Grizzly G0602 10x22 Lathe Conversion

[Steelpolish]

Hello Everyone -

I am new to this forum, but after looking around I decided to convert a lathe to cnc control. I need a small lathe for semi-production work, so I choose a Grizzly G0602 lathe to convert. My plans are to convert it to ball screws, three phase variable speed spindle, and an automatic tool changer turret. Mach3 is what I am going to use to control it all.

Here are some pictures of the new lathe:

[Steelpolish]

Electronics I am using:

Xylotex Drive Board

(2) 425 oz.in. Nema 23 Stepper Motors

PMDX-122 Break-Out Board

PMDX-171 Hall Effect Sensor (for spindle index)

CNC4PC C6 Variable speed control

Fuji AF-300 Mini Variable Frequency Drive

Dayton 3 phase Motor

I got everything wired up and tested on the bench today. It all seems to work good. Next is mounting the motor and waiting for my ball screws to come in

[yantra3d]

Looks like you are already off to a great start... Those are some nice quality parts and a great machine choice to boot. Good luck with everything and thanks for posting!

[Steelpolish]

Today I installed the 3 phase motor, and started to calibrate the spindle index signal. The signal is within 25 rpm of the called for rpm from Mach3 - Does anybody know if this is close enough for accurate cnc threading?

My ball screws came in today, so hopefully I will get those installed soon.

Work has started on the turret changer based on the design posted elsewhere on this forum. I am using a hirth type of coupler instead of dowels however. Enclosed pics are of the progress.

[SpeedsCustom]

Yes, I like this thread already! Keep it coming!!!!

[RotarySMP]

Nice start. I have been eyeing up once of these lathes also. Can you fit the Z motor within that threading gearbox housing?

What space is available under the cross slide for a backlash free X axis ball nut? On my 7X1 2conversion, I have a little Roton ball screw for X, but haven't installed it cause I'd need a second nut and anti backlash widgit, and dont have space for them.

The commanded RPM is not used for threading in Mach 3 (or EMC, or TCNC), and would not be accurate enough for threading with these low powered machines.

For threading, Mach will read the spindle index pulse, and thus know the actual RPM. It then adjusts the the Z axis speed each time the indexer pulses to maintain sync .

You can increase the resolution by providing multiple pulses per rotation, as long as one pulse is twice as long as the others, and a minimum pulse width is maintained, then Mach works out for itself how many pulses per rev it is getting.

Mach has a speed correction (look up table ) function where you tell it the actual speed verses commanded speed for four speeds per pulley setting. Say 200 RPM commanded gives 220, Mach then interprets an S200 like a S180 so that the actual speed is set about 200. It interpolates within the speed range.

[Crevice Reamer]

Hi Steelpolish. Welcome to the Zone!

Congratulations on choosing a good lathe. You seem to have a lot to contribute, and I'm looking forward to following your build.

I have one reservation though--Your choice of driver/motors. The Xylotex will not hold up to any kind of production use, and the 91V 425s are seriously underpowered at 24V. My choice would have been G540 (Which has the C6 function & charge pump built-in and is unkillable), Keling 381s and 48V PSU.

When the Xylotex dies, get the G540. That and a 48V PSU will allow your 425s to work a little better.

CR.

[Steelpolish]

There is not enough room in the gearcase housing to mount a stepper motor unless you do quite a bit of modification inside of it. You would have to shave off the center casting that hold the gear shafts, and bore into the casting about 1/4 of an inch to fit the motor.

The space under the x cross slide is 1.16" wide x 1.08" high. I am planning on shaving a bit from my ballnut to fit it in.

My question on the spindle index is its bouncing around a little bit. When I command it to spin at say 750 rpm, the actual speed will show 745 - 760 and bounce between those numbers a bit. It will never at any speed show a single constant number. Is this normal, or should it show a constant number all of the time?

[RotarySMP]

Thanks for the reply on the gearbox housing and X ball nut space. What ball screws have you chosen?

I use Turbocnc, any my knowledge of Mach is theoretic, as I have been considering changing to it.

Having RPM fluctuations within a 2% band does not sound to me like it is a problem. It will depend on what you are trying to make, but I doubt that a <2% error on a thread will be noticeable for most practical applications.

If you try to make a 4 foot long lead screw for an telescope mirror polishing machine, then it is probably unacceptable.

[Steelpolish]

Yes, I am a bit worried about the quality of the Xylotex driver. I might be switching to some 350 oz servo motors driven by Gecko G320's. I have two other mills using steppers, and I am liking the idea of a closed feedback setup using encoders for this lathe. We shall see........

[Steelpolish]

I am using the 20mm ballscrew for the z axis, and the 16mm for the x axis purchased from homeshopcnc.com. They seem to be good quality.

I was hoping the threading will be accurate enough. My main threading is 3/4 x 10 tpi, which is a pretty forgiving pitch size.

A telescope mirror polishing machine? You never know...... LOL!

[RotarySMP]

I like the work you are doing on that turret. Keep the great photos coming.