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Could use some help with start of job issue with Z axis...

Discussion in 'Control Software' started by WR_Rider, Dec 1, 2019.

  1. Fred Quarles

    Fred Quarles Well-Known
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    I just noticed that the PP file you posted has a .txt extension (OpenbuildsGRBL.cps.txt), that might be why he cant see it in the program.
     
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  2. David the swarfer

    David the swarfer OpenBuilds Team
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    sharmstr and Peter Van Der Walt like this.
  3. sharmstr

    sharmstr OpenBuilds Team
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    I sent that after he had the issue. That's why I sent it.
     
  4. WR_Rider

    WR_Rider New
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    Thank you
    I'm thinking there is something else here going on. 1st i have the hard and soft limits enabled (see jpeg1). i also have the max travel set to 5mm less then max (see jpg2).

    First thing i'm doing now is "homing" the machine (house on the tool bar). the router travels to my lower left corner and hits the limit switches and backs off 5 mm, that leaves the router up off the table. all good. That should tell the program where machine 0,0,0 is.

    Now in the display (jpeg3). if i jog the machine to 20,20,0 and re zero the x,y,z to set the working coords to 0,0,0 (lower left corner of work project). In the drop down box (circled in jpg3) there are to options,

    1-go to work x0 (work coords) or
    2- go to machine x0 (machine coords).

    if i select work coords the router comes back to x0 (20mm from the limit switch where i zero'd the x,y). If i select machine coords the router travels to the right max x position and stops. That seems odd to me since homing i thought set the 0,0,0 at the lower left corner. Why would that drop down say to go to machine x0 but take the router to the x max position and not back to home x0?

    I'll save the 2nd oddity for later.
    thanks again.
    Doug
     

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  5. sharmstr

    sharmstr OpenBuilds Team
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    When you home the machine, you are setting machine 0,0,0 but your spindle is NOT at 0,0,0 or even 5,5,5. Machine 0,0,0 is always in the upper right hand corner (meaning grbl default). Since you have put max travel values in, then grbl knows that when you home your spindle will be X-525 (530 max travel - 5mm pulloff), Y-740 (745 max travel - 5mm pull off), Z-5. You can obviously move your limit switches to the right back corner if its more comfortable for you.

    Spend some time in the grbl wiki. It might not click all at once, but its all there. gnea/grbl and specifically: gnea/grbl
     
    #35 sharmstr, Dec 2, 2019
    Last edited: Dec 2, 2019
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  6. WR_Rider

    WR_Rider New
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    Thanks, will do on the reading. It just seems odd to me but it’s probably from the surveying i do.

    We like to work in the +,+,+ coord system (positive quadrant). So I picture home at lower left 0,0,0 and with the max x,y,z set then the working coordinator sb inside that area.

    any way the 2nd odd thing going on is if during a job I stop it, or after I set the work coords, I send the router home either work or machine, the router goes up pass the the limit switch. ( the switch stops the router but it does hit it). It’s bothersome as well.

    well onto reading
    Thx
     
  7. David the swarfer

    David the swarfer OpenBuilds Team
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    can you give us the exact command you are giving for this?

    and maybe a picture of the machine and switch layout?
     
  8. sharmstr

    sharmstr OpenBuilds Team
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    Going to machine 0 I would expect that it would hit the switch. The reason why there are pull off values for homing is so that the spindle isnt sitting on the switch after you home. Remember, when you home, machine Z0 will be where it triggered the switch.

    Going to work 0 shouldn't hit the switch unless when you stopped the job you received an alert that you should rehome because there was potential that you lost position.
     
  9. WR_Rider

    WR_Rider New
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    Thanks for the help. It’s now making more sense on what the machine is doing and the work and home commands are doing.

    I do think I have something miss adjusted or miss aligned with the z axis though but I might have an idea what that is. I’m thinking I have to have the router up to high to clear the bit. That brings the z up closer to the switch, so I only end up with 25mm of up travel clearance.

    thanks again
     
  10. David the swarfer

    David the swarfer OpenBuilds Team
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    the command
    G53 G0 Z-10
    will raise Z safely to a point 10mm below the switch at the top of Z. (Z machine 0 is always at the top of travel)
    if you have more clearance you can change the -10 to -5, so long as it reliably misses the switch.

    you can set this as a macro so you can instantly raise Z safely for tool change.
     
  11. WR_Rider

    WR_Rider New
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    Apparently I still have something either wrong of I just can't figure out why this is happening.

    1 photo 1, I have the router just off the table bed (48mm at bottom of router mount). I raise the router up to the point it trips the limit switch (73 mm). In photo 2, I raise the router 67mm high (photo 2). In photo 3 I have the z limit set for 65mm.

    When I run either the goto work 0,0,0 for all 3 axis's or goto machine 0,0,0 the router will raise up in the z axis and trip the limit switch. This happens no mater where I have the z axis prior (bed level or higher) as well as to where ever I zero the z axis also. Prior to this i have "homed" the router and it will do that ok. X, and Y works ok.

    So I'm still trying to figure out what i'm missing here as to why the router needs to go up pass max travel.

    Thanks once again. Sorry I'm just not getting this but it seems odd as well as annoying.
     

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  12. David the swarfer

    David the swarfer OpenBuilds Team
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    so if you:
    turn everything on
    home
    click 'setzero XYZ'

    you now see x0 y0 and z0 in the display and you can jog .
    when you jog the displayed numbers should become negative (because going positive will very soon hit a limit switch), this is normal.

    now if you have a 15mm long bit in the router and a 10mm thick piece of material on the table, and you jog to where the bit it touching the surface of the material the router would now be 25mm above your lowest point.
    if you now click 'setzero XYZ' the display will show 0's. (this would be what you would do at the start of a job, putting the till at the point on the material that was defined in the CAM software as being the 0,0,0 for the job)

    if you now jog away from this point and then click ''gotozero work coord'' it should return to this point at the surface of the work. this is the expected behaviour.

    if you click 'goto machine' then Z will raise up till it hits the switch and you will get an error stop with Z up against the switch.
    if you create a macro button with this code
    G21 G90 G17
    G53 G0 Z-5
    G53 G0 X-5 Y-5

    then pressing that should end up 5mm short of all the switches. the X Y and Z displays will end up with positive numbers. there should be no limit error.

    pressing 'gotozero work coord' will return to that point on the material.

    @Peter Van Der Walt the user needs to be able to set a (negative) offset from the home switches to prevent hitting the limit when going to MCS. But each persons switches will require different offsets, though some assumptions can be made for defaults for those using the OB switch kits.
     
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Can you PM or Git Issue please :) ( can't focus on it at the very moment, loadshedding is eating my working hours )
     
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  14. David the swarfer

    David the swarfer OpenBuilds Team
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    Done.
    aye, loadshedding (due to go off again at 9pm, 3rd time today), and campus maintenance, power to the building I work in will be off from 8 this morning till 17:30 tomorrow, which is why I was at work all of Sunday (did manage to upgrade 6 PC's to Win10 while no-one was around).
     
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