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IndustryArena Forum > CAM Software > Uncategorised CAM Discussion > Wanting better G-code to speed up cutting time.
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  1. #1

    Wanting better G-code to speed up cutting time.

    I'm trying to speed up my cutting time by improving the G-code generated by my software.

    Currently, toolpaths cause the machine to carve one depth, then return to the zero position of that path, plunge to the next depth and repeat. I figure it can save a lot of time by plunging to the next depth at the end of the toolpath and reverse its direction back to zero... since raising and lowering the bit is slow, and time is wasted moving back to the zero point without cutting.

    So by example... imagine a toolpath from point A to B, with a 0.1mm depth per pass.

    Currently:
    1. Move to point A
    2. Plunge 0.1mm down
    3. Move to point B
    4. Lift up
    5. Move to point A
    6. Plunge to 0.2mm down
    7. Move to point B
    ....

    What I want:
    1. Move to point A
    2. Plunge to 0.1mm down
    3. Move to point B
    2. Plunge to 0.2mm down
    3. Move to point A
    ... repeat.

    I'm using Easel to import an SVG and export the GCODE, and CANDLE to control my CNC machine. I know Easel isn't the best, but I like it because it's super fast/easy for what I need. And it runs in a web browser so works on a Mac). However, I am willing to try other software if I can speed up the cutting time. Is there any software that can easily import an SVG (or DWG/DXF) and export GCODE like this by default?

    Any ideas? Opinions? Thanks...

  2. #2
    Join Date
    Jun 2018
    Posts
    362

    Re: Wanting better G-code to speed up cutting time.

    May not be exactly what you are looking for but with SimplyCam available from MR-Soft Nc Software Tools you can do what you want by choosing multiple cutting profiles for the same vectors, changing the depth for each DoC and then using the "Reverse" setting to change the start and end point for the cutting profile.

    You can also tell it to cut all vectors at the same depth so for multiple vectors, they all get cut at the first depth, then the next profile would use the second depth and the reverse setting and so-forth.

    Depending on how complex your drawing is there could be quite a bit of manual steps on your part to tell it how to do the cuts but using different layers of the same vectors for the "forward" and "reverse" cut directions might make it easier to manage.

    In some cases, you could possibly do the above for the first forward and reverse directions, then use a text editor to copy the text blocks to change/increase the DoC parameters because the X and Y motions would be the same.

    If you have a somewhat basic sample DXF file I'd be happy to try it and post a code sample (sounds like an interesting idea). If you do, let me know the order in which to process because with SimplyCam you can also select the order of the vectors.

    It can open and save to DXF files.

  3. #3

    Re: Wanting better G-code to speed up cutting time.

    Interesting. But I was hoping for something a little more automated, since my cuts are always complex and it would take time to plan it all out manually. Plus, I'd be afraid about what if I made a silly error at some point in the preparation.

    Good to know it's theoretically a good idea though! If you want to try, any sample would do because the process would be the same. And I'm wondering why this isn't the default behavior of making multiple passes.

  4. #4
    Join Date
    Dec 2013
    Posts
    5717

    Re: Wanting better G-code to speed up cutting time.

    I had this conversation with my son a few minutes ago. He told me that there are G code optimizers available, but crazy $$$$$. You load the G code into the optimizer and out pops G code that actually makes sense from a production perspective. Probably worthwhile if you are doing high end production, but I think out of reach for the average small shop environment, definitely out of reach for my shop.

    There are some things you can do in the CAM software to optimize the cutting, but depends on the CAM software that you are using as to how much flexibility your software has.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
    Join Date
    Jun 2018
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    362

    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by Jonnygexter View Post
    Interesting. But I was hoping for something a little more automated, since my cuts are always complex and it would take time to plan it all out manually. Plus, I'd be afraid about what if I made a silly error at some point in the preparation.

