In this story, my own products were made by monkeys. My company had a great staff that assembled the radio receivers that we sold. Staff members were able to follow instructions and use their initiative when something unexpected arose. Sometimes, however, the instructions did not reach everyone.
Our top-quality radio used an oak cabinet. Inside the cabinet we mounted a four-inch speaker. The inside of the cabinet was just slightly larger than the speaker, typically by 1/8 inch. The speaker could be dropped into place and then held with four wood screws. Because wood is not as precise as metal, occasionally the inside of the cabinet was smaller than the frame of the speaker. I had instructed the staff to bring these few cabinets to my attention. Since I had more physical strength than anybody on my staff, I took a sharp knife and cut the inside of the cabinet so that the speaker would fit, and then they mounted the speaker in the normal fashion.
One day, someone from the office was helping to mount the speakers. She was not told about those cases where the speaker would not fit. Instead of giving the cabinets to me, she bent the frame of the speaker so that it would fit. Needless to say, the cone was distorted and I considered the speaker destroyed. I checked and found another cabinet with a bent speaker and had it replaced. A month later, a new radio was returned with the complaint of excessive distortion. To my dismay, the speaker had been bent to fit the cabinet.
Our speakers were made in China and supplied by a local distributor. Once, when our supplier was out of stock, we bought a shipment of very high quality speakers from another source at a good price. The magnets were heavy and the speakers sounded great. We installed them into the cabinets and sold the radios.
A few months after shipping, some of the radios were returned marked “no sound.” Upon examination, we discovered that the magnet had fallen off, probably because the radio was dropped. Then it would grab the frame, which was made of steel. In other radios the speaker appeared normal, but with a sharp pull, the magnet could be removed. There was no sound because the voice coil was pinched between the magnet and the frame.
It seems that the magnet was glued to the frame, carefully centered so that the voice coil could move freely through the steel projection from the center of the magnet. When the glue aged, it lost its strength and the magnet either fell from the frame, or moved sufficiently to pinch the voice coil.
The speaker was well designed and carefully built, but somebody substituted cheap glue that didn’t have the strength to hold the magnet. Or perhaps the glue was not properly applied. Clearly, monkey business!
This entry was submitted by Frank Karkota and edited by Rob Spiegel.
Tell us your experiences with Monkey-designed products. Send stories to Rob Spiegel for Made by Monkeys.
I really enjoyed this story since it addresses the real world issues of manufacturing. It's fine to design something on a CAD program, but somewhere along the line, the actual parts have to be assembled and that, it turns out, is every bit as important and the design itself. Attention to detail, proper assembly techniques, training and clear work instructions all matter. Thanks.
I spent a lot of years as a club musician and speakers were tossed around quite a bit, not like Pete Townsend, but things get dropped, bounced around on the stage, and in vans. I've heard voice coils rub, seen them melt, and shatter (titanium horns). I've seen surround dry rot and fatigue, but I've never seen a magnet fall off, not even on the big 20lb magnet JBLs. This sounds like a pretty low quality vendor.
Scott, that is a good point. This reminds me of a number of situations I have seen with small manufacturers over the past few years. The problem was parts testing over time (life testing). You really need to trust your supplier or have a good warranty program. On the other hand, even with a good warranty the failure often leaves a bad taste with the consumer.
This story exemplifies the importance of good work instructions. A good system will account for a new employee and still make quality product. Documentation of task steps and quality risks on each step is important.
And in this case it sounds like someone forgot to check and see if the glue would give the product the life it needed. Could have been one of those cost out ideas. Or more than likely, someone just thought it would work as good as the other stuff.
I liked the article as well. Kind of makes one wonder if the tolerance stack was done to understand if the process was capable of producing repeatable parts with the process being used.
I agree with the use of good instructions or standard operating procedures. However, I don't like the idea of standard operating procedures being, "bring it to me and I'll fix it with some baling wire and twine."
Even with a good statement of work, I asked the manufacturing staff for "as built" drawings to try to catch things like this. Wouldn't have had an effect on the magnet glue problem, though.
When a 15$ radio fails because of poor quality components it's my fault for buying rubbish in the first place. But if I buy a top quality audio product, maybe a radio from a company whose name sounds like an Italian dish, or a term in trigonometry, or the capital of a US state, I don't expect it to fall apart because someone saved a few pennies in production, or sold "quality" at "quality price", without actually verifying the quality of the product. In the long run, the cheap mass produced products have more stringent manufacturing procedures and automated final test methods, and are more reliable.
This story also illustrates how one cheap component makes the entire product cheap. With a high quality product, each and every aspect of the product and the production needs to be high quality.
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