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  1. #16
    Join Date
    Sep 2009
    Location
    Newcastle
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    549

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    Not too hard to chip off, but if I do any more epoxy I'll just go over the top, as it's flatter than it was before the epoxy.

    The problem is now I've moved the machine position and the table needs to be on the same plane as the large beams (which worked ok). I don't have a precision level or long straight edge either.
    At present I'm thinking of getting the router going and using it to skim the epoxy.

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  3. #17
    Join Date
    Dec 2014
    Location
    Hobart
    Posts
    28

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    Yours is one of the machines I have book marked in my browser to follow as parts of my machine are almost copied from yours. I have decided to change the channel in my gantry for an "H" beam to provide more stiffness without distortion when welding it together. What size steppers are you using to move your gantry.
    philip

  4. #18
    Join Date
    Sep 2009
    Location
    Newcastle
    Posts
    549

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    Phil,

    It's a pretty simple design but quite rigid.

    I'm using 381oz-in steppers (Homann designs or AusCNC / AusXmods both carry them) and they are fine. I'm using 20mm pitch ballscrews to drive the gantry, and 16mm pitch screws across the gantry and on the Z.
    If you don't have ballscrews already, I recommend the 16mm pitch screws from BST Automation on Aliexpress. A bit more expensive than the standard 1605 (5mm pitch) chinese screws, but quality seems higher and they will make for a much faster machine.

    I've made a lot of progress and the machine moves and cuts. I've cut some aluminium faceplates for buttons, and a couple of circuit boards. It's helping to complete itself.

    Unfortunately I'm now working much longer hours and as such things have slowed down a lot.

  5. #19
    Join Date
    Sep 2009
    Location
    Newcastle
    Posts
    549

    Default

    I've been slowly chipping away at this.

    Everything takes a little longer than I expect...

    I've now got a working basic machine.
    Things I've knocked over:
    Linear rails: Drilled, tapped and aligned the linear rails. This took a fair while. For alignment I eventually used the tight wire method, with thin steel wire over some pulleys with weights hanging on the end. I searched for ages for piano wire, but couldn't find anywhere with thin enough stuff. In the end I found that fishing shops have thin stainless wire with rated breaking strain (fishing leader wire) and it worked great. I used 27lb stuff. It's pretty cheap too. I then used a simple circuit with an LED ring and a razor blade on a cart on one of the linear bearings. When the razor contacts the wire, the LED ring lights up. I was able to get it so along the whole length it just skimmed and only just lit up the ring. I think the rails are straight within 0.05mm per metre or so. This was a painstaking process. I had to turn the heads of the bolts down for the gantry, as I'd hand drilled using the rails as a guide, and the rails are not straight when not bolted down.

    Ballscrews mounted and aligned.

    Homing (and limit) switches.

    Wiring / electronics: Managed to kill a G540 driver (just one of the G250 drivers in my G540) due to making an incorrectly wired connector. I've since moved to a Mesanet 7i43 + 7i76 for step generation, and Leadshine DM856 digital drivers. I'm very happy with the combination. They are very quiet at low speeds, with the G540 the machine was loud at low speeds. I'm happily rapiding at 20m/min. I fit the PC and the electronics in an old aluminium mid tower PC case. I've got some buttons on the front: ESTOP, feed start, pause and stop, feed rate increase, decrease, spindle speed increase and decrease.

    Table top: Two layers of 18mm MDF, will have a spoilboard on top. Involved using a very long bit to skim the epoxy flat. Then, because the back table support beam is outside of my cutting area, I had to level it to the others. I used an angle grinder and a straight edge, and just kept grinding until it was flat compared to the other beams. Then drilled and tapped mounting holes. Then drilled the mounting holes in the MDF. Then I drilled a grid of holes, on 6cm centres, and milled pockets for tee nuts to sit in. I have 242 tee nuts in the table. They take a while to install - use a screw to pull them in to the MDF, don't use a hammer (I've seen some people recommend using a hammer).

    Tee Pockets.jpg
    Holes drilled and pockets routed for tee nuts

    Table tees.jpg
    242 tee nuts installed - took a while!

    Table on.jpg
    Very bad photo of the table installed

  6. #20
    Join Date
    Sep 2009
    Location
    Newcastle
    Posts
    549

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    Did a bit of cutting today.

    6mm carbide single flute spiral, 6mm DOC, 24000rpm, 5metres/min (~200ipm) - cut beautifully.

    On my old machine I was cutting at 3mm DOC, 2metres/min with poor cut quality.

    Next step is definitely dust collection. I'm going to build a floating dust shoe.

  7. #21
    Join Date
    Nov 2008
    Location
    somewhere
    Posts
    152

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    Just a suggestion for next time you make a spoil board - I found routing hex shaped pockets about the same size as a 1/4" nut (very slightly oversize so you have a tight fit) and then press fitting 1/4" nuts into them works just as well as T nuts and was substantially cheaper. From memory a box of 50 was $2.50. Flip the board over obviously, so the nuts are on the bottom.

    I can then use standard 1/4" bolts and screws (which are easier to get and cheaper than metric ones where I am) with my hold down blocks.

  8. #22
    Join Date
    Sep 2009
    Location
    Newcastle
    Posts
    549

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    That's a great idea and hadn't occurred to me for this. I've used that technique for other projects in the past.

    The tee nuts didn't too much - I found a huge variation when I shopped around.

  9. #23
    Join Date
    Dec 2014
    Location
    Hobart
    Posts
    28

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    Not sure whether you can still get them or not, but in the mild steel range you used to be able to get 1/4 & 5/16 nuts with an over sized hex which would make them even better (not able to pull through the MDF if over tightened).
    Philip

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