    Good to know it's theoretically a good idea though! If you want to try, any sample would do because the process would be the same. And I'm wondering why this isn't the default behavior of making multiple passes.
    As Jim says, $$ :-) You can have all the basics for $x but when you determine (quite quickly) you need extra function to make life easier, add the $ at a great rate!

    Part of the basic reasoning might be the start cut and tool chatter during initial plunge. Always starting the plunge at the same spot only gives rise to one end being possibly "distorted" but that's just my observation. I notice this a lot in single DoC circles with just a tichy bit or a "spike" at beginning and end, an overlap of the tool diameter would solve this.

    MR-Soft Nc Software Tools has just this morning released a version update. Don't know what changes yet so off to get the latest version to find out for me! Hopefully, he's included some of the suggestions I made last year and what you have asked would make an interesting request for "enhancement improvement" for future versions...

  6. #6
    Join Date
    Nov 2012
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    1267

    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by Jonnygexter View Post
    Currently, toolpaths cause the machine to carve one depth, then return to the zero position of that path, plunge to the next depth and repeat. I figure it can save a lot of time by plunging to the next depth at the end of the toolpath and reverse its direction back to zero...
    The toolpath you are describing is maintaining the same milling direction (either "conventional" or "climb"). If you can tell your software to not care about the milling direction, it may generate a faster toolpath (at the expence of cut quality).

    I am not familiar with "Easel", does it have any options for the toolpath generation that you can tune?

  7. #7

    Re: Wanting better G-code to speed up cutting time.

    It sort of sounds like you're slotting, and if not you'd typically want to maintain a climb cut so you're lift and start over is the only way to go with that in mind. Not imperative but...

    If that doesn't matter then something like CitizenOf Dream said. Or maybe you can find a function called zig-zag. If not then there's always the simple thing to do. Do it semi manually.

    I don't care how complicated the tool path is. If it has a start point and an end point that begin and end in the same places as the post suggests, generate the code going one direction, put a G1Z-0.1 at the end of it. Then generate the code going the opposite direction. Add a G1Z-0.1 at the end of that. Then take those two hunks of code as one copy unit, and copy and paste them over and over until the Z-0.1's add up to the total depth you're after. Then remove the very last G1Z-0.1 and replace it with a G0Z5. or whatever the clearance plain height you like and you're done. In lieu of copy and pasting, you could also turn that code into a subroutine and call it up that way with a repeat count. Quick. Easy. And there's practically no chance something will screw up unless you're completely not paying attention.

    Ahhh... the joys and problem solving available to semi-manual programming. Plus it's free. :-)

  8. #8

    Re: Wanting better G-code to speed up cutting time.

    Re: Easel... nope, it's super basic and meant for the CNC noobs / hobbyists.

    Awesome, I think I'm motivated to dust off my programming skills and write a script to do it. One day

  9. #9
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    1206

    Re: Wanting better G-code to speed up cutting time.

    Two things stand out from this thread.First the machine is taking tiny cuts,is it because its a tiny machine with corresponding tiny power?Because the obvious way to speed up the job is to cut a bit deeper.Second the reliance on only the software listed.There should be any amount of software that will import ,dwg or .dxf files however the challenge might be finding something that will have a suitable post processor.Take a look at DXF2CNC for instance.

    Is the machine running it's own control or is it Arduino based?

  10. #10
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    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by routalot View Post
    Two things stand out from this thread.First the machine is taking tiny cuts,is it because its a tiny machine with corresponding tiny power?
    Most likely the limiting factor is the rigidity of the machine.

    It might be possible to speed things up by dividing the job into a roughing pass (fast but inaccurate) and a finishing pass (slow but accurate).

  11. #11

    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by routalot View Post
    Two things stand out from this thread.First the machine is taking tiny cuts,is it because its a tiny machine with corresponding tiny power? Because the obvious way to speed up the job is to cut a bit deeper. ... Is the machine running it's own control or is it Arduino based?
    Thanks for noticing. I actually have another thread about that (that lost some traction). https://www.cnczone.com/forums/chine...95726-cnc.html
    The issue was I heard an unpleasant knock sound when plunging, when the bit penetrated the material. The way I got it to stop was by drastically reducing the plunge rate and depth. Of course I would like to speed that up too, but I consider that another issue. I'd be super grateful to get more info on that thread (or here), as I plan to do some testing today to try increasing the speed/depth today.

