Boxford TCL 125 stepper motors. Worn out?

Hi

I am converting a Boxford TCL 125 to Mach 3. I have got it working but it is losing steps on the Z axis. I have set the motor tuning to a low level, any lower and it wont be usable. Am I better off replacing the motor and controller?

TIA

Cheers Michael

What are the stepper motor specs, what power supply and controller have you got, do the motors get hot in use? There are probably other questions that will need an answer but we need to start somewhere.

Martin

Hi Martin

It has the original motors so around 36 years old. The power supply is 20 volts linear and it has Boxfords own stepper driver. No idea on the specs, I could measure the size of the stepper motors and get an approximation. What I am wondering is do the permanent magnets in the steppers lose their magnetism over time and hence their power.

Cheers Michael

I've a Novamill with original motors that must be the same vintage. I've fitted modern micro step drivers, with a 36 volt PSU, and it works fine. The motors are size 23 on X and y and 34 on z. New steppers are quite cheap and modern drives at a higher voltage probably work much better. You could try new drivers, maybe just on the z axis first and a higher voltage. If the mill is anything like mine replacing the z stepper motor is a real pain, so worth finding an alternative if you can. I have read that old steppers lose magnetism, but as I say mine seem fine.

Hi John

Thanks for that.

The Z motor is the one that suffers from resonance, X seems fine.

It's probably worth biting the bullet now, the heat from the stepper load resistors warms the whole of the back of the machine!

Cheers Michael.

If there is a lot of heat build up then the magnets may be degrading. I think I have seen 70° as the maximum working temperature for some stepper motors. This will be the temperature at which either the insulation starts to degrade or the magnets suffer or any adhesive used in the assembly fails. If the step and direction inputs are easy to connect to I would think about replacing the motor and its power supply. You could also consider a hybrid servo stepper as they can be used like an ordinary stepper motor but can give an error signal if steps are lost. The Leadshine three phase ones give a good torque in a small package but unless you can change the value in the software you need to match the steps per rev to what you already have.

Martin

I presume you've eliminated mechanical issues like lack of lube on the Z slide and screw, or a gib strip too tight or too loose ?

Hi Martin

The heat is from the current limit resistors (old technology). Will be fantastic in winter as a hand warmer.

I have just realised I have a stepper card of modern build driving the tool turret on my ORAC lathe, might just borrow that and see if the resonance and lost steps go away!

Hi David

First thing I did was check and lube everything up. You can turn both axis by hand and they feel free enough.

Cheers Mike.