Re: [CAD_CAM_EDM_DRO] Re: 5-Axis help

isaiah_bellais wrote: (snip) My main concern

> with a 3-axis mill is the depth at which it can cut without hitting
> the rest of the 3d object. For example, when milling something like
> the hull of a boat, how deep will I be able to go without hitting the
> peak

I think one thing everyone overlooks when talking about deep profile cutting is what is being used for a spindle. I had a long discussion about your "typical" spindle with a good friend who I used
to cut 3d foam molds for.
Mounting a typical Router to some type of plate or bracket usually adds to the "radius" area of the spindle that can affect plunging operations. It is not that long nose spindles do not exist, just
that no small company can afford to buy them muchless hobbiests. And, even then, that spindle has to be "fixed" to an existing moving component.

What one really needs, is a very small diameter spindle that in itself >IS< the 3rd moving axis. Over this last year, This fellow built his own machine which has turned out quite impressive, and
accomplished a prototype of that moving Spindle Concept.

Picture this:

A 2" diameter, by 4' long Hollow Round Linear Rail, step machined on each end to accept a pressed in bearing.

A machined and balanced Shaft to go thru the middle of this hollow shaft, with a center bearing held inside the tube with spacers.

This shaft is machined in such a way to accomodate the tooling you are going to use. In the case of this prototype spindle, it was just a hole and a few setscrews, but, one could incorporate a
collet system.

The shaft "rides" in a fixed stack of "open" linear bearings, mounted on a carriage that runs back and forth in the Y direction.

A section of Rack (rack and pinion) is bonded with Loctite 609 to the Round linear rail and moves smoothly thru the "open" of the bearings. A drive mechanism is made to allow a motor to move the new
axis/spindle up and down in the bearings.

The top of the shaft is equipped with a Toothed belt, and a bracket is clamped to the top of the shafting that holds an inverted variable speed router with corresponding toothed belt.


The result is a 3rd axis that >IS< a spindle. One with a lot of travel and small footprint. There is nothing else in the way !

This fellow generally cuts foam for RC vehicles. So rigidity is plenty good for his application. I beleive he mentioned that if you really lean on the shaft when extended, you can see .020" of
movement. Cutting foam, I doubt it really moves much at all provided you run sharp tooling and "let gravity do its job"....

Clearly Anyone trying to do any cutting on more rigid materials will likely see some flex with only a 2" diameter shaft.
But, he thought of that too when he made the WHOLE GANTRY slide up and down on the Gantry uprights via linear rail and motor ! This way he can cut more rigid materials to some extent, allowing the
adjustable gantry height to minimize how much "spindle" actually sticks out of the bearings. With a few wire swaps, he could just use the moving gantry to do all the z work and the spindle could
stay fixed.

I would like to think that one could move up to a 3" diameter shaft and thin it out on the cutting end.... In any regard, I think the idea solves a lot of the clearance issues involved with 3d
cutting.

Chris L