Tools you need:
- Something to press on the seam (ideally silicone roller)
- Baking paper or a scrap of silicone coated fabric
- Straight piece of wood/metal/anything that can handle the iron heat
- masking tape
Items you need:
When deciding on the design it’s important to avoid strong peeling forces. Particularly high stress points are at the baffle ends or convex seams.
Marmot Strato – a nice and comfortable pillow, but it will sooner or later start leaking on the convex seam stress points.
To avoid high stress on the baffle end, take a look at the Neoair xlite or similar pads – look how all the baffles end near the edge of the pad. If the baffle ends like this, the stress on the baffle end is significantly lower.
Creating baffles takes a long time so it is hard to be 100% concentrated and precise, but remember – one failed baffle will probably ruin your whole work so I recommend either putting the baffle end near to the pad edge as described above or making a small reinforcement at each baffle end as seen on the photo below.
First you need to make sure you adjust the heat setting on your iron for optimal welding. I recommend checking the DIYpackraft video on this topic (or his entire channel as it is very informative). He explains it better than I would with photos.
Beside the heat, a pressure is also needed for the best results. Pressing hard with your iron and once you remove it, press on the hot weld with silicone roller (or find something else to press on)
When making inflatable pads/pillows we mainly have to deal with peeling stress. It is important that weld is the strongest at the along the joint – at the thin line at the edge of the weld. This is the exact point where fabrics would separate if they would be peeled away from each other. I will call that a weld line.
I tried several methods to get a good weld line but only one proved to work pretty well.
The most obvious method was to place the weld line next to the ruler and join the fabric pieces together. The problem is that most irons have rounded edges so you can’t apply the needed pressure and heat to that weld line. Results are not the best. Modification to the iron to have a sharp edge of less than 90° could possibly do the trick.
The method that is working well for me is just placing the weld line to the straight edge of the wooden board and let both fabric pieces hang down from the table. This way you can apply the pressure with the flat part of your iron and you don’t rely on the iron’s edge. It is important that both fabric pieces lay completely aligned and flat. Before that I attached the baffle to the body just so it stays in place. I recommend using the tip or edge of the iron to pin it every 5-10cm (try to do it away from the weld line where the stress is low). Or use some masking tape instead but keep in mind that you might need to heat the fabric for the perfect weld longer when tape is in between the fabric and iron.
I marked the baffle positions with a thin sharpie and the weld line is 1cm from the marked line (seam allowance 1cm)
Keep in mind not all valves work with TPU. Check before buying one. Some valves are compatible with PVC and the other ones with TPU. If the valve is welded this way it should be enough, but I recommend adding another ring of tpu fabric from the inside as on the photo below to ensure 100% seal and peace of mind.