[rcpilot82]

I recently converted my Bridgeport clone (Enco) Mill to CNC. I am using DMM Servos and their DYN4 Drives. I started with a .75KW servo and when that didn't work we went to a 1.3KW (over 3000in lb ) and it is not working either.

The z axis is set up with a 18 tooth pulley on the motor and a 40 tooth pulley on the quill. I have enough power to do plastic and light aluminum, but can not even drill steel without tripping the servo.

Can anyone please let me know what they are using for a Z axis quill setup and help me diagnose my problem.

Thanks,

Rob

[rcpilot82]

bump

[hanermo]

Its the wrong way to do it .. and wont work.
(Yes I tried it).

You need about a hands strength, vertical pull, on the quill handle, say 10-15 kgf force.
The pulleys you are using are (99.x% likely) no-where near strong enough to support this force.

Even large pulleys on industrial-type stuff, will be marginal (at zero rpm !).
Large pulleys, like I use on my lathe, are HTD8-30 mm wide - probably 10-15 x more rigid than what you are using.
(Mine supports 2.5 kW continuous power, and 90 Nm peak torque (at rest) via 72 teeth pulley, HTD8-30-72).

Looking at the technical data ie tables, max power (=> torque) is very low at zero rpm, which is effectively what you have.
Eg. HTD-5, 9 mm wide, at zero rpm, is about 10W of power transmitted, and this is about .5 kgf or less of pull on a 100 mm (long arm) pulley. Ie about 10-20x too little (radius 100 mm is probably much more than what you have on your pulley).

Options:
Gears (can do 10-100x more torque at 0 rpm), or a worm drive, will work fine.

I went to a VMC, and the whole bridge goes up/down, mass == 800 kg.
A small 400W servo is plenty (over 100 kgf vertical force from servo).

[rcpilot82]

Thanks for the post. I understand what you are saying but most of the conversions ( see flashcut CNCs conversion they sell) is set up the same way mine is. My X and Y axis are set up similarly with no issues so far. The belt is 3/4" wide also and the pulleys are L series as I have seen in most conversions.

See here at 13:15, This is pretty much what I have. https://www.youtube.com/watch?v=6b0Jf-xzE0s

Thanks,
Rob

[bhurts]

Without seeing what you have actually done it's impossible to guess what your issues may be. Did you connect to the down feed worm drive like they did in the video? Have you made sure the quill lock is loose and the quill moves freely by hand?

Ben

[rcpilot82]

Ben,

Yes, I am connected to the down feed worm drive as they show. My quill can be moved by one finger in "manual" mode so there is not a drag issue.

Attached are some pics of my setup. These are from when I had the smaller .75 kw servo installed with a 10 tooth pulley. as you can see it is very similar to the flashcut setup.

[bhurts]

Is the feed selector disengaged/diassasembled like they show?

Ben

[rcpilot82]

It is not disassembled but yes, it is disengaged. The z axis can be moved with one finger through the motions.

[hanermo]

Ok .. now I see .. and its different to what I thought.

If you are actually driving the worm drive, it definitely must work .. or something is wrong.
Also..
Your belts are pretty good/rigid/strong (L is quite rigid (less accurate, but that should not matter for this app)).

Can you move the z by twisting with fingers from the pulley ? Sure (all positions ? No binding?).

If you can, I think it must be a servo (setup ?) problem.

(I originally thought you were driving the quill directly, without a worm gear in motoin control train).

[rcpilot82]

Yes I am driving the worm. I can move the pulley with one finger as well so binding is not an issue. I am really stumped by this, as is DMM.

[rcpilot82]

Still trying to figure this out. Here are 2 videos showing what's happening. Note: the DRO in mach is not calibrated in the video.

https://www.youtube.com/watch?v=UrHreApeeeo

https://www.youtube.com/watch?v=X2uMrzQv1dk

[hanermo]

An idea.
Disconnect belt.

Try stopiing the motor by hand, when jogging..

[gus]

A stock bridgeport cnc has a motor 3 times the size although not sure the rating, and it drives through a ~.200 pitch ballscrew, so for every revolution of the motor it is dropping the quill .200" I think your mechanical advantage is too low.

[gus]

BTW my old Wells drove the quill pinion, and it had a special setup to eliminate back lash, complete crap way to drive the z. Only ever used the machine for hole drilling.....

[rcpilot82]

Any ideas for a different pulley or gear reduction system that wont cost me my soul?

[rcpilot82]

The smaller motor I have is a NEMA 34 size

[WilliamT4450]

RCPilot

Good job with the video. I watched it a number of times; very informative.

Because you can move the quill handle up and down easily with one finger, and because you can move the outboard pulley easily with one finger too, says a lot.
It shows that you have no interference in the head of the machine; that the quill runs true in the bore, and that the Quill pinion shaft runs true and the balance spring is adjusted properly. Absolutely no need to investigate this further.

I see the fault 'High Temp' displayed on the DYN4AC Servo Drive page; I suspect this is part of the motor setup. Since the fault is logged on the DYN4AC page and passed over to Mach3 to interrupt the reset, I would not look at Mach3 for a solution.

The Quill pinion from the motor perspective sees the lightest load. It has to lift the Quill and Spindle assembly which weighs approximately 20lbs. The Quill Pinion is assisted by the Quill clock spring to offset some of the dead weight for operator comfort. Without a doubt, the Quill Pinion has the lightest load. I'm not talking cutting forces here; just mechanical load of the machine to move the axis.

