Trapped Air !!
Trapped Air !!
(OP)
Folks,
I am working on a project to produce a prosthetic product for trans-tibial amputees (below knee)
The product is tapered in the length direction and closed at the smaller end. It is circular in cross-section and thin-walled (5mm). It is approx 500mm in length and the larger outer diameter is 150mm (approx). A cross section has a 'U' shape.
A fabric is placed over the core of the mould and a soft elastomeric material is injected in through the bottom. For this stage there is no air evident in the product. The product is then removed from the mould and ‘ turned inside out’. It is put back on the core, the mould is closed and the product is re-formed with the fabric on the outside of the product. This is achieved by heating and then cooling the core.
Everything works fine, except for a small amount of air, which is trapped between the core and the product as it is turned. This manifests itself as a few air bubbles on the inner surface of the product. I have produced a number of products and all have this air bubble, regardless of how much I message the product and try to work the air out. I have even tried putting a small flexible pipe between the core and the product and drawing a vacuum but to no avail.
Any suggestions greatly appreciated!!
Speedy
I am working on a project to produce a prosthetic product for trans-tibial amputees (below knee)
The product is tapered in the length direction and closed at the smaller end. It is circular in cross-section and thin-walled (5mm). It is approx 500mm in length and the larger outer diameter is 150mm (approx). A cross section has a 'U' shape.
A fabric is placed over the core of the mould and a soft elastomeric material is injected in through the bottom. For this stage there is no air evident in the product. The product is then removed from the mould and ‘ turned inside out’. It is put back on the core, the mould is closed and the product is re-formed with the fabric on the outside of the product. This is achieved by heating and then cooling the core.
Everything works fine, except for a small amount of air, which is trapped between the core and the product as it is turned. This manifests itself as a few air bubbles on the inner surface of the product. I have produced a number of products and all have this air bubble, regardless of how much I message the product and try to work the air out. I have even tried putting a small flexible pipe between the core and the product and drawing a vacuum but to no avail.
Any suggestions greatly appreciated!!
Speedy





RE: Trapped Air !!
Oh, it might be moisture , not air - make sure everything is hot and dry as well as free of air.
Cheers
Greg Locock
RE: Trapped Air !!
RE: Trapped Air !!
Thanks for your help. We managed to solve it. The fabric was locking in one direction which created folds in the gel when it was turned. It was within these folds that the air was trapped. We changed the fabric and EUREKA.
Speedy.