Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: gporthos on June 12, 2018, 10:24:50 PM

Post by: gporthos on June 12, 2018, 10:24:50 PM
Im new at this of the cnc world, i have a question and hope somebody can help me, i have a cnc rpouter, the spindle is controlled by a vfd, in the display of the vfd when is working is showing n and a four digit number, in the manual of the vfd say that n is operstion speed, i attached picture of the manual, my question is operation speed is equal to rpm in the spindle divided by 10 because of the four digit number? for example if the vfd show n1596 is equal to 15,960 rpm? i attached photos of the manual and the vfd showing the numbers

Title: Re: VFD HELP
Post by: joeaverage on June 12, 2018, 10:42:11 PM
that is probably a good explanation. May I suggest have the VFD display frequency, that means
revs per second for a two pole motor.

Freq=400 Hz or 400 rev per second = 24000 rpm.

Title: Re: VFD HELP
Post by: gporthos on June 12, 2018, 11:06:47 PM
Thanks a lot craig for your fast reply, another question in the manual the H is setting frequency and the P is operation frequancy, of this two wich one would be the hz that you tell me to check? h or P?
Title: Re: VFD HELP
Post by: joeaverage on June 12, 2018, 11:25:11 PM
try both, but I think either will be fine, they will differ only by the slip, typically only a few

Title: Re: VFD HELP
Post by: gporthos on June 13, 2018, 12:00:29 AM
Thanks for the support, ill try and will tell you the results
Title: Re: VFD HELP
Post by: joeaverage on June 13, 2018, 03:31:38 AM
I have a Delta Model B VFD. It, like almost all VFDs has several programmable digital outputs. These outputs, depending on the manufacturer can tell you current say, or temperature and
various other parameters. There is one available output on my VFD that produces a pulse every revolution, ie an index pulse, or rather a synthesized index pulse.
I've never used it so I cant tell you whether it is sufficientlty accurate to use for rigid tapping say but it certainly is good enough for Mach to use to work out how fast the spindle is going.

The top end of my highspeed spindle (24000 rpm max) is enclosed so I can't readily attach a pulse generator and I don't want to take the top off it. I paid big bucks for a German made one
and I do NOT want to bugger it up!

Mach, or more technically correctly your ESS, measures the time between index pulses and then calculates how many rpm. Mach can display that figure and it is a VERY accurate measure of
the actual speed of the spindle.

I seldom find that I need a really accurate spindle speed, within  5-10% is adequate for most things, rigid tapping however is a specialized procedure and requires an accurate measurement.
My highspeed spindle is very low torque and so I don't even try to use it for rigid tapping, consequently I don't really care about accurate speed. If however you are interested or have a specific need
then you may want to think about attaching a pulse generator to your spindle. If its not practical maybe your VFD has a synthesized index signal as mine does.

Can you post the manual for your drive?