Mill Upgrades – Spindle Motor – Part 2

Running into many more roadblocks than expected on this. I missed some critical factors when planning the installation of the original motor and as such had to recut the motor mounting plates (which required reinstalling the original motor and all the head gearing), and I’ve been distracted by working on the air compressor.

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I finally got around to testing the upgrade VFD, only to discover that it’s throwing a ‘low DC bus voltage’ error, which probably means something inside is not working right. I couldn’t get it working again and a replacement is $1k (I paid much less for mine on Ebay, but there don’t seem to be any floating around there now). I confirmed the motor worked with my Huanyang VFD, but I don’t trust one of those enough to make it permanent. Also, the cast iron motor I have is crazy heavy (100 lbs), so both for ease of installation and Z-axis acceleration a lighter motor is a plus.

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I went out and bought a used Baldor EM3610T (3 HP, two pole, 240V, steel banded case) on Ebay, and had to wait a few days to find out which face mounting kit was correct (according to Baldor, the 35-1325GLD, the 35-1325 will work too but the color doesn’t match). Finding C-face kits can be a pain and I strongly suggest you buy a motor which is sold with it already installed, like the CEM3610T.

I also bought an LS (formerly LG) VFD from Wolf Automation. There are a lot of good options for cheap single-phase drives in this horsepower range, including Fuji and Delta.

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The motor and VFD have been tested and are working, just waiting on the face mount to show up. The VFD is currently running the original 1.5 HP motor. Once the new face mount shows up it’ll be time to pull the head back apart and mount the new motor.

Mill Upgrades – Spindle Motor – Part 1

The first order of business is to uninstall the old motor. That’s pretty simple: unscrew the wires in the junction box, pull the four bolts that hold it to the head, and lift it off. At 50 pounds, it’s heavy but not too difficult (note I’m 6’2″ and 230# — possible bias).

While I’ve got the chance, I’m going to pull the gears from the stock drivetrain out of the head. This will remove a little weight (any more weight I can remove is a good thing — the new motor is 100 pounds), but most importantly it will prevent the gears from engaging by accident. It’s also a good opportunity to drain the oil from the head.

Gears and gearbox cover pulled off the mill. The shaft closest to the top is the motor driveshaft, the second on is an intermediary that transfers power to the high/low gear shaft, which is the one laying down. The final shaft is more of a collar that fits onto the spindle.

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Here’s the inside of that shaft. It looks like this part was made by pressing a few separately made parts together, although I’m not 100% sure on that. It’s certainly a complex part, with the internally broached keyways for the spindle spline and two sets of gear teeth.

This could probably be removed at this point, but I left it in since it liked helps to stabilize the spindle. This will be particularly important once the belt drive setup is applying force all the way at the top end of the spindle.

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Here’s the top of the spindle. That cover (covered in oil, with the three screws, around the spindle) is the oil seal, which I’ve left in for now.. I’ve drained most of the oil out at this point (into the pan below the head, somewhat visible).IMG_2493.JPG