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  1. #21
    Member mantalos's Avatar
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    Post Re: How to avoid premature tool failure

    Hello,

    I finished milling the "larger_board". You can see the results in the attached picture.

    Settings:

    1) Feeding speed = 20mm/min
    2) Spindle at 22V (~7333 rpm)
    3) Tool: Cheap V-bit 30°/0.1mm
    4) Milling depth 50 um
    5) In FlatCAM I set the tool tip to 0.2mm to get good results. Probably this is needed because my tool is not actually a 0.1mm tool and/ or my spindle has a huge runout.
    6) 4 passes 40% overlap
    7) Auto leveling using bCNC.
    8) Added some sunflower oil on the blank pcb board. This was just an experiment because I didn't have any cutting fluid and it seems that it helped!

    In this board I use 10 mil tracks. The smallest isolation distance is 0.2 mm (pad to pad for the TSSOP chip).
    I edited the gcode and removed 3 out of the 4 board outlines to accelerate the milling. However, I forgot to remove a gcode command for the z axis and the machine milled a huge straight line throughout the board.
    Other than that, the improvement is obvious with respect to the "cheap_v_bit.jpg?" I uploaded in the first post. What is your opinion?

    Attached Thumbnails Attached Thumbnails How to avoid premature tool failure-larger_board_03-jpg  


  2. #22
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    Default Re: How to avoid premature tool failure

    Yup, that looks pretty good... Results look quite nice for the TSSOP chip - I don't even go below SOIC typically (which I know for sure I can mill without issues) or preferably even use DIP - size tends to not matter that much for me and DIPs either let me pass a track between pins (very useful on a single-side PCB) or offer a free "via" (if I decide to bother with double-side registration).

    I'm sure there's room for experiments with other milling bits or even another spindle, but it looks like you've reached what a 3020/6040 should be able to do.



  3. #23

    Default Re: How to avoid premature tool failure

    Hi,
    that is a marked improvement but is still pretty raggedy.

    I suspect your spindle has too much runout to do a good job. I would suugest you look to improve your machine with a 24000 rpm
    spindle. They (usually) have angular contact bearings and will bring the runout down to 5um or so. You don't need alot of power
    for PCB's, 750W is more than enough. If you want to do wood or aluminum then consider 1.5 -2.2kW.

    The Chinese made spindles are pretty good....for the money.

    I use this one from Germany:

    https://www.mechatron-gmbh.de/filead...08-24-ER11.pdf

    Craig



  4. #24
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by joeavaerage View Post
    Hi,
    that is a marked improvement but is still pretty raggedy.

    I suspect your spindle has too much runout to do a good job. I would suugest you look to improve your machine with a 24000 rpm
    spindle. They (usually) have angular contact bearings and will bring the runout down to 5um or so. You don't need alot of power
    for PCB's, 750W is more than enough. If you want to do wood or aluminum then consider 1.5 -2.2kW.

    The Chinese made spindles are pretty good....for the money.

    I use this one from Germany:

    https://www.mechatron-gmbh.de/filead...08-24-ER11.pdf

    Craig
    Craig, you are right the results were not perfect. I will consider buying a new spindle. The one you suggested seems really good but it is too expensive for me right now. Do you think this one from aliexpress would be OK for milling aluminum?

    https://www.aliexpress.com/item/3280...175b2e0e5X0dtn

    Today I milled another "larger board" and I think the results are much better (see the attached pictures). Here are the settings:

    1) Feeding speed = 20mm/min
    2) Spindle at 22V (~7333 rpm)
    3) Tool: Brand new cheap V-bit 30°/0.1mm. The one used in the last board was also used for three other failed milling jobs and it seems it wasn't as sharp as a new one.
    4) Milling depth 60 um
    5) In FlatCAM I set the tool tip to 0.2mm to get good results. From the results in this board probably a value of 0.15mm would be better.
    6) 4 passes 40% overlap
    7) Auto leveling using bCNC. In this case I used a much more dense auto level grid. Auto level probe speed set to 5mm/min.
    8) Sunflower oil on the blank pcb board.
    9) Used a single sided blank board of better quality.

    Also, I didn't have to scrub the board. Total milling time of 4 hours. The results are actually comparable (quality not speed of course) with the $20k LPKF's ProtoMat S64 that we have in our university. What do you think?

    Attached Thumbnails Attached Thumbnails How to avoid premature tool failure-larger_board_04a-jpg   How to avoid premature tool failure-larger_board_04b-jpg   How to avoid premature tool failure-larger_board_auto_leveling04-jpg  


  5. #25

    Default Re: How to avoid premature tool failure

    Hi,
    yes that spindle has enough power to cut aluminum, but is your machine rigid enough?

    Many have tried cutting aluminum and other metals only to find that their machine is not rigid enough and
    therefore cant cut metals worth a damn.

    Can you post your code for the test board an I'll try to cut it and post the pics.

