Good evening, I want to make a silicon sinker m

J

JustPlainSHARK

Sealiner
Good evening,

I want to make a silicon sinker mould and am planning to use polystyrene to set the sample sinkers in to make the first halve of the mould.

Now I just want to know if the silicon mixture will damage/dissolve the polystyrene base?

Thanx
JPS
 
B

benniejordaan

Sealiner
JustPlainSHARK wrote:
Good evening,

I want to make a silicon sinker mould and am planning to use polystyrene to set the sample sinkers in to make the first halve of the mould.

Now I just want to know if the silicon mixture will damage/dissolve the polystyrene base?

Thanx
JPS
Click to expand...

I don't think it will harm it. But still best to do a test.

What silicone do you intend using?
 
B

benniejordaan

Sealiner
JustPlainSHARK wrote:
Thanx Bennie. Will be using mold max 30 from AMT
Click to expand...

I thought you would. MM30 not the best for heat actually, especially if you don't have a vacuum chamber. MM60 is the right stuff. Not quite as durable but it won't distort. Neither will be good for high volumes, for that you should use an aluminum mould.
 
B

benniejordaan

Sealiner
MOLD MAX 30

MAX USE TEMP
-19°C to 205°C

MOLD MAX 60

MAX USE TEMP
-19°C to 294° C

Lead melts at 330degrees. Although mm60 doesn't quite make it, it will handle the temp better. Some temp is drawn out of the lead into the silicone.
 
T

tackle whore

Senior Member
mould max 30 wont do more than 5 sinkers it will get tacky and melt go as bennie says else i can try to get you so silicone rubber i use for spin casting .
 
B

benniejordaan

Sealiner
tackle whore wrote:
mould max 30 wont do more than 5 sinkers it will get tacky and melt go as bennie says else i can try to get you so silicone rubber i use for spin casting .
Click to expand...

Can you give me a price for the silicone you use, please? Id like to give it a try.
 
J

JustPlainSHARK

Sealiner
benniejordaan wrote:
JustPlainSHARK wrote:
Thanx Bennie. Will be using mold max 30 from AMT
Click to expand...

I thought you would. MM30 not the best for heat actually, especially if you don't have a vacuum chamber. MM60 is the right stuff. Not quite as durable but it won't distort. Neither will be good for high volumes, for that you should use an aluminum mould.
Click to expand...

Yes, was informed similarly by the AMT sales person and that the right product would be SmoothSil 950, but that its very expensive. So I went with the moldmax30 as they said that it will suffice.

 

I might have a contact to make me an aluminium mould, so I will make a mirror copy of the silicon mould for this. I don't know how much THAT will set me back. Was thinking of making the mirror copy out of plaster of paris. Would this withstand the heat of the molten aluminium?
 
B

benniejordaan

Sealiner
JustPlainSHARK wrote:
benniejordaan wrote:
JustPlainSHARK wrote:
Thanx Bennie. Will be using mold max 30 from AMT
Click to expand...

I thought you would. MM30 not the best for heat actually, especially if you don't have a vacuum chamber. MM60 is the right stuff. Not quite as durable but it won't distort. Neither will be good for high volumes, for that you should use an aluminum mould.
Click to expand...

Yes, was informed similarly by the AMT sales person and that the right product would be SmoothSil 950, but that its very expensive. So I went with the moldmax30 as they said that it will suffice.

 

I might have a contact to make me an aluminium mould, so I will make a mirror copy of the silicon mould for this. I don't know how much THAT will set me back. Was thinking of making the mirror copy out of plaster of paris. Would this withstand the heat of the molten aluminium?
Click to expand...
Firstly, SmoothSil 950 will only work IF you have a vacuum chamber and It is only rated for up to 230 degrees. It is so difficult to use without a vacuum chamber. I'm afraid you have been given crap advice in this regard.

But never mind the operating temps. Your biggest issue is air. If you have air bubbles, as soon as you start pouring lead, the air expands and causes deformities in the mould. It also causes the mould it's self to deform. After a few pours the bubble pop and leave cavities.

The reason I recommend MM60 is because not only can it handle the highest temperatures and is the best at expelling air, I have also used it extensively. I have also used MM30 and it is a nightmare with hot pours.

I cant believe they give such rubbish advice. On their website, if you click on "tin cure". i.e pouring tin, you will find the following about MM60.

"MOLD MAX 60

Description Mold Max 60 is a Shore 60A tin catalyzed silicone rubber formulated for applications requiring high heat resistance (up to 560°F/294°C). It features a low mixed viscosity and cured rubber exhibits very low linear shrinkage. Parts A & B are mixed 100A & 3B by weight. Pot life is 40 minutes and cure time is 24 hours.  Applications include making foundry patterns, flat pattern reproductions and casting low-melt metal alloys such as tin and pewter. PLEASE NOTE: THI-VEX Silicone Thickener is NOT recommended for use with Mold Max 60

And this is the image to go with the description.

MOLD%20MAX%2060%204.jpg

MOLD%20MAX%2060%201.jpg


If you have not used it yet, they will swap it for you.

POP will not handle the temperature of molten aluminium. I've tried it, it just shatters!
 
B

benniejordaan

Sealiner
JustPlainSHARK wrote:
:cens:cens There goes my mould making enthusiasm!!

 

What do you use to make the die for the aluminium? (instead of POP)
Click to expand...

What you do is to make a "dummy" mould with POP. This is called a pattern. You then send it to a company who does aluminium sand casting. They use the pattern to make a sand mould that they can pour the aluminum in. Once you get it back, you need to polish it.

Do a search for a thread I did some time ago called "mould making" lots of detailed were posted there with regards to sinker mould making.
 
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