PM-728VT CNC Conversion Instructions

chipinator said:
I haven't found any precision ball screws for this machine that are ground. If anyone finds precision ground ball screws for this machine, I would be interested in receiving that information.
Click to expand...
You will not find ground ball screws that are anywhere close to what you want to spend. For example, the precision ground ball screw for my Sharp mill is $2000, which is ONLY for the x-axis. Generally, for a mill the size of the 728 you would be looking at $1500 for the x-axis and probably $900 for the y-axis. That will get you started.
 
@7milesup Thanks for posting. Ouch! That's a good amount of money that I'm not willing to spend for precision ground ball screws. Maybe I'll just go with what PM is selling and be gentle with them.
 
chipinator said:
@7milesup Thanks for posting. Ouch! That's a good amount of money that I'm not willing to spend for precision ground ball screws. Maybe I'll just go with what PM is selling and be gentle with them.
Click to expand...
As 7milesup stated, ground ball screws are very spendy. The reason I mentioned them was not for durability/strength but precision. Many have the idea that ac servos are more precise, and they can be, but only if they have ground ball screws and Abec 7 super precision support bearings to match. If you have a limited budget as many hobbiest do, your limited to rolled ball screws and abec 3 bearings. Not to mention very few have precision ground spacers between the support bearing. And so your accuracy is limited and therefore why use ac servos over closed loop steppers? Accuracy is only as good as your weakest link.
 
Last edited:
I'm not cheap but I'm not rich either. I would like good accuracy but I don't know how accurate a closed loop stepper motor can be. Anyone have any really good brands/companies for closed loop stepper motors I can research? Of course I'm looking for NEMA23 for the X and Y axis, and NEMA34 for the Z axis with a spring set brake/electronic brake.
 
You might take a look at the Automation Direct LS servo line, comparable to DMM with better documentation and better setup software. I have used these on one project and was happy with the result. https://www.automationdirect.com/selectors/ls-servo

The other option is the slightly more expensive SureServo2 line. I have one of the 7.5kW units on my lathe spindle and am quite happy with it.

I have also used DMM servos on a number of projects, they work OK. A bit of a PITA to tune and adjust. I do have 4 of their 1.8kW units on my lathe.
 
@JimDawson Thank you for the reply. I'll have a look.

Then there's the software option. I have a dedicated computer and monitor specifically for this build. I would like to use a conversational software package, however, I emailed the Mach4 developers and they stated it was not conversational software. Aye yie yie! Anyone know of a good conversational software package I can use as well as use CAD/CAM?
 
chipinator said:
Anyone know of a good conversational software package I can use as well as use CAD/CAM?
Click to expand...
Centroid Acorn Pro version has full conversational programming, in addition to normal G code. And will work with any of the above servos or steppers.

Acorn CNC controller, Step and Direction 4 axis CNC Control board with ethernet communication.DIY CNC kit

Acorn Do-it-Yourself CNC control board for Mills,Lathes,Routers,and other Machine tools. Mach3 replacement CNC controls for new machine tools as well as Retrofits for older NC machinery
www.centroidcnc.com
 
@JimDawson Thanks again for the reply. I appreciate it. Looking back over which motor to use, I looked at the SureServo2 line you suggested. The page for the SureServo2 is asking for Torque Required from the Motor. For a mill such as mine, how much torque would you suggest?
 
You must log in or register to reply here.
Back
Top