forum.cncdrive.com

Hi all, this is my first post here so please be kind as I'm still new to these things

the back story is that I have got hold of an older Emco 5 cnc lathe, it had all old style electronics which needed a printer port to control it and as I didn't have a pc with one I deceased to fit it with an axbb board, that was the start of my electronics learning curve, it was a steep one at that..

so roll on almost a year and I have managed to get it all wired up, I have followed what I can understand in the manual and it seemed to be working ok, then I got on to testing and try to screw cut a thread, this is where I leaned it would need to have a spindle encoder.

I looked around and found an encoder and have connected it all up..

here is where its got a little complicated and I'm not sure where I have gone wrong as I'm not getting the correct speeds or speeds that I expect.

I have programmed it for 1000 rpm and when measured with a cheap tacho its way off, the spindle encoder also reports a different speed other than what I expected[pdf][/pdf]

I think the encoder has 500 ppr. and have entered it as 2000

any help would be appreciated

I think the encoder has 500 ppr. and have entered it as 2000

Is the encoder driven directly off the spindle or is it belt drive? you would need to calculate that ratio as well and enter the correct Encoder PPR into UCCNC. I would start there.

hey, thank you for the reply..


the encoder is driven off the spindle with a 1:1 ratio I don't remember the number of teeth on each but can count them if needed.

Ok so if the encoder is driven 1:1 and it is a 500 ppr encoder then in the software under the encoder field change the value I think you had 2000,change it to 500. That should put you where you need to be.

Looking at your pictures you sure the encoder is driven @ 1:1
I would count the teeth and make sure. At any rate I think you have the wrong value entered in the software.

thank you for the help, I have set the PPR to 500 like suggested and the results were

at programmed speed of 1000rpm M3 s 1000
spindle motor was recorded at 1270 rpm with a hand held tacho
on the encoder spindle the speed was 800 rpm with the hand held tacho
the displayed Act speed on the screen was reading 5170 rpm

below I have uploaded the encoder I am using, maybe I have wired it incorrectly ?

Not sure where you get encoder 500ppr? The encoder specs list it at 2048ppr... you have 2000ppr entered in the software.

here is the table where it shows which pules per rev it is according to the part number. 2048 is the max PPR this model is available in from what I understand of it?

Here shows my part number



I got to 2000 because I thought it was considered quadrature and needed to be multiplied by 4 but I'm not sure I understand the meaning of this fully

thanks for the help...

Dave,

I have been through a similar exercise very recently with my Denford Orac (as it happens, based on an Emco Compact 8) in which I have replaced almost all the electronics. I had problems with motor speed and I found that the first thing to do was to check what the VFD was producing for a given control signal from the motion controller. I needed to set 2000RPM in the software, so that the motion controller produced a nominal 10V at full speed (which I double-checked by measurement), and then make sure that the VFD maximum speed parameter was set to 100Hz - the motor in my machine needs 0-100Hz for the full speed range, even though the motor is nominally a 50Hz unit. You should be able to check the output frequency of the VFD on its front panel display. Then use your handheld tacho on the motor spindle to make sure that this is consistent with the input frequency, and start from there. Can you double-check the tacho accuracy against a known machine/motor? Can you estimate the motor-spindle pulley ratio, to then work out what the spindle speed should be for a given motor speed and double-check this with the tacho? Then check what the encoder says for that spindle speed. In my case, I was scratching my head for a while until I started going systematically through the various connected bits starting with the motion controller output until I found an inconsistency.

hi thanks for the information

I will check out some of that when I get more time, I did have a quick look at the motor speed in manual mode from the vid and at 50Hz I was getting around 2,800RPM the hand held tacho is just a cheap on off amazon but I have tested a motor in work and it was pretty close, it does jump up and down a bit but I kinda expected that for the price..

on the motor name plate it shows 2,790 at 50 Hz and the motor has a 40 tooth pulley going to the spindle pulley that has 64 teeth. I make that at 2,790 at the motor it should be about 1400 RPM at the spindle which looks about right but I need to get a stable measurement...

I have the VFD set with a max frequency of 1000Hz at the moment

on the UCCNC control I didn't think that the min and max spindle speeds had any relation to the VFD, is that correct ?

should I set my max spindle speed on the control to 2790 and run it at that and check to see if I get 10Volts going to the VFD?

can you explain more about the 100Hz ? does your motor run at 2000RPM at 100Hz?