Consider the X and Y Axis. The X axis drive motor reacts against the weight of the table, well over 200 lbs, and the Y axis reacts against the weight of the table plus the weight of the saddle; in all pushing 275 to 300 lbs, or more. Granted, the ways are lubricated, but the motor must produce break away torque to move this massive amount of iron.... Your X and Y axis have no problems. Your Z Axis is a fraction of this!

Pilot, I would not purchase any more equipment. Your NEMA 34 servo motor has more than enough power to move any one of the axis, X, Y or Z all day long without interruption. You've already proved this to be true with you own X and Y axis, as you have no problem with them. Likewise, a number of Bridgeport/Clone conversions on CNCZone support this as well. One here in the Metal Cutting Forum built a FlashCut style Z Axis and others have built the Elrod style Z Axis. Some have used 1:1 ratio, some have used 2:1 ratio, and others have used 2.5:1 ratio. They all work well.

You have changed the motor, increased from .75KW to 1.0KW,(approximately) but the problem persist. You must consider, 'Why does the motor set a 'High Temp' fault before the 'Torque Limit' is achieved? Torque and Heat are synonymous; they move somewhat together. But in real motor applications the Torque limit is set at a point where the motor does not overheat. Your fault is 'High Temp' not 'Torque'. Another reason for 'High Temp', low voltage? But for the moment I believe the motor is good and your new controller is also good.

Troubleshooting time!! This is where I would start.

1) Apply one of the other motor configurations to the Z-Axis motor. Calibrate the Z-Axis distance in Mach3 as done before. Retest the motor.
2) Swap one of the other data cables with the Z Axis cable. Retest the motor.
3) Swap one of the other controllers with the Z Axis Controller. Retest the motor.

BTW.. Good choice using the Flash Cut Z Axis design. I think you'll be happy with it as soon as you get this problem solved.

[rcpilot82]

RCPilot

You have changed the motor, increased from .75KW to 1.0KW,(approximately) but the problem persist. You must consider, 'Why does the motor set a 'High Temp' fault before the 'Torque Limit' is achieved? Torque and Heat are synonymous; they move somewhat together. But in real motor applications the Torque limit is set at a point where the motor does not overheat. Your fault is 'High Temp' not 'Torque'. Another reason for 'High Temp', low voltage? But for the moment I believe the motor is good and your new controller is also good.

Troubleshooting time!! This is where I would start.

1) Apply one of the other motor configurations to the Z-Axis motor. Calibrate the Z-Axis distance in Mach3 as done before. Retest the motor.
2) Swap one of the other data cables with the Z Axis cable. Retest the motor.
3) Swap one of the other controllers with the Z Axis Controller. Retest the motor.

BTW.. Good choice using the Flash Cut Z Axis design. I think you'll be happy with it as soon as you get this problem solved.

William,
Thanks for the in depth reply.

I have asked DMM why there is an overheat error and they have not found a solution yet.

As for troubleshooting, I have tried 3 different motors, swapping cables, swapping drives, as well as configurations multiple times to no avail.

Through e-mailing another cnczone member here we have determined that my x and y axis are at about a 7:1 reduction between the ball screws and the 2:1 belt drive. last night I measured my z axis and like all other B.Ports the quill moves 3.25" approx. for each rotation of my large pulley. This is the factory ratio inside the head. with the smaller motor on the belt reduction I was getting a 4:1 reduction which actually works out to a total ratio of 1:.75. this is more than the flashcut ratio that works out to a 1: 2.25 so should be fine in theory.

Thanks,
Rob

[mactec54]

rcpilot82

I just watched your video, you don't have the drives set correct as well as you need a much lower gearing as we have discussed

First set the Drives electronic Gearing to 500 main gain to in the 60's and the integration gain to around 12

when you reset the Gearing you will have to changes the step/per in Mach3

When using step/Dir, the electronic gearing is best set at 500

You also need to set the Drives ID at some time, 0=X axes 1=Y axes 2=Z axes, you have the Z at 0, this won't affect anything while just testing like this, but will when you run all 3 axes together

For those that don't know what is happening here, this is the same as driving a rack & pinion, with one turn of the front pulley the Quill will move 3.250" approximately, so this is mostly a gearing problem

What was the feed you had set for the drilling you were testing

[mactec54]

B.Ports the quill moves 3.25" approx. for each rotation of my large pulley. This is the factory ratio inside the head. with the smaller motor on the belt reduction I was getting a 4:1 reduction which actually works out to a total ratio of 1:.75. this is more than the flashcut ratio that works out to a 1: 2.25 so should be fine in theory.

This is where you are not working out the correct ratio, with your 18 on the motor and the 40 on the pinion, you only have a 2.2:1 ratio, nowhere near where it needs to be

Flash cut are using a 3:1 pulley ratio, so this is giving them almost 1:1 and a very big high torque motor, which would also be marginal to do the job, certainly not ideal

If from your motor, to the pinion, the pulley reduction was 3-1/4 to 1 then you would have a drive ratio of 1:1, to do what you want to, you would need another 3:1 minimum to move the quill, so this would then be a minimum total of 6:1 reduction at your motor to the pinion, to have reasonable control over the Z axes