The RotoZip bit was insufficient: too slow and it burns the wood, too fast and it breaks. I’ve ordered some endmills from Enco, which I’m much more optimisitc about.
The gear below was cut out of 1/4″ plywood, with and endmill too shallow to do the MDF. The partial gear in the background is made of 3/4″ MDF; the RotoZip broke just before completion, despite taking passes only 1 mm deep.
If you cut MDF too slowly, it will burn. Patrick recommends a speed of between 50 and 80 inches per minute, depending on the quality of the lead screw. The chapter on milling, in my upcoming book on Personal Fabrication for Make, will include a chart of suitable spindle and travel speeds for different materials.
I went to Lowes and Harbor Freight over the weekend and bought a few router bits. The best of the collection is the Bosch 1/4″ x 1″ Downspiral Straight Bit ($17.97). It’s long enough that, with multiple passes, it could reach a depth of 1.5″. I also bought a RotoZip chuck adapter, with a 1/8″ straight bit. We tried one of these bits in a ShopBot at the MIT Fab Lab last October, and it performed poorly, dragging behind the tool and eventually breaking. I’m hoping it will perform passably with shallow cuts and at low speeds. More important is the 1/8″ adapter, which will allow me to use other 1/8″ endmills that I already own. I also bought a 1/16″ Dremel Carbide Grout Removal Bit ($9.97). Its maximum depth is 1/4″. Of course, it’s made for grout, so we’ll see. It’s the only 1/16″ bit I was able to find.
Finally, I picked up a 5 Piece 1/4″ Shank High Speed Steel Start Set from Harbor Freight. It’s the finest router bit set $8 can buy. Router bits are so expensive, I figured I’d experiment with these before ruining anything nice. Another advantage is that they’re steel, so they won’t fly apart like I’ve heard of cheap carbide bits doing. Once I know what I’m doing, I’ll probably purchase some mid-rangs bits from MLCS.
The next day I went to an auction and bought a tool chest full of end mills for not much more than what the Bosch bit alone cost me:
Of course, most of them have 3/8″ shafts, which I don’t have a collet for.
The mill is working and I’ve been familiarizing myself with CAD and CAM software, and EMC. QCAD and Inkscape are first rate. I’ve had trouble finding anything I like for CAM, but dxf2gcode seems to work very well. The labels aren’t very intuitive and everything’s metric, but it’s more reliable than the others that I’ve tried yet.
The only end mill I have at the moment is pretty short, so I’ve mostly been playing around with engravings:
With “It’s Alive”, I tried to cut the outline of the font, but my end mill was too large in diameter, which you can particularly see in the ‘A’ and the ‘e’.
I ran into a snag with my decTOP, which I was planning to use as a radiation monitor: it does not power itself back on after a power failure. This should be changeable in the bios, but it’s inaccessible and emails to Date Evolution have gone unanswered. The power pin is normally 3.3v, and powers up on a rising edge (i.e. you have to release the button before it will start). I described this to Mike Fincham, and he suggested I connect a resistor and capacitor in series, from ground to the power-up pin. The capacitor acts as a switch. When power is first applied to the decTOP, it will begin charging, connecting the power-up pin to ground. When charged, the capacitor stops conducting, allowing the power-up pins voltage to return to 3.3v, and the computer to power up.
It works! The capacitor is obviously a bit large (10 microfarad), but it’s all I had on hand.
I’ve gotten into the habit of keeping a pack of bottled water and some granola bars in my truck, for occasions when I miss lunch. I figure it’s cheaper, more convenient, and probably healthier, than fast food, but I usually end up with bottles scattered all over the place. I have some old barn siding left over from a chicken coop I’m building, so I figured I’d use it to make a box. The wood is from the early 1800’s, so I thought some rusty old cut nails might look nice. The handle is an old leather belt, cut to length. It’s held in place on each end by two nails, bent a bit past 90 degrees.
The CNC router is now complete, mechanically. It took longer than I expected due to a couple missing/incorrect parts, but I’m pleased with how things are looking. I haven’t started with the wiring yet. I have a computer to run EMC2, but I was using it as a test server for another project, so right now I’m in the middle of transferring everything important off of it. With some luck, I’ll get everything wired up tomorrow.
I just got a player piano on craigslist. The veneer needs some repair and it ought to be refinished, but it plays! I’ve been casually looking for a player piano for the last couple years, but everything I’ve come across has been either too expensive, or in need of significant restoration. This piano is from 1921, but it was restored in the 70’s. It came with over a hundred programs on paper tape, so I spent this afternoon sorting through and playing songs.
I ordered a CNC Router kit from Patrick Hood-Daniel’s BuildYourCNC website. There are a lot of bolts in this kit! The wood is medium-density fibreboard. I suspect it’s plenty sturdy for most of what I’ll be doing, but I still want to mount it to the table.
I’m short a few pieces, but I hope to have those early next week, and have everything working by Friday.
I have a pair of industrial robotic arms that allegedly came off a pcb assembly line. This evening, I tried one out for the first time. It works! I plugged everything in, hit the green run button, and the arm sprang to life (the poor thing thinks its still out on the factory floor). I was able to directly control the motion with the teach tool, but unfortunately, some of the buttons no longer work, so I may try to open it up and repair it. More likely, I’ll just forgo the teach tool altogether, and program it via the serial connection. I haven’t come up with any good projects for it yet, although I do want to try mounting the RepRap extruder on it.
