O-rings come in many different sizes and thicknesses. You wouldn't think that a little rubber thing like this would be the cause of so many problems. But for me they have been the root of two of the most stressful work days I have had since I started working for this company.
Let me provide a little background for those of you who are new to my blog or who have been slacking on reading my archives (shame on you). I work in the injection molding industry. Specifically, the company I work for makes medical devices. Really small, cutting edge type stuff that can be put inside the human body. These devices are bio-absorbable, meaning that over time the moisture and heat in your body slowly dissolves the polymers used. Which is great because in the old days you had to have one surgery to implant such devices and another to explant them. With this stuff only the first surgery is necessary. Anyway, I digress.
We have a 500 piece order of a certain product that needs to be shipped tomorrow to our main customer in Florida. But it's not gonna happen. This run will ruin a perfect 18 month string of 100% on time delivery and (in most cases 120%) quantity of pieces ordered.
Normally the production schedule is planned out well enough in advance to allow plenty of time for manufacture, inspection, packaging and shipment. We were originally scheduled to make this order at the end of October.
After taking the time to set the machine up (a lengthy, time consuming process) in October, we started the run. But somehow the mold got severely damaged shortly after start-up, so we had to stop. Once we took the mold out it had to be sent out for repair, which it was that same day. That took until this past Monday when we got the mold back. What a crappy job they did!!
So on Tuesday we put the mold back in the machine and hoped to get some of the run in and finish it today, so that inspection, etc. could happen today and Thursday. After we got the mold installed we intended on running until we discovered the leaks.
With these machines running at such high temperatures it is necessary to have coolant running through both parts of the machine, which are the barrel (where the material gets heated) and the mold itself. Much to our dismay the o-rings in the mold went bad. So we replaced them. They leaked again. After going through about 10 sets of o-rings yestreday we thought the problem was fixed.
Assuming we had conquered the mountain, we began today with every intention of running all day and into the evening. So we started everything up again this morning. Four shots (a shot is what is produced during one cycle of the mold closing, injecting material and opening to reveal the molded product) into the start-up phase we discovered more leaks in the same places.
After what turned out to be a day's worth of unsuccessful attempts to correct the problem, we're down to ONE LAST HOPE.
In the morning, one of my co-workers is going to pick up an epoxy that we had frantically reserved from a local company tonight (for pick up tomorrow) that we hope will seal the leaks long enough to complete the run, which should take about 10 hours if all goes well. What adds to the problem is that our yields from the machine are horrible with this particular piece. Last time we ran it (in Nov. 2004) we had a 67% yield. Which is to say that one third of the shots we make will be garbage. At this rate, we'll need to make 665 shots to get 500 good pieces. If this epoxy stops the leaks, that is. And these figures don't even consider the amount of rejects that will be found during the secondary inspections. Once the run is done the mold will be sent out for more work, so the next time...
With any other type of injection molding, a coolant leak here or there would be no big deal. But because these babies go inside a human body, the coolant effectively contaminates the pieces, if contact is made with it.