As part of an ongoing development we use inflated plastic bladders to lift parts of the equipment. I have been using a bag sealer, described further on, but it really didn't have either the versatility or the grunt, to weld serious bladders and I spent an amount of time chasing leaks. I also glued sheets together to make bladders as I will describe further on. We had a local company welding these on a high frequency welder, but due to the delay, travel and labour costs we decided we needed our own machine. The cost of the commercial units was outside our budget and I only have 240v single phase power. In this article about welding plastic sheet to make inflatable bladders, I will cover: 1. Various types of plastics sheet and its properties. 2. Basics of welding plastics sheet, various methods and machines, including plastic bag sealers. 2. The original prototype welder I made and set up on my mill and what I learned from this. 3. Pitfalls I had and how I got around them, elements and insulators. 4. Details of the building of the welder with drawings and photos. 5. Details of the building of the timer, with circuit diagram. 6. Techniques for making inflatable bags 7. Ideas for temperature control, using air guns, soldering irons, bar heaters etc. to form and weld.
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