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Thread: Xairflyer's first MDF CNC router

  1. #61
    Registered xairflyer's Avatar
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    The driver board is the K179 kit basicly the same as the piker.

    I hgave altered the value of the pot and limit resistor (used for manual control, not connected to PC) and when I go too far, the motor just buzz'sssss

    I assume the motor can only go so fast.

    Does the speed vary in motors ? I am wondering if my 2A 127 ozins vexta 266-2b motors will go any faster.



  2. #62
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    can't find any numbers on the website, but my 80 oz/in motors are capable of 120 rpm so I can't see yours being slower. Check that your screws are not binding at either end of travel, as that has in the past caused just buzzing with no turning. You'd have to turn 400rpm to get 20 ipm, right? Huh...don't know how that math works out then, cause Steve Manzer is getting 20ipm and I think he is useing the the same cheap motors. I'll do some reading on his site today, post later.

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  3. #63
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    Higher oz/in does not mean faster unless you go higher VOLTAGE powersupply. 24 volts with the right resistors will double your speed.

    Trust me on this one.

    Oh, and don't worry for now about speed. Get the machine going first.

    Trust me on this one too.

    Also, I am not sure how/if you can accel with the setup your using, but that is a factor as well.

    Eric

    I wish it wouldn't crash.


  4. #64
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    Balsaman is right, if your drive nut is not causing lots of friction the problem is in your drivers. Get a chopper board, run it at 30V and amaze yourself at the speed you get

    John



  5. #65
    Registered xairflyer's Avatar
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    Now I know that 10" min is normal for this setup I will stick with it. I thought I was doing something wrong.
    I don't want to fit a different driver board or bigger power supply, the idea was to make this machine as cost effective as posible to prove the principle to myself.

    If I can speed it up a bit with 10mm threaded bar then I might change to that.

    I will go with Xylotex board and proper drive screws and all the bells and wistles for the all alloy machine I will build next.
    First I want to understand how to get this one setup.



  6. #66
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    he driver board is the K179 kit basicly the same as the piker.
    I wonder if the mosfets are being driven hard enough by the cmos logic at 5volts...

    do the mosfets get warm(er) when the stepper buzzes?

    the z44s are sufficiently hefty...

    maybe...


  7. #67
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    Not sure if they get warm as I adjust the pot, until it starts to buzz then back it off slightly so it is at maximum speed.

    I measured the 100k pot at this setting and it was about 900ohms, so I increased the in series 1k limit resistor too 2k2 so I can just screw the pot the full way now, just for practicality.

    I am using this board (K179) as a stand alone at the moment just for testing, a 4093 is used as a pulse generator.
    The values of the pot and series resistor shown in the documentation have been changed to values above.

    As I know full speed is a pulse frequency generated by approx 1k9 with the cap fitted (1uf) I will try a 4k7 pot in place of what's there and adjust that to the optimum, that way I will be able to get the motor at it's optimum speed before it buzzes.



  8. #68
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    Seen somewhere diodes added from each side of the coils to positive, so I decided to add them in and see what happens.

    I connected each one first by mistake to the 12v (bypassing the dropping resistors) and the motor ran at the same speed by sounded very rough.

    Connected them then to the other side, matching the centre taps, as I am using two resistors (just in case it would make a difference) and the motor ran very very slow.

    Realised then afterwards that fitting diodes like this was really for protection of transistors and as I am using fets, it just made things worst.

    Any views ?


    NOTE I have not shown the diodes on the circuit below, I just attached it to show the ouput.

    Attached Thumbnails Attached Thumbnails Xairflyer's first MDF CNC router-driver-output-gif  


  9. #69
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    Been working on the Y axis, as you can see from the pics I used angle and roller bearings again. In order to get the angles nice and square I milled/routed two slots for it to sit in.

    Had to also mill out some clearance for the nuts.
    Set my rails up first like the x axis, but this was a mistake as I then had to make the spacing piece to fit the setup of the rails, which meant machine the spacer 58.8mm !

