Solved Stepper motor repair/replace

Hi gang. Additonal to the presumably burned up board, I have a stepper motor that is just plain dead. The only trouble shooting I've done with this (it's the extruder motor by the way..) is to switch it to one of the other drivers on the RAMPS board to see if I had a bad controller. Still dead.

While I am making no assumptions at this point as to where the problem lies, the above trouble shooting step does indicate that the problem is somewhere downstream of the driver. I'm preparing for the worst by ordering some new stepper motors. Even if the problem is something else, like wiring, it's good to know I have the additional steppers just in case.

I'm not a robotics or stepper guy, ok? But from what I've seen, there are several factors to take into account. It seems like the most important of these, assuming the current rating and torque are correct, is the number of steps per revolution. I checked Mike's link at Robo3D and this information is not given. Does anyone know how many steps per revolution these motors are, or if there is a way for me to determine that myself?

 

With a little digging around, I've discovered something that passes for an answer. I first checked Robo3D's technical specs and became confused by their assertion that the stepper needs 48oz/in holding torque:
http://www.robo3dprinter.com/collections/3d-printers/products/robo-3d-abs-model-fully-assembled

That seems awfully high. So I went to Reprap's technical site:
http://reprap.org/wiki/Stepper_motor
There I see that the motors require at least 13.7 N/cm of holding torque, with the extruder stepper having been tested with even less.

What does all this mean? It means that Robo3D has a typo in their spec page. I believe they meant to state that the steppers are 28oz/in instead of 48oz/in. I derive this because a common torque rating for NEMA 17 motors in this application is 20N/cm, which works out to 28oz/in. Another bone headed move by Robo3D .

Here is a link to a supplier out of New York City for NEMA 17s (and many other parts) that I believe will work. I have just ordered a few and will be able to report in later:

http://www.adafruit.com/products/324

If no one minds, I'd like to drop a nice plug here for Adafruit. We use the Robo3D for fast prototyping of drone parts. We were looking for a U.S. supplier that kept quality and customer needs in mind for this enterprise, and so far, Adafruit has filled that bill extremely well. Their order filling has always been accurate and timely. Rarely do we wait more than 3 or 4 days for a shipment to arrive. Moreover, if there ever should be a problem with a defective product or wrong order, we have confidence based on our interaction with the company that it will be handled promptly and to our satisfaction. I recommend anyone who has not yet been to their website to give them a look. We've been EXTREMELY pleased with this company.

 

If its not too late a dead stepper is a good opportunity to upgrade the z-axis motors and swap one of those into the dead spot.

 

I have a binding z-axis stepper and would love to upgrade if I knew what the specs need to be or if someone knew of a stepper that fits the job.

 

http://www.omc-stepperonline.com/th...per-motor-48mm-body-300mm-t635-x-2-p-225.html

DonHuevo has installed these.

 

You know Robo has a set of 5 steppers on their site for just under $50, that is if you just want to replace a bad motor. ( I think they have singles too)

 

I knew about the steppers at Robo but I want to upgrade the holding power. The ones DonHuevo has installed are a possibility..

Thanks for that!

 

I understand. I'm building direct drive bowden feeders using NEMA 23 steppers. A great deal more power.

 

Update on the extruder stepper. This motor also began to have sticking issues and I noticed that it's pretty hot. I therefore put a GPU cooling fan from an obsolete video card on the bottom of the stepper and wired it into the active cooling leads beside the hot end. No more sticking. For an adhesive, I have discovered that using Loctite Super Glue in the ultra control pack is much better than that silver gunk. It transmits heat wonderfully and does not come lose. Give it a try. It works very well for all sorts of applications in 3D printing.