    Craig



  6. #26
    Member CitizenOfDreams's Avatar
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    Default Re: How to avoid premature tool failure

    You can try increasing the feedrate - your chip thickness is only 0.003mm now, which is probably one of the reasons for rapid tool wear. My usual parameters are around 200mm/min at 10,000RPM.



  7. #27
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    Default Re: How to avoid premature tool failure

    Concerning aluminium - well, there's cutting aluminium and cutting aluminium; I don't think one can do with this kind of machine anything close to what one tends to see in videoclips where aluminium is simply ripped away like it isn't even there, in seconds, by full-size machines. On the other hand, you can cut as slow and as shallow as you like, and there's nothing magical about aluminium that would prevent you cutting it slowly enough (preferably with a dedicated Alu tool though...). I've cut 1mm thick steel plate with my bog standard 3020 and spindle - granted, slowly as hell, and I broke a half a dozen bits on the first 5cm - until I remembered to use some oil and completed the remaining dozen holes with the same single bit. So, I wouldn't count on being able to do production work in metals with these mills, but that said nothing stops you from occasionally cutting fairly soft stuff if you're patient enough...



  8. #28
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by joeavaerage View Post
    Hi,
    yes that spindle has enough power to cut aluminum, but is your machine rigid enough?

    Many have tried cutting aluminum and other metals only to find that their machine is not rigid enough and
    therefore cant cut metals worth a damn.

    Can you post your code for the test board an I'll try to cut it and post the pics.

    Craig
    Yes find attached the gerber files.

    Regarding the aluminum milling, I think my machine is rigid enough for some light milling. No heavy production of course. Future experiments will show the actual rigidity.

    Attached Files Attached Files


  9. #29
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by CitizenOfDreams View Post
    You can try increasing the feedrate - your chip thickness is only 0.003mm now, which is probably one of the reasons for rapid tool wear. My usual parameters are around 200mm/min at 10,000RPM.
    Yes I will make some new tests with higher feeding speed and report the results. Till now I believe that the most important factor that caused premature tool wear was that I was cutting very deep because of the lack of the auto level procedure. Now the noise level during the milling process is much lower and I am sure this is because the machine cuts much less of the FR4 substrate.

    At the beginning I was able to mill only with the Stepcraft's V-router. Now that the process is substantially improved I can test the life of a new V-router bit.



  10. #30
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by blinkenlight View Post
    Concerning aluminium - well, there's cutting aluminium and cutting aluminium; I don't think one can do with this kind of machine anything close to what one tends to see in videoclips where aluminium is simply ripped away like it isn't even there, in seconds, by full-size machines. On the other hand, you can cut as slow and as shallow as you like, and there's nothing magical about aluminium that would prevent you cutting it slowly enough (preferably with a dedicated Alu tool though...). I've cut 1mm thick steel plate with my bog standard 3020 and spindle - granted, slowly as hell, and I broke a half a dozen bits on the first 5cm - until I remembered to use some oil and completed the remaining dozen holes with the same single bit. So, I wouldn't count on being able to do production work in metals with these mills, but that said nothing stops you from occasionally cutting fairly soft stuff if you're patient enough...
    I would be really happy if I could achieve something like this:


    I think the specs of this machine are similar to mine.



  11. #31

    Default Re: How to avoid premature tool failure

    Hi,
    I too used to believe that it was possible to cut any material PROVIDED I took light enough cuts.....but......you run into the problem
    that if you take a really light cut you risk the tool just 'giving it a good rub' and you generate heat but no chips.

    The two determinants as to how successful you'll be are spindle torque and machine rigidity.

    Without sufficient torque you will stall the spindle and break the tool. There is always the temptation to run the tool fast, once you've had a tool
    where the tip turned cherry red in a few seconds will disabuse you of that idea.

    The next problem is rigidity. If you create Gcode to cause the tool to engage the material for a depth of cut of 0.1mm . If the machine deflects under
    that pressure by 0.09 mm then the actual cut will be only 0.01mm and you are in the territory of 'giving it a good rub'.

    Best advice is try it and see.

    Craig



  12. #32

    Default Re: How to avoid premature tool failure

    Hi,
    tried cutting your test board.

    Imported the Gerber into Eagle and used the Gcode generator tool with the following properties:
    Tool Tip Diameter=0.1mm
    Step Over= 0.05mm (50%)
    Depth=0.06mm
    Speed=600mm/min, plunge 300mm/min.

    I used my existing engraving tool which has had about 4-5 hours cutting prior to this job, so about 1/2 worn.

    It took 43 min 45 sec.

    Craig

    Attached Thumbnails Attached Thumbnails How to avoid premature tool failure-dsc_0007-jpg  


  13. #33

    Default Re: How to avoid premature tool failure

    Hi,
    I notice there are a couple of places where the Gerber Import has not worked well, namely around the SMD capacitor pads and notice
    also a little burring at two of the corners.

