dai sensei
9th November 2009, 08:14 PM
For those of you that have followed my journey into moulding would know I have been trying to refine my banksia casting and overcome the issues. I established that vertical moulding was best, but my electrical tubes presented a few issues (too slow to seal, leaking etc).
I had a 1.1kg pack of Barnes M4642 RTV2 Silicon Rubber and decided to make a mould of multiple 25mm casts. This allows the banksias to be sanded down to around 20mm dia but still leaving enough room for the resin to flow around the seed pod. I can also use it for vertical coffee bean casts, and other odds and ends.
I started with 65mm lengths of 25mm dowel glued to a piece of ply with around 10-15mm between them. I wanted a well above the tubes, to allow overflow or extra resin to be drawn in under vacuum etc. So I trimmed the ply and glued it down to another larger piece of ply. To this I glued some ply walls tall enough to enable plenty of room for the mould floor. I then used plenty of glue in between the walls to help hold it all together. All the time the glue I was using was cheap hot melt glue, the whole mould former took me less than an hour.
As a release I just filled the former with BLO, it also helped me check the volume of silicon I was going to use, which in this case was the entire pack :(. Drained out the oil, mixed the silicon and poured it in. Only 24 hours later the silicon seamed to be set, so I pulled the hot melt glue away and dismantled the walls and bottom away leaving a solid block of silicon with the dowels in it. Quick tap on the bottom and even the dowels came out easy, so BLO is an excellent release agent.
All done :2tsup:
I forgot to take photos as I built the former, so I just placed some of the timber parts back temporarily for the photos, but you get the idea :rolleyes:
Cheers
I had a 1.1kg pack of Barnes M4642 RTV2 Silicon Rubber and decided to make a mould of multiple 25mm casts. This allows the banksias to be sanded down to around 20mm dia but still leaving enough room for the resin to flow around the seed pod. I can also use it for vertical coffee bean casts, and other odds and ends.
I started with 65mm lengths of 25mm dowel glued to a piece of ply with around 10-15mm between them. I wanted a well above the tubes, to allow overflow or extra resin to be drawn in under vacuum etc. So I trimmed the ply and glued it down to another larger piece of ply. To this I glued some ply walls tall enough to enable plenty of room for the mould floor. I then used plenty of glue in between the walls to help hold it all together. All the time the glue I was using was cheap hot melt glue, the whole mould former took me less than an hour.
As a release I just filled the former with BLO, it also helped me check the volume of silicon I was going to use, which in this case was the entire pack :(. Drained out the oil, mixed the silicon and poured it in. Only 24 hours later the silicon seamed to be set, so I pulled the hot melt glue away and dismantled the walls and bottom away leaving a solid block of silicon with the dowels in it. Quick tap on the bottom and even the dowels came out easy, so BLO is an excellent release agent.
All done :2tsup:
I forgot to take photos as I built the former, so I just placed some of the timber parts back temporarily for the photos, but you get the idea :rolleyes:
Cheers