Resin/silicon mold question

[HobbitFertang]

Hi all, can someone advise me about making the first resin object from a silicone mould that I've made? (the idea is to make several stanchions for a parapet on a raised section of track) Do I need to use a release agent or is the flexibility of the silicone mold sufficient?

 

[JimmyB]

I normally use a release agent, but assuming your item has no fine detail (thin), and your mood is not to thick, you should be okay.

 

[HobbitFertang]

Thanks JimmyB

 

[dunnyrail]

H HobbitFertang I have done quite a bit of Resin moulding never finding the need for a release agent. Some brands tend to be a bit sticky after removal, some time in daylight tends to resolve that.

 

[Northsider]

Just to add to the confusion, I always use a release agent! Usually a light coat of silicone spray...

 

[JimmyB]

Just to add to the confusion, I always use a release agent! Usually a light coat of silicone spray...

I think as long as the old has dried/hardened correctly i.e. no sticky bits (normally due to bad mixing) and the first cast is is a practice, in most cases I think you can manage NOT to use a release agent, however these days, I nearly always do, it is just practice and experience, and what suits the user.

 

[HobbitFertang]

How many repeat uses can be expected from a silicone mould (have I spelt this correctly?) before it comes apart?

 

[Zerogee]

How many repeat uses can be expected from a silicone mould (have I spelt this correctly?) before it comes apart?

I've had moulds made in the old platinum-cured silicones last for literally hundreds of pulls, but with cheaper/weaker rubber you could be as low as single figures before it starts to degrade. Yours looks to be a simple shape with little or no undercuts, so hopefully it will last a bit longer than that.

All depends on the stresses that the mould is subjected to.... I wouldn't expect the "plugs" of silicone that make the three holes through the casting to last very long, they will probably tear out in fairly short order - however this isn't disastrous if you're prepared to drill out the holes in each finished piece where necessary.

Jon.

 

[JimmyB]

How many repeat uses can be expected from a silicone mould (have I spelt this correctly?) before it comes apart?

Really a “how long is a piece of string” question, depends on mould material quality, quality of the mould thickness etc, normally I get double figures and then have sufficient items.

 

[dunnyrail]

How many repeat uses can be expected from a silicone mould (have I spelt this correctly?) before it comes apart?

My experience tends to be as Jimmy and Z said. Most of my moulds using different rubber tended to be 20-30 pours. But one of the cheeper hand mixed ones only managed around 10 pours, happily that was enough for me. However even with a bit of a tear you can get a few more pours if your rubber is well supported. The excess via the tear can be sanded off when fully dry.

 

[Paul M]

It's a shame, but I suppose silicon moulding will soon obsolete, and replaced with 3D printing

 

[dunnyrail]

It's a shame, but I suppose silicon moulding will soon obsolete, and replaced with 3D printing

I can certainly see the attraction of that but some things are not 3d print capable. Take wood tables made with a big gap in the middle of 2 bits of interesting shaped edges filled in the middle with super clear resin, an art to be appreciated.

 

[HobbitFertang]

How many repeat uses can be expected from a silicone mould (have I spelt this correctly?) before it comes apart?

 

[HobbitFertang]

Btw, the breaking out of my first stanchion worked fine without release agent. There are however, a lot of microbubbles in the resin. Maybe I'm using the wrong resin? Point taken about the dominance of 3D printing. I'm toying with getting one, It's finding the space for it

 

[JimmyB]

Btw, the breaking out of my first stanchion worked fine without release agent. There are however, a lot of microbubbles in the resin. Maybe I'm using the wrong resin? Point taken about the dominance of 3D printing. I'm toying with getting one, It's finding the space for it

Mix gently, pour slowly, down one side if possible and let it flow along the bottom of the mould, and GENTLY tap the sides of the mould (when full) and this will help release air bubbles than stick to the bottom of the mould, it takes practice.

 

[John Fedak]

Btw, the breaking out of my first stanchion worked fine without release agent. There are however, a lot of microbubbles in the resin. Maybe I'm using the wrong resin? Point taken about the dominance of 3D printing. I'm toying with getting one, It's finding the space for it

You also need good ventilation as the fumes are quite prevalent and toxic. My experience.

 

[dunnyrail]

What Jimmy 100% on the mark, it is easy to get a bit excited with the first few pours. The Resin takes a good while to dry so there is no hurry in mixing or pouring. Just make sure you mix enough only for the job, or like I did have a spare small mould of something useful to use any over mixed resin.

 

[JimmyB]

What Jimmy 100% on the mark, it is easy to get a bit excited with the first few pours. The Resin takes a good while to dry so there is no hurry in mixing or pouring. Just make sure you mix enough only for the job, or like I did have a spare small mould of something useful to use any over mixed resin.

Spare/extra moulds, always a good idea, you need to mix enough for the task in hand, but it possible have a capability, where any extra will go.

 

[dunnyrail]

When I was making resin barrels for my factory, I made a lid mould as the prototype I was basing it on had odd piles of barel lids, ideal for the surplus resin.