Logo rework, prep for 3D

For my next project I'm working on a 3D version of the Kung Fu Machinist logo. I've added the typography to the sun and bird image. I bounced some ideas off a friend who's a much better designer than me. He helped me focus my ideas for integrating the type with the form. Here's the color 2D design with the type:

Here, kungfumachinist is all one word. My blog title is Kung Fu Machinist, but I seem to have grown attached to the idea of it being all one word. I definitely like it in all caps. My goal was to have it look like drafting lettering.

Here's the 3D concept:

The bird will be black and the base raw aluminum. The sun will be aluminum, too, painted in a transparent cherry red acrylic. I did a test of the painting and engraving of the lettering. When it first came off the mill, I wasn't terribly impressed. There seemed to be some rough edges in the path. I carefully cleaned off the chips and cutting fluid and looked at it with a magnifying glass. The technique I used to generate the lettering had the paths all doubled so each was cut twice. Also the paths didn't seem to be linked in the most efficient way. I suspected these 2 things contributed to the apparent rough points in the path. But then... I grabbed a tooth brush and scrubbed the lettering and all that ugly stuff disappeared!

I think the actual part looks better than this photo. Obviously I didn't paint the whole region. I left room on the scrap part for another practice run. You can see some "balls" at the ends of some of the lines. I'm not sure if these are entry or exit wounds, so to speak. I'm going to take a shot at removing the double-stroking of the paths. I think that will contribute to an overall cleaner cut.

Feed Speed

I've implemented feed speed. In machining, "speed" usually refers to the rotation speed (RPM) of the spindle/cutter. Feed rate refers to the speed that the cutter moves through the material - the speed of the table. Here, I'll just use speed for the latter.

Up until now my gcode interpreter has simply been building a 3D path and ignoring the speed information in the file. I've been "babysitting" the program runs, moving the speed override ("throttle control") as I need to. I've added support for the speed information in the gcode.

For the acceleration development I've been rendering little boxes around each location point and coloring it according to the speed through the point. I thought it would be cool to change the color of the line as the speed changes. I thought such a thing would be pretty challenging and I'd give it a try later on. Using the point-coloring method or printing speed values to the console isn't very readable. I came up with a clever idea for coloring the line and it turned out to be pretty easy. Here's a shot:

I created a list of colors like the ones used on weather maps to indicate storm intensity. The vertical traversals in white in the center look a little funny because the up speed is different than the down speed and the colors kind of jump back and forth as the scene is rotated. Having the color blending in the lines really helped develop the support for speed changes.

I've calculated the maximum feed rate of my mill to be 18.75 IPS (inches per minute). Obviously since this is the first time I've had IPS support, I've never considered the speed in any sort of objective way. I just run the mill and position the throttle "by feel". So now I need to calibrate my brain and learn what speeds work for what materials and processes. I don't think there will be too many values I'll actually use. I'll probably use something like 1, 5, and 10 for nearly everything (and 18.75 for rapids, of course).

First Real Project

My friend Bob is a rock star. Well, he's the bass player in a band, I don't know if that counts. Anyway, the band is called Phoenix Rising and Bob did the logo design. Probably more than a year ago he did a graphic design job for me and I suggested I could make a key chain for him with the band's logo on it. So right on schedule, I finally got it done. It's not really a key chain, though, it's 3/16" thick aluminum and over 2" x 3". I decided to call it a "plaque" and put a couple holes for screw mounting to a guitar case or something.

It's a simple design, an etching with a profile cut out. I really didn't have a suitable bit to do the etching with. I bought a Dremel engraving kit with a mix of grinding and engraving bits in it. I assumed the bits all had a 1/8" shank as most do. I've got a 1/8" collet just for Dremel bits. Unfortunately the engraving bits were 3/32" shanks. So I went ahead and used my drill chuck to hold the bits. This is considered bad form, drill chucks aren't designed to take side loads, but the engraving was only 0.015" deep and went slow. I'm not terribly happy with the cuts, but after breaking a small bit doing PCB milling a year ago, I was reluctant to invest in another high-quality engraving bit without being sure what I wanted.

I did a couple of tests in a vinyl sheet material. I mounted the stock over a sacrificial plexiglass piece and held it with the same hold-down clamps I use for my vise. I ran the engraving program and everything went fine.

Then I switched to the 1/4" collet and mounted a 1/8" bit to cut the profile. I immediately realized my first error when I brought the head down. With the stock mounted so close to the surface of the table, the head with the short 1/8" end mill won't come down far enough to cut through the stock. So ends practice run number one.

One of the greatest challenges with this mill is the work envelope. You've got to plan ahead to make sure the bit can get every where it needs to go without running into the limits of the machine. I took some measurements and figured I needed to raise the work surface 1/2". I even took off the lower Z-axis limit switch to get a little more room. Fortunately, I had in the works a large tooling plate I mentioned in my last post. I didn't have any holes in it, so I had to take a quick detour from this project.

I mounted the tooling plate, and found the center rear edge. I then made a number of holes on a 1/2" grid clustering them on either side of center figuring I didn't need too many holes in the middle. Anything small enough to fit in the space in the middle likely could go in the vise just fine. Tapping lots of holes is tiring. I lost focus at one point of the drilling phase. My wife called me while I was in the middle of transiting the spindle from the left to the right side. I took the call and when I finished I assumed the head was at the target location and proceeded to drill the hole. Then I looked at the DRO and realized I was a little more than 1/4" short of the target. I made another hole to pair up with it, so now I've got 2 holes that are off the 1/2" grid, but they're actually in a pretty useful spot for holding the vice.

After completing the drilling and taping of the tooling plate, I mounted the sacrificial piece and another vinyl practice piece. I ran the engraving job again, then did the first roughing pass of the profile with the 1/8" bit. I've been using Cam Bam to generate the gcode. It supports "tabs" to hold the inner material in place while the profile is cut. The size of the tabs I chose turned out to be too small. I switched to the final finishing pass with a 1/16" bit and the tabs broke free. So I doubled the size of the tabs. A valuable practice run...

The blank stock mounted:

Engraving:

Profile cut:

You can see the tabs in the above picture. I had to grind them off and clean up, of course. This was a bit of a drag. The final milling pass was pretty clean so to have to grind and sand was a bummer. If I had to do it again I'd drill the holes first and screw the stock down. This would leave the complete perimeter free so the tabs wouldn't be needed. That's OK, I got a feel for the tabs and I know what the correct size is and what I'm up against for future jobs that don't have any interior holes for securing.

After milling, I painted the face gloss black, let it cure and sanded it with a random orbital sander. This left the black only in the engraving path. I took a shot at polishing the aluminum with my Dremel. I bought some polishing compound and hit the sides and the back. I figured the back isn't going to be seen so it would be good practice. It's not perfect, but it shows promise. Polished aluminum looks really nice.

Bare aluminum in the hands can feel a little dirty, so I sprayed on a clear coat enamel. And here is the final piece: