VF1 not reading true rpm on spindle

Well we have the trans back in and running. I noticed quite a different in control read speed and actual. I use a laser tach for this. Spindle test at 7500, actual was 7540 and control speed on crt was 7100 and some change.

Also tested in low at 1500 and actual was 1515 and crt speed was 1450. I am sure this will bite is in the ass with tapping. Is there anything but the encoder, belts, and pulley that might cause this?

My 96 VF3 is probably similar, with Magnetek drive? This is open loop they tell me.

There is a parameter which you can adjust directly in the drive itself, if you have your manual still in the door. I forget exactly what it was now, I can look tomorrow. However, it is in essence, the drive is guessing how fast the motor is turning, and it was not possible to get an exact matchup in rpm throughout the entire speed range of the motor.

So even yet, I see a few rpm difference between commanded and actual rpm on the CRT, but in some manner, the Z axis must slave to the actual rpm, because I've never had trouble with single, double or triple repeat tapping #0-80 threads

I was thinking about this for a few and wondering if that worn out trans side pulley for the encoder could or would cause this? I need to better understand how rpm is commanded and verified. Maybe the encoder is nothing but a tach until in rigid tap modes?? That would make more sense if the pulley is jacked. I seems at least close from commanded actual, just the tach on the CRT that is WAY off.

I wonder if all the mid 90s machines were like this because we have a 97 and 98 in another shop and the rpms pull down quiet a bit when cutting. I would sure think if that was closed loop, it could command more power to maintain rpm.

I don't know if any controller 'knows' how to obtain a given rpm from the spindle drive. The spindle drive is commanded often with a +-10 volt signal, and the entire range of rpm is proportional to the input voltage. So, rotor slip causes the uncertainty between what you command and what you get. The best a tech can do is through trial and error, modify the parameters in the drive to try to match max rpm with a full 10 volt command signal.

When I adjusted my drive to get a dead on match at full rpm, its still out something like 1 or 2% at midrange speeds. It will pull down a bit on a heavy cut, but this is because it is an open loop drive.

I don't think a worn encoder pulley is the cause. You'd probably have a lot of grief with rigid tapping if that were the case, because the belt would literally have to slip to make a difference.

We have yet to even cut any material with this mill. Not sure if it rigid taps OK or not. I agree, that belt would have to be smoking to lose 400 rpms and I doubt that is the case. I was also wondering if the diameter is worn enough to cause this. Remember that pulley is cheap Al, not steel. I plan to replace it anyway but if that is not the problem, I need to figure out how to fix this.


Do you happen to remember how to access debug on the Haas? I must be doing something wrong.

No, I don't know how to use debug.

One thing you can perhaps do, is contact Haas for a parameter list for the spindle drive. Then on the drive's own display, run through the list and see if everything is set as per their recommended starting parameters. Because these older machines are not vector drives, the parameters are not all in the control as I understand they are in the new machines (?)

E stop
Settings 7
Parameter Lock Off
Alarm Page
Type in Debug
Enter


And away you go!
Gary

I will write it down this time. I forgot to unlock the parameters. Thanks