[mrpackethead]

So, i was looking at the PocketNC ( Pocket NC Company ) which is a $4000 5 axis mill.. Pretty cool.. Its down side is that is working space is really quite limited. It got me thinking, that maybe it might be possible to add an A and B axis via a bolt on table. I did a bit of googling and found this project at some students did at CalPoly in the USA

https://www.youtube.com/watch?v=joGv4ErUJgY

Theres some plans and doco.. http://digitalcommons.calpoly.edu/cg...2&context=mesp


What do you think.. Nuts?


PocketNC

https://www.youtube.com/watch?v=13872p-UynI

[Hamzter]

Hey Mrpackethead,

I had a similar thought a while back, I already have a 4th axis which I purchased from Arc Euro Trade in the UK, so I'm halfway there already! There is, of course, no 5th axis available off the shelf, it would need to be a fully custom design. My initial thoughts were for a double taper bearing arrangement, and driven by a worm gear, I put together a rough design...

Attachment 354046 Attachment 354048 Attachment 354050

Attachment 354052 Attachment 354054 Attachment 354056

The big disadvantage with this arrangement is that it's fairly tall with the rotary table being about 100mm above the machine table, so that limits you to parts about 80mm tall before you run out of travel. I'm planning on dropping the bearings in favour of ground surfaces (the same as my 4th axis), which should claw back some of that travel.

I've also thought about using a belt drive in place of the worm gear, but not convinced it would be stiff enough.

Talking of the worm and wheel, that would be the toughest bit to make, but I have a plan!

- Machine up two identical worm gears in silver steel, using a trapezoidal thread as the profile, I plan on using my mill lathe attachment (here) for that bit
- Machine teeth and relief into one of the worm gears to act as a cutter, heat treat and sharpen the edges
- Press the worm wheel onto its shaft, and mount in the 4th axis, then gash at the required angles with a saw cutter, the SX3 rotating head will come in handy here as the gashing should ideally be at the worm gear pitch angle
- Disengage the 4th axis motor so it's free to spin, mount the heat treated worm gear into the spindle and push it towards the worm wheel, with a bit of luck it should start cutting and rotating the wheel as it goes, leaving with you with a well meshing (but completely non standard) worm and wheel.

I may actually start making something in the next few months, as I have some time on my hands, I'll keep you all updated