Wobblycogs CNC Mk2

Hold on.!!! . . . . You are having gantry sides aren't you.?? . . . .Your not planning on having it open like those pics show are you.?

I just thought you where showing it like that to save drawing them.!! . . . If not having sides then your in trouble and this won't work very well.!

Edit:

Ok on looking again it's not that bad but think it would be benefit from gantry sides has it would help stiffen things up. Also it would make a better stronger connection to the ballscrew.
Sides and the plate on front would make it quite bit stiffer with less flex.!

The way you have it now this would need beefing up anyway.

One beefed up gantry with added sides. Now I draw it I can see this is significantly stiffer than what I had, I was relying on the 10mm plate not bending along it's weakest axis, doh!

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As you suggest there will be 3*10mm thick plates on the back with the rest covered with a thin sheet. The front will be a full 10mm sheet with a slot for the ball screw. Feel free to imagine bolt holes all over the place ;-)

Thanks again for all the help.:encouragement:

EDIT:

There you go it's drawn up

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It's close very close but not quite Carling.!!. . .Lol

Gantry's fine but those drop brackets for X axis ballnut mounts are too flimsy so make bit wider at top and beef them up a bit and your there.!

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Gantry's fine...

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:yahoo:

I've bunked off work for the afternoon to do some CNC design so I'll get those x-axis brackets beefed up a bit. I'm also swapping the ballscrew and stepper around inside the gantry (so the screw is at the top) that way the slot is further from the chips.

I've been reading a few posts of yours regarding aluminium machining. I'm going to have a crack at using my circular saw to cut most of the pieces and then clean up with a router bit. I've tried routing aluminium in the past but only 5mm sheet. It went well but I'd agree with you it was scary at first.

I was also having a read up on pulleys. I've got 9mm 16 tooth on there at the minute but I think I'll upgrade them to 15mm 20 tooth (all HTD5). Will a 15mm pulley (like this) mount cleanly onto the shaft of a typically 3Nm stepper? I'm just a little concerned because the L dimension on the pulley is 26mm and the shaft of the stepper seems to only be 16 to 24mm long depending where I look.

P.S. Bloomin' love this design by the way. Once I have my workshop built I think there might have to be a bit of creative copying for CNC number 2 :whistle:

Another weekend comes and goes with much work on the house and little on the CNC, sigh. Anyway, after getting a tick for the gantry :biggrin: I've been going around the design putting in all the bolts. I figure it's better to find bolt hole collisions at this stage rather than when I come to build the machine. It's a really slow process even (even using the hole wizard) but I think it's worth it. For example I thought most holes would be using M5 bolts with some M6. In reality it's turned out most will have to be M4 with some M5. Also the thread depth on the linear bearings is surprisingly short so some careful counterboring will be required. The Z-axis stepper has grown a bent metal box cover. I'll probably end up adding a hinged flap on the front at some point - there was a front originally but I realized would wouldn't be able to fit the stepper through the hole I'd left!

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The X-Axis is still has quite a bit of work to be done on it. As you can see there's no stepper, pulleys etc. The rails and screws are in the final location though as this is dictated by the rails. After reading this thread I'm toying with the idea of designing in the ability to use liquid coolant when cutting aluminium, I suspect that might be biting off more than I can chew at this stage though. I think I'll keep it in mind as a potential future improvement.

The rails, fingers crossed, should be with me fairly soon. Parcel Farce reports that they are in the country awaiting customs clearance. So far my first purchase from the far east seems to be going smoothly. Phew.

I got to thinking over the weekend about whether I would manage to finish this project (actually when because I'm going to finish it if it kills me) and it occurred to me that a lot of projects don't seem to make it past the planning stage and a good few seem to fail in the building stage. I wonder what percentage of people who want to build a CNC actually finish the task and end up with a machine that works (at least reasonably well).

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Originally Posted by Wobblycogs

The Z-axis stepper has grown a bent metal box cover. I'll probably end up adding a hinged flap on the front at some point - there was a front originally but I realized would wouldn't be able to fit the stepper through the hole I'd left!

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I would make the Z front plate just bit narrower than Rear plate and put a full cover over the z axis so it protects rails and everything.
Easy done with 1.5mm Ali sheet, just make a cardboard template and then cut around. Don't need fancy bender or saws just score profile edges with stanley knife, trim with tin snips into straight length then bend to break off.
Easy folded with simple scores on fold lines (back side.!!). The pics below show cover which was folded by hand without clamping to make a permanent template then unfolded, (see pic.). . . If you clamp the sheet on top surface before folding and fold on edge of board then makes a better fold.

Takes about 30mins to make.!!

That looks more like a tank than a cnc machine :-). I bet it effective at keeping the chips out though.

Well, I've been hard at it putting bolts in the design and I think I've got to the point were there's not much point adding any more as they clearly wont clash. So with that done here are some shots of what will get built unless anyone comes up with a show stopper. my estimate for maximum cutting sizes are X: 840mm, Y: 840mm and Z: 125mm assuming a 50mm bit. I cab squeeze a bit more out of Z by moving the spindle up a series of holes.

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Is the plan still to mount it vertically?...how is it going to be attached to the wall?

The original plan was to go vertical but the design has grown quite a bit since then to the point where it's not practical to vertically mount it, at least not in my current workshop anyway. When I move to a bigger workshop I might look into mounting it vertically again but to be honest I think what will probably happen is I build a steel base for it and use underneath the machine for storage.

Ah, ok - my next question was going to be how will you level it if its going to be horizontal...but I guess you'd put adjustable feet on the steel frame in that case?

Also - I got my wrist firmly slapped by Jazz for my design with the stepper motor mounted on the Z axis front plate...he said it should be on the Y axis plate instead to help keep it out of the way & reduce the weight on the z axis.