought it was the strongest, though. I’ve never been able to break it free without serious force.
I just took a bunch of extruder gears off of stepper motors using a nut splitter+vise+2’ breaker bar. It took less than a minute per stepper motor to remove the gear.
So next week I hope to have the electronics wired up, and to beging testing a MPCNC using a pen on the tool-mount.
