Best of Swarfblog: Machining a Pancreas

By Lloyd Graff

The Today’s Machining World team is on vacation this week. We will be back next week with our regular blog and podcast. We hope you enjoy this edition of Swarfblog from August 7th, 2019!

The Futurism newsletter ran a piece about Liam Zebedee, a software engineer in Brooklyn who struggles with diabetes while trying to live the semblance of a normal life.

He built his own “artificial pancreas” because he was frustrated with the daily hassle of dealing with hospitals, doctors, insurance companies, and pharmacies.  He started with a good piece of hardware, an insulin pump.  He then developed his own software and purchased the necessary hardware for $979.  He pays $225 per month for off-the-shelf glucose sensors plus his monthly cost for a supply of insulin.

“I know that it’s pretty insane to run your basic metabolism on untyped JavaScript code,” Zebedee writes.  “But if you were in my shoes, you’d realize it was safer than going to the hospital, intentionally or not.”

The homemade “artificial pancreas” shows the hand of ingenuity that builds businesses out of ideas.  In a small way our machinery business has been grappling with a mechanical challenge which most of the “smart people” we consulted told us would likely end in failure.

We do not tackle a lot of setups on screw machines these days because if folks want us to do it, it usually means that they cannot do it themselves and don’t know anybody who can.  We took on this one for several good reasons that seemed to trump the obvious impediments.  It was a big opportunity to sell machines, but failure would be very expensive.

The job was to thread both sides of a 4-1/2” long, ¾”-diameter pipe.  The customer made a couple million of them a year, but their process either on CNC lathes or screw machines and threading machines was laborious and even dangerous.

On the face of it, at least to me, who did know enough to understand why they had done it the old-school laborious way for 50 years, it was quite doable on a Wickman.  Thread chasing on one end, die head threading on the other, a piece of cake.

What I did not know was that steel pipe, 4-1/2” long, presents nasty problems for threading.  Pipe is not uniform in surface quality, wall thickness, and machinability.  There are significant differences in the products of each manufacturer.  It is not perfectly straight, it will wobble—more the longer you attempt to machine.  Cutting tools usually are not durable enough to compensate for the roughness and wobble of pipe.

Wickman has a husky and generally quite useful thread chasing attachment for the end of the pipe closest to the spindle.  Unfortunately, it was really not expected to cut steel pipe to connect a hot water heater.  It normally rests on an aluminum base on top of the cross slide, but to our own dismay, we consistently got unacceptable chatter using the attachment.  After tearing our hair out in frustration, Javier, our engineer, mentioned that at his previous job they had occasionally used a steel base when chasing difficult stainless steel components.  Luck had it that we had a scruffy old steel base on our parts shelf.  To our shock the chasing worked.

We ran into similar issues trying to do die head threading on the other end.  The cutting tools broke, the die heads fell apart, chatter was a constant companion.  We put a Logan air threading attachment on to replace the mechanical one.  Better, but still not good enough.  Then we slowed down the clutch by changing gears.  Still no good.  Finally, we put it on the slowest possible threading speed, and we got a good thread, but the cutters had a maddeningly short life.  It required a different coating to finally make it work.

Through all of the experimenting we labored with four different varieties of seamless pipe.  Only one worked reasonably well.  We asked our customer for more pipe.  They could not seem to provide it for us.  “Purchasing” and “Politics” continually got in the way of providing us more raw material to perfect the process.  We offered to buy it ourselves, pick it up ourselves at another plant, do anything to move the process, but the pipe did not come.  Finally ten 10-foot lengths arrived.  Not enough for a full run off, but enough for samples and a good tryout of the process.

“We did it.”  At least we think so for now.  Not a homemade, artificial pancreas, but a satisfying, improvised solution to the problem for Graff-Pinkert.

Question: Tell us about an “impossible” job that you solved.

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