Day four of the Shenzhen trip and the destination was a contract manufacturer called Eagle. They had both a plastics injection molding side and also an electonics assembly manufacturing side. Bunnie chose this site to provide a contrast to Colinda which is the injection molding factory we saw earlier.
For the injection molding side, it's our third plastics factory we visited so there wasn't a whole lot that was new to us. However it was interesting to see how their process differed from the others. It was obvious that Colinda was a smaller factory, Kunda was specialized in huge automotive tooling and specialty plastics, and Eagle had more of a polished operational process.
As the factory tour guide was discussing the process of their plastics injection molding flow, she was also talking about the specifications and standards that dictated the operations. For example, in the steel mold polishing room, she was not only discussing why the steel molds had to be polished the way they did, but also the different levels of polished molds.
An A2 polished mold gives a high gloss finish but requires a lot of extra labor and cost. So if an A2 level of polish is not needed for the the particular part or the particular region of a part, its best not to do it to save cost. Apple specified an A1 level of polish for the original iPhone 3's. To get this level of polish, it's not only the skill of the worker polishing the die, but the quality of the steel comes into play. When the steel block is created from molten steel, if there are any air bubbles in the steel, the whole mold needs to be discarded and started over again. Only perfect steel polished to an extremely high level could create an A1 level of polish and it usually requires retooling a few times to get it right. It's an extremely expensive process and the finish would be blemished or scratched easily on the final product. Her recommendation is to not even think about an A1 polished finish unless you have a huge budget. Incidentally, she mentioned that Eagle was not capable of an A1 level and something at that level would need to be done at a specialty tooling shop.
As we continued to look through the steel tooling we saw a lot of molds with strange shapes. It turns out that Eagle has a lot of customers that are perfume manufacturers. Those manufacturers have special designers to design strangely shaped bottle enclosures for the perfumes. These enclosures give the perfume character and make them more appealing, especially in the display cases. One perfume enclosure we saw required twelve separate plastic parts with a complex assembly process just to enclose the perfume bottle. The perfume itself was from a line by a certain pop star and the amount of work that went into just the enclosure was "unbeliebable". It's going to be hard for me to look at perfume bottles in the same way again.
One of the things that struck me was how automated and well thought out the operations were. For the injection molding machines, each machine had a robotic arm to remove the work piece and a conveyor belt to bring it to the worker, who inspects is, cuts off the sprues and runners, and does the finishing work. The tour guide explained that it's important to automate that process to guarantee that the work pieces get pulled out of the mold within a well defined time window. The longer the pieces stay in the molds after the injection process, the higher the possibility of defects in the final pieces. It's not possible to just have a worker reach in and remove the piece since there's too much variability. To control that process variable, they needed to automate it.
They had a clean room right next to the injection molding line which we though was strange. We would normally see clean rooms for finishing processes like painting. The guide explained that the clean room was built to handle optically clear parts. There's a clean room standard that they follow to provide a dust free or low dust environment for the clear parts. We asked if they made optical lenses there and she laughed it off. For lenses, the standards require a very high level clean room. Essentially, its a clean room within a clean room and a dust free environment.
We then were taken to the finishing processes. There were some interesting techniques they used. Eagle happens to do a lot of car stereo enclosures which use backlit, illuminated buttons. To do these, they make optically clear buttons, spray paint them black, and then laser etch the illuminated design specified by the customer. The laser etching removes the black paint and exposes the clear plastic, hence making the design illuminated when there's a backlight.
They also had an embossing machine and we spent a lot of time studying it since it uses the same technique that Jie wants to use for her printed foil circuits. Seeing the embossing machine in action was really interesting because its possible to get a feel for the technique as well as see what kind of tooling is required. In this case, no die was used because the finished work pieces had raised areas that would get embossed. By pushing the heated stamp into the foil and on to the raised parts of the work piece, it was possible to just emboss those parts. If not all the raised pieces would get the embossed foil, then they would have required a die to selectively emboss.
Other than the laser etching and the embossing, the printing methods were approximately similar to what we saw at Colinda with the pad printing and screen printing stations for the lettering and logos.
The next stop was to another wing of the building where they had the electronics assembly line. The tour guide didn't know much about the electronics assembly process because she worked as a project manager for the plastics side of the factory. Luckily, Bunnie and I have a bit of history with electronics so we were able to explain to the group the different parts of the SMT line.
Electronics assembly is considered a much more stable process than plastics manufacturing and the process variables can be tightly controlled. They essentially had a conveyor system connecting an automated solder paste screen printer, SMT pick and place, and a multi-zone reflow oven. They could also insert inspection equipment into the line to check the solder paste thickness and also machine vision inspection equipment to check the end of the line for defective solder joints, ie: tombstoning, opens, and shorts. From what I understood, the plastics side of manufacturing is much more complex and error prone than the electronics assembly side of manufacturing.
Finally, we got to eat lunch in the canteen. We were excited because we wanted to eat lunch with the workers and perhaps try to talk to some of them. The canteen we ate at was separated from the worker canteen though and it seemed like we ate with more of the managers and office people rather than the assembly line workers. It was nice though and the food was excellent. Well, except for this weird heated coca cola drink that kind of freaked me out.
I think it was a good decision by Bunnie to take us to this factory. It was obvious that this factory had a process control level that was on a different level than the ones we saw earlier. It was also obvious that this factory catered to larger customers or at least was more costly and likely inaccessible to smaller, lower volume customers. For someone like me, I'd probably end up working with a company like Colinda that would accept lower volumes and still provide the flexibility to scale if needed. That's also the factory that Bunnie is using for his designs, mostly for the same reasons. It's interesting to see what its like at the bigger or more advanced factories though and to get an idea of the techniques that are available. All of this knowledge that I'm seeing and experiencing first hand can be translated into improved design skills. From my experience, one of the most valuable traits of a good designer is understanding the available options. In that respect, this trip is providing an amazing experience for me.