Schaublin 125-CNC retrofit.

And another thing...

Even if your Boley is a little light for big poly-v pulleys, your Maho sure ain't.  Add a chuck or mandrel to the horizontal spindle, clamp a tool in the vise, and pop out a couple of pulleys CNC-style.

The tricky bit is getting the 40 degree cutter to match the belt profile.  Iscar and others sell poly-v specific inserts, but you could always fiddle around with an HSS threading bit to get the angles good enough.

Fabbing the pulleys on the Maho should make the Schaublin jealous enough it'll reassemble itself in an attempt to regain Alpha-Lathe status.

-R

I already bought one, and it is shipping. Thanks for adding clarity Ralph.
Mark

Pulleys you get usually for a reasonable price. I bought them for my lathe conversion als well.

It’s a great thread here. I didn’t know about line reactors (Netzdrossel in German) I’ll get one for my lathe. Though I will still limit the range from 30 to 50hz cause the main Schaft also Runs the Pump for the hydraulic clutches.

Have you considered using a manual switch to chose between the the two windings? Or two modern 24v contractors or a „wendeschütz“ they are way smaller then they used to be.

But, but, but, the variator is so cool, why replace it even if the original motor breaks? I think you owe it to this machine, and its creators, to keep it in.

RotarySMP wrote:

It will be interesting whether i can come up with a sensible control logic for VFD + CVT + Back gear. If I only do VFD + Back gear, guys like Andy have already written the comp.

For the control logic, perhaps something like this would work:

1) Aim to keep the motor speed as high as possible, to maximize power.
2) Use the variator as much as possible since it can set the reduction while running (and only while running?).
3) "Manually" set the gearbox to the lower speed range, only if you need the torque (or if you know the next cut will use only very low spindle speeds). How is the gearbox controlled? Either use some special codes in the G-code to engage/release it; set it using a "software switch", or use an electrical switch and feedback its setting into LinuxCNC.
4) Finally use the VFD and the feedback from the spindle to get to the target speed.

This maximizes the use of the gearing during constant surface velocity cuts.

I'm assuming here that there is no way to get LinuxCNC to report the spindle speed range needed during "the next cut". If there is, then you could of course automate the gearbox too.

Thanks guys.

As long as the current motor is in there, the CVT will stay. If that motor dies, I'd have to replace the CVT, as that original motor has an extended length shaft for it.
Making a tool to cut the poly-vee groves is no problem, that is what the Clarkson is for. Actually I already made one for the Poly-Vee of the mini lathe.

Good points.  I'd forgotten that the CVT can only change gear whill running. That will complicate the control logic a bit.
The back gear is pneumatically actuated, and will be controlled though the Festo CPV and 7i84.

I dont see any point further complicating it with the two additional contactors necessary to bring in the 8 pole windings. Whether the motor runs at half frequency or on 8 poles, the speed is the same and the power is approx halved right? I dont have space for those contactors, and would be nearly guranteed to blow up the VFD by swithcing it's output by mistake.

I need to look at Andy's back gear + VFD to see how he inhibits back gear selection during CSS cuts.
Mark

Hi Mark
Have been enjoying your new conversion journey , and a big thank you for all the videos an discussions .
Wondered if you have considered space requirement  of a VFD with output -input filters + external resistor .  Input filter to keep family an neighbors happy when Dad is in the basement .  CSS turning may exceed the VFDs speed drop duty cycle thus requiring a external  load dump resistor + fan .
My thinking is that a external VFD power supply could be a multi use feature, but it is your Schaublin sand box .
Bob

 

Hi Bob,
Indeed I haven't considered the space for an input filter. I am adding an output  line reactor based on Ralphs suggestion. Might have space for an input filter beside it.

Braking resisters are only necessary if you use the VFD for braking, an I have an electro mechanical brake in the gearbox for that. While theoretically you could need a braking resister if doing a CSS outwards cut, fast enough that the cutting forces are insufficient to act as the braking load, I think that is a somewhat unlikely case in my home shop. I will never run this machine anywhere near the performance limits, as I dont have production pressure.

Mark
 

Less done this week than hoped, but enough for a short video update...


Mark

In the comments section to this video I am getting a few comments like...

The line reactor is for the input side of the VFD to improve its powerfactor. For the output you will need a LC-filter also called Sinusfilter or dU dT filter. A reactor alone will do almost nothing to flatten out the PWM voltage spikes of the VFD.
or
A line reactor is not the suitable device for that. Thats why its called a line reactor, it is for the mains side of the VFD to improve its power factor. For the motor side you want to use a LC filter often times called a sine wave filter. They will smooth out the PWM mess coming out of the VFD to a sinusoidal voltage and protecting the windings.