[Willyb]

Hi Steve

You have got to be a happy man. :-) That is some nice looking thread you cut. I think you are doing the right thing using the VFD/3 phase Motor on your CNC Lathe. It's the only way to go with a CNC Lathe. With your Spindle RPM Sensor you can use Constant Surface Speed with Mach. Here is some information on it.

http://www.cncathome.com/vfd.html

How about a Video of it threading now?

Willy

[the4thseal]

thanks for the vfd info.....i am going look into it right away.1hp is all i need at least while i am awake:-]

[the4thseal]

sjh-
what motor are you using?

[handlewanker]

Hi Steve, about your 5V problem not being activated, do you have full 5v at the pin when it's connected to the whatever it is you had on it?

The reason I ask is you can have 5v shown on a digi multimeter with very little current, micro amps will still show, but the input device could drop the volts if there's not enough current, making a no work situation.

We had this on a relay on a herbert CNC some 25 years back and it stumped the electrician for days, untill he noticed the volt drop when the relay was triggered.

You could apply a known 5V supply to the input pin to see if it activates.

BTW, many years ago in 1958, when I was serving my apprenticeship, we had a big German face plate lathe, a Ravensberg, 6ft centre height, and one day I was called on to machine a thread on the end of a shaft attached to a large drum.
The speed of rotation was 60 rpm.
Now on a conventional lathe this is just everyday practice, set the gears, engage the half nuts and away you go.

This lathe was diffrent, in that the headstock sat on it's own base and the bed and saddle were free to be moved around as the job need it, totally seperate from the headstock and tailstock.

In other words if you had a job 10 foot long, you placed the bed parallel to the job and used it like a conventional lathe, but if the job was a large diam like a 6 ft diam wheel to be faced off, you placed the bed across the face of the faceplate and so gained a large facing movement.

So the bed of the lathe, with saddle and crosslides, was free to be moved to suit the job size, and was bolted down onto an iron bed plate as was needed.

A long story short, I puzzled as to how screwcutting was to be done when the bed had a leadscrew but was not connected to the headstock.

It had a stepping motor that drove the saddle via a connecting cable to the headstock.
The ratios were all set mechanically by gears on the end of the bed, so the stepping motor on the bed just received a pulsed signal from the headstock at a fixed rate as it rotated.

This was the first time I came into contact with stepping motor drive, long before CNC.
Screw cutting at 1000 rpm must be breathtaking.

Ian.

[S_J_H]

Yeah I am pretty happy now. That it could take that deep of a cut without chatter and under stepper power makes me think the machine is pretty rigid. Although I won't push it that hard normally. Once I get tailstock mounted it should be even better.
In post #149 I have a link showing it threading using the old dc motor drive.
It won't be operational again for a while now that I need to swap the vfd off the 9x20 and retro the 3/4 hp chinese motor back on that machine. Then I need to decide on a permanent location for the lathe as no way I am bolting up that 40lb 1hp 3ph motor to the lathe. The motor will have to be bench mounted.
On second thought about the polyflex pulleys, I may just try and find a smoother running belt and keep the step pulley I made. I went to a lot of work to machine it for very low runout and it's a perfect pressfit to the spindle. Plus it is cast iron and adds a little needed flywheel effect to the small spindle.

Willy, thanks very much for that link!

John, 5000$... well I would let it go for that sum.

the4thseal, I am using a marathon brand 1hp mighty max motor I bought from automationdirect.com. You could find a much cheaper 3ph motor though. But it's a nice motor with a 4000rpm max limit and runs cool even at very low rpms.

Steve

[S_J_H]

Ian, great story about the old lathe! As for the pin problem, not sure what is up with pin 15 but everything is working fine now on a different pin.

Steve

[the4thseal]

can i use any ac motor with a vfd controller?

[handlewanker]

Hi Steve, I replied 2 pages late and didn't see the reason for the dead pin.
Next time I'll check the page to reply to.
Ian.

[Willyb]

can i use any ac motor with a vfd controller?

You will need to use a 3 phase Motor.

Willy

[the4thseal]

i understand....i think......110 vhd drive 1 hp or smaller 3phase motor and it should work......do i need an encoder? ....and thanks willyb

[the4thseal]

this one in the 1hp range.
http://web5.automationdirect.com/sta...nhorsetprs.pdf
thoughts?

