milling
Weighty Subject
A fellow ham radio operator Dennis (KI4DW) was in need of replacement weights for his Brown Brothers “bug” keyer. The weights are the easy part. I thought he needed the thumb screws duplicated too. Turns out he has the screws.
The weights I turned from a 3/4 in leaded steel bar on the PD400. The slots are cut with a 3/32 end mill on the X3. The digital readout was a real big help in free handing the slots. (CNC automation spoils me.) In the picture, the slots still need a bit of internal filing to square the inside corners.
The 8-32 thumb screws would be a lot more work to make exact copies. I was afraid of the time (and cost) I would spend on two of them. I have since discovered a good source for these at McMaster-Carr.
If I make any more weights, about a half hour in BobCAD should make the slot cutting easy work starting from dead center. Heck, the G-code would be easy to write from scratch.
Just a few hours work on developing these parts. CNCing the slot would make it much faster to produce more.
Letting the Cat Out of the CAD
I am taking an opportunity in my project schedule to try another CAD/CAM package. I had looked at it long ago and it has been around for over 25 years. When I first saw it (back then) I believed it was one of those,”yet another CAD/CAM packages.” I am sure at some point I registered and ran at least the demo, as it seems I have been receiving occasional marketing from them forever. Back in that time, I was looking for a cheap all in one CNC solution. I was still a bit naive of all the requirements. I did find and purchase DeskCNC with its serial port interface. That worked OK but I am now using much stronger and expensive Rhino and Vectric 3D software and MACH3 from ArtSoft. You get what you pay for.
The product to which I am now referring to is BobCAD-CAM. I knew it was created by a guy named Bob (Bob Twaalfhoven) so I assumed he just called it BobCAD after himself. I was thinking simplistically it was Bob’s CAD. Today it is a more professional play on the image of a Bobcat, just change the T to a D. Whatever the thought on the name, it has survived the test of time.
Soon I will see if it survives the test of Dan.
DeskCNC is still around too but the web page has changed little to none. BobCAD-CAM is on version 24 and a first web site look, while allowing for marketing hyperbole, seems impressive.
It will take me a few weeks or a month or so to give it a full workout and use it to construct a CNC project. I’ll probably leak a few comments here in the blog, but I am considering doing a full report, probably… Continue reading
4″ Mayan in Wax
I use the Mayan calendar as my CNC test program. It is highly detailed and makes the stepper motors really earn their keep. In these photos I show where I have reduced the circle diameter to just under four inches. This is about as small as I can go with this design. I got it off center a skosh. That’s OK, it’s not a keeper. The test is not of the Taig mill but rather the tiny wax profile bit I bought from Bits & Bits.
The bit is 1/8″ in diameter half round with a 15 degree included angle. The end of the tip is 0.005″ It looks and feel like a very sharp needle. The RPM was 10600 (max for the stock CNC Taig) and the feed I had set for 30 IPM. With ramp up it seldom got to 30 IPM except for long paths.
The total run was just over four hours. The Taig and CNC controller took this run without a blink.
I use plain air to clear the wax chips but you can see they still liked to stick around. The problem could be the slow feeds because of the intricate details. I am going to try a faster more aggressive feed on the next Item. I am thinking of trying a small lithophane carved in wax.
CNC Gun Part
A local person here in Frisco asked if I could duplicate this part (the black one). I don’t usually like to take on outside projects as I have enough of my own. This part looked interesting. It is part of a tripod bracket for an expensive, but what the owner called a “toy” gun. Actually is is a very sophisticated collector item.
As can be seen in the photo the bracket had the tab broken off. It is a very nice injection molded aluminum casting but the crystallization left it vulnerable to breaking where it did.
I was going to make a duplicate by manual milling. That’s the rotary table setup in an earlier post. I changed my mind and decided to do it with CNC milling.
I had to first very carefully measure the part in every detail then make a 3D drawing in Rhinoceros (Rhino) You can see the screen capture and a couple of output pictures.
I converted the drawing to two G-Code files with RhinoCAD, one for top and one for bottom.
I did a test run in oak then made the one in aluminum. I used my Taig CNC mill running mist cooling. Overall size of the part is rather small, about 1.5″ x 1.5″ x 3/8″
I’m not setup for doing anodizing and I have never done any. I have studied the process and it can be done in the home shop. The new part really needs to be anodized like the original, but that is not my “thing” right now. That’s all I need is another skill to master. 🙂