Mill – Mods & Upgrades – Future Plans

These are some of the additional things I have in mind to inflict on my little machine.  I’ve tried to make my purchase and upgrade priorities and decisions a matter of requirements rather than just cool stuff I’ve heard about or imagined.  I’m also building a work center, not a research center, so I really DON’T want to plan progress by the buy-and-try method, I want to plan by engineering discipline and design intent. 

In all of the upgrades I’ve applied and am yet planning (unlike a LOT of the other upgrade projects I’ve seen out on the web – without mentioning names…) I consider the structural integrity of the tool itself.  I am not going to introduce a weak link in an otherwise strong chain – and I am not going to introduce components or design strategies that will reduce the rigidity or strength of the power-train or work-platform.

CNC retrofit

A lot of the parts in projects I already have on the board are excellent candidates for CNC fabrication.  Some of the features that I anticipate CNC will bring to my shop are: simplifying setup, enabling complicated geometries, and exact part consistency; just to name a few.  One design factor I’ve already decided on is belt-drives rather than direct-drives.  The belt allows me to tuck the motor in a lot closer (or even completely) than sticking out like a bad afterthought.  I’m also going to fabricate mount boxes that I can put strain gauges on to measure the deflections, so I can independently measure the torque the motors apply in moving the table, head, and spindle so I can detect a collision or some other kind of binding condition, that will allow me to dynamically limit the movement BEFORE I break something.

Ball (Lead) Screws upgrade

The stock nut-screws are functional, and fairly acceptable in their own right, but Ball Screws give less table movement friction (because rolling surfaces are better than sliding surfaces) and better reduction of backlash (because of higher quality finish).  Also, I’m pretty sure I’ll do the Ball Screw upgrade before the CNC upgrade, because it will allow me to specify longer screw lengths, thus allowing me to put the CNC motors where I want them to be (rather than simply putting them the only possible place they COULD be). 

I also want to retain the hand-cranks (after the CNC upgrade). Because the X-Axis has two hand-cranks, which one I commandeer doesn’t really matter, so the new X-axis screw will be pretty much the same. The only way to preserve the Y-axis hand-crank would be to put the motor on the back-end of the screw, but upon further consideration, I decided that would actually be a MUCH better idea anyway because I REALLY didn’t like the idea of the motor sticking out in front; and in the back it will be totally out of the way.  The Z-Axis is kind of a problem – it really doesn’t have a good length of screw stock to attach the motor to, so extending the length of the screw a little higher, I could put it on top (preserving the hand-crank on the side) without jerry-rigging something to attach the motor to.  So in other words, the ball-screw shaft will be almost identical in dimensions to the stock screw, but the Y-axis screw will need to be much longer to extend out the back to attach the motor to (and will also need a rear stabilizing bearing) and likewise the Z-axis will be a little longer to extend out the top to attach the motor to.  All the screw bearings are cheapies, so at the same time I’ll replace them with higher precision ones.

Spindle Bearings upgrade

This upgrade falls under the category of simply replacing lower precision parts with higher precision parts.  At lower RPM (and side loading), the lower precision bearings don’t seem to matter, but the higher the speed a shaft spins (and the harder the cuts) the higher precision the bearings need to be to retain precision and avoid overheating.  I intend to upgrade the motor and drive mechanism (see below) which will spin the shaft fast enough that the bearing precision needs to upgraded first, and because the CNC will push harder than one would do by hand, this will be essential.

Coolant & Chip Enclosure

Presently, I use movable splash and chip guards that contain the vast majority of the coolant and chips, but admittedly, the mill still makes a big ‘ol mess all over my shop, so I’d like to have an enclosure that contains it completely.  I have no intention to build a big box, but I am thinking about the problem, and watching for good ideas on the internet…

Presently, I work mostly aluminum parts, but I have a lot of steel work to do pretty soon, and steel chips all over the place are a much bigger problem than aluminum, so I can’t delay this upgrade for too much longer.

High-Speed/Torque Spindle Motor and Controller

I definitely would like to spin the spindle a lot faster, but I’m still debating in my mind the need to add the motor controller to the CNC equation.  I’m just not sure of the benefits to me.  Perhaps if I had an automatic tool changer (ATC), and/or automatic part changer (APC); but that seems like such an overkill for this little machine...  I think that if I decided I needed an ATC and APC I really need to consider a different mill system altogether.

4th Axis Fixture

I can see how a 4th axis fixture – or in other words a horizontal- or vertical-axis CNC-controlled rotary table – would dramatically expand the scope of parts I could make.  And I can see the value of that class of parts, so, Yes, want to buy or build a 4th axis capability.

But adding additional CNC-controlled axii’s to the fixture would give me the ability to rotate the part being machined simultaneously in multiple axii’s - and that would be used to make really complex features – and that capability is TOTALLY outside the scope of my interest in (and ability to design) those kind of parts.

Even-further-out

· Ligh/Low speed spindle gear box – like a 4:1, 1:1, 1:4 transmission.

· Quick-change tool holder – like the Hoss-man built for his machine.