Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.

we managed to get a few of these compact 5 pc from a local school. As most of you I started searching the internet for info on the lathe. I found this artical

http://www.maxton.com/ebay/emco/EMCO...to%20Mach3.pdf

from the digital machinist mag that explained how to remove the octal latch from the interface board, switching the board to step/dir and setting up mach. I did a search for the 74ls374 chip discussed in the artical. It looked like I could use linuxcnc to send the clock signal to the board. So after some figuring and searching I found figured out the printer port pins..

x step pin 2
x dir pin 3
z step pin 4
z dir pin 5
index pin 12
estop pin 11
100 ppr sensor pin 10
74ls374 enable pin 14
74ls374 clock pin 1

So I hacked together a hal file that used the 'reset' function of the printer port driver to send a clock every base period to latch the 74ls374 chip. After not remembering to set switch 1 to on on the emco interface board (sets the interface to step/dir) and scratching my I got linuxcnc communicating. The performance was not stellar. The article above talks about setting your max velocity to 19ipm. This is what I was seeing. Just pretty poor performance. Sounded crappy. Now it could be that I didn't have the timing perfect but read on.. (according to the article above - the original software did around 30ipm)

When I forgot to set switch 1 on the emco interface board - I had decided (by twiddling bits on the printer port with linuxcnc) that the default setup must have been phase drive. The original software controlled the 4 phases of the stepper drives/motors. I didn't have much to lose so I modified the linuxcnc hal file to do 4 phase drive for each axis and set switch on on the emco board back to 'off'.

HAL Component Descriptions

So pins 2-5 ran one stepper and pins 6-9 ran the other.

the stepgen in linuxcnc will do a bunch of wave forms - I was interested in - 5 through 10. (4 phase patterns)

I started with pattern 9. This is Unipolar Half Step
-This acted the same as the step/dir I started with. 19ipm max and sounded crappy.

Next I tried pattern 10. This was a long shot as it is Bipolar Half Step
-I don't think it worked at all - or at least it was way worse..

Then I tried pattern 5. Unipolar Full Step (one winding on)
-I had to half the steps per inch obviously - but it acted the same as the above. around 19ipm and sounded bad.

finally I tried patten 6. Unipolar Full Step (two windings on)
-Wow. This sounded nice. We started pushing it and it started sounding rough at around 40ipm. (didn't seem to be losing steps but I think I might be just fine with 35ipm max)
We still have to up the acceleration as that could be pushed a bit also. this is around .0005 per step - very usable.

Very happy.

Now we need to get the index and 100ppl setup in linuxcnc and I will take some videos (threading and such). with this performance initially - I don't know if I will change the drives/steppers until they fail...

one last thing I would like to try is putting the interface back into step/dir mode and from what I have read - you can put it into full step mode.

So - Again - this is without modifying the emco electronics in any way. Setting up linuxcnc to output the 'clock' to latch the chip.

when I get the encoder setup within linuxcnc - I will post the hal/ini files here.

sam

index and 100 pulse per rev hooked up in linuxcnc hal. It threads air! video soon.

sam

45ipm seems repeatable... (back and forth to an indicator..)

video soon
http://www.electronicsam.com/images/...OThreading.JPG

sam

quick threading video.. (yes - not the correct cutter - and the exit move is a bit shallow.. but shows the spindle sync is right on...)

https://www.youtube.com/watch?v=ERMizV-yy8U

sam

initial config

Index of /images/emco/linuxcnc_configs

sam

5/8 11 thread in plastic..

emco lathe PC 5 cutting 5/8 11 thread with LinuxCNC - YouTube

sam

So - as far as I can tell - the original control did 1/2 stepping up to about 19ipm - then full stepping from there to 30ipm. Now the lathe runs fine on full stepping from 0 to 40 (maybe 45)ipm. Half stepping only works well up to 20ipm-ish. (stalls above that)

But why stop there..

I started thinking about if linuxcnc could do that.... (without coding anything)

A couple advantages of halfstepping..
1 higher resolution 0.000273403/step vs 0.000546806 per step
2 reduced resonance.. (I have not run into this with full stepping on the lathe)

Then at normal cutting speeds - < 16ipm you get a higher resolution.

