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  • First Z plunge too deep

    I have a small Taig with Mach 3.My wife wants a plaque for her project.On using Desk Engrave all goes well after the first plunge which goes too deep.Reloading Desk Engrave didn't help and no good answers on Mach 3 forum.No tool offsets are being used and it doesn't seem to be backlash either.The code should raise cutter 0.1 inches and plunge to 0.05 for the cut but the fist plunge goes at least 0.1 and then the rest are OK.I am starting with all DROs @ 0 and the cutter just brushing the workpiece.

  • #2
    Check to see if the code includes G90 or G91. Post the first 10 lines of g-code here as well.
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    • #3
      G 90 T0 F60.0
      N0 G00 Z0.10
      N1 G00 X0.00 Y0.00
      N3 G01 Z-0.05 F10
      N4 F60.0
      N5 X0.15 Y0.38
      N6 X0.20 Y0.38
      N7 X0.36 Y0.00
      N8 X0.30 Y0.00
      N9 X0.26 Y0.12
      N10 X0.10 Y0.12

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      • #4
        Code looks OK.
        What driver are you using and how many steps per inch are you set up on the Tiag.
        It maybe that the steps are too course causing it to go lower.

        .
        .

        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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        • #5
          Waitaminute. Engraving at 60 ipm? And why is F10 immediately followed by F60? Edit the F60 statements to read F10 and see what happens. It's probably losing position.
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          • #6
            I'm with Evan, 60ipm is way to fast.
            I would remove the F60 behind the G90 and then remove the F60 farther down where you are machining and try something more reasonable like F5-F15

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            • #7
              If he is doing wood 60 IPM is OK, heck, I do aluminum at 40.

              The code looks OK, The F10 Sets the Z plunge to 10 IPM then resumes cutting at 60 IPM.

              Might try getting rid of the G90 and T0 and see what happens. Dont really need it as it default to absolute mode.

              Otherwise I would say there is a setup issue.

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              • #8
                Yup, it's line 3 that's causing the trouble.

                N3 G01 Z-0.05 F10

                It should go 50 deep at 10"/min and according to the OP it's not.

                What goes after that doesn't matter if that line is correct and there is nothing wrong with that line.

                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • #9
                  I just had a look at how Desk Engrave handles numbers. The default accuracy for all calculations is integer with all decimal fractions rounded up. If I enter a z depth of -.5 it produces -1 in the code.

                  To change the default go to "Create">Set Parameters and set the value of "Dec. Places" to 4 instead of 0 (or 2).
                  Last edited by Evan; 06-19-2008, 06:58 AM.
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                  • #10
                    Originally posted by Evan
                    I just had a look at how Desk Engrave handles numbers. The default accuracy for all calculations is integer with all decimal fractions rounded up. If I enter a z depth of -.5 it produces -1 in the code.

                    To change the default go to "Create">Set Parameters and set the value of "Dec. Places" to 4 instead of 0 (or 2).
                    Well spotted but Sopfiedocs code HAS put out Z-0.05 so if that's in the code it should move 0.05 units, so it looks like the OP's defaults are set correct.

                    Still waiting to see what the settings are, a Taig has 20 tpi screws as standard unless it's been converted to ballscrew.


                    John S.
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                    • #11
                      Z-.05 is pretty deep for an engraving cutter.
                      Most that I do are Z-.005/Z-.010.

                      I also limit the retract to Z .005/Z.01 as a timesaver.
                      But then I'll usually flycut the surface first.

                      Feeding up and down .150 @ F10. takes lots of time
                      on long engraving projects with hundreds of moves.

                      Time is money!

                      Does your control need an "H1" and G43 to pick up the
                      tool # 1 height?

                      I don't see where you are putting a tool number in.
                      T0M6 or T0Z0 is ususlly used to home the z axis isn't it.

                      I don't know what options you have on your software or control.

                      Kap

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                      • #12
                        Kap,
                        He says engraving but I get the impression he's working in wood at which 50 thou with a vee cutter isn't excessive. Without more feedback the post is stalled.

                        .
                        .

                        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                        • #13
                          Originally posted by Sophiedoc
                          G 90 T0 F60.0
                          N0 G00 Z0.10
                          N1 G00 X0.00 Y0.00
                          N3 G01 Z-0.05 F10
                          N4 F60.0
                          N5 X0.15 Y0.38
                          N6 X0.20 Y0.38
                          N7 X0.36 Y0.00
                          N8 X0.30 Y0.00
                          N9 X0.26 Y0.12
                          N10 X0.10 Y0.12
                          I only have commercial machines, so don't know about Mach controller.

                          But, none of my machines will go above Z0 unless a tool offset has been set with respect to the part's top surface. The spindle itself (without tool offset active) will not go up beyond the Z0.0 level.

                          Above Z0.0 you would hit a soft stop and eventually a hard stop. Is this an open loop system? Is he losing position some how by hitting a stop?

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                          • #14
                            The mill is standard.What puzzles me is why the depth goes too deep on the First plunge only and then is OK with the other plunges.I've considered starting the engraving line outside what SWHMBO wants so the thing is stabilized before the actual placque is encountered.She is pushing for me to get done so she can incorporate it into her stained glass project for my brothers 50 years of married bliss.I will try the things mentioned -unfortunately the machine is at the farm shop where there is no internet access which delays my responses.

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                            • #15
                              Just in case there is a problem with rounding errors try setting the Z to -.051 instead. Also, try the various suggestions one at a time. It's always nice to know what works or doesn't work.
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