BW April 2018

4/2: I sanded several thick fibers in bundle 405 to get them through the chimneys more easily. Andrew put the fibers back in the collar and aligned them before I left, but we still wanted to improve the alignment. I recorded the new configuration and tried to improve the alignment, but a Kapton strip broke and after I replaced it I did not get a very good alignment.

I also practiced fusing today.

4/4: This week I started polishing a fourth bundle of sci-fis. I am still twisting right in front and left in back. The wheel is running in reverse.

Yesterday during fusing practice the hook on one of the 500 g weights broke, and today Jim suggested wire as a replacement.

I worked on preparing light guide bundle 403 for testing today.

4/5: After several attempts by Andrew and me, I put bundle 403 in the dark box with a satisfactory alignment. I started running tests.

I changed the 400 grit sandpaper, and polishing went much faster. Bundle 4 is now less than 0.005" from the target length of 0.787". However, it is hard for me to tell where we bottom out - i.e., which is the smallest feeler gauge that prevents the bundle from touching the sandpaper. There seems to be a gradation of contact between the fibers and the grit, with a thick feeler gauge such as 0.025" allowing slight brushing contact while 0.015" allows the paper to scrape vigorously against the fibers.

4/6: Dr. Jones said it would be good for me to start fusing soon. We won't throw away fibers if fusing goes wrong. We'll just cut them and polish them again.

When the fibers are all tested, I need to come up with charts showing bell curves of all the test results. There should be one peak. However, I would expect two because of the difference between offset fibers.

I asked about telling which end of a sci-fi is highly polished, and Dr. Jones suggested using a microscope. I responded that it would probably be faster to polish both ends of the fibers. He said that would be all right if it doesn't take too long.

4/10: We may need some more fine-grit sandpaper. Ideally I want each sheet to suffice for four sci-fi bundle ends, which means two bundles if we polish both ends of the bundles and four bundles if we polish only one end of the bundles. However, it might sometimes take more than one circular piece to polish one bundle end, so it's more likely that I will need more sandpaper than less. I may need more 5 micron grit too to sand fibers for the chimneys.

4/11: I am not satisfied with the results of using a razor blade to remove wings from fused fibers. I keep making holes in the cladding. I want to compare using a razor blade with using 5 micron grit. I marked the fibers I used a razor blade on with purple masking tape, and I will leave the ones I sand unmarked.

I think I would still use the razor blade for big wings, but once they are cut short I would use the sandpaper. I have to experiment with sanding to be sure.

4/12: This week, after much practice, I started doing real fuses. They are meeting the strength requirement to hold 850 grams, but they might be too thick. I don't trust the thickness measurements because the wings are probably making them too large.

Since the fibers are normally strong enough, my main concerns about fusing are how thick the fibers are, how to remove wings without damaging the fibers, and how to avoid unwanted dust and material between the fibers to be fused.

I have sometimes removed dust by wiping the end of a fiber with my glove. That seems to work well. Wiping it with a lint-free cloth also works but can leave a thread behind.

A Lesson On Fusing

Jim said I should score the wing before removing it. That will help to guide the cut so the razor blade does not nick the cladding. He also suggested using sandpaper, maybe even 400 grit, on some of the fibers, but Dr. Jones said I should not do any sanding to remove wings. I tried using 5 micron grit on some of the practice fibers, but the fine grit was little help for removing wings.

Jim looked at my fused fibers and saw that the wings were not only at opposite corners but also at adjacent corners. He realized that one of the quartz ferrules is probably cracked.

He said the cladding has a lower boiling point than the core of the fiber, so sometimes it can boil away in spots. There can be a bubble that pops and leaves a little pothole, for example.

I should remove the wings before weight-testing the fibers because they could be strong when the rest of the fuse is weak.

To remove the wings, I should put the fiber down and run the point of the razor along the side until it cuts through the wing. I could also try sandpaper and look with the microscope or camera at the results.

I need to do some test fuses to find out where the crack in the ferrule is. The fibers are marked with masking tape on one side. That side will be facing up and towards me as I fuse. I also marked one fiber with a Sharpie, but that did not go as well and the mark should be disregarded.