Don’t Gamble on Quality
As we have become more involved in architectural coatings we have seen a significant increase in the amount of aluminum extrusion we finish. Most of this material is mill finish stock length and is anywhere from 10 to 24 feet. We pre-treat and powder coat it per customer specifications, usually prior to any fabrication or cutting operations. Due to the nature of the product and its’ high visibility, superior quality is expected, and defects due to dirt or contamination are not acceptable.
We have had very good success to date, with a few exceptions. We once ran a large fencing job with several thousand pickets. Near the end of the run, we started to find an increasing number of contamination particles under the powder coating. These particles were as small as a spec of dust to as large as a flake of freshly ground pepper. By the end of the run, most of the parts were scrap and we had to strip and re-coat them. The customer was pressing us to ship, so we didn’t have time for a full investigation.
After the parts shipped on time, we checked our wash line for concentration, temperature, and possible contamination, and found everything to be in order. We counted on our wash line to physically and chemically remove any oils, soils or contaminants. Next, we checked the dry oven to see if maybe there was dirt in the oven that was blowing around and sticking to the parts but a quick walk through proved that the oven was clean. Then, it was on to the spray booth and the powder. Because the problem gradually increased, someone suggested that there may have been some contamination in the box of powder, and as the box became empty, the concentration of contaminants increased as well. A quick check with the sprayer eliminated that possibility, as he had opened a new box near the end of the run. Besides, we ran some posts behind the pickets with the same powder and they all looked fine.
So, as the mystery remained unsolved, I continued to search for the answer. Because the contamination was under the powder, it had to be there before the parts were coated. And because it was limited to the pickets, and was not affecting the other products, the problem had to be originating somewhere else.
Time went on and other work got in the way of my sleuthing until a new job came along and the issue reared its’ ugly head again! The parts had been cleaned and coated and were being taken down when we noticed the contamination under the coating, only this time we had caught the culprit red handed. We took a part showing a few nice sized pieces of contamination and hit it with stripper. The stripper removed the powder coating, but left the contamination on the part– it was a piece of aluminum chip pressed into the part! A little more investigation revealed the whole story.
First, the type of product was not mill finished full lengths of profile, they were cut to size and had machined areas. Just like the fence pickets, the parts were covered with aluminum chips from the cutting operation. But we have run parts with chips before and our wash line removes any chips. We had not seen this problem in the past, so why was it happening now?
This answer can be found in the old saying, “The road to success is filled with many pot holes”. As we have become more successful in the architectural market, we are finishing more aluminum. And, more of that aluminum is work in process, so it has chips on it. And because we are running higher volumes and bigger jobs, the cut product is shipped to us in larger bundles, and larger bundles have more weight. More weight caused the chips to be pressed into the parts. This explains why the problem became worse as we moved further down the bundle of parts, with the worst parts at the bottom of the pile.
So what have we learned? Well first of all, when we run a job consisting of cut aluminum parts, we examine the parts for pressed chips, especially if the job has some volume. Second, we recommend that our customers do not try to stack all of the parts on one skid. If possible they should break up the load into smaller stacks of product, or try to wipe off the parts before they pack them. Finally, when we see the potential for this problem, we notify the customer that we may have to charge extra for wiping each part to be sure there are no imbedded chips.
With this mystery solved, we can safely say that we are the best option for all of your aluminum extrusion finishing needs! And I humbly remind you to never gamble on quality–cash in your chips before you run the job!