    My machine is the cheap DIY kit CNC 2418, so it's not very strong, but adequate for my needs (a hobbyist cutting thin polycarbonate). I'm sure its solidity doesn't compare to a professional machine, and also, I only get max 7000-8500 RPM on the spindle. Yes, it is Arduino based.


    Quote Originally Posted by routalot View Post
    Take a look at DXF2CNC for instance
    Thanks, I will have a look.


    Note: I forgot to mention I'm on a Mac.

  12. #12
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    Re: Wanting better G-code to speed up cutting time.

    You should be able to do better than 0.1mm in polycarbonate. My plastic CNC machine ( an upgraded Zen Toolworks clone) cuts polycarbonate with a 2mm cutter at 600mm/min and 0.5mm depth of cut.


  13. #13

    Re: Wanting better G-code to speed up cutting time.

    In general, plunging is the worst way to get to depth in any cut with any diameter cutter on any machine regardless of size or rigidity.

    I would suggest pre-drilling, but I'm betting there's no tool changer involved so that might not be the best idea.

    If the tool path that was originally talked about has a move at either end that could be used, you could ramp down to the next level either during the final move of the sequence, or in the first move going back toward the starting point. In short, and in about any tool path needed, try a ramping move to get where you're going. There is plenty of information out there about maximum ramp angles or helical ramping to depth if that's your pleasure.

  14. #14
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    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by Jonnygexter View Post
    Thanks for noticing. I actually have another thread about that (that lost some traction). https://www.cnczone.com/forums/chine...95726-cnc.html
    The issue was I heard an unpleasant knock sound when plunging, when the bit penetrated the material. The way I got it to stop was by drastically reducing the plunge rate and depth. Of course I would like to speed that up too, but I consider that another issue. I'd be super grateful to get more info on that thread (or here), as I plan to do some testing today to try increasing the speed/depth today.

    My machine is the cheap DIY kit CNC 2418, so it's not very strong, but adequate for my needs (a hobbyist cutting thin polycarbonate). I'm sure its solidity doesn't compare to a professional machine, and also, I only get max 7000-8500 RPM on the spindle. Yes, it is Arduino based.




    Thanks, I will have a look.


    Note: I forgot to mention I'm on a Mac.
    I would suggest you take a look at Freecad and GRBL for running the machine.Freecad costs nothing and is very capable once you learn it's ways;it allows a ramp entry and has a GRBL post processor built into the list of post processors.I can't offer much advice about Mac matters or GRBL,but being Arduino based you can probably figure that part out.

  15. #15
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    Re: Wanting better G-code to speed up cutting time.

    Quote Originally Posted by the_gentlegiant View Post
    In general, plunging is the worst way to get to depth in any cut with any diameter cutter on any machine regardless of size or rigidity.
    Very true, that's one of the reasons why the OP should invest some money or time in a better CAM program.

    I am personally in love with CamBam (which is a paid product but has very generous trial terms). It's mostly suitable for 2D and 2.5D work though.

  16. #16
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    1662

    Re: Wanting better G-code to speed up cutting time.

    Is there any software that can easily import an SVG (or DWG/DXF) and export GCODE like this by default?
    For those file types I really can't recommend FreeCad. For svg/dxf I usually use Fusion360 although I'm not proud of it, I trust AutoDesk about the same as a used car dealer.
    FreeCad is is very good and open source but dxf/svg is a weak point, I hope they fix it soon.
    Fusion360 is currently free to hobby use, in the future who knows(?). It has excellent CAM to fine tune a toolpath.
    As gentlegiant points out, straight plunging should be avoided if possible
    Anyone who says "It only goes together one way" has no imagination.

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