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    Registered Tadas25's Avatar
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    Default my new MDF project

    Hi,
    I have created new design in solidworks. This is concept for today. I need to know what you guys think about this design, to move forward with it.
    The material is MDF 30mm (1,2") thick.
    overall size is 2000x1500x500mm
    Working area is about 1600x1300x350mm
    Rails are from 25mm steel shaft.
    Stepers from probotix 400 oz:
    Green Monster 400 OzIn 8-Wire Stepper Motor
    400 Oz In. Hybrid
    1.8° /200 Steps Per Rev.
    3 Amps Current Per Phase
    8-wire Uni-polar or Bi-polar
    NEMA 23 Frame
    Factory Enameled Green Body
    Dual Shaft

    16mm acme screws with bronze flange nuts.







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    Those rods are going to flex on you, even with the supports you have in between. I suggest using fully supported rods.



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    I agree, 16mm fully supported rod with linear bearings would be enough and would give you far greater rigidity and precision than the skate bearings. Besides, it would allow you to place the Y and Z screws between the bearings (always a good idea), and since it will be smoother you'll be able to take more speed out of your motors/drivers. It you want to go on with your design I would at least turn the ribs into torsion boxes, and perhaps make them a little wider. The X-axis motor should be at the center, it's going to become a headache to use it at the side unless you use two motors (one at each side); rigidity will be greatly affected with the current X design.

    ¿How are you going to control the motors? I have the Green Monsters and they really don't like 24V. If you're in a budget you can get one of those 350W 36V switching PSUs from Ebay and adjust the pot up to 38-40V (check that it keeps below the built-in safety margin so it doesn't shut down). Using this at 2.5A per axis should be a good combination. If your drivers can take more than that (Gecko, for example), then it's better to get the 48V version of said supply (seems to be the same with few modifications); don't get the 48V version if you are using a Probostep, since it probably won't be able to be adjusted to 42V even when the datasheets says it will (I had to replace a resistor to be able to get it down to 42). Oh, and the yellow motor from Probotix should be enough for the Z axis.

    Regarding the current design: I would lenghten the Z and Y's (specially Z) aluminum parts so the bearing pairs are further apart (as you did on the X axis), it would add rigidity.

    ¿Do you really need as much Z travel? a lower gantry would help a lot.

    What I would do (and actually did) is to make the machine by hand, and then get linear rails and bearings, cut the needed parts on the CNC and then assemble the final build (if you can build the first machine by hand but using linear rails you'll save yourself some trouble and have the second machine sooner and with probably more accurate pieces).

    I recommend you these anti-backlash nuts: dumpsterCNC - anti-backlash solutions for home and industrial linear motion



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    Quote Originally Posted by Walky View Post
    I agree, 16mm fully supported rod with linear bearings would be enough and would give you far greater rigidity and precision than the skate bearings. Besides, it would allow you to place the Y and Z screws between the bearings (always a good idea), and since it will be smoother you'll be able to take more speed out of your motors/drivers. It you want to go on with your design I would at least turn the ribs into torsion boxes, and perhaps make them a little wider. The X-axis motor should be at the center, it's going to become a headache to use it at the side unless you use two motors (one at each side); rigidity will be greatly affected with the current X design.
    I will update my drawing with DIY supported rods (give me about 2h).
    Here on pics, I have not shoed that X axis have 2 motors (one for each side).


    Quote Originally Posted by Walky View Post
    ¿How are you going to control the motors? I have the Green Monsters and they really don't like 24V. If you're in a budget you can get one of those 350W 36V switching PSUs from Ebay and adjust the pot up to 38-40V (check that it keeps below the built-in safety margin so it doesn't shut down). Using this at 2.5A per axis should be a good combination. If your drivers can take more than that (Gecko, for example), then it's better to get the 48V version of said supply (seems to be the same with few modifications); don't get the 48V version if you are using a Probostep, since it probably won't be able to be adjusted to 42V even when the datasheets says it will (I had to replace a resistor to be able to get it down to 42). Oh, and the yellow motor from Probotix should be enough for the Z axis.
    I will buy 4 axis set from probotix:
    4-Axis Monster CNC Stepper Motor Driver Kit - 4-Axis Monster CNC Stepper Motor Driver Kit
    With 40V PSU


    Quote Originally Posted by Walky View Post
    Can you recommend seller like this stuff on europe ?

    Tadas M.



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    here My new design. I think that would be fine. What you think guys ?







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    check out Joes 2006, seems like you may have drawn your design from here so no point reinventing the wheel so to speak.

    good luck

    I'll get it finished sometime after I start it.....


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    Quote Originally Posted by robe_uk View Post
    check out Joes 2006, seems like you may have drawn your design from here so no point reinventing the wheel so to speak.

    good luck
    honestly I have not seen this joe's model. I saw only JOE'S HYBRID model.
    Its looks a bit same as mine or vise versa. But there are differences between them.

    Speaking about wheels, the reinvention is great thing.
    example:

    and




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    Nice, that torsion box will sure reduce flexing. The Probotix 4 axis kit with 40V supply is nice, I've built 2 machines using those Probostep drivers and they still work like the first day.

    Beside Joe's, you can also check the Lionclaw for some ideas:
    http://www.cnczone.com/forums/cnc_wo...law_lc50b.html

    Actually, I think the best advice I can give you is to check as many machine designs as you can, since they are all different and there are a lot of ideas to get from most of them. Googling (both on websites and images)) things like "diy cnc", "cnc gantry" or "cnc z axis" will make your project a lot easier; I always do that when I'm designing a specific part.

    Regarding the nuts, I have no idea about similar products in Europe, but it seems these guys can send to any country and shipping cost is not too high (I got some sent to Chile).



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    It looks a lot like the ones I have designed: New build… Here we go again



    If you go forward a few posts your can see that I am almost done with it. The design is set up for 1 or 2 screws on the X axis, either underneath or on the sides. The one shown is a small single screw version, I have 2 other end pieces for the 2 screw version (underneath and out to the sides). I can tell you that using 1/2" gas pipes (5ft) on my prior machine, I got very little flexing: A sagging concern.

    -GrumpyGeek



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    Quote Originally Posted by grumpygeek View Post
    It looks a lot like the ones I have designed: New build… Here we go again



    If you go forward a few posts your can see that I am almost done with it. The design is set up for 1 or 2 screws on the X axis, either underneath or on the sides. The one shown is a small single screw version, I have 2 other end pieces for the 2 screw version (underneath and out to the sides). I can tell you that using 1/2" gas pipes (5ft) on my prior machine, I got very little flexing: A sagging concern.

    -GrumpyGeek
    Nice machine ! Thanks for sharing ! I would like to see it in action.



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