The Project:
In 1999, a customer came to us with an unusual request: to take over production of a partthey were already sourcing and using without major problems. They had the foresight to realize that poor quality management procedures by their blow molding shop could eventually lead to big trouble. And when the safety of the nation’s blood supply is at stake (see below for details), preventing problems before they happen is generally considered a wise practice.
The Cliff Notes:
Every single blood donation is tested for various diseases and contaminations before being added to the blood supply. This part is a vial used for drawing off a small amount of the blood for testing. The idea is to do it as efficiently as possible while preventing contamination.
The Challenge:
The part is blown in packs of six units, which are snapped off into the individual parts by our customer. The shape of our finished part is rectangular, which means the far corners’ walls get stretched, making them thinner than the rest of the part.
The most important functional requirement was the ability to draw off a single drop of blood at a time, with the hole small enough that nothing would leak out if it tipped or fell over. Mobile blood van crews don’t get excited about the prospect of mopping down blood-drenched floors every night. Also, the vials get centrifuged to separate the blood into constituent parts, and it would not be cool to turn the centrifuge into a giant Spin Art machine.
If the part had been one single vial, we could have used a blowpin to size the hole exactly. But with six in a part, the critical inside dimension of the hole had to be controlled by the direction and force of the air through the parison (a great Scrabble word that means “the plastic goo-tube that turns into a blow molded part”).
If you were forced to play recorder in elementary school, you may recall that you could alter the pitch of the instrument by blowing slightly harder or softer into the mouthpiece. Think of the machine that molds this part as a really big recorder player, trying to play six recorders in perfect pitch at the same time by making six identical 0.025 inch holes with its breath.
(Our client originally asked for 12 units per part, which we nixed because we couldn’t guarantee enough control over that process. We hate saying no to clients, but it’s better than saying yes with our fingers crossed behind our backs.)
Also, the plastic has to be squeeze-resistant, meaning it rebounds to its original shape after squeezing. Think dropper cap, not toothpaste tube.
The Result:
This modest little part has, to a large extent, turned us into the company we are today. We’ve been working on it for almost 10 years, during which we’ve become a quality-driven company.
Although this customer trusted our quality management processes enough to work with us initially, they pushed us to create an entire quality management system around the entire relationship, not just the part. With their prodding (through lots of tough questions from their lead project engineer), we established our now-famous (at least to us and our immediate families) Value Development Process. It encompasses everything we do, from the initial approach to the customer relationship to engineering to quality control.
We became ISO certified to make sure we could turn this part out without problems. It was a huge learning experience for us. The customer pushed in very supportive way to improve ourselves. The customer, and especially this part changed our business in significant ways.
Quality control became its own division in the company, and not just part of the production team. We adopted Statistical Process Control techniques and still work to expand their use in our facility.
If they ever made a superhero movie about Blow Molded Specialties, this project would be the radioactive spider bite that turned Tom Boyd into Captain Meticulous.
Ongoing Quality Control:
Every hour, we pull several parts off the production line and make them perform for us. We weigh the parts, inspect them visually to make sure the part is clear and uncontaminated, and then deploy a force gauge to test squeeze resistance.
To ensure the spout interior diameter is 0.025 inches, we cut the top off and insert a pin gauge. The magnetic micrometer checks wall thickness by measuring the magnetic attraction of a tiny ball bearing inserted into the part.
When any of these tests uncover a problem, the air horn sounds and the Captain Meticulous theme music swells to a crescendo (if you have a really good imagination). We immediately quarantine all production that’s occurred following the last inspection, and the technical team descends on the molding machine, looking for what changed since the last perfect run.
The technical team consists of two technicians plus the engineering manager and the process engineer, at the very least. Often the quality inspector and the supervisor join the party, and sometimes the quality manager comes running as well.
Sometimes we find and correct the problem right away, within 20 minutes or so. Other times, we poke and prod and measure and hypothesize and test for up to two hours until we’ve identified and corrected or compensated for the change.
Our molds undergo routine wear and tear, which can affect the 0.025 diameter opening. Any maintenance, repair or sharpening of the machine can change the internal geometry of the mold. We try to anticipate these changes as we’re performing the repair or maintenance, but we’ve learned over the years that this part of blow molding is as much an art as a science. No matter how much time we spend working with a repaired part to make sure it won’t mess with the critical dimensions, we’re still surprised sometimes at the effect of the interactions of hundreds of variables.
Sometimes, a difference in the material we get from our plastic supplier can throw off the process. Occasionally we find some contamination, but more frequently a batch of the same stuff behaves slightly differently.
And of course, how the Red Sox and Celtics are doing affects the blow molding process in mysterious yet powerful ways.
