WM18 - Z Axis power feed

I was going to suggest it might be the current settings. Stepper motors are current driven, more voltage has the potential to make them go faster but care then has to be taken to limit the current to keep the motor within operating temperature. The switch settings tell the controller to throttle the current to suit the size of motor connected.

The Motor is rated 2.8A per phase so the controller should be operating at the high current end, I'd be tempted to try it on the maximum setting (3A RMS) :

I put the arrow the image on before seeing PetrolHead's edit in case he hadn't spotted the DIP switches tucked away between the terminal blocks. He has...

Dave

Thinking about it, that's true, the Z axis is a bit harder to move than the X axis - I must have wrongly assumed they required similar force. I'm sorry for misleading you.

Did you manage to make it move with 2.8A?

At either 2.8a, 3.1 or 3.7 its truggles at the top end with the jibs loosened off.

So I am going to see if they will swap the motor for me.

I'll send you the bill Chris

What do you mean by 'top end'? At high speed ( top end of) or top end of the column? Where on the column's height should make no difference, unless there is binding at the top and not lower down. You may need to do some setting up and move the axis only with the handwheel ( stepper mechanically disconnected) so you can feel if the movement is smooth up and down - I would suggest you try achieve that first, regardless of the torque of the chosen motor..

That motor should be able to move the axis downwards with repeatable ease and if not, there must be some binding somewhere.

The Oscilloscope - I would have liked to see the width of the step pulse from the PWM generator to the stepper driver - the driver normally requires a certain minimum width and nowhere can I find what the pulse width is of that PWM generator that you have. However, if this is a problem, it normally manifests as lost pulses, which may or may not be part of the problem you experience.

A larger stepper needed , I think...

Joe

Oh no! Looking at your photo showing the stepper on the column and noticed it's a fair bit short compared to the one I have. Checked mine and it's a 3NM NEMA 23...I need to go hide for a while - I'm really sorry!

Down in the workshop, I took a spring scale and measured the force required to move the handwheels on the Z and X axes. The Z axis requires 1.8kg force to break away and around 1.6kg force to rotate the wheel. The X axis on the other hand requires 0.8kg force to break away and around 0.6kg force to rotate the wheel.

With a wheel radius of 5.5cm this gives a torque of 1Nm for the Z axis and 0.45Nm for the X axis. So in theory the 1.9Nm motor should work - but that's just the theory!

Top end of the column :0

Is this any help: Frequency: High: 5.8KHZ-127KHZ, Mid: 590HZ-15.8KHZ, Low: 82HZ-2.3KHZ

Aggggggggggggggggggggggggggggggggggggggggggg, FFS!

You are in the dog house!

I cant send the motor back becuase I shortened the wires

For sizing the motor, here's what it look to overcome stiction and lift my WM18's head:

A weight of 6.5kg suspended from the manual winding handle was necessary to get movement. The handle is 55mm from the axle. 6.5kg is approximately 64N.

T = 0.055m x 64N = 3.52Nm

The handle turns the screw via 1:1 gearing.

Th e measurement confirms the 1.9Nm motor recommended by Chris is too small and a 3 to 4Nm motor as recommended by Joe is in the right ball-park. Not sure how typical my WM18 is: certainly raising the head is hard work!  Given my figures a 4Nm motor would be needed for my WM18.

As my maths is awful, grateful for corrections...

Dave

Edited By SillyOldDuffer on 06/08/2019 16:25:33

Probably wrong, but not necessarily insurmountable. Might just need some extra balancing forces to reduce the effective weight of the head

My WM14 is quite heavy to lift the head. I saw that Andrew Whale has fitted a gas strut to assist on his Sieg Mill. Is this an option on the WM18?

My WM18 has the gas strut and was std

Thanks for that. Does your WM18 have the gas strut

No, not really. Its the width of the actual pulse that is of interest, but I think safely ignored with your other findings..The motor is just a little on the small side..A pity your are so far away - I have many steppers languishing and would be happy to donate! Problem is shipping from Namibia is twice, or more, the Ebay cost for 4NM motor!

You can always use that motor on the x axis now..

Joe

Wow! Are you sure you have a gas strut on your WM18 petrolhead? I mean no wonder you want a power assistance with 6.5kg force to move the head. I have checked mine and it's not more than 2kg to break away. Can someone else with a similar mill check as well please?

If you can't send the motor back, maybe you can use a different mounting setup? Say with a belt, and use a reduction to gain a mechanical advantage?

Trying to somehow redeem myself....🤔

No such luxuries on my machine. If a strut were fitted, I'm sure less weight would be needed to move the head!

There's distinct stiction on my Z-movement and once the head is moving it needs noticeably less torque to keep going. Trouble is the motor has to be big enough to get the head moving from a dead stop.

Dave

I have the Warco one, however the motor has now stopped working, so in the bin it goes

My WM18 has the gas strut, had to reinstall it when I assembled the machine in the hut.

It was SillyOldDuffer's machine that needed 6.6kg as his does not have the gas strut

You will have to try harder than that

Edited By petro1head on 06/08/2019 17:54:04

Progress report. Yeh it a slow progress due let downs by ebay suppliers

I ordered the replacement 3Nm motor which arrives within 2 days, well done EU Stepperonline

Control box is built, wiring done.

I have one question re limit switches. I have one at the top but unsure where or even if, the lower should go. My thinking is depending what I am doing the lower stop will never be in the right place?

I have completed my project. Thanks for the great input guys

Edited By petro1head on 10/08/2019 20:10:30

Will it move slowly enough to power feed while cutting?