MDF and alu sandwich router

[Tom]

The shakedown runs of this router are finished, and I'm growing in confidence with it.... Purely for posterity here is a before screengrab from sketchup, and an actual photo of the thing for real! (complete with deadly MDF dust)

There are a couple of weaknesses with it so far. Some are easy to build out with some re-cut panels, which I'm in the process of doing. Others are slightly more fundamental (but happily, not too serious).

Improvements to make:
1) The gantry is not sufficiently strong along the Y direction. Looking at it now it's obvious! But there are no diagonals, and I'm re-cutting these before even attempting alu. If you remember, this is supposed to be an alu sandwich router, but it's going to need gantry #2 before I can cut the alu for gantry #3...

2) The X leadscrew is not perfectly straight (well actually, bent!), and combined with the poorly braced gantry leads to wavy sides (pitch of 4mm!) on the x edges of parts I cut. Hopefully the braced gantry will fix this. If not, a new screw....

3) Some poorly placed drill-holes during the initial build means that at the moment the Z axis sits a couple of degrees away from vertical. The collet end of the router hands back under the gantry. Again, some re-cut panels (with computer aligned holes, not pencil aligned ones) will solve this.

4) The final, slightly more thorny problem is that the Y rail support twists slightly (tucks under) in the x direction, when the router is at full Z travel down. The problem is worst in the centre of the Y travel. A fix to this would involve spacing the Y rails further apart, and re-drilling the Z carriage to accept new skate bearing positions. It's not impossible, but I will try alu skinning first, possibly followed by replacing that piece of MDF with a chunk of solid alu if that doesn't work (it's only 100mm x 700mm).

Current max axis speeds are (so I don't forget):
X 40mm/s, accel 80mm/s/s
Y 100mm/s, accel 110mm/s/s
Z 30mm/s, accel 60mm/s/s

X and Z are conservative, put there to stop the machine shaking itself to bits with a wobbly gantry and bent screw. I hope to increase these as the improvements are added...

A happy speed I've found for cutting MDF so far is 1800mm/min, with a 6mm 2flute mill, and 4mm of cut on each pass. This is definitely limited by the current rigidity of the machine, but onwards and upwards... Rooolll on the improvements....