Well, it’s a little too late for Star Wars Day (“May the Fourth be with you”) but here is my version of the traditional “Hello World” message. It is the first thing (besides facing the spoilboard) that I have machined using the Nomad. This is one great little mill!!
It is a 2-sided MeshCAM job, with supports added as here–a single flattish support centered on the engine exhaust area, and circular supports at the side and front. I placed the supports where they would not be hard to trim and sand flush with the vertical walls (obviously with two-sided machining there will be no sidewall details)
I pre-drilled dowel pin holes in the spoilboard to register the rawstock (which was a scrap, thus the extra holes, I had already squared up and measured accurately) on side and end, for when I flip the stock for the bottom side machining. I drilled two clearance holes through the stock for hold-down screws, then used my Proxxon hand tool to drill pilot holes in the spoilboard for the sheet-metal screws. This is the first side machining after roughing, showing the pins and screws.
And here is the first side after finish milling. The finish is a little uneven, but given that I was running the finishing bit at half the RPM I intended, I’m pretty satisfied. I could hear the bit stuttering a little in places.
Here is the parameters screen
I ran the .125" roughing mill at 5000RPM, and intended to run the .063" finishing mill at 10000RPM but overlooked that and had it set also for 5000RPM. I have fixed that for the second side machining, which I’ll do after work tomorrow.
Finish of second-side roughing. Finishing is going on now, I left the machine running after I changed to the finishing cutter and left for work. I showed my wife where the emergency stop button is and told her hit it if the machine sounds/looks like it is hurting itself (cutting outside the machining area…)
But all is not right on Tattoine. The yellow encircled wall should be vertical and unbroken. Somewhere along the line there was a shift in the X axis, which means I was too agressive on the cutting parameters. From the depth of the offset, I can tell it was on the first side. The rawstock is about .50" thick and I set max depth to .35 from each face, so a little more than halfway through the stock to overlap on the vertical sides on the workpiece.
I forgot to mention the material is acrylic. If I do the Falcon again (what’s this if–I know I’ll redo it…), I’ll search-and-relace the 30 ipm roughing moves to maybe 20 ipm. And maybe up the RPM for the roughing. Or maybe just up the roughing RPM. The chips were coming off fine and unmelted. I have some homework to do on feed/speed.
And the dish antenna is a separate job. I found the STL on Thingiverse and used MeshLab to lop off the facets that form the antenna. It is pretty crude–you can only select factets in a rectangular selection area, so it was a matter of rotating and zooming until there wasn’t any geometry behind the facets I wanted to remove. Then I repeated the process to isolate the antenna itself.
But Han should be flying his ship anyway instead of watching HBO!
The only other thing I’m thinking here is if your center-line/zeroing and the alignment of your stock on-center was off, that would explain some shift… but knowing your experience level from other posts I’m thinking that while it’s possible that’s unlikely.
But, I am curious, did you set your zero to the center of the stock, or to your registered/pinned corner?
The zero is front top left corner of the stock. That makes the location pins the best way to go. The stock could be a random width, and only really needs the one good long side and a perpendicular face at each end just long enough to pick up the end stop pin. And since I had powered down the Nomad overnight I re-touched all 3 axes. But I would not have had to, it turns out.
The Nomad obviously keeps the user zero point in nonvolatile memory, and as I’ve posted elsewhere (or maybe just in an email to Rob) the home switches you guys use are excellent and homing repeatability is within .001" on repeated homes (measured by dial caliper to fixed points on the structure). The re-touch was dead on on Y, and off in the X by .02mm, which is less than .001". That is several times better homing repeatability than my Tormach mill. The Z was different because I had removed and remounted the toolbit but I’m wondering if Carbide Motion would have taken that into account anyway since the Nomad seems to remember the machine vs user coordinate offsets…
I really like using the semi-kinematic location (depend on freshly-skimmed flat plane for Z levelness, and use 3 location points to align the rawstock in X and Y) because I think it is the easiest way to get a really good alignment between the top and bottom setups.
This assumes that you’re flipping around the X-axis, that is to say your flip is “end over end” in your setups, not around the Y-axis, which would be having the falcon do a barrel-roll
You may want to check which way it’s flipped in MeshCAM between the top and bottom round, because it may be that while you physically flipped it the one way, that the center of the falcon isn’t the center of the stock, and therefore if it flipped “barrel-roll” style, that might cause the mis-alignment.
I agree on the semi-kinematic locating, the important thing being that it match the fixed and flipped axis in the CAM.
Then, if it’s still not that, we’ll have to look at where that pesky offset might have come from!
MeshCAM does flip as a loop (somersault) rather than barrel roll. (notice the “horns” facing the front on the first side machining and facing the rear on the second side machining) That is what makes the two-pin “fence” and one-pin endstop so nice to use. The geometry doesn’t even need to be centered in the stock in either direction. Just measure the “good” edges of the stock and enter that Y size, and a reasonable X size for the stock into MeshCAM and lock the stock size. As long as the stock is generally the right size to fit the geometry, most of it can be just rough-cut.
The thickness does need to be uniform and accurately measured and entered for the two-sided job since that is the only thing that relates the Z position of the first and second side machining.
But as I said, I know now I was a little too agressive on the roughing settings. I wasn’t in the room the whole time of the cutting, and did hear some funky noises at a couple of points. After some X step skipping, the cutter would have been encountering a big vertical wall it didn’t expect to be there, instead of the little .020" vertical bite it was expecting.
