And so it begins, new PM-30MV...

I'm thinking run the stepper servo motors via a driver in the interim with something like this:

Stepper Motor Pulse Signal Generator |

High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components.
www.automationtechnologiesinc.com www.automationtechnologiesinc.com
 
I have had a PM-30MV for about a year now (did buy the x-axis drive with it). Thinking of CNC'ing next year. But latest project drove me crazy with the manual z-axis. Going to get a closed loop stepper kit from Stepperonline and control it with a simple Arduino for now. Then when I CNC I will have the motor, driver and power supply for the z-axis already purchased.
 
I have a PM-30MV also and do not really plan on cnc in the near future but got tired of cranking the Z axis up and down. The handle is so high up that you have to reach to crank it and it is hard to see where it is. You have to stop and look and crank some more, look some more etc.

I threw together a Z axis lift and feed from mostly parts I had laying around, borrowing the idea from a fellow PM-30 owner. I used a wiper motor and a voltage supply and speed controller that allows slow enough speeds to bore with and fast enough speeds to aid in tool changes.

I made it to disengage if desired and return to the original handle and design, but I rarely disengage it as it is so handy and controllable. You can set up for tool changes or clean chips up, or whatever while the head is moving to it's next spot. I don't know how i survived without it now that I have it. I highly recommend a motorized Z axis in whatever design you care to use.
 

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sdavilla said:
I figure at least $2500 for ball-screws/mounts and motors. That's with AC Servos.
Click to expand...

So ive gotten this question a lot about closed loop steppers vs ac servos. and my advice is if you are keeping your spindle stock (not going to upgrade the motor and bearings) is to just save the money and get closed loop steppers. here are some numbers instead of just reading the pro-con fact charts to help make my position more understandable.

If you check the pull out torque of stepperonline's 4.8 Nm closed loop stepper, at 600 RPM there is still 2.4ish Nm of torque left before it will start skipping. as for holding torque, there are some losses with microstepping but with a 1/2 microstep you get 70% of that available 4.8Nm and will still have a theoretical resolution of .0005".

At 600 RPM with a 5mm pitch ball screw, it will translate the table just over 118 IPM. With my PM30 conversion I find that I am limited by spindle speed, not the table speed.

The big benefit of a servo over a closed loop stepper is having torque torque at high RPMs. But if you never use those high RPMs besides for stupid fast rapids (3000 RPM rated servo would be 590 IPM which is scary fast for a machine this size) is the cost worth it when you can better spend it other toys? I cant answer that for you, but these are some numbers to think about while making your decision.
 
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Decided AC Servos were way overkill. For the price of one axis for an AC Servo, I can do all three with closed loop stepper. Ordered one to play with. But first puzzle to solve. For Z, motor on top, coupler with 14mm keyed motor shaft, threaded M16 x 1.5 on other side. Idea is remove 1st retaining nut, lower hub screws in place of it. Seems simple but I don't have much threaded shaft there. My general rule of thumb is one diameter of threads and life is good. This looks like about 1/4 diameter which starts me twitching. :)

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Here's a picture I found searching around. Note how much thread is sticking past the top retaining nut.

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Grrrrr.
 
While I think about how to solve the ^^ problem, the obligatory pict of a motor spinning blue tape. :)

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Dirt simple. Just love the Preciva wire crimps. Keeps things nice and clean and oh so easy to daisy-chain.
 
While that 1xD for thread engagement is nice, this should not see any tensile or comprehensive stresses. You are using the clamping ability of the coupler so it doesn't need to resist those axial forces. I wish I still remembered how to rough estimate the clamping force, but I've been doing project management work too much these days, and not much real engineering... Hopefully someone else could add that info for me.

It's hard to tell how much length you have, but a 16mm diameter would give a considerable amount of clamping area with what would seem like not much length.

If you are sticking with the lead screw that it came with, honestly I see you swapping that out in no time once you realize how much backlash compensation you will have to use with the slop in those screws.
 
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Well, that was easy. 1/2 inch steel plate with course 1/2 inch HSS end mill. Took it easy on DOC but could have eaten much more.

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