Thread cutting in EMC

[mattinker]

Hi!,

I'm extremely new to CNC and Linux. I have on two occasions come across references to "you can't do threading on EMC", for me, this is one of the principal reasons for going over to CNC, that and acurate taper cutting. Maybe someone can clarify for me.

Thanks in advance, Matthew

[samco]

threading was added recently and is in the latest live cd. 2.1.0. It can be downloaded here http://www.linuxcnc.org/index.php


the manual has a bunch of info on lathe setup
http://www.linuxcnc.org/docs/2.1/EMC2_User_Manual.pdf


Here is a page of what features are going to be add (some have already been- they have a 'done' next to their title)
http://wiki.linuxcnc.org/cgi-bin/emc...anced_Features

Here is a video of cradeks lathe cutting threads (he integreated threading into emc2 - amoung other things )
(right click and save as)
his servo lathe
http://lerneaenhydra.shacknet.nu/ima...readingnew.avi

his stepper lathe
http://timeguy.com/cradek-files/emc/dscn6185.mov

sam

[harty]

hi mattinker

emc 2 will and does cut threads very well i have been using it for a couple of months and cut about 50 threads
you will need an encoder of about 100ppr to put on the spindle and away you go

the guys on the emc irc channel are very helpful

cheers
harty

[mattinker]

Harty,

Thanks, I'm very new to all this, also in metric France! What a ppr?

Matthew

[unterhaus]

ppr == pulses per revolution

[harty]

hi Matthew

as unterhaus said ppr is the number of pulses per revoultion of the encoder for emc you need to have a fairly low resolution encoder 100ppr works great
the higher resolution encoders mean you have to run your lathe at a lower rpm

cheers
harty

[mattinker]

Thanks for the replies. I have noticed that a lot of people in the US use abreviations (maybe a text message habit), I!m a Brit! So my language isn't quite the same, when I see things written I have no problems! Sometimes I stare at abreviations (LOL being one of them!) and think what are they talking about!

Thanks again, a pulse counter shouldn't be too hard to sort out.

Matthew

[RotarySMP]

Do you need both a 1/rev signal to index plus a 100/rev to sync to?

This would be required for multiple passes so you always engage at the same place.

The latest Image is the first time I have ever had an EMC BDI or Live work for me. I must have downloaded EMC images 10-15 times over the years, but they never liked any of the miriad of computors I tried them on. This latest Live disk seems to work find on a Compag PIII Laptop I have. I am using TurboCNC on my Lathe, but have been thinking of trying EMC on my mill if I ever get it finished.

[unterhaus]

does it have to be a low count encoder just because it uses the parport for input? I generally prefer to have a counter, although that costs money.

[samco]

You can do it without a quadrature but you still need a index pulse.

If you’re using a quadrature encoder and the printer port.
Most people can run a base period of 20us, which is 50khz. Emc2 can count an edge per period. You should be able then to count with a 100ppr-> reading all the edges is 400edges. The max emc should be able to read is 50khz/400edges=125rps=7500rpm. You normally want some headroom though.

If you’re using a non quadrature you should be able to double that.

sam

[mattinker]

My thread seems to have taken another turn, how about ideas and supliers of pulse counters. How to hook them up etc. I feel sure that it can't be hard, but why not set down some ideas on how to do this. Maybe somebody also has some links on the subject.

Thanks, Matthew

[samco]

I have bought from http://www.usdigital.com/ their parts anyways.
http://www.electronicsam.com/images/...t/Endoder1.JPG

I am planing on buying some from http://web3.automationdirect.com/adc...oders/Encoders

From the specs - it seems that even their light duty shaft encoders have an index pulse. I would have to see it to believe it.

sam