I got some new microfluidic chips to play with today (courtesy of the Microfabrication Group at TKK). This must be cutting-edge research, since there's an article about using laminar flow cells for single molecule experiments in the latest issue of Nature Methods. I'm testing our custom-built pressure controller which controls the inlet and outlet pressures between 0 and 7 kPa with about 2 Pa resolution. There are three inlet channels (~40 um wide) with blue fluid in the top channel, clear fluid in the middle, and red fluid in the bottom channel. They all meet in the middle of the chip and there's a wider (120 um) outlet channel.
The video shows a sinusoidally modulated pressure applied to each of the input channels as well as varying the pressures manually between zero and maximum.
We've mounted a 500 cpr encoder on the spindle-motor which means it's possible to do rigid tapping. Above some spot-drilling, then a 2.5 mm drill, and then an M3 tap at 500 RPM and 0.5 mm Z-feed per revolution. Below the same thing but with a 5 mm drill and an M6 tap (1 mm Z-feed per rev).
Last weekend we made some rings for mounting a finderscope on the main telescope. Today I got the holes drilled and tapped so the rings are ready to use. The gallery below shows the adaptive pocketing paths that were used to cut both the part and the jig that allowed drilling the holes at +/- 120 degrees.
There is a video of the roughing operation at 2000 mm/min that will be online soon.
Jari made this steel bulb over the weekend. It has a slightly triangular cross section in the beginning which flattens out to a 'beaver-tail' at the end.
JPK Instruments hosted a one-day Optical Tweezers meeting in Berlin on Thursday. We heard 9 talks and looked at about 30 posters, one of which was mine. As I had not been to Berlin before I reserved a day and a half for looking at the city and its attractions.
Public transport works very well in Berlin. With one ticket you get to ride the S-Bahn (trains), the U-Bahn (underground), and Strassenbahn (trams). They're all on time, fairly fast, and not too crowded. In addition you get to see the nice train stations, some from 1880 or so.
The Mauermuseum at Checkpoint Charlie was interesting, but presented so much pictures, text, and newspaper clips that it was hard to stay focused towards the end.
This is the first time I'm using the WordPress gallery feature. It seems to work although right now the ordering of the pictures is a mystery to me. How do you like it?
After the test run on Saturday Jari made a complete bulb in steel on Sunday. The first half can be milled with the stock clamped to the vises, but for the second half we need this jig. It's in aluminium and was fairly simple to make - which also means making a bulb mould in aluminium should be easy. If someone is interested in a bulb mould, do drop me an email.
Milling the second half proceeds exactly like the first half. Here the rough-program is run leaving about 1 mm minimum of material for the finish pass. We now adjusted the program for a bit faster feedrate and much faster plunge-rates as it is clear the program is error free and all plunges are outside the stock.
Surface finish is slightly better than on the trial bulb. The design weight was 2410 g and this one came out at 2416 g - pretty good. With a 100-150 g fin trimming the total weight close to 2500 g shouldn't be a problem.
As a first serious test-run for our now servo-controlled cnc mill we decided to make an IOM bulb out of steel. It ends up a bit bigger in volume when made out of steel compared to lead, but the difference isn't huge. Making it with a cnc mill allows designing almost any reasonable 3D shape you can imagine.
The mill worked fine during the whole run, about 3 hours of rough-cutting and 1.5 hours of finish cutting, but there was a slight operator error in the setup which means this bulb will likely not sail. The following error stayed low throughout the run, and the servos weren't even hot to the touch after the workout.
We used adaptive roughing paths and then a simple parallel finish path. Both operations are cut with an 8 mm flat cutter. The adaptive paths did seem to work, and on this size machine they are really handy since a slight over-cut will likely stall the spindle motor (1.5 kW and 5000 rpm, small by big-iron cnc-standards).
0:00 rough cutting begins. The stock is a 45 mm diameter steel bar, face-milled down on the sides so it can be clamped to the machine vises. Note the cutting feedrate which is 500mm/min and 'high-feed' in the (x,y)-plane when the tool is positioned for the next cut. When the tool lifts up to the clearance plane it does normal G0 (rapid) moves.
1:34 more rough cutting on the other end of the bulb.
1:58 still pics of the rough-pass almost ready
2:15 view of emc2 while cutting. Note pyVCP bar widgets showing commanded PWM to servo motors.
4:29 beginning of parallel finish cut. programmed feed 1500 mm/min which is attained briefly in the middle of the move.
5:00 more finish cutting, about 2/3 done.
5:50 another view of emc2 and the pyVCP panel. Note Y and Z motors working to position the tool. The following error for each axis is also shown.
6:15 still pictures of the finished bulb (well, one half of it anyway). Note at the front of the bulb we tried to run the program at 150% of programmed feedrate, but that didn't work at all and resulted in a poor surface finish. We did try to slow down also from 100% but that didn't improve the surface much.
Google video doesn't really do justice to the nice 640x480 video and 5 Mpix still-photos that come out of the N95, so if you've bothered to read this far, here's the original 100 Mb mp4 (I hope I don't exceed my bandwidth limit).
Model Expo along with cats, dogs, snakes, and Llamas at PetExpo, and everything family-ish you can imagine at Child'08 happened over this weekend at the Helsinki fair centre. Like last year (see here and here), we had the MicroMagic's sailing in the pool. This year with four less noisy fans and up to 10 boats.
The RC-pilots were only allowed to fly in a large hall with a net separating the planes from the public, but after the doors had closed the braver pilots did some flying over the pool!
