Setpoint Systems Blog

“Let’s go to the whiteboard.”

Setpoint was asked to retrofit a two up pick and place to a four up pick and place on a leak check machine.  This would be no problem, but due to space constraints we were only allowed to use one gripper. One gripper gripping four pars is not trivial due to the fact that the world is not perfect and every thing is not exactly the same size and shape.  We quickly made a prototype to see if this was even going to be possible. 

When we got the grippers in we tested them on some parts given to us by the customer. The test showed potential. We did, however, see that some parts if rotated became loose.  To solve this, we made some UHMW inserts that would give some compliance to the grippers.  After bench testing the UHMW gripper inserts on the parts given to us it looked as if the grippers would work.  The machine that we were retrofitting ran parts with three different heights.  After retrofitting the machine and running it we found that for the two taller parts the grippers worked fine, but for the smaller one the gripper did not work. 

To make the grippers work on the smaller parts Warren suggested using O-rings.  Instead of using O-rings we went one step further and made the UHMW gripper inserts out of polyurethane.  The polyurethane were more compliant and we could shape it to hug the whole part unlike an O-ring.  This gave us our best result yet.  The only problem with the polyurethane is that it would wear too fast and the gripper inserts were being replaced every three days.  This was unacceptable so we went back to the drawing board. 

We decided to make the gripper a three-point gripper.  This helped, but then we were told that we could not use polyurethane any more due to its poor wear properties.  We were so close to making the grippers work, but if we could not use polyurethane then this 4 up gripper tooling was not going to work.  Then it just so happened that I found an O-ring that worked perfectly with the current configuration of our gripper.  I quickly put them on and found they worked great.  I knew that I was going get an “I told you so” from Warren… and I did.  I took the grippers up to the customer and put them on and they ran fine.  I guess the moral of all this bla bla bla is listen to your shop guys.

Saturday night I sat down on my nice futon in front of a good movie.  Changing an inner tube can be a very mundane experience unless accompanied by a series of unexpected events.  I had my road bike tire (flat), the new inner tube, tire tool, my pump, and I even had a great movie on.  No hurry, I will just take my time and enjoy the movie while I’m working.

The inner tube I put in was one of those goop filled tubes.  They build these inner tubes differently than the “Non-goop” innertubes, because there has to be a way to get the stuff into the tube.  The presta valve has a removable core in it that is threaded into the valve stem. 

So. . . I get this goop filled inner tube into the tire.  I’m sitting on my futon with this tire in my lap occasionaly peering through the spokes of my wheel at my movie.  Before I pump, I recall the advice Steve Nuetzman gave me to keep the stem up on top so the goop won’t leak out if air does escape.  I turn the wheel until the valve is up and proceed to attach the pump clamp to the presta valve.  At about 85 psi, the clamp starts to leak heavily - so I unclamped it, forced it on further and reclamped it.  At about 95 psi the air began leaking so excessively that I knew something was wrong.  The pump clamp was stuck and refused to disengage but was still bleeding air. 

Everything happened quickly after this and became a blur, so I can’t remember the exact reason why - but somewhere in the process of trying to remove the pump clamp I rotated the wheel back down so the valve stem was at the bottom.  I couldn’t get the clamp off with just one hand, so I leaned the wheel spokes against my forehead and employed both hands to remove this stubborn clamp.  Well, it came off.

In the split second it took to blink - the valve core shot out with a loud blast.  My forehead was still on the spokes, eyes down.  That valve core shot out like a bullet and caught me square in the forehead.  If it was only the valve core it wouldn’t have been a problem.  But by now all the goop had worked its way back down to the bottom.  Don’t let them lie to you when they tell you how much goop they put into the these tires.  “It’s only about a tablespoon, barely enough to lightly coat the tube.”  I am willing to bet money on about 1/2 cup.  This yellow stuff came spewing out of the stem like the snorkel of an angry diver that just swalled salt water.

Trying to protect my face, I lost grip of the wheel and it fell to the carpet.  It didn’t just fall, it rolled and danced like a quarter on a table top.  The first sensation I remember is the taste.  Classic Elemers school glue flavor.  I looked down at the wheel on the floor, still slowly spitting this yellow goop onto my carpet with no remorse.  I got up and walked to the bathroom to wipe off my face.  It was all over, my eyes, my hair, my ears, my teeth.  When I saw myself in the mirror, it was mixed emotions.  Next, I saw the carpet.  Glad my wife wasn’t home.  Next I noticed the futon, and the ceiling, and the wall, the tv, and the speaker up in the CORNER of the room, all spotted with this evil stuff. 

I woke up at about 2:30 am, and brushed my teeth again because every breath still hinted of rubber cement and Elmers school glue.