casting
Ring Carved on 4th Axis
Everything came together for the first real use of the forth axis mandrel for ring carving. It’s nice when the plan comes together and everything works as intended. There was of course far more than just making the mandrel. There is the CAD design stage and the CAM (Desk Proto) for generating the G-code for the 4th axis. Then running the G-code on the micro-mill. I use LinuxCNC and I had to write my own metric post processor for Desk Proto. Not all that hard, actually. I made a USC (inch) version too. One tiny code change.
The first picture is the carved ring blank on the mandrel. I can accommodate a wide range of wax sizes. There will be much more experimentation and determination of the correct wax width for a project. This example worked fine.
The second photo is after the wax master model was hand finished and at this point is ready for casting. Sprue’s were added the ring put into a flask and the investment added. This post is not about the lost wax process. However, I thought it was interesting to show the wax carving and the final result the mandrel helps create.
The last picture is the finished Sterling silver ring shown on my hand (size 11). It really looks great. I will be doing a lot more wax carving on the 4th axis of the Taig micro-mill.
Milling Wax Adventure
The year is running out fast. I will soon have to say good-bye to 2011. This is the year (last Saturday actually) that I became 65 years old. Time enough for pondering that event, now to keep moving. Ha!
I did some machining of wax on the Taig CNC mill Saturday. I love machining wax (the hard blue kind). The wax is not good for creating real finished useful items but it makes excellent models for making molds and doing casting.
I spent the morning doing the design work in VECTRIC Aspire software. I was creating a Christmas ornament as a negative. I learned how to mirror and reverse the lettering and other “thinking inside out” processes in 3D design.
The afternoon was spent machining the design into the wax, using the Taig CNC mill. That was an adventure.
I haven’t run that machine for some time. The milling started out OK, but I got a couple of stalls and lost steps in the Z axis. The mill has never done that before so it was a surprise. I wasn’t pushing rapid travel or cutting speeds that hard either. Lifting the spindle and motor is fairly hard work.
The rapids are only set at 65 IPM and I was running about a third of that. So I ran through the software set-up and MACH3 warned me I was pushing the limit on pulses for the pulse generation frequency for which I had MACH 3 set. The Taig has twenty TPI screws so it takes a lot of very short pulses with 1/8th stepping (32,000 per inch) to get any speed from the drives.
That’s 32,000 per inch so at 60 IPM travel (keeping the math simple) that’s 1 inch per second requiring 32,000 Hz (32 kHz)… Continue reading
Looking Ahead 2012
I offer a little machine shop rambling today. It’s getting close to the end of another year so I have been taking stock of what I have accomplished this year and what I need to be thinking about for the next year.
One big item is my operation of the “The Hobbyist Machine Store” website store. I already have written that I dropped one of the “me too” product lines. The store is too small to be a good income producing venture. I would have to say it financially compares to being slightly better than leaving my money investment in a low producing CD or savings account. However, the investment of time is nowhere near justified by that financial return. It certainly does not produce what I term a living income.
I began the THMS business because I wanted to establish a reputation for the store and myself. The next big driver for starting this small business was and still is my access to the mini-mill and lathe steel replacement gears. That product will definitely continue for the foreseeable future as long as the supply is available.
Future products will be single source or self manufactured. I will move away from only hobbyist machine tools. I am working on some saleable product ideas I can personally produce with small machine tools. I.E, products manufactured within a small machine shop. The store will be the outlet for those products rather than offering the machine tools themselves.
One consideration rejected was to bring back the model locomotive wheels I produced by CNC machining. Unfortunately rejected because it is an extremely narrow market niche. I have decided I am not going to invest effort (mass produce) extremely specialized, speculative products. I made the wheels for myself so it was not… Continue reading
“Proofs” of Concept
I was doing some product research today. This is something I made in about five to six hours. I had been thinking of how I was going to make these all week. I just needed a good Saturday to give it a shot.
As the title indicates this is a proof of concept not a real project. I didn’t want to slow myself down doing all the pictures of the process. The process is still experimental so full disclosure can wait until a better time. I have my camera at the ready.
Long time readers know I have experimented with pewter casting before. Here is the LINK.
The “thumbs up” graphic is a 3-D rendering received free with the Vectric Aspire software. I used it to create the medallion. The finished result is seen in the first picture above. The picture was created within the software. I combined the thumbs up with some freelance drawing to form the disk. Actually in my opinion the disk is much thicker than it should be.
The edges of the disk did not come out well in the tool pathing. I need to find a better way to create the disk in the software. As this was a trial, I didn’t want to spend all day on the drawing so I accepted some imperfection in the edge rendering and moved on.
Next I had Aspire produce a roughing toolpath for a 1/8 inch ball nose mill bit. Then I had Aspire produce a spiral finish pass with a 5/32 inch ball nose. The disk is 1-1/2 inches in diameter. The aluminum (both pieces) is 1/4 x 3 x3 inches. The back plate is not machined in this test trial.
The machining was done on the CNC Taig mill. A… Continue reading
…and a cast of thousands.
That’s a famous movie intro tag from when I was a kid. (Ben Hur, Moses and The Ten Commandments, etc.) In this case the “cast” is a bit different. No Charleston Heston. Yes, a pun.
The process here is casting pewter into a mold. Perhaps thousands could be made given enough time. What I find interesting is the use of a rubber mold. When I was much younger I remember toy soldiers cast in metal molds. (The metal ones are still available.)
The mold shown here looks like it was made with hot vulcanized rubber but hot metal casting process is also shown to work with RTV (Room Temperature Vulcanization) rubber. Of course metal and plaster molds can be used.
You will notice a few have short guns. The pour was a bit too cold and the flow didn’t get to the end of the rifle. Thin parts like that are tough to fill. I cast many more than shown here (just remelted them) before I got the process right.
All I did for the pictures was cut off the sprue while still hot and then file the flash from the bottom so each one would stand up. No clean up of the casting at this point.
My plan is not to make toy soldiers. This is just an inexpensive all-in-one kit I bought on sale to get the “hang” of casting pewter. I plan to make and cast my own mold designs and perhaps offer them for sale (the molds and what they make).
I choose pewter and this variety is lead free. There is so much concern about the “dangers” of lead, it is not a good idea to offer it to the public. Of course the other metals in pewter are not intended for… Continue reading