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IndustryArena Forum > Other Machines > PCB milling > Some tracks wider, some tracks thiner
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  1. #1
    Join Date
    Sep 2014
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    13

    Some tracks wider, some tracks thiner

    Hello everybody,
    I am looking for your help as I believe an experienced eye from the forum will know the problem and the solution.
    My setup does not seem to loose steps.
    I am using Eagle, Pcbgcode and Autoleveler.
    The tracks at Eagle are same width 0.4mm.
    Bit is 0.1mm / 45Deg.
    Feed is 250mm/min.
    Any ideas?
    Attached Thumbnails Attached Thumbnails pcb4.jpg   pcb2.jpg   pcb3.jpg  

  2. #2
    Join Date
    Jul 2013
    Posts
    27

    Re: Some tracks wider, some tracks thiner

    I'm going to venture a guess and say you are using cheap(er) lead screws. If you are, they might be the cause of your problem.

    They might not even be bad. If they are not aligned properly, they may be flexing. I know with MACH3 you can do leadscrew mapping. What controller are you using? Is it a commercially produced machine or is it homemade? I know on my homemade machine, the entire fixture flexes JUST enough to cause your problem but not enough to see.

  3. #3
    Join Date
    Mar 2004
    Posts
    1804

    Re: Some tracks wider, some tracks thiner

    You also may want to look at backlash. Either in the bearing setup or the nut to lead screw. Also possibly just plain looseness in various joints.
    Art
    AKA Country Bubba (Older Than Dirt)

  4. #4
    Join Date
    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    Thanks a lot for your replies
    First pls forgive me for my bad english.
    My machine is this chinese CNC3020 from ebay.
    So the hole system is Cheap.
    But I didn't have this problem before some days.
    After many adjusting , and tests I notice this, but I am not sure what is the cause.
    I m going to post a 4th Picture which shows clearly that the problem exist when moving in two axis (diagonaly) and not horizontal or verical.
    I tested this with two controllers. The original of the BOX and one homemade. Both give the same problem Matthew.
    I recently re-screw the nuts between step Motor and lead screw but nothing changed Bubba. This is the only Joint between step Motor and lead screw.
    Any other ideas?

  5. #5
    Join Date
    Mar 2004
    Posts
    1804

    Re: Some tracks wider, some tracks thiner

    Are you relying on the stepper motor bearings to limit axial play in the screw???
    Art
    AKA Country Bubba (Older Than Dirt)

  6. #6
    Join Date
    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    A Picture of the same circuit some days ago.
    It seems almost perfect for such a cheap machine.
    Tracks are 0.4mm in design and in milled PCB
    Attached Thumbnails Attached Thumbnails pcb5.jpg  

  7. #7
    Join Date
    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    There are no mechanical modification by my site on this Commercial machine,
    if I understood well your point.
    The transmission is from step Motor to the screw via a coupler and the from the screw to the frame via a bearing.
    This is the machine.

  8. #8
    Join Date
    Jul 2013
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    27

    Re: Some tracks wider, some tracks thiner

    If there are inequalities along one of your screws you'll only see it on diagonal moves. If you have a caliper I suggest testing the actual travel of x and y individually for very small moves i.e 0.1mm.

  9. #9
    Join Date
    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    thanks, I ll check this tommorow with the caliper.
    But how at my last Picture some days ago seems fine (the diagonal tracks), I cannot understand...

  10. #10
    Join Date
    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    Does the spindle runout influencing this or to rule out this cause?
    Because I see the dots at the pcb4.jpg are seem fine.

    I noticed that the bit is not moving freely all the times.
    It seems to stuck somewhat while moving on the X-Y plane.
    I am suspecting the collet.
    How can I check if the collet is ok?
    Or just to order a new one?

  11. #11
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    Jul 2013
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    27

    Re: Some tracks wider, some tracks thiner

    Just a thought but hand tightening is never enough

  12. #12
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    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    To tight the coupler allen screws with Electric tool?

  13. #13
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    Jul 2013
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    27

    Re: Some tracks wider, some tracks thiner

    Well I wouldn't go so far as electric tools, but a pair of pliers with some electrical tape on the ends is my favorite way of tightening without scratching my nice shiny nut

  14. #14
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    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    I measured the travel of X and Y individually with the caliper and they are correct

  15. #15
    Join Date
    Nov 2012
    Posts
    154

    Re: Some tracks wider, some tracks thiner

    Just a stupid question - have you looked at your engraving bit (very closely, with a magnifier) lately, to make sure its tip hasn't slightly dented / broken off or something? This is just the sort of thing that can happen from one day to the other and it would certainly have an impact on your results...

  16. #16
    Join Date
    Jul 2013
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    27

    Re: Some tracks wider, some tracks thiner

    Well let's consider the facts:

    It used to work a little while ago, so barring some freakish motor damage or you doing some modification your not telling us about, it has to be something that you've done to the machine since.

    The only things I can think that you might be doing to the machine are:

    Changing bits
    Tightening rod nuts
    Changing feedrates

    The most likely culprit is the bit change. Are you using the proper collet? It may feel like it fits, but you need a collet made for the specific size bit you are using. I ordered a pack of 20 different collets on ebay for 10$. Like I mentioned before, are you tightening the nut enough? Also, you can check manually for any play in the machine. Try to move one axis at a time and feel if its loose, even a tiny bit.

