[Biermann]

I am looking to convert a 1960's Clausing 8520 knee-mill as well as a Clausing 11x30" later model ~90's lathe (actually a re-branded Harrison M250). Both machines never saw any heavy use so they are in very good condition. Originally I had bought a pair of closeout Anilam (Acur-Rite) DRO's for them, and then after looking around found out that I could CNC them for not much more money.

Therefore I have been reading all I can this last week but still have some lingering questions. I have decided to start with the mill. So far I have purchased a Gecko G540, a copy of Mach3, and a IP67 stepper, that will eventually power the knee, so I can start playing around while I acquire/build the rest of the parts. These are just home shop machines and I am looking to hold a thousandth accuracy if at all possible without dumping a bunch of money into them.

On to the questions.

Screws & Backlash:
Does Mach3 compensate for backlash or should I look at replacing the screws. The mill with current original screws have 0.006" lash in XY and .010" in Z. The screws are 7/8-10 on XZ and 11/16-10 Y. Since these are not common sizes I cannot easily pick-up some anti-backlash nuts. If I need to replace the screws should I use 16mm and 20mm ball-screw, or for non-production just stick with new Acme? If ball screw, what is the cheapest source for screws that will hold a thousandth, do I need a single-nut, double-nut pre-loaded?


Retaining manual control:
I want to keep manual control fro both machines. If I keep the original screws on the mill I can power the X from one side as I don't need a handweel on both ends since the table is small. On the Z I should be able to get a pulley/gear in on the crank shaft or the actual screw. However on Y it will have be on to be adapted to the crank shaft. So in this case I can either direct couple a double ended motor and then re-attach the crank to the motor-back-end. Or run a pulley and possibly put a handle on the remaing motor shaft. Or then of course I can replace the screw and machien the shaft to fit the pulley and handle. What are your suggestions?

DRO use:
I have read it is possible to use encoders to feed back position to Mach3 so you can use it as a DRO. If I am able to do this I can scrap the dial on my current Y-axis to fit a pulley, and also use screws with alternate leads without issue. Currently which is the most bullet proof method to accomplish this. I have seen the RogersMachine BOB mentioned, will this interface with the G540, or just run along side it. What other BOB's or drives feedback encoder position to Mach3. Is it ultimately cheaper just to use servo motor's and drives instead of stepper and adding boards and encoders? If so which would you recommend for the most complete package.

Maintaining Position:
Is the only way to maintain position during a cycle stop or between operations by using encoders and a feedback board. If so which is the best setup to do this. Is it possible to use encoder positioning to maintain travel limits or do you have to use limit switches etc. If limit switches are required does the G540 have I/O's for this or do I need an additional BOB to add enough channels.

BOB's and PLC's:
For oher PLC and control I have built I am used to 24V, is there any BOB's that run 24V control or are they all 5V. It seems some are hybrid with combo 5V with some 24V I/O's. CNC4PC seems to have a ton of different crap some with RJ-45, some not, and their website is not informative with simple lists of how many channels, how many I/O's etc. that I have found. If I want to make a control panel/pendant with jogging, coolant, cycle stop, e-stop, etc. what is there a quality BOB that has a bunch of analog and digital I/O's without having to add further daughter boards? If not is there a PLC that people are using that already has a script for Modbus com's with Mach, as admittedly coding is not my strong suit.

Motor's, Drives and Gears:
How do the (I assume Chinese) drives from Keling etc. compare with the Gecko's. Is the new Keling digital drives a true adavntage? Is the wide variety of stepping setting and logic take the place of the smooth stepper? Regarding motor's how do the Keling (insert other import brand) drives compare to the Oriental Motor Vextra or the Gecko Lin motors. Not all models have torque graphs so i figure those are not as linear?? For the lathe I am contemplating using Servo's, which are currently the best bang for the buck, Gecko 320X's with DC, DMM AC, Dugong drives and xxxx? On the mill the knee plus table is probaly 120lbs, with a 3:1 or 4:1 reduction and the considering the low efficiency of the current screws what amount of motor torque should I shoot for. I am not looking for any crazy IPM, especially on the Z. Lastly, regarding gearing, will standard .200" pitch x 3/8" belt suffice for the mill, or should I look for a wider/finer setup? Currently I was planning to just order stuff from Stock Drive, is there any better quality/precision brands or is it all pretty much equal?

Well that about covers all the stuff that currently comes to mind, any help would be greatly appreciate as I am anxious to get the remainder of figured and the parts ordered while I have the free time to retro-fit these machines.

Thank you for your help.

[ptk28164]

how are you doing with the mill?