Top speed failing after a bit

[Robin Hewitt]

Nothing wrong with a bit of healthy paranoia, so long as you can rise above it

My mill worked at 25mm/s for a couple of parts then failed one lift.

One failure in one axis and I'm seriously considering cutting all axes below 20mm/s forever more. Obviously I think the machine is out to get me.

What I should do is figure out why 25mm/s failed, fix it and go for 30mm/s. :naughty:

[Jonathan]

What I should do is figure out why 25mm/s failed, fix it and go for 30mm/s. :naughty:

Sounds like what I'd do!

After finishing the new frame on my router I started with X and Y on 250mm/s ... which was fine, then X developed a stalling habit so I got the ballnuts better aligned and threadlocked anything in sight. Went down to 200mm/s just to be safe ... couple of months later it randomly stalled so I reduced X again, and again ... now I'm at only 150mm/s.
That's clearly sufficient and I guess it's generally less wear at that speed (the ballnuts will last longer), but I do wonder if it might still go at 250mm/s.

The same was true for my mill - started off fast then decreased. If I put my milling vice on I have to drop the feeds because it's so heavy.

If you really want 25mm/s have you considered changing the pulleys? I did that to the extreme on my router and got 1000mm/s on Y (not tried X yet)...just depends if you can live with a little less resolution. Try it and see? Add about 30% more teeth to the motor pulley.

I'm not sure if the stepper heating affects the torque. The magnetic flux from the permanent magnets will decrease marginally with temperature, but I don't know it the effect is enough to notice without modelling it.

[Robin Hewitt]

If you really want 25mm/s have you considered changing the pulleys? I did that to the extreme on my router and got 1000mm/s on Y (not tried X yet)...just depends if you can live with a little less resolution. Try it and see? Add about 30% more teeth to the motor pulley.

Been there, done that already :naughty:

I quarter step at .005 mm so the positioning is already a bit springy and I can be up to minus 0.01 mm out on a width according Mr Mitutoyo. It never seems to go plus for some reason.

I prefer to call it 0.4 thou, or maybe 10 microns, because that sounds better :whistling:

I gave it a few hours with 15 mm/s rapids yesterday without losing position. Think I will wind it up to 20 mm/s next time I have a job where I am not particularly worried if it goes tits up.