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View Full Version : Spindle mounting (height) strategies?



Kosh
11-23-2015, 03:26 PM
Hey all, curious to get some opinions on this.

I got the kinks on the Pro 4x2 worked out over the weekend once the MX4660 arrived. Running smoothly now (sans ESS while I wait for a power supply for it).

Mucho thanks to Ahren and company for the great support.

So here's the issue I'm struggling with (or maybe over-inflating it?).

My extreme (and #1 justification) use case for the machine is to carve acoustic guitar necks for me. These are a bit more involved than an electric due to the heel.

The heel will typically be 3" in height. Add to that the holding fixture (hopefully 3/4"), and I need to be able to clear 4" with BOTH the bit and the z-axis carriage. I'm probably going to lose 1.5" of height once I get the vacuum hold down table installed. So how should the spindle mount be positioned on the Z-axis? Should I make the end of the collet even with the lowest part of the z-axis mech? That would just allow me to retract Z enough to clear the heel with the end of the bit (assuming a 5" bit here). But, then I might have issues when using shorter bits for inlays, etc, as that z-axis would be to low maybe?

Another option would be re-position the spindle up and down in the holder for those types of bit changes. If I did that though, mounting a dust show to the router would be difficult.

Last option, make as much of the vacuum table fit BETWEEN the 8020 base so I don't loose much height that way. I think I could do it with 1/2" for the grid part, with 3/4" hanging below that for the plenums, and so only the 1/2" would be laying across the top of the base.

Or, do you just try and program so that the z carriage never intersects with the workpiece?

Thoughts/suggestions?

Kosh
11-23-2015, 03:28 PM
Actually, heel height will be 3 3/8", then 3/4 for fixture, so 4 1/8" to clear?

Kosh
11-23-2015, 03:33 PM
Adding a picture of the neck for visual reference.

MobiusConcepts
11-23-2015, 03:58 PM
On my Pro 4x4, I set the lowest part of the collet on my router to be 1/16" lower than the bottom of the Z-axis extrusion. For me this means with a 3/4" spoilboard I can clear 4" (1/8 - 1/4" clearance) material with a bit length of 2.5".

Kosh
11-23-2015, 07:54 PM
Ok, I did a little playing around (like my simulated 1/2"x5 bit?) and this is what I found.

I positioned the mount so that when bottomed out (the router), the collet was 1/16" below the carriage. Then I placed a neck at about the height I expect it to be
on the jig. I found that I then reposition the router higher in the mount, with the bottom of the body flush with the mount, then I can easily clear the heel and still reach to
full depth needed for the cut.

Before doing that, I verified that the tool path generated by Fusion360 always stays tight to the workpiece, and as long as I orient it to cut from the side, the carriage will never
need to crossover above the heel.

So this works for now. It'll just be a little extra step in zeroing the bit for that cut.

Another option I guess.. would be the just mount the z-carriage one bolt hole higher on the gantry carriage? Can't think why that wouldn't work, not much of a leverage change.

298814
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LeeWay
11-29-2015, 07:40 PM
Nothing says you can't mount a table surface down into the extrusion. That would gain you another inch or so of Z. It is plenty tall to reach down in there. even with a short tool. Then replace the top when you don't need to machine necks. If it is designed right, you could build a fixture to support vertical stock to do dovetails, finger joints, etc the same way. You could similarly install a forth axis lathe like that. Make it all hot swappable so to speak. :)