[Willyb]

For the 1hp setup you could go with the GS2-11P0 VFD and the MTR-001-3BD18 3 Phase 1hp Motor. If you want a lower hp setup, just match the Motor to the VFD.

No you do not require an Encoder with this setup.


Willy

[svenakela]

Steve, what is the feedback from the spindle to the software, one click per revolution?
It can't be running without feedback, can it?..

[balsaman]

No feedback. A VFD varies the frequency. The frequency sets the speed. Sorta like a stepper actually....kinda.

Eric

[S_J_H]

A few things to consider,
The MTR-001-3BD18 motor has only a 2:1 constant torque rating and a 1.5:1 constant HP rating. This means anything under 900rpm and the motor will lose torque and anything over 1.5 x 60hz(~2700 rpm) and you lose hP.

I am using this motor which has a 20:1 constant torque rating so it can run well as low as 100rpm and will maintain full Hp at ~3600rpm.
http://web2.automationdirect.com/adc...s_(by_HP)/Y364

It is more money but I have used this combo over the last year and it is very nice.
Just my .02

Steve

[dkowalcz]

dkowalcz, very interesting! Can you post some pics of your machine? I would love to see it.

Sure. These pictures are pretty old - approximately May of last year. I've since gone to a ballscrew on Z and added some way covers. Interestingly enough we have almost identical designs for the Z axis ballnut bracket.

Basically what I did here was very carefully mill off the "V" on the bed on the old lathe and stack up the linear components chosen such that the height of the tool posts and clearances all worked out to be exactly the same as they were with the old boundary lubricated ways.

It was a bit of a rush job - I was getting buried by work and needed to do something to speed things up a little and improve the tolerances it can hold. Much better than the wobbly old setup. The better way would be to build a new bed as you did.

This is pretty much the end of the line for the old 7x10, as I've replaced/upgraded/repaired every single part of it now after 14 years in the shop. Note the headstock is the "wrong" color, I've embedded steel nuts in the castings to repair stripped out threads, and that's probably the 4th iteration of spindle and stepper motors to grace the assembly.

I'll post some more pictures later after work of what it looks like now...

[svenakela]

No feedback. A VFD varies the frequency. The frequency sets the speed. Sorta like a stepper actually....kinda.

Eric

Yes, I know the VFD part, it better be stable then. But... I'm amazed! The threads looks awesome and not even a single feedback from the spindle!
When it comes to lathes I can only compare to production machines and EMC. Maybe it's possible to run EMC without feedback too, but the guys that runs it for threading uses at least one click per rev as far as I know.
I see one problem with the no-feedback version, what happens if you want a thread to start exactly on a specific place? But on the other hand, even if I have been producing stuff with that requirement - how often will that happen?

Still amazed,
Sven

[Willyb]

A few things to consider,
The MTR-001-3BD18 motor has only a 2:1 constant torque rating and a 1.5:1 constant HP rating. This means anything under 900rpm and the motor will lose torque and anything over 1.5 x 60hz(~2700 rpm) and you lose hP.

I am using this motor which has a 20:1 constant torque rating so it can run well as low as 100rpm and will maintain full Hp at ~3600rpm.
http://web2.automationdirect.com/adc...s_(by_HP)/Y364

It is more money but I have used this combo over the last year and it is very nice.
Just my .02
Steve

Steve

Good point Steve. For an extra $75.00 the Y364 Motor is the only way to go. It would be a better Motor for this Lathe application. Thanks for bring that to our attention.

Willy

[balsaman]

Yes, I know the VFD part, it better be stable then. But... I'm amazed! The threads looks awesome and not even a single feedback from the spindle!
When it comes to lathes I can only compare to production machines and EMC. Maybe it's possible to run EMC without feedback too, but the guys that runs it for threading uses at least one click per rev as far as I know.
I see one problem with the no-feedback version, what happens if you want a thread to start exactly on a specific place? But on the other hand, even if I have been producing stuff with that requirement - how often will that happen?

Still amazed,
Sven

Actually it's not that close. If the VFD says its 1000 RPM, you are probably running under by up to 10%, depending on the torque. The less torque, the closer it runs to the actual freq. Some drives have a setting to compensate for this.

Eric

[samco]

I am assuming that those threads where cut in one pass. (no multiple passes) Multiple passes would not work without spindle feedback.

sam