[syn08]

I plan to replace my Taig mill motor and headstock with a VFD.

The VFD is an air cooled 1.5kW square VFD and needs a dovetail mount to fit in the Z axis dovetail plate. I did some rough measurements (don't have a digital protractor) on the headstock plate and got an odd number of 53 and something degrees, so most likely it's gonna be hard to find a dovetail cutter to fit.

I'm planning to mill the dovetail mount in the vise, with the angle set via angle blocks. Does anybody knows the exact angle for the headstock dovetail plate?

Thanks,

[syn08]

Thank you to all that replied. For whatever (unknown) reasons, none of the posts are displayed here (I got them via email, unfortunately without attachments).

Meantime, I did my own precision measurements. The Taig mill headstock dovetail (that I was trying to reproduce for the new VFD spindle mount) angle is 50.7 degrees, +/-1 degree tolerance is perfectly fine.

I machined the new mount out of 1/2" 6061 aluminum plate (not an easy task without a sine vise, or a dedicated dovetail mill, which I don't have) by using a standard precision vise, an angle block set to define the angle, and some geometry calculations. I targeted at 50 degrees and got it right on spot.

The VFD air cooled spindle is now happily spinning on the Taig mill. The runout is better than 1 mil. I can post pictures is anybody is interested.

[BAMCNC.COM]

I am! We all love pictures!

[voere]

Me too

[syn08]

- The left side (fixed) dovetail clamp
- The right side (adjustable) dovetail clamp
- A view from the top
- The Taig mill with the new spindle

The VFD is hosted in the same housing (it's a standard Al enclosure, available from many CNC parts providers) with the G540, a MeanWell 48V/10Amps power supply brick and two output relays (240V/10A). Output #1 is currently used for the spindle on/off (a much smaller relay would actually work well here), Output #2 relay feeds 220V to the backpanel extra mains jack (for future developments).

Wiring is critical, needs shielded cables for the control part and a good star grounding. Otherwise, nothing outstanding, it should work right away. I can now control the spindle from the G-Code and have 1.5kW of power. This spindle is not recommended for anything beyond aluminum, brass, copper and similar. For mild steel, the old Taig 1/4HP motor and the standard headstock can be reinstalled in 15 minutes, absolutely no changes were made to the Taig mill itself.

[JohnLucas]

Why do you have to go back to the 1/4HP motor for steel? 1.5Kw is about 2HP or 8 times the original motor's power?

[Jeff-Birt]

Spindle motors liek he is using are not made for cutting steel. If you try it you will quickly trash the spindle.

[syn08]

Spindle motors liek he is using are not made for cutting steel. If you try it you will quickly trash the spindle.

Yep. Also steel needs rather low RPMs ( <2k ), where VFD spindles usually don't work properly (minimum RPM for good torque is usually ~6k), while aluminum needs rather high RPMs ( >10k ), usually to high for AC motors + pulley.

A feed and speed calculator will tell the story about steel vs. aluminum.

[JohnLucas]

Thanks. It's a good day when I learn something new.