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  1. I see Vic, hadn't looked that closely. How thick is your steel angle and are you planning to prepare the edge in any way? The side load will translate into a vertical and horizontal force due to the shape of the vbearing. If they are rated for 1700N axially then I would have thought that was fine - I suspect the bearings would force the rails towards each other (or the studs apart) and pop-off the rails long before the bearing gave up!

  2. #22
    Apart from cleaning them up I wasn't planning on preparing the edges, they havent in Joe's design, the V is running on the natural small radius of the edge of the steel angle, the V bearings can be run inside an angle which seems a better way but I could'nt think of a simple way to mount an angle in a suitable attitude.

    Angle I've shown is 25mm x 3mm I would rather use 4mm or 5mm 20mm angle but that isnt a size that we stock at work.

  3. #23
    Hi Vic
    FEA looks good, I need that program.....looks so much quicker, dose it also generate a list for validating? How does it calculate the fixing type at the bearings or is it asuming a rigid connection?

    From the analysis it looks like the z axis plate is the weakest as its only a 2d plate. Id mount some angle on it parallel to the spindle for strength.

    For the C channels on the long axis you could flip them 180 deg so the web is on the out side and directly below the angle also it might be worth getting some unequal angle for the vee bearings, something with only 10 or 15mm upstand would be much better. Alternatley you could stick with the original config but add a plate to close the channel, this could extend up and bolt in to the angle as well to help brace them, two birds one stone etc.

    This would also be a good idea for the x axis (?) as the open C channel is weak in torsion, need to move the ballscrew tho. As a final observation the vee bearings are only bolted to the end plates, it might be worth incorporating their mounts with the C channel uprights.

    Anyway good luck.

  4. #24
    To be honest I'm not that experienced with the stress analysis side of the software, I design specialist vehicles, mainly steel framework, sheet metal with some mechanical elements to it www.jsfraser.com all the CAD stuff on the site is mine. We've only had the version of the software with FEA for a year now and so far I've just used it for testing framework bending over distance and seeing what sort of lightening holes I can get away with, so I'm not really qualified to answer your question, I have the disks though which will install as a 30 day trial version, you want a fairly decent PC though.

    I keep having different ideas for my router, I settle on one idea get it modeled then think of something else, I've got to draw a line soon and go with what I've got or it's never going to get built ;-)

    I know what you mean about the z axis plate, one of the other designs had angle along the side, this one has two 16mm supported rails bolted to the back of it, I bought them from a member on here, the bend on it is extremely slight, it's not to clear from the still pictures but when you can spin the model round you get a much better idea of what is bending and what isnt, its mostly the channel deflecting, I'm thinking about going back to box for this.

    I've also thought about using steel box for the long axis, with 25mm angle tacked top and bottom with the ends of the angle laid on the box so it looks like a pyramid when viewed from the end, this would give the V bearings much more contact area and the angle is less likely to deflect, I've been trying to avoid welding because of distortion though.

  5. #25
    I know diddly squat about stresses torsion ... etc etc etc so if I am out of line here I'll shut up. The Mechmate Machine is a real beast and that runs a heavy steel Y axis Gantry on Hepco style V wheels (size 3) and they grind a V onto the top of the Angle iron leaving a 1mm flat surface on the top. There are a whole load of those beasts cutting 8' X 4' sheets and bigger in commercial operation
    Tim G-C

    I disapprove of what you say, but I will defend to the death your right to say it.

    (attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)

  6. #26
    Hi Tim

    The Joe's Hybrid machine seems to have quite a following with the V bearings (smaller than the ones I have) setup the same as my model, have you got a link to how it's done on the Mechmate ?

    Vic

  7. #27
    Vic,

    http://www.mechmate.com If you sign up to the forum (no charge) you have full access to all the drawings for a machine ... the Forums are a wealth of information but only about these machines ... There is a massive section on the pros and cons of V wheels and masses of info on grinding the angle iron ...

    If I had the space for one of these, I would build it without hesitation. For a machine that can run all day machining 1" MDF with a huge router some of the stuff produced is stunning some very good fine detail 2.5D work etc.
    Tim G-C

    I disapprove of what you say, but I will defend to the death your right to say it.

    (attrib. Voltaire but written by Evelyn Beatrice Hall "The Friends of Voltaire" 1906)

  8. The Following User Says Thank You to Wobblybootie For This Useful Post:


  9. #28
    Thanks Tim, I have seen that before but did'nt notice they were using V bearings, have registered will browse around later.

    Like the Eddy avatar by the way !

    Vic

  10. #29
    I keep having different ideas for my router, I settle on one idea get it modeled then think of something else, I've got to draw a line soon and go with what I've got or it's never going to get built ;-)
    Unfortunatly the best way to find out if it works is to just build it. if its only your time then I guess it dosnt matter and is part of the fun eh.

    I've had a quick look at the hepco site and those bearings should be fine as when used in opposing pairs the double vee forms a 4 way equal loading. not sure about relying on the load capabilities if using the rounded edge of the angle as a rail tho. as the contact area is reduced to only 2 or 3 points.

    I've also thought about using steel box for the long axis, with 25mm angle tacked top and bottom with the ends of the angle laid on the box so it looks like a pyramid when viewed from the end, this would give the V bearings much more contact area and the angle is less likely to deflect, I've been trying to avoid welding because of distortion though.
    Using the corner of the angle would be better from a load point of veiw but I feel you may have problems aligning them, the reduced contact of the rounded angle maybe more forgiving. (test if you can).

    An easier option IMHO is to use a rectangular box and rotate it, as the pic, No bolting requred and both corners will be parrallel, there is also space for the ballscrew. The box section is better at resisting the torsion from the z and y axis's.

    I still think that just adding some closing plates to your original idea is the best. its still modular as you wanted and the smaller contact from the edge of the angle should make alignment and adjustment easier

    I have the disks though which will install as a 30 day trial version, you want a fairly decent PC though.
    Are you offering to loan them to me? I could probaly get most of what I want to do done in 30 days, Ive got a dell precision 470, 6.4 Ghz 3mb memory and nvidia quaddro 540 (I think) will that do?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  11. #30
    Thanks for taking the time to do the drawing, the closing plate idea was going to be my strengthening measure if the channel flexed to much. Using box section as a rail but rotated had occured to me, but I was put off by the radious on the corner of steel box section, Ally has a nice square corner but wouldnt last long with the bearing running on it, I'll try running a bearing along the edge of some steel box and see how the V matches the radius.

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