    The tracks/pads in the vicinity of the IC are good.

    Craig

    Attached Thumbnails Attached Thumbnails How to avoid premature tool failure-dsc_0007-jpg  


  14. #34
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by joeavaerage View Post
    Hi,
    I notice there are a couple of places where the Gerber Import has not worked well, namely around the SMD capacitor pads and notice
    also a little burring at two of the corners.

    The tracks/pads in the vicinity of the IC are good.

    Craig
    Nice! Apart from these two places the PCB looks pretty good. By the way they are not capacitors but resistors at the gates of the MOSFETs. The board is a single layer stepper controller I designed to upgrade my machine. I will upload the design to github as soon as I verify it's functionality. What tool you used? The traces seem a little thinner. Maybe 50 um would be better for your machine and/ or the tip was not sharp so the 0.1mm was not valid for the CAM software.



  15. #35

    Default Re: How to avoid premature tool failure

    Hi,
    I think that the tip of the tool is 0.2mm, so by me nominating a tool tip diameter of only 0.1mm would confuse the Gcode generator and make narrower tracks than target.
    I did that in hopes that it might resolve the issue with the Eagle Gcode generator not 'seeing' the gap between the SMD pads.

    It looks however that its the Gerber import that into Eagle that is not quite right.

    Ordinarily when I design in Eagle I can quite happily use 0603 and SOT223's with this tool, but for some reason the imported Gerber does not work as well.

    Craig



  16. #36
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    Default Re: How to avoid premature tool failure

    Quote Originally Posted by mantalos View Post
    I would be really happy if I could achieve something like this
    Oh, you can definitely do that. I do similar things with alu enclosure end-plates with no issues whatsoever. It's more about finding the right tool/speed/feed/depth combination that avoids chips sticking/galling to the tool - that can happen and it definitely is a problem when it does.

    Quote Originally Posted by joeavaerage View Post
    It looks however that its the Gerber import that into Eagle that is not quite right.
    Are you sure Eagle can handle polygon type pads? The thing is, in traditional Gerber there is no such concept as a "rotated" pad - everything is either a circle, a vertical/horizontal rectangle, or a vertical/horizontal oval (obround). As soon as a part gets rotated with ANY non-90-degree-multiple value, its pads simply can't be expressed as standard pads any more*, only as filled polygons - which is a very much "legal" Gerber thing, but only recently becoming popular which means a lot of older Gerber implementations may have undetected issues with them (if they support them at all). And I can't help but notice that only those pads have rotation on the board...

    * okay, I lied - obrounds are an exception: they can be rotated without issues to any degree because they just become "tracks" with rounded caps instead of being "flashed pads". However, recently rounded rectangle pads became popular (and IPC-7351 recommended apparently) and those can DEFINITELY be only expressed as polygon fills at ANY angle, driving the need for support. But this trend is definitely not that old in the hobby world, where Kicad wasn't even capable of any non-90 rotation for a part not that long ago.



  17. #37

    Default Re: How to avoid premature tool failure

    Hi,

    Are you sure Eagle can handle polygon type pads?
    Yes, Eagle uses polyangonal pads, round pads and obround pads no problems and can be rotated to any given angle.

    I believe the translation from Gerber to Eagle is a bit suspect, looking at Eagels rendering of the Gerber file seems to indicate that
    the outermost boundary line of a feature has considerable thickness, maybe 0.1-0.2mm. It seems that the thickness of the outer line
    is encroaching on the space between features. That would describe what I saw today.

    As I design in Eagle and use the ULP Gcode generator I can isolation route features as fine as 0.2mm no problems.

    Craig



  18. #38
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    Default Re: How to avoid premature tool failure

    Yes, it looks like whatever is reading the Gerber file is doing it wrong - it's "painting" region fills with the current aperture thickness (as one would do for tracks) instead of considering the contour a zero-thickness ideal geometric object. As per the UCAMCO Gerber spec rev. 2018/11, section 4.8:
    Outside a region statement stroking is used to convert a segment into draw or arc graphics object. Inside a region statement a segment becomes the linear or circular contour segment.
    That distinction is clearly lost on the importer which adds the thickness of the line to the region's contour. It's a bug...

    At any rate, trying to read a Gerber back into a CAD software for CAM purposes is really a bad idea anyway - That's what things like FlatCAM are for...



  19. #39

    Default Re: How to avoid premature tool failure

    Hi,

    At any rate, trying to read a Gerber back into a CAD software for CAM purposes is really a bad idea anyway - That's what things like FlatCAM are for...
    Its the first time I have tried importing a Gerber file and it was not 100% sucessful. Your description of what is happening to the outline of a geometric part
    sounds spot on.

    I do have FlatCAM but have not really experimented with it enough yet. I also have Kicad, but have not really used it yet. I'm using my machine at work so
    I tend to design in Eagle because I'm so familiar with it and I can depend on the results.

    Craig



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