 We have a very new addition to our workspace. A few months ago, we decided to purchase the Sustainable Design Studios Injection Mini machine. As of this writing (Sept '23), it's literally brand new to us... I've only run one shot of plastic through it, and we are still trying to dial in the settings and establish a workflow. This post will be more about our decision to purchase an additional machine, and the setup process.
There are a couple of reasons why we wanted a second injection machine. One is size. Our primary Precious Plastic injection machine is mounted on a table with a precious plastic shredder, and as a result it's really heavy. Moving it around is a production, so it lives in our shop. It also requires 220 volt power. These two facts make doing demonstrations with this machine very impractical. Another reason for this machine is that it can be operated by one person, rather than two. Injection force is supplied by an air cylinder instead of manually, so pressure can be controlled very uniformly from shot to shot. It also allows for something called "hold time," where you keep the pressure on the molten plastic after it fills the mold. This reduces defects caused by shrinkage. A third reason was to try out a different nozzle design. The Injection Mini has an unthreaded tapered nozzle rather than a threaded type, allowing the molds to be simply pressed against the injector, rather than having to be screwed on. This is something that I've wanted to try on our larger machine. We ordered our machine assembled, rather than as a kit. If we were to do it again, we would get the kit. While it doesn't save you much in terms of the cost, it's nice to have an assembled machine ready to go- or so we thought. Our machine suffered some rough handling during shipping. The frame wasn't bent, but there were several places where it had shifted by maybe 2-3mm. As a result, the air ram wasn't properly lined up with the heater tube- it was maybe 2-3 degrees out of parallel, and it would hit the edge of the tube rather than entering cleanly down the center. So the entire thing needed to be disassembled, lined up square, and screwed back together. The frame is made with 8020 aluminum extrusions. This is a great system for building machines, and it's commonly used in industrial applications. But there's a tiny little detail that caused a mountain of frustration. The screws that hold the entire frame together are held with special nuts that slide into the slot on the 8020 rails. It turns out that there are two types of these nuts. One type is called a "drop-in" nut, the other is called a "slide-in" nut. A drop-in nut can, in theory, be added to the frame at any point in the construction. You simply place the nut, and then when you tighten the screw it rotates 90 degrees to secure the connection. That's the theory. In practice, the nut can rotate five degrees and catch on an edge, giving the impression that it's secure, but resulting in a very weak connection that's easily loosened with vibration or a jolt... like when something is shipped across the Atlantic ocean. We had multiple points on our machine that were not secured at all. In fact, when we laid our machine down to begin assessing the problems several fasteners just fell out of the machine from unknown places. The solution greatly slows the assembly process and requires planning, but it prevents these problems. We bought some slide-in nuts, slid them onto the rails before assembly, and located them in their correct position with a small spot of craft glue. Since they cannot rotate, these connections are much more secure. If one of these machines is built from a kit, you should replace ALL of the supplied connections with slide-in nuts, which is possible when you start from scratch. Since our machine was pre-built, I spent a long time locating the nuts in the correct position, rotating them in place, and holding them in place with a small spot of glue. It required great care, because if something wasn't correct and needed to be unscrewed, more often than not the nut rotated out of position and fell out. I swore. A lot. But the machine is now corrected and operating nicely. As I said, we haven't developed the proper setting and workflows yet, but it can be operated by one person rather than two, and it's very portable. I believe it will be a useful addition to the shop.
0 Comments
Leave a Reply. |
RSS Feed
