3rd Generation CNC Mill

TWS-1850

a 3rd Generation CNC mill (Part #2)...

The table has had 2 coats blue, 3 coats black (on edging) and 2 coats of yellow (Masked over the black) in case you hadn't noticed...

If it wasn't so much work I'd mask & paint every edge of every table, step, corner, shelf drawer and chair that I encounter on a daily basis with the same Black & Yellow pattern.

The White panel accent is the most creative design I could come-up with shy of not doing anything at all.

If you really are looking for meaning, think of it as a minimalist energy plateau flame.

Cosmetics aside, the real work of construction resumes with the rail mounting to the frame. The bearing races are shown to the left above fully populated (note the races were cut back to 3/5th's their original length to gain greater travel within the same length rail.

The rails are staggered 2 (two) times the bearing race reduction to offer supported travel over the increased bearing race movement...

The rail stagger is positioned equally over the 48" center point of the table length. The above brief sentences sum-up the days of initial positioning and measuring. Certainly there is a mathematical formula that would best describe the variables and travel increases within a confined plane, similar to the Cannon ball stacking problem, but I'm pleased that I've made an adequate proof in a practical sense.

I know! enough about the rails and the travel and the ... Given that my first thought after running each of the previous mills was "I should have made this bigger"

...so I verified the travel by fixing a steel square securely to the moving rails (inside the fixed rail) and ran the travel against a tape measure.

Since this isn't my first "Goat-Fuck" I had previously checked that the rails were inter-changeable and parallel, the table top was oversized to allow exactly 1/4" clearance for the gantry supports. The point being that once the rails were lined-up to the pre-drilled holes progress was quick with no binding issues.

The gantry is mocked-up to allow for the 6" over-hang of the Z axis assembly and the weight of the spindle being positioned over the center of the rails.

The swept back look creates the illusion of speed as well.

The level position is calibrated against the table-top as the floor is less than even.

If the table sags or has a twist, I'll weld on 6 (six) adjustable post legs (that's why the MDF skirt doesn't go to the floor).

I knew that I had to add more bracing to the gantry but was at a loss as to how to keep the near perfect alignment that I had found on a quick test assembly.

So I just rolled it out with ball-bearings dropping out all over the floor on both sides, while my hands were full.

After staring at it for over an hour I ended-up just taking it apart. Though at this point the rolling rails are matched and tagged to their corresponding stationary rail.

If I'd missed that I'm sure that it would be a lost day trying to figure out what went where.

The Stepper motor mounting points had to be registered against the supports while it was apart.

The motor flange has a 1.5" ridge that snugs the motor centered into a corresponding hole.

The ribs mounted onto the supports are positioned to reduce any lateral or sway that may occur in opposition to a cut the spindle is making.

Each Gantry Support panel is pilot drilled heavily, and there was lots of clamping and counter-sinking going on as well.

All mating surfaces are glued...

In an effort to reduce splitting I used 1 1/2" screws close to any edges, and all edges are screwed at least 1 1/2" in from the end. The remaining screws were 2 1/2".

The MDF is starting to get lots of oily finger-prints on it regardless how much I try to remember to wipe my hands clean.

The completed Gantry parts are hung-up and sealed with 2 coats of water-based wood sealer that looks like diluted Elmer's white glue and dries clear.

2 (two) coats of Gloss Black enamel...

In total I think that there are 83 wood screws and 18 1/4" #20 bolts that make-up the gantry assembly...

From this view it looks like some sort of S & M torture device from a James Bond movie...

The Gantry has since had the physical aluminum and steel assembly mounted.

The box assembly is made of 1/2" and 1/8" plate with 22" rods of 1/2" polished steel and linear bearings identical to those used in the NexMill-15.

My wife thought it was clever how I got the gantry tilt to match the white graphic...

Though I have to admit that it just worked out that way.

The assembly is crazy heavy (I'd guess between 30 and 40 lbs) so requires some force to overcome inertia, but once in motion it rolls very smooth along it's length with minor resistance over the last 6" of either extreme.

I'm hoping that the cantilever weight of the Z-Axis and the router will reduce that by an inch or two.

Given that fishing season is practically here, I can see one last burst of work, prior to starting the electronics and having another post by early to mid July (2006).

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