Starmill Stepper Motor Questions

[NylonAdmiral]

Hi all, I am looking for some advice regarding the possibility of replacing my stepper motors.

A short while ago I had an issue with my Y axis wandering because my Starmill couldn't cope with running at higher speeds:
(viewtopic.php?f=2&t=2380&p=8636&hilit=w ... axis#p8636)

I now have a problem where both my X and Y axis are failing to achieve their target values. For example if the cutter should be moving to X10, Y10 it may make it as far as X8, Y9 and just carry on to the next line of code. Over the period of a few lines the tool is nowhere near where it should be. The machine is well lubricated and the gib strip adjustments seem to be fine.
However when I used my lathe the other day I noticed that I could feel increased resistance (compared to normal) when moving the tool in both the X and Y axis. I think this is because it is so cold in my garage at the moment. Its poorly insulated and we've been seeing -10degC at night.
Based on this I wonder if my starmill is failing to achieve its target values because the cold is having the same effect on the mill as it is on the lathe, with the increased resistance being too much for the stepper motors?

I am therefore now begining to consider replacing my stepper motors. If nothing else it would be nice if I could machine things a bit quicker without the machine stalling/losing position.

I am wondering what is the best way to go about doing this? My plan was to examine the existing motors and try to find equivalent replacements, or better still, suitable upgrades. Can I just undo the fixing's circled in the attached picture and try and find a part number or will removing the motor in this way cause any kind of calibration error?

Any suggestions or guidance on this would be great!

[Denford Admin]

I think you may find it easier to remove by undoing the other 4 cap-heads which cover the whole of the gearbox and lift it up and out (it looks like a belt and pulley behind the motor)
Although it looks like any information plates will have been painted over, hopefully someone will know the spec of the Starmill motors...and what you can replace them with

[NylonAdmiral]

Brilliant, thanks for the super quick reply! Doing this won't require any kind of recalibration? Can I just bolt it back together once I've had a look?

Have you ever heard of temperature affecting a machine like this before or does it sound crazy to you?

[Steve]

Heat can affect the drives.

Also the motors shown are not as efficient as newer ones which have higher torque. You can identifie the newer ones by the round body.

The motor in the photo has a pully on the end and is connected to another pully on the Ballscrew by a toothed belt.

No calibration is required in the reassembly.

[Steve]

The replacement motor would be a BI00422Z they are available from Denford at around £40 plus P&P

[NylonAdmiral]

Great, thanks for the help. I just had a look inside as previously described and can't see anything obviously wrong, the pulley also seems to turn freely so maybe the "increased resistance because of low temperatures" idea was crazy after all. In the situation I have described, does replacing the motors sound like a sensible course of action? If I order a new motor is it just a case of simply swapping them over? Also how would I go about changing the motor for the Y axis? It doesn't appear to be very accessable...
Thanks again, thats a lot of questions!

[Steve]

Hi,

The new motor is a direct swap for the old one.

The motor is 8 lead and is wired as a 2 A

The connection diagram is attached.