Home arrow Blog arrow MIT Media Lab Shenzhen, 2013-01-08, Colinda Plastics
MIT Media Lab Shenzhen, 2013-01-08, Colinda Plastics | Print |
Written by Akiba   
Friday, 11 January 2013

2013-01-08

The first day of tours started and it was an amazing experience. I've never been really super interested in the process of injection molding but after seeing how things are done, I found the subject fascinating. We started the day off taking the van to an injection molding factory. The owner of the factory welcomed us with open arms and surprisingly allowed us to take pictures inside the facility.

Our first stop was a meeting room where the owner brought out samples of injection molded devices for us to examine. Coleman, an injection molding expert from AQS (a contract manufacturer that's helping us organize the tours) and Bunnie were explaining how the parts were made, the materials, finish, what decisions went into making the mold, defects, and identifying the markings from the different parts of the mold. I was impressed how much information could be had just by looking at a plastic enclosure. They were able to reverse engineer the design tradeoffs that the designers had to make, some bad decisions, and were easily able to approximate the cost of the tooling and cost per part.

After we had the discussion and an intense introduction to plastic injection molding, we headed to the tool & die shop where they make the tooling for the injection molding. The tooling is the actual steel mold that you specify to the shop for the enclosure that you want. You would normally send them your design files and an engineer from either the injection molding shop or the contract manufacturer would review the files. They'd make recommendations on how to modify the design files to improve yield and make the design more robust. From there, it'd get sent to the tool and die shop to have the design cut out of steel. One thing they cautioned on was that they were able to cut the steel molds on site, but the mold blocks which hold the molds are usually custom designed and outsourced. These have a lead time and during a busy period, could extend up to a few months. So as soon as they design size is fixed, they recommended to pre order the mold blocks to make sure they're reserved. Then have the mold and tooling made. 

The tool and die shop was amazing. I had no idea how massive the tooling was just to make a simple enclosure. The tooling is cut out of steel using CNC, EDM (Electron Discharge Machining), and manual milling. Each steel mold can weigh a ton or more and requires a lot of manual and automated work. Depending on the finish, the molds also need to be hand polished. To tool and die shop consists of a lot of heavy metalworking equipment. The steel blocks are first cut on the CNC machine. The EDM machine is used to remove steel in parts that can't be cut accurately using a CNC machine. It uses electrical current to remove steel at a rate of 5 microns per electrical burst. They can also use EDM machines to slice large blocks of steel. The one we saw was around one foot tall and six inches thick!

After the tool and die shop, we checked out the plastic injection molding area. They showed us how the tooling fits into the injection molding machine. They then load plastic pellets into the hopper and turn the machine on. The two sides of the mold are closed, plastic is heated, and then it's injected into the mold cavity. The plastic is then cooled using water cooling, the mold halves are separated, and the worker takes out the resultant part. Finally, the worker trims off the plastic runners and excess, adds a protective plastic covering to the part, and then puts it inside a box of finished parts.

We then were taken to the printing area of the factory. The printing area adds lettering and logos to the finished plastic parts. There are two main methods they add the lettering. The first method is to add lettering via pad printing. This is to print on curved surfaces and consists of a round rubber pad that picks up ink in the form of the desired lettering. The rubber pad then gets pushed onto the surface and deposits the ink on to the target surface. The second form of printing is silkscreening. This is basically the same method as t-shirt silkscreening where ink is forced through openings inside a screen.

Finally, we went to see the high spec finish room. This is for finishes that are extremely high spec and we had to take precautions to wear shoe covers to prevent tracking in errant dust. The high spec room was sealed and we weren't allowed inside, but we could see what goes on there. This room is mainly for highly polished surfaces and special finishes that have an extremely high tolerance. Customers would request this if they needed high spec finishes and wanted to improve their yield.

This concluded our tour of this injection molding factory and the boss of the factory took us all out to lunch. I didn't realize that lunch included drinking alcohol and we had many "ganbei" (chinese for "bottoms up") glasses of beer with the boss. By the end of lunch, I was fairly trashed and Bunnie was getting there too. Interestingly enough, we had another factory tour immediately after.

We weren't allowed to take pictures of the second factory that day which was a shame because it was amazing. They were also an injection molding shop but had the capability to do a technique called IMD/IML (In Mold Decorating/In Mold Labeling). This technique makes it possible to embed graphics into injection molded parts. If you see designer cell phones with graphic designs integrated into the body, its likely that an IMD or IML technique was used to make it. This injection molding factory had another special characteristic which is that they made monstrously gigantic tooling and mold sets. They would crank out a car dashboard in one shot using a steel mold that weighed nearly 100 tons. That tooling would go into an even more gigantic injection molding machine to stamp out the part. Everything at this shop was just on a completely different scale in size. Bunnie fell in love with the huge CNC machine to cut out the tooling and he kept on subconsciously rubbing the gigantic steel mold :)

The day didn't end there though. AQS, a contract manufacturer that was helping to organize all the tours and also a company that Bunnie works closely with, took us all out to dinner with their staff. It was a wonderful dinner and we talked about a lot of the things we saw with them. They also broke out the Chinese hard liquor (53% alcohol) and proudly proclaimed that they wanted to drink with us. I hid from the "white liquor" since I've had a few bad experiences with it but most of the others were game to try it out. Overall, it was a fun evening with AQS and it was our first real dinner together as a group. It was a wonderful chance to meet everyone and hear about what they were working on, why they were on the trip, and just randomly ramble on in a happy, semi drunken state :)

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