Colchester chipmaster advice.

[Joe84]

Hi fellas,

So after getting the lathe up and running I feel its nowhere near as fast as it should be, in the 350-3000rpm range at a guess I'd say it might not be doing 1500rpm, I'm waiting on an rev counter to be delivered.

But anyway, I've git my vfd set to 60Hz, my question is can I up the Hz to say 70/80Hz or will I do damage to the motor? If I can't up the Hz what are my options for more rpm?

Motor speed itself is 1440rpm


Cheers.

 

[6ply]

Hi fellas,

So after getting the lathe up and running I feel its nowhere near as fast as it should be, in the 350-3000rpm range at a guess I'd say it might not be doing 1500rpm, I'm waiting on an rev counter to be delivered.

But anyway, I've git my vfd set to 60Hz, my question is can I up the Hz to say 70/80Hz or will I do damage to the motor? If I can't up the Hz what are my options for more rpm?

Motor speed itself is 1440rpm


Cheers.

Are you referring to the spindle/chuck speed? 1500rpm is probably plenty (I never go over 1200rpm) and you need to be careful not to exceed the chuck max rated speed.

 

[Joe84]

Are you referring to the spindle/chuck speed? 1500rpm is probably plenty (I never go over 1200rpm) and you need to be careful not to exceed the chuck max rated speed.

Yea that's what I mean, I'll smwait on the rev counter and see what thar says.

 

[Agroshield]

...I feel its nowhere near as fast as it should be, in the 350-3000rpm range...

The original speeds were calculated when the variator was fitted.

From the factory, the machine came with a 1440 rpm motor, connected 1:1 to the input of the variator. The variator has a 9:1 speed range, from 1/3 input to 3 times input.

The output pulley on the variator is very roughly half the diameter of the input pulley on the clutch shaft.

As your motor is connected directly to the clutch input (variator removed), nothing written on the machine related to speed will be correct.

In high speed, the clutch connects to the spindle with the wide, short timing belt. Count the pulley teeth (or look in the manual) to see ratio between clutch and spindle. Then work out the ratio between motor and spindle by measuring the pulley diameters.

You would have to look in the manual to see what the ratio is in low gear as all the gears are inside the headstock. As a rough guess, you could work on 10:1 from the data plate (30-300 and 350 to 3000).

Without a tachometer, you could do a rough assessment by putting the machine in low gear, turning the VFD down to a known (but really low) number and timing 30 spindle revolutions with a stopwatch.

That is the trouble when people remove the variator from a Chipmaster: you never achieve the 30-3000rpm range it left the factory with.

 

[Joe84]

The original speeds were calculated when the variator was fitted.

From the factory, the machine came with a 1440 rpm motor, connected 1:1 to the input of the variator. The variator has a 9:1 speed range, from 1/3 input to 3 times input.

The output pulley on the variator is very roughly half the diameter of the input pulley on the clutch shaft.

As your motor is connected directly to the clutch input (variator removed), nothing written on the machine related to speed will be correct.

In high speed, the clutch connects to the spindle with the wide, short timing belt. Count the pulley teeth (or look in the manual) to see ratio between clutch and spindle. Then work out the ratio between motor and spindle by measuring the pulley diameters.

You would have to look in the manual to see what the ratio is in low gear as all the gears are inside the headstock. As a rough guess, you could work on 10:1 from the data plate (30-300 and 350 to 3000).

Without a tachometer, you could do a rough assessment by putting the machine in low gear, turning the VFD down to a known (but really low) number and timing 30 spindle revolutions with a stopwatch.

That is the trouble when people remove the variator from a Chipmaster: you never achieve the 30-3000rpm range it left the factory with.

I agree, if the variator is removed then the machine needs to be geared accordingly via pulleys or what have you.
Unfortunately I can't go any smaller with my motor pulley, what if any are my options for getting more speed at the spindle?

 

[6ply]

I agree, if the variator is removed then the machine needs to be geared accordingly via pulleys or what have you.
Unfortunately I can't go any smaller with my motor pulley, what if any are my options for getting more speed at the spindle?

Can you add a stepped pulley on the motor and the lathe?

 

[Hopefuldave]

I agree, if the variator is removed then the machine needs to be geared accordingly via pulleys or what have you.
Unfortunately I can't go any smaller with my motor pulley, what if any are my options for getting more speed at the spindle?

I've run the VFD on my Holbrook up to 85Hz, to get higher spindle speed for Small Parts - that takes it up to ~2500 RPM instead of topping out at 1500 for short bursts (although pumped oiling, the spindle bearings are plain not roller), and I've gone as low as 10Hz for 4RPM occasionally / jogging, it has worked well so far!
If you need more speed, a *bigger* pulley on the motor will help, but you'll lose some torque at low speeds (and need a longer belt!).

Dave H. (the other one)

 

[Joe84]

I've run the VFD on my Holbrook up to 85Hz, to get higher spindle speed for Small Parts - that takes it up to ~2500 RPM instead of topping out at 1500 for short bursts (although pumped oiling, the spindle bearings are plain not roller), and I've gone as low as 10Hz for 4RPM occasionally / jogging, it has worked well so far!
If you need more speed, a *bigger* pulley on the motor will help, but you'll lose some torque at low speeds (and need a longer belt!).

Dave H. (the other one)

That's the thing the chippie has no issues running at 3000rpm it was built for it, I'm just concerned if the motor can handle it.

 

[Hopefuldave]

Chippies exported to the american market ran fine on 60Hz power, so the motors can definitely handle that - and the dustbin-sized motor in my lathe was designed for 50Hz and hasn't protested (yet!) about being run overspeed! Maybe a compromise, is in order, top out at 75Hz or so, with a pulley change to get maximum speeds at the spindle, and run down as low as 10Hz if you really need to - have you aimed for 3000RPM as "that's what came from the factory" or do you need the speed for the size and material of what you're doing? I've not yet needed over 2500, probably could cope with 1500 max.

Dave H. (the other one)

 

[addjunkie]

Your over thinking this, many older machines do sterling work and never go over 1200 rpm! 2000 is a bonus.

 

[Joe84]

Chippies exported to the american market ran fine on 60Hz power, so the motors can definitely handle that - and the dustbin-sized motor in my lathe was designed for 50Hz and hasn't protested (yet!) about being run overspeed! Maybe a compromise, is in order, top out at 75Hz or so, with a pulley change to get maximum speeds at the spindle, and run down as low as 10Hz if you really need to - have you aimed for 3000RPM as "that's what came from the factory" or do you need the speed for the size and material of what you're doing? I've not yet needed over 2500, probably could cope with 1500 max.

Dave H. (the other one)

Hi dave,
I'm sitting at 60Hz at the moment I was thinking of going to 70Hz and leaving it at that.
I've not done much on the lathe yet other than get it going and had a quick play really, I just feel that max speed is not fast enough... although I can't be certain until I get my rev counter. I can't ever see me needing 3000rpm

 

[indy4x]

What the other guys said, don't really need high rpm, 1200 is ample

 

[Geoffm]

My chippie has a 940 rpm, 3hp ish motor and the vfd overdrive it to 75hz. This gives a good speed range without losing torque. I found the 1440rpm motor I had before was underpowered at low speed. This is a v/f old vfd, so a modern vector drive vfd would be better.