[kn6za]

Removed the old encoder from the servo and got the new one adapted to the shaft.


The old one is a 200 line low resolution metal disk unit. I want a 2000 line encoder, so I went with the us digital HEDS style units. Conversion was pretty strait forward, I drilled and tapped 4-40 threads to hold the HEDS module to the back of the motor, and turned some press fit delrin disks to pinch the encoder disk to the shaft. Time will tell if this method of fixing the disk to the shaft will work long term, but seems like a solid connection with little axial or radial run out.

The math on the resolution will be 2000 line x 4 in quadrature = 8000

2:1 belt drive servo to ball screw 8000 *2 = 16000

5mm ballscrew lead = .1968" or 5.081 turns / inch for 16000 * 5.081 = 81296 encoder counts per inch.

This gives a design resolution of 1 / 81296 = .0000123007"

The motors are 170w 2600 rpm at 32volt no load. I will be using a 48 volt axis drive power supply to start out with. This will give approx ~3900 rpm no load speed. 300 ipm is my target rapid speed on this machine, and with a no load top rpm on the motor of 383 ipm, I think this will be a stretch, but a 60volt power supply can be obtained if necessary. The 48volt is what I have, so I will start there.

[DICKEYBIRD]

Very interesting Andrew; looks like you have a strong electronics background. Please keep posting & I'll keep learning.

Your project is coming along very well!

[kn6za]

Thanks Dickeybird!

So Far, so good. Its been fun too.

[kn6za]

Ok, so I have done some more work on the cross slide. Cutting down the linear rails to fit the carriage was tough! I used an abrasive cutoff wheel in my circular hand saw. Not sure if there was a better way to cut those things or not, but considering how hard they were, I could not think of any other way. The rails mounted up very nicely to the top of the carriage and the cross slide moves like the Z axis, very smooth! The servos are mounted up with 1/4" aluminum angle motor mounts.

I checked and rechecked how square the machine work was done to the carriage, as the machine work on the bottom relative to the top will determine how square the x and z axis are to each other. Now that the cross slide is assembled, mounting a machinist square to the cross slide and indicating the travel revealed about .0005" deflection in 5" of cross slide travel. Im happy with that!

I got more work done on the enclosure too. I wanted the section of the machine enclosure that covers the lathe work envelope to be removable for maintenance, or what ever? This part went well and I got some sheet metal applied to the outside of the removable enclosure section, and the internal sheet metal way covers put on. Way covers are all 1/8" alum plate.

Still needs a door and door track installed on the enclosure cover.

The block that is on the cross slide in the photo will be the tool changer base, but for now its a solid piece of fortal aluminum.

I also stated machining the operator panel. Not sure how to engrave the nomenclature of the respective buttons yet. I don't have a cnc machine large enough to mount the operator panel so direct engraving of the panel will not be an option.