[I think your gantry and everything it attaches to will have to be extremely heavy-duty if that long Z-axis is to be held steady, especially when cutting wood.]I'm about to start a build of a 4 x 8 router. I will be using a driven uniguide from pbclinear mounted backwards for the z-axis.
[That could work.]
I have designed the way my gantry attaches to my carriages in such a way that I can quickly (well, could take half an hour) re-bolt it much higher from the table top. The gantry will weigh at least 150 lbs.
[Don't try to change it over all by yourself...]
I was initially planning on purchasing a uniguide with a stroke of 13.5 inches. Now I am thinking about purchasing a uniguide with a stroke of either 19.5 or 25.5 inches.
[That's really long. There's a reason most routers keep the Z-axis short. The longer it is, the more leverage he cutting forces will have to deflect the tool.]
When routing parts from wood, the gantry height will have a clearance from the table of around 12 inches. Any more than this and I am concerned that the moment caused by the cutting forces could have detrimental effects.
[You're right about that.]
However I would have the option of increasing the gantry clearance to 25 inches by moving the gantry upwards when routing a foam block. Also, I would now have 25 inches of useable travel.
[Useable for what? How long is the longest tool you'll be running?]
This will also be helpful for more clearance from the table with the addition of a rotary axis, although in this case I may not need any more travel as the piece would already be higher off the table. It would be pretty neat to carve a 12 inch thick piece of foam with a rotary axis though.
[It would be easier to lower the rotary axis than to raise the gantry height.]
The only drawback is that when using the router for wood I would have a whole lot more Z axis sticking up above the top of the gantry and my Nema 23 motor would be much higher (12 inches). I'm not even sure this is a drawback but perhaps there's something I'm missing.
[How high is your ceiling?]
So what does everyone think?
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