Centroid Community CNC Support Forum

Encoder and parts can approach $300
Simply belt the encoder to the spindle at 1:1 with a timing belt. The trick is mounting the pulleys and encoder.
I would encourage you to go with a 3 phase inverter duty motor....

Setlab wrote: ↑Fri Oct 30, 2020 7:32 pm ...I do want to use exact speeds/feeds to get out of the just get-er-done good eunouf approach....

Show me where "exact" speeds and feeds are defined. You won't find a consistent value from any of the manufacturers of tooling or machinery. Generally it will come in the form of a wide range of surface speeds for a given material and tool eg "400 - 1000 sfm".

The difference between unloaded and loaded spindle speed with an induction machine is typically only 5% or so. The "more industrial" VFDs allow for some degree of speed compensation with load to make up for this. After all, they know how the motor speed sags with load and can make such compensation. But as I said, there is no operation you will do where the speed is remotely critical. It's called "horses for courses" - think about what you are actually trying to achieve.

There's nothing to stop you fitting a gold plated servo motor and a deadly accurate speed control to your machine. But then you will presumably at some point mount a piece of stock and think about machining it. Does it care how precisely the cutter rpm is controlled? What is this component going into when it's finished?

Hi.

Regards the servo drives.

I have just finished an up grading my hurco CNC Knee mill that has +10/-10v servo drives

It has a Hurco utipath Software on it that I like because it give me a true encoder feed back So i can use it as dro and part manual part cnc.

howere it will not take a Gcode program or work in true 3 axis.

So I got my self an acorn to have a play around with. to get around the driver problem I used
https://www.machdrives.com/

They take a step and direction input along with the encoder on the servo and use this to control the motor position.

mach drives and very cheep for what they do... seam great quality easy to set up with great support.... So I would highly recommend them


So now I have the acorn and original hurco controllers set up side by side and I swap the motor cables from one to the other depending on what controller is best for what I am doing.

good luck with your upgrade

Unfortunately, moving to Acorn you will loose the ability to manually move the machine.

The original poster's machine is purpose built CNC. No manual option.
Machdrives, CNCDRIVE are options. Provided the servo motors are in good condition and they also have proper encoders.
For a machine this small, I would probably just go with closed loop Hybrid Steppers and I think that is what the original poster ordered. Cost effective hybrid closed loop control. The cost of one of the Machdrives or CNCDrives along with new encoders gets very close if not over the cost of the hybrid closed loop solution in my opinion.

Marty

Also, save the drive/motor power supply in the cabinet, measure the DC voltage, you may be able to use it with your new hybrid drives/motors.
Never throw anything away until the conversion is complete and you are satisfied.
Marty

Marty: I didn't realize an encoder was so expensive. As luck would have it, I found a pretty nice wire EDM machine at my local scrap yard and pulled a bunch of useful looking parts off of it last year. I pulled a driver servo motor with this model of encoder on it https://www.ebay.com/itm/HEIDENHAIN-ROT ... SwpsRfj1Jr I have no reason to think it doesn't work, it looks almost brand new. I also got a nice looking tachometer from the same machine, but I don't think I'll need that here.

Definitely will be saving my old stuff and add to my pile of useful looking parts.

Muzzer: That's true, this is the first really nice mill I've used that isn't worn out in some way or another and I can control these details so I guess I'm stuck on the mental notion that I need to use precisely the feeds and speeds of whatever particular calculator I'm using at the time. I think I'm stuck on being 'exact' in everything I can be is because of my underlying goal to build a resume for a mechanical engineering internship and or full-time job when I get done with my mid-life crisis college education lol.

Kcarpenter: Thanks for sharing that much drive link. I'll look into those drives and give the manufacturer a call. My 'old' spindle servo and drive run off a 150-170 vdc power supply and that's been a limiting factor in searching for just a step/direction to the analog controller. If this is a reliable solution this could be the most affordable and least work spindle option I've seen yet. For my 3 axis, I ordered closed-loop stepper kits from stepper online. For a little bit over $300 for drivers and motors, it seemed like a really good solution.

Search for 5VDC Line Driver Differential encoders at automationdirect.com. 1000ppr is OK
Example:
https://www.automationdirect.com/adc/sh ... 0r1n1000vd