Build Log: 3-4 Axis Mill/Router

[Ross77]

Since you only need the Z-travel to machine plates 'stood on end', you can leave the bed at the best position for cutting what you will cut most often and just clamp the plates on the end of the bed to machine them. If the bed ends just inside the X-axis travel, then you can move the gantry (just) off the end of the bed for machining the plates.

If you are doing a lot of repetitive work of the same size then you could also make a slot in the table and clamp it down low.

I have seen vertical moving gantry's on routers before, in fact I mentioned it when I first started and got talked out of it. As John said it is just transferring a massive load to the gantry sides and the distance vs bearing spacing would be huge. Not impossible just difficult and defiantly not a cheap or quick fix.



Just bolting a fixed gantry to a moving gantry design is also not the most effecient way to do things. I would redesign as new and if you went for the fixed gantry then you can get rid of the high sides at each end as they are not doing anything. It would be stronger if you went for an 'A' frame arrangement (two a frames opposite each other. Main gantry at the top and transmitting load to the ground through the legs, the bed can sit at the horizontal section of the 'A' and extend as far as required to support the table. As the gantry is fixed the cutting load is only directly below the cutting head therefore all the force is contained and distributed within the A frame. table only needs to support its own weight


The moving table also needs beefing up, as it is there will probably be deflection in the middle. Most designs I have seen have the rails at third points. The table itself will then need strengthening to overcome deflection in the middle and the cantilevered edges. To some degree having a fixed gantry just inverts the flexing problems associated with the z axis and to the table as this is now compromised.

A fixed gantry will get you closer to cutting steel as you can really beef up the design, the same weight and strength on a moving gantry has to be accelerated and decelerated which means big motors and drives.


Edit
The moving table is all wrong. It should be the other way up. bearings fixed to the frame and rails mounted on the table. that way the work is always fully supported under the cutting tool and the bed support can be drastically reduced. And will fit within the 'A' frame I mentioned, look a VMC designs. You basically looking at a 2 sided mill arrangement. Fixed gantry machines are a completely different design to moving.