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IndustryArena Forum > MetalWorking Machines > EMCO CNC Machines > EMCO Lathe > Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.
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  1. #1
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    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

  2. #2
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    index and 100 pulse per rev hooked up in linuxcnc hal. It threads air! video soon.

    sam

  3. #3
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    45ipm seems repeatable... (back and forth to an indicator..)

  4. #4

  5. #5
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    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

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    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.
    Click image for larger version. 

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ID:	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

  9. #9
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    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)

    Click image for larger version. 

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

    Click image for larger version. 

Name:	betterstep_de-accelerating.jpg 
Views:	1 
Size:	75.9 KB 
ID:	192866

    sam

  10. #10
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    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

  11. #11
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    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

  12. #12
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    Re: Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.

    This is the waveform generated by linuxcnc

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

    Is this what you were wondering about?

  13. #13

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

    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
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........

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

    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

  15. #15

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

    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
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........

  16. #16

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

    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
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........

  17. #17
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    Re: Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.

    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

  18. #18

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

    it shows up in the picker . It looks like it's ready to run it but then linuxcnc shuts down
    A poet knows no boundary yet he is bound to the boundaries of ones own mind !! ........

  19. #19
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    Re: Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.

    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?

  20. #20
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    Re: Emco compact 5 pc lathe - linuxcnc setup without circuit board hack.

    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

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