    If, like you mentioned, the axis are moving properly, then it HAS to be the bit. Let me know how it goes!

  17. #17
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    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    Quote Originally Posted by blinkenlight View Post
    Just a stupid question - have you looked at your engraving bit (very closely, with a magnifier) lately, to make sure its tip hasn't slightly dented / broken off or something? This is just the sort of thing that can happen from one day to the other and it would certainly have an impact on your results...
    I have inspected the bit, not just with a magnifier but with microscope and it seems fine , thanks

  18. #18
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    Sep 2014
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    13

    Re: Some tracks wider, some tracks thiner

    Quote Originally Posted by matthew798 View Post
    Well let's consider the facts:

    It used to work a little while ago, so barring some freakish motor damage or you doing some modification your not telling us about, it has to be something that you've done to the machine since.

    The only things I can think that you might be doing to the machine are:

    Changing bits
    Tightening rod nuts
    Changing feedrates

    The most likely culprit is the bit change. Are you using the proper collet? It may feel like it fits, but you need a collet made for the specific size bit you are using. I ordered a pack of 20 different collets on ebay for 10$. Like I mentioned before, are you tightening the nut enough? Also, you can check manually for any play in the machine. Try to move one axis at a time and feel if its loose, even a tiny bit.

    If, like you mentioned, the axis are moving properly, then it HAS to be the bit. Let me know how it goes!
    You are right about mofication. I had been pissed of with this router since I bought it. This Info maybe much usefull to many CNC3020 or similar Routers:
    First I found that the motors cable are bad, since I measure wire by wire from controller to Motor the Connection with Multimeter (conductivity with the buzzer)
    I was so suprized that a wire of X-Axis at a specific turn inside the plastic chain stop making contact. So I replace all the motors wires.
    Then I realize I m loozing steps in X-Axis again, so I changed the capacitors of the Board. It improved much!
    But again sometmes steps were missing. I suspect a bad design of the controller and this has not selection of division of steps (i.e if you want to make it half step, 1/4, 1/8 or 1/16.
    It was fixed on PCB to 1/16.
    I thought why the heck do I need 0.00125mm step on PCBs???
    Isn't it a big unneccesary risk of losing steps?
    So I decided to design my own controller thought 0.01mm is enough (half step in my case)
    Now with my controller Works good and I have selection of microsteps resolution.
    As I said before I made for many modifications like tight again the screws, and play with different feedrates, accelaration and microsteps resolution.
    Also I changed the mounting of PCB from double sided tape to pins holding.
    There was also a hit of the spindle on the table with speed
    After all these modifications I noticed the problem we are discussing.
    I suspect if it is something wrong with pcb-gcode or Autoleveler and I run a Mach3 wizzard for cutting Circles.
    This circles was VERY GOOD!

    After this I realize that the machine is OK, so there maybe a matter of Software settings
    I changed for half step to 1/16 microsteps , 1/8 and finally again to 1/2 step.
    Change to G-code the parameter "max isolation", it was "0", i changed to 0.2mm.
    Feedrate to 1000mm/min and acceleration to 100.
    After all theses midifications just the last hour the pcb engraved fine!
    I design just triangles and circle on the pcb for testing at width 0.1 0.2 0.3 0.4 0.5mm and the pcb seems almost perfect now !!!!! I ll post the Picture later.

    Sorry But I still dont know why before 2 days was "some tracks wider and some thiner" and now they are very good!!! I neved milled 0.1mm track!
    So because I dont know what was the reason, I am afraid if this happen again in the future

    P.S I also suspected if the PCB is moving while milling because the pins holding the Board have 1.13 mm diameter and the dril I used is 1.2mm, so I thought maybe it is moving. I mounted again with double side tape.
    Same result...
    Maybe the Wood under the pcb is moving? Tighted the screws more... just for the history...

    I am using the machine's collet I never changed it. It is ER11 - 3.175 and ALL my bits are 3.175 so they fit in this collet. Because I also suspected the collet I order a NEW one. Now it seems it wasn't the reason since I think it plays a role only for the run out. Please pm me about this Super price 10$ (the link) for the set of collets. It would be usefull to have such a set for future Works.

  19. #19
    Join Date
    Sep 2014
    Posts
    13

    Re: Some tracks wider, some tracks thiner

    This is the today work.
    Tracks are with order 0.1 0.2 0.3 0.4 and 0.5mm wide
    Dimension of the pcb is 30 x 30 mm.
    Feedrate = 1000mm/min , Accel = 100,

    PCB-gcode settings : Isolation : Default: 0, max: 0.5mm, Step size:0.25mm. Etching tool size 0.55mm.
    Milling Feedrate = 250mm/min, Z down = -0.25mm.

    Controller steps are set to half step (1 step = 0.01mm).

    Bit nominal 0.1mm / 45Deg (chinese)but it is actually engraves with this settings around 0.55mm.
    Probed with Autoleveler.

    It is a very satisfied result with such a router.
    I guess it would be better with a spindle setup with less run out.
    Attached Thumbnails Attached Thumbnails IMG_20141030_010302.jpg  

  20. #20
    Join Date
    Sep 2014
    Posts
    13

    Re: Some tracks wider, some tracks thiner

    "Caution: Keep collets clean, a piece of debris or dust between the collet and bit can cause the bit to spin elliptically, harming bit, part or even operator"

    from:
    Router Bit Basics

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