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  1. #11
    I'd like one of these work tables and Iwould construct an overhead gantry to support a motor which would take a grinding wheel positioned over the bed,then I could milldown aluminium bar.

  2. #12
    Quote Originally Posted by ecat View Post
    There is a spread sheet around here somewhere, I'll get back to you...
    There are two here, one from Ross (#1) and one from me (#3). Mine includes the torsion calc (due to the cutting force being offset in Z from the gantry, trying to twist the gantry). You might want to consider that on top of the vertical and horizontal forces mentioned above.

    As for cutting ali with simple tools, you can cut profile with a mitre saw with a metal cutting blade, so should be able to cut plate. Mine was a Rexon ~100, but there are cheaper ones. Blade was a branded part at 44 - you can get cheaper but I didn't want it to let go and do me some damage.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #13
    Hi George,

    I don't think you can grind aluminium because it is soft and quickly clogs up the wheel. You need to flycut it - remember that operation ?!

    This also reminds me of a friend who tried to grind ali on an overhead grinder machine where the baseplate to hold the workpiece was a magnetic table. Luckily we didn't need to reach for the accident book that day, but it could have been very nasty.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  4. #14
    Doh! I meant mildsteel,RCNC,tsk its all this talk about aluminium this and aluminium that....I'll be going to bed dreaming of the stuff next.

    Seen one constructed,bit crude in the nature of the design but it worked well.

  5. #15
    ecat's Avatar
    Location unknown. Last Activity: 08-02-2014 Has been a member for 6-7 years. Has a total post count of 157. Received thanks 5 times, giving thanks to others 8 times.
    Ahh, the internet!!! Lucky I didn't get as far as P in the alphabet

    Here's a nice page , the numbers are easy. For a horizontal force my imaginary plate has an I of 133333.3333 so...

    Supported at 1 end only (option 14), the plate deflects by 0.86mm which is about the same value returned from the 1st web calc.

    Simple support at both ends, force applied in the middle (option 4) which should match the Bosch calc configuration, gives a deflection of 0.05mm. About right?

    Deflection due to 200N vertical force:
    Plate: less than 0.00mm (-0.00054)
    Profile: less than 0.00mm for 40x160 (Bosh profile deflection calc)

    Deflection due to 70N horizontal force:
    Plate: 0.05mm
    Profile: 0.01mm

    Plate now looks much better, and more plausible. The extra width of the profile still gives it the edge vs 70N where deflection is 1/5th of plate. The profile should also win the weight race, though the ValuFrame extra density may mix things up a bit!

    Also found routercnc's excellent spread sheets

    Simply Supported = both ends simply supported and the calcs agree with each other :)


    Thanks for the links routercnc, you were typing while I was thinking... This gives you time to type a lot :)
    Last edited by ecat; 22-08-2010 at 08:05 PM.

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