Joining injection molded plastic to fabric (Nylon,Cordura..)

Hi all,

I’m currently working on a project, we will call it a “glove” that wraps around that hand. This “glove” will be wrapped around both a bare hand, and gloved hand, and must accommodate people of all sizes from small to large hands. In addition to these factors (see; very customizable, potentially very flexible to factor these criteria in), I also need to have a back hand made of a fairly in-flexible fabric or material (not hard, think-leather flexibility wise) that will then need a small injection molded enclosure fastened to it in some way.

I have attached a quick sketch of what I am talking about, I have censored some aspects but there is a callout on the injection molded part (light grey Trapezoid on backhand).

Does anyone have any ideas as to how this plastic piece can be attached to the fabric base? Thanks in advance!

I was at a molder in Israel a few years back and saw them using fabric for in-mold decorating. If you match the right plastic with the right high-heat fabric you could co-mold the plastic section directly to the fabric. You’ll need a molder & tool shop that likes to experiment.

For manufacturing you might consider ultrasonic welding. It’s performed on equipment that looks like a sewing machine expect it uses high frequency to fuse plastic.

For prototyping you can use a technique called staking, which is a heated probe pinched onto the material to give a stitched look. It is similar to spot welding-but instead of electrical current and molten metal fusion it uses mechanical pressure and heat to soften the plastic.

Ultrasonic welding seems like the way to go, but I am intrigued by the idea of co-molding them. Also, how hard does the plastic piece need to be. What about molded foam? It can definitely be molded to that size and tolerance but would provide less protection for the electronics.

Alternatively, you’d mould the inflexible material with a stitch plate, which is an outer area of the part thin enough to be stitched through.

The inner section of this part would then have to be thick enough to support the fastening to the injection moulded part.

I couldn’t view your posted image, so apologise if this is completely irrelevant!

I think I found your solution:

seriously though, I think that sonic welding is probably your best bet, though I’m unsure about foam, since it has to “melt” the plastic, and foam might just collapse…

Last post…awesome! haha. Thanks for the responses everyone, Ultrasonic welding seems to be the overwhelming favorite, I’ll have to look into it for this purpose

Ultrasonic welding or heat sealing is going to depend on the materials used. Materials that are not the same generally don’t like to be joined with either method.

I’d second sam’s suggestion of molding in the stitch plate. Sewing the two together will be easy and cheap.

Another vote for stitching here, done all the time to put bumpers, runners, and corner protectors on luggage.