[jderou]

200 ipm seems dreadfully slow when in production. I would like to see if I can get this machine in the 400 ipm rapid area. The current setup is Mach4 -- Hicon Integra controller -- Viper 200 servo drives -- Anilam DC servo. I am running about 90vdc on the power supply. I can get up to 250ipm but not as reliably. I am looking to switch to AC servos, possibly something from DMM, but I am finding it difficult to determine what is equivalent to what I have, and what is better.

Current servo specs are:
3.5Nm
140 Max V.
30A Peak
31 in-lbs
6.5 Cur-A
2400 Max RPM

Screw is 5 tpi, pulley ratio is 2:1. This results in .0001" resolution with the current setup.

So, end goal is 400ipm with the same resolution. This is a decent sized bed mill, 7.5hp spindle. 20 x 40 x 20 travels.
Is direct drive an option on the screws?
I would like to start with just the z-axis (biggest bang for the buck).
Thanks!
Joe

[WesM]

90v DC PSU could be an issue. Seems like thats pretty low voltage when your motors can handle 140v and your drives are rated up to 170v.

[Jim Dawson]

I agree with Wes, bump up the voltage to the motors. That will increase the available torque and thus the acceleration. If the motor max RPM is really as stated, then you are limited to 240 IPM because of the 2:1 ratio. If the motors will actually spin faster, the higher voltage should allow that.

A 140VDC power supply is easy to build, you just need a 240/120 x 100V transformer, a bridge rectifier, and a couple of capacitors. A quick ebay search turned up this transformer that should work https://www.ebay.com/itm/Signal-Tran...-/152536683168

I have the same motors on my mill but I limit the rapids to 100 IPM, and I'm operating them at 75V

[jderou]

You are correct, I was mistaken. 90v is on the AC side, which rectified becomes 130vdc. So my actual voltage is 130vdc

[Jim Dawson]

In order to increase your rapid speed, the torque is going to have to increase a lot. The Anilam motors are rated about 900 watts, continuous. About 4200 watts peak power. I can't find any torque curves on those motors to figure out what the peak torque would be.

The problem is that even the motors you have would drive the table to 400 IPM, but it might take 60 inches to accelerate to that speed which of course would not be acceptable. I'm exaggerating here, but you get the idea. The highest power DMM servos should give you better performance, but there don't seem to be any published torque curves to be able to compare those with the existing motors to get an idea of what performance increase you might expect.

[WesM]

Is this what you are looking for Jim? This is from the DMM DST manual.

An interesting exercise would be to use a 1:1 pulley/belt and see how long it actually took to accelerate to 400 IPM. Ramp up acceleration and speed slowly to the 400 IPM, while monitoring your current draw. I suppose once you meet/exceed your continuous current rating (not peak!) you would have maxed out the capacity of your current servos. Without actually doing the math, I suspect you will be basically doubling the torque requirements if you go from a 2:1 to 1:1 pulley. It would be a fairly cheap experiment, since you could grab a pulley from one of your other axis and buy the correctly sized belt for the 1:1 setup. Let the wiser heads around here chime in on that idea though

Not sure what encoders you are using, but any of the DMM servos would probably be a huge resolution upgrade from the motor/encoder standpoint. Your mechanical systems would be the limiting factor.

[Jim Dawson]

Is this what you are looking for Jim? This is from the DMM DST manual.

Yes, thank you

[jderou]

encoders are Renco 1000ppr. So direct drive would only give .0002" resolution, correct?

[Jim Dawson]

encoders are Renco 1000ppr. So direct drive would only give .0002" resolution, correct?

Yes, that is correct.

[jderou]

Think this would do it?
https://www.ebay.com/itm/3-8KW-AC-Se....c100010.m2109

[Jim Dawson]

Maybe, that's a lot of motor. The rated torque is about 4 times the rated torque of your existing motors and the peak torque should be plenty. With a rated RPM of 2500, I would expect the max RPM is 3000 to 3500. The link to the manual seems to be broken. The 2500 line encoder should give you the resolution you need.

