Build Log: 3-4 Axis Mill/Router

**Ross77** · 04-05-2013

Originally Posted by IanS1

Thanks for your input Ross.

The A frame type design is interesting I'll look into it. The mechanically adjustable height on the gantry is worth some thought too but immediate concerns are, being a pain to set the gantry parallel to the bed every time.

The table definitely needs more work with regards to support/beefing up. I am very intrigued though about the idea of fixing the bearings to the bed and the rails to the table, I will look into it.

Yeah adjustment would be the tricky bit. You can either predrill holes at say 50mm ccs and its just a case of un bolt, move, rebolt (could still give alignment issues) or go for linear rails and lead screw to guide and adjust, then reclamp to to make it solid.

This is the way I was going to do it on mine if went down that route, except id add encoders to the lead screws and a dual display to show the position, i figure ballscrews are ott as the weight of the gantry will keep the load on the leading edge of the screw so no backlash will be present. Add hydraulic clamps job done.

**IanS1** · 25-09-2014

After loads of thought I've decided to stick with a more traditional router design for my first machine. The frame work is almost built so now my attention is more focused on the gantry design. To start with, this machine will be used for cutting aluminium, plastics, acrylics, MDF and plywood. If the machine is successful I will eventually build a dedicated machine for cutting the acrylics, MDF, plywood etc and keep this one for aluminium cutting only, hence the strong heavy frame. Overall the cutting area will be approx 700 x 1400mm and I'm hoping to get around 100mm for the Z axis travel. The bed will probably be a 30mm thick aluminium plate.

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The frame work is built mostly from 80x80x5mm, the overall size of the frame is approx 1160mm wide, 2000mm long and 650mm to the bed height. All of the diagonal bracing is 40x40x3mm.

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The Y axis section is 100 x 50 x 8mm, I still have to add the bracing for either end of the Y axis. The extended Y axis is for future plans of a possible ATC at the rear, a rotary axis and a clamping system for machining the ends of ali plates at the front.

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I'm really pleased with the way it has turned out so far. Using a spirit level across the bed and across the X/Y axis indicates it's pretty flat but with the adjustment I've built in and if needed the use of epoxy I should be able to get it clocked in quite nicely I would think.
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Anyway, on to the gantry. The design I've gone for is fairly straight forward and hopefully strong enough. The gantry is mostly drawn in 25mm plate with the Z axis plates done in the 30mm. All plates attatching to the bearing blocks are drawn in 30mm. The overall gantry width is 1250mm and height is 270mm.
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The bearing blocks on the Y axis are spaced at 370mm end to end and the X axis are spaced at 230mm end to end. The linear rails on the Z are spaced at 150mm and the bearing blocks have a vertical spacing of 310mm.
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Would really appreciate some input on whether this gantry design will be up to the job.

**IanS1** · 28-09-2014

Any thoughts on the gantry would be very much appreciated.

Ball screws: Would a 16 be OK to use on the Y axis or would I be better off using a 20? It's going to be about 2000mm long.

**JAZZCNC** · 28-09-2014

Originally Posted by IanS1

Any thoughts on the gantry would be very much appreciated.

Ball screws: Would a 16 be OK to use on the Y axis or would I be better off using a 20? It's going to be about 2000mm long.

Gantry will be fine Ian it's tried and tested. 2000mm is just too long for 16mm so definately go with 20mm. To be honest at this length it's worth using 20mm pitch not 10mm and using a 2:1 ratio so you get the same speed as 10mm pitch but half the screw speed. This reduce chances of Whip.
The ratio increases torque as well so your in front here as well thou the higher pitch looses some mechanical advantage but still your in front and the slower screw speed is more beneficial as the inertia is lower than 20mm 10mm pitch screw.