So why not have 2 stepgens running. One that half steps (type 9) with input scale of 3657.6073152 and the other full stepping (type 6) with a scale of 1828.8036576 (lathe calculation - metric screws)
Then switch between the two stepgens at a specific feed (I picked 16ipm with a hysteresis of 1ipm)
All I can say is - HAL IS AWESOME
I setup a Lut5 with Jeff E's help (thanks jeff!) that switches the printer port between the 2 stepgens.
A offset componant was used between the 2 stepgens to better align the phasing. (not tweeked 100% yet) but we jogged it around - could not tell that it was switching between the 2 stepgens and it always came back to 0.
there is a bit more than that.. (ddt for calculating the axis velocity, abs of that, comp w/hystorisis, and stuff I have forgotten already.)


And here is a halscope capture. Left side is halfstepping - right side is full stepping. The trigger is the velocity threshold.
Attachment 192600

I think the offset could be tweaked more scientifically to maybe get rid of the blip. But as it is running the 4 phases directly - it didn't seem to effect the motion.

here is the initial configs.

Index of /images/emco/linuxcnc_configs/full-half_step_test

again - jmk and everyone that has worked on hal - Very very awesome work!

sam

After some slight tweaking... (it hasn't lost steps - but I wanted to get the
alignment as close to perfect as I could.) it ended up being 1/2 step
(0.000273403). Obvious I guess with the way the patterns line up...

accelerating (halfstep left side - full step right - xswitch is the velocity
trigger point)

Attachment 192868

de-accelerating (full step left - half step right xswitch is the velocity
trigger point)

Attachment 192866

sam

linuxcnc doing variable pitch variable diameter threading on the stock emco lathe.. (fusee for a rat trap powered car... - just playing around..)

Attachment 194464

reference here
Magic Smoke

Hi SAMCO,
That do you do to "So I hacked together a hal file that used the 'reset' function of the printer port driver to send a clock every base period to latch the 74ls374 chip", i 've got a problem, i do'nt know how to generate a pulse for the clock of the 74.
Can you explained.
Sincerly

This is the waveform generated by linuxcnc

http://electronicsam.com/images/emco/Waveform.svg

Is this what you were wondering about?

Hey Sam , I've got a few questions about this . I've got the exact lathe on it's way , and though I was prepared to do a tear down on it , it would be nice not to have to break into the core of the lathe and it would be nice to use it as is .
I've been all thru the web looking for a software solution and I've come across your mods on a few different sites and I'm intrigued by what you've done .
I've noticed that you have a few versions in the parent directory , which one do you recommend using ?
I see that version 2 has something to do with spindle rpm , are you getting full spindle control with this ??
It's been a while since I've used emc but I'm no stranger to the milling portion , and it's probably the best software solution for a lathe , at least from everything that I've read over the years . I honestly don't think that mach can touch it

Sorry - missed this post. We have not modified the lathe at all.

Let me look over what I have - I could pull what is currently on the machine also.

sam

I looked at the files and in the latest version you have the half step which I assume is the config to use . I've seen your video's and it looks like your lathe runs great . I don't need something that runs at mach feeds , and it looks fast enough with the stock setup .
I'm not familiar with the hal stuff and some of what you've posted is greek to me , but it looks as though you've managed to nail it . I'm still a week or two away from having it sitting in my shop , so at this point I'm surfing the net to pick up some info on these and I've watched nearly every youtube video on the net . Sorta anxious and I'm looking forward to playing with it

Got my lathe today . Aside from having to do some snugging up on the ways , it's a sweet lil unit . Anything that I've learned in the past about linuxcnc is gone from my brain and I'm not sure as to what directories I need to drop the files into . I've been dropping them into the home / linuxcnc . Ive been searching around at different directories and I'm a bit lost . Linuxcnc doesn't like anything that Ive done and won't start up the emco setup .
Any input would be great , I know that it's straight forward stuff but I'm somehow walking a crooked line

Does the configs show up in the config picker?
what errors do you get?

I will grab the configs from the running machine tonight.

sam

it shows up in the picker . It looks like it's ready to run it but then linuxcnc shuts down

wait - it loads the linuxcnc gui - then exits?

Could you open a terminal and type

linuxcnc

Then copy and paste the text after linuxcnc shuts down?

Ok - I downloaded my configs here.

Index of /images/emco/linuxcnc_configs/Latest

Installed the latest linuxcnc livecd on some random hardware I had with a printer port and updated it (running linuxcnc 2.7.3 now)

I put the configs in /home/user/linuxcnc/configs

Launched linuxcnc and it errored. :) In 2.7 (I think) the 'probe_parport' command was removed. So - you need to edit the emco-lathe.hal file and remark out line 6 (see screenshot)

sam