    Should have made the spacer a fixed demension i.e. 60mm or
    2 1/2" and adjusted the rails to suit.

    Also got the rails perfectly set up, only to realise, I needed to remove one of them to fit the y carriage !!
    Rails needed to be fine tuned again anyway - you learn these things as you go !:

    Attached Thumbnails Attached Thumbnails Xairflyer's first MDF CNC router-y-axis-detail-jpg  


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    Great carriage design...how is the flex in the steel rods though?

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  11. #71
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    The rails are 25mm (1") Stainless Steel tubes with a 1.5mm (.060") wall and are very ridget (can never spell that word).

    If I push down on them, I can get them to flex about 0.2mm (.008"). I am going to fit a support block under the lower rail and above the top rail once I get everything setup.



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    Are your bearings pre-loaded into the tubes? Just curious, as it doesn't look as though you have any adjustment for the tubes themselves. Oh...its rigid. Gonna go for now...uncle Bushmills is calling my name!

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  13. #73
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    If you about 15 posts up you will see the four jaw chucks fitted to the side plates.



  14. #74
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    Messed about with the driver board, and now have 12" min with the 20tpi screw.
    Going to stick with that now until I get the machine running, will then try 10mm and 12mm threaded bar.



  15. #75
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    Working on the Z axis, and decided to have a go at making my own bearing blocks for these great simplicity bearings from Pacific.

    Main concern was accuracy, as I did’nt want them binding. Decided to go with a mixture of mdf and nylon.
    Made the two end plates for the 12mm shafts out of mdf and milled them perfectly square. I put one on top of the other and then used a 12mm milling cutter that I under sized slightly to drill the holes. I clocked up the spacing on the cross slide vice, to have a reference for the bearing blocks.
    The 12mm shafts were now a rubber hammer tap into the mdf end plates.

    The simplicity bearings have an OD of 22mm and in the manual it shows fitting ‘O’ rings to the groves to allow for slight misalignments which I thought would suit here.
    The hole in the bearing block is oversized 0.2mm to allow for this, so I modified/ground a flat wood bit to 22.2mm. These are great for cutting accurate holes.

    Made up the two nylon bearing blocks and drilled them like the end plates, with the exact same centers. Holes came out 22.22mm (.02mm oversize less than a thou) I was happy with that.
    Bearings were a nice tight fit in the blocks. As I used 25mm nylon I milled down to 20mm to allow for the retaining circlips.
    I can see now how the ‘O’ rings work, it is a really good idea, keeping to the manufacturers sizes would be important though.

    My two blocks slide really nice up and down the shafts, I still have to fit the router holder to the blocks.

    Really glad I went this route, simplicity bearings are cheap and are designed to run on any type of shafting, provided it is true. The cost of the Bearing housings put me off before going this route, but reading mikeschn thread got me thinking.

    Attached Thumbnails Attached Thumbnails Xairflyer's first MDF CNC router-z-axis-bearing-blocks-jpg  


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    And the Z axis itself, temporarily fitted to the Y


    Note. Nylon block between bearing housings is only a temp spacer.

    Attached Thumbnails Attached Thumbnails Xairflyer's first MDF CNC router-cnc-190s-jpg  


  17. #77
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    Looks soild, that should work fine.

    Thank You,
    Paul G

    Check out-
    [URL="http://www.signs101.com"]www.signs101.com[/URL]


  18. #78
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    Are you going to have more space between the bearings when the spacer is removed? I would be concerned about flex in the tool carrier without enough space.

    Stop talking about it and do it already!!!!!

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  19. #79
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    There won't be any movement, this is one of the reasons for going with this type of slide.



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    Originally posted by xairflyer
    There won't be any movement, this is one of the reasons for going with this type of slide.
    Wouldn't the unsupported pipe/rod be the source of almost all of the flex in this configuration? In that case, you would get less flex by putting the bearings further apart.

    Arvid



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