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  1. #11
    cheers thanks for the advice best order a stack load more slide blocks then mounting is no sweat as i can put them on to the rail and then just slide it strait on to the aluminium. Next job i think is to make sure it is all perfectly level on the floor and get a plate made up to bolt the carriages too. If i can get the plates laser or water jet cut do you think i can rely on there accuracy to get the two carriages to aline or do i need to factor in adjustment with a oval hole or something?

    many thanks again

  2. #12
    been working on modifying the design a little bit to try and simplify the build as its my first. I have just got the parts to build the z axis however annoyingly the mounting holes on the bearing blocks are not spaced the same as the ali extrusion so i am assuming the best way to solve this is by having some plates made up to go between and allow me to bolt one to the other?
    Last edited by charlieuk; 27-11-2014 at 11:56 PM.

  3. #13
    This is not unusual. I think you are suggesting adding a plate under the bearing block to bolt to, which is in turn bolted to the extrusion rails. This is fine, but will raise your ballscrew by the thickness of the plate - is that a problem?

    If it is a problem, these blocks normally have both vertical holes and horizontal holes for mounting. So instead you can use the horizontal holes to bolt into a thick plate/block which is next to the bearing block, and is in turn then bolted vertically down onto the extrusion. The trade-off this time is a small loss of ballscrew travel equal to the thickness of the block/plate.

    If none of these options work, you can drill and tap straight into the face of the extrusion (i.e not using the rails) - but you will need to check if there is enough material to tap into and you avoid the slots.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  4. #14
    yes that was what i had in mind.They do have horizontal holes but i am going to have to get the parts made for me so flat plates may be easier. i was wondering if i could bolt it directly but the holes are right on the edge of the slots so it would only be going properly through the very middle of the extrushion.

    i have not chosen any steppers yet but was just wondering if i was going to need a reduction with belts and pulley that i plan on the top or wether normally it is just 1 to 1. the plan is to use a 2.2kw spindle and then there will be the weight of what is in the picture and what ever stepper i use.

  5. #15
    Last edited by charlieuk; 28-11-2014 at 12:15 AM.

  6. #16
    a few more pics
    Last edited by charlieuk; 27-11-2014 at 11:31 PM.

  7. #17
    Last edited by charlieuk; 27-11-2014 at 11:32 PM.

  8. #18

    It's a very unusual machine and I can't quite work out which bit will be which, so the question you've asked about motor sizes is probably proving difficult for anyone to answer.

    But be aware that you can move a fair amount of weight with a 3Nm Nema 23 if you give it enough voltage as the ballscrew gives you lots of mechanical advantage. Don't rush out and buy 34's until you posted the final design sketch of the finished moving parts as you'll get a more definitive answer.

    Your earlier question about pulley ratio on Z is also tricky since your Z appears to be quite long. Lots of designs are just 1:1 on a 1605 ballscrew for Z. But your travel (if I read the design right!) is quite long so this mught not be your best option. Again, a picture of the overall finished design would get a better answer from the forum on that question.

    The wooden template motor bracket looks OK as a concept (assume ~20mm ali in the finished design?). Probably get away without triangulating back to the extrusion. But you'll probably need to recess the underside of the motor mounting area to raise the stepper and leave enough shaft sticking out the top. Also the ballscrew end might also need some pocketing on the top to clear the pulley / grub screw access.
    Last edited by routercnc; 14-03-2014 at 09:10 PM.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  9. #19
    I dont have any 3d drawings at the moment i tried to get sketchup to load on my mac but it didnt like it.

    If you take a look at thins video it shows something similar to what i am building however i just have the flat table and i have decided to have the two beams coming out on the gantry rather than one so as to stiffen it up and split the two rails apart, then the z axis will go inside the square frame you see on the top in my picture.

    the z is quite long i wanted to get as much as posable to be able to work on large block of poly styrene and by large i mean i buy it in 16' x 4' x 2' blocks so should i have aprox 500mm of z travel when done.

    the plan is to get all axis bolted up and rolling before getting the motors which hopefully wont be too long, im hoping to get the plates for all the carriages this week. I wasn't to sure how thick the motor mount for the z was going to need to be, i was thinking only 10mm as i didnt think there would be to much load on it using a ball screw but happy to take advice on that and as you say ether recess the some of the areas to get the pulleys on or extend the shaft if that is posable?

    many thanks Charlie
    Last edited by charlieuk; 28-11-2014 at 12:00 AM.

  10. #20
    That makes more sense now in terms of the final design. Should have guessed with the O'Neil logo on the wall.

    I think 10mm motor plate would also be OK stiffness-wise. What you will need to watch out for is if the bolt heads hit the belt then they will also need to be recessed. M8 cap heads would need 8mm depth of pocket so 10mm plate is then a bit thin.

    In terms of recess or pockets for the motor - if you can find the drawings for the motors you might use you can check the length of the shaft. They are not usually that long plus you need access to the grub screw at the base of the pulley so that often means a pocket is required.

    The motor plate extends past the extrusion and over the ballscrew - is that bit required? Are you hoping to bolt it to the bearing block as well? If not, you could cut it short and give more space for the pulley on the ballscrew. Just some thoughts . . .
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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