[WesM]

I have no experience with those particular chinese servos. Based on past experience with a few chinese steppers/servos though, their documentation and support is nearly non existent. I would be really worried about sending almost $2400 to an unknown entity. If you do run into a problem you have to pay the return shipping (both ways) to get them repaired or replaced, all while having a machine thats not making parts for a few weeks.

Just for reference the Dyna Mechtronics 4400 used Mitsubishi DC servos HA40CS on the X and Y in direct drive config and was supposedly good for 400 ipm

Rated Torque
30.0 kg/cm at stall (2687 oz.in.)
27.2 kg/cm at 1000 RPM
24.4 kg/cm at 2000 RPM
Max. RPM 2000

It used HA80CS on the Z Axis

Rated Torque
60.0 kg/cm at stall (5375 oz.in.)
54.4 kg/cm at 1000 RPM
48.7 kg/cm at 2000 RPM
Max. RPM 2000

Looking at those specs you could probably run the 1.3KW DMM servo on the X and Y and the 1.8KW on the Z and be within a 1.5-2 factor of safety. Its all a guestimate without knowing the weight of your Z/X/Y axis or the live loads put on your machine when running parts.

[jderou]

Good info. That looks like a similar sized machine. I cant tell if the Z-axis is counterbalanced on the 4400, mine is.
Here is a pic of my machine before the retrofit.
Attachment 381902

[Bob La Londe]

What type of work are you doing?

The reason I ask is when I first started CNCing I had a machine that would barely do 20IPM. Eventually I upgraded and adjusted until it would do 80IPM, but on lots of jobs with the small cutter high rpm 3D detail work I was doing it never even got up close to the programmed feed. I backed off the top speed made and made some adjustments to get better acceleration, and my total job times improved dramatically. I also tweaked my programming style to reduce the number and distance of rapids and saw another huge improvement in job time. I did things like program jobs to use 5 or 6 operations instead of one to clear an area more efficiently with fewer rapids. I used mixed milling for roughing, and even for finishing on my better machines, Once I got machines I could trust I used clearance planes only a few hundredths above the work piece. Those all improved performance. Years ago I did a 3D job that was 1.3 million lines of code and it took 30+ hours to machine. (I slept on the floor with the machine running.) I did one a few weeks ago that was 2.3 million lines of code and it took 7.75 hrs. Part of that is due to them being better machines, but most of it is due to using better methods of machining. A significant amount is from better acceleration.

I know. That's not the question you asked. Sorry if its no help.

[jderou]

The parts I am running right now are pretty simple and short cycle. About 8 minutes per part with 5 toolchanges and there are very few gains left to be had in the toolpath. I just recently got an auto toolchanger working, which helps a lot but adds a lot of rapid time. Guesstimate is 2 minutes out of the 8 are in toolchange.

[jderou]

We have a machine here at work that I just did some digging on. It has almost identical castings, it is a milltronics RH20 RH20 | Milltronics USA - Let's Invent. It looks like it is capable of 500ipm x/y and 300ipm z. Got the specs off the Z motor and it is .85kw 7.1A 1500rpm (yaskawa SGMG-09A2ABC). I can't tell the gearing but I would assume 5tpi screw and 1:1 gearing would yield 300ipm. Based on this the 1.3kw servos might be just the ticket. I am going to try and get a look at the x-axis if it isn't hidden.
Side note, why are my belt drives so noisy? They scream at 200ipm, I can't imagine what it would sound like at 400. This milltronics machine appears to have the same setup, but not near the noise.

[Jim Dawson]

''Side note, why are my beltdrives so noisy? They scream at 200ipm, I can't imagine what it would sound like at 400.''

Bearings or maybe over tight?

[WesM]

Look at any support bearings maybe? Bad bearings can make all kinds of noise.


EDIT: Jim was quicker on the draw