Specific Pressure

Doesn't matter. If you have enough pressure to close the mold and extrude the excess material out of the mold, it will come to rest on the mold parting line surfaces. Could be 1 ton, or 20 clamp force.

Too many variables to calculate force required. Just get a big press.

What's that enough pressure required.we are having a hydraulic press with 800 ton capacity.it has 4 rams with dia 320mm.the platen size is 1200x2200mm.Our product is a W shaped fender with cross sectional area 1507.785 sq.cm.the mould size is 1750x500 mm.

What's that enough pressure required.we are having a hydraulic press with 800 ton capacity.it has 4 rams with dia 320mm each.the platen size is 1200x2200mm.Our product is a W shaped fender with cross sectional area 1507.785 sq.cm.the mould size is 1750x500 mm.

The numbers needed to work this out are; the area of the cavity at the mould part line, and what pressure you are wanting in the molding compound = what injection pressure you are using.

That injecting pressure times the area should not exceed the clamp force of the press.

Or the volume, or cross section of the part has nothing to do with clamp force.

Provide the proper numbers and we may be able to help.

The surface area of cavity=8750 sq cm.The hydraulic working pressure of the press is 250 kg per sq cm.How much force is required to mould a product(rubber) for the above?

Well that's one number - now tell me what pressure you need in the cavity the cure the "rubber"

That's what i want to know.how much pressure required to fill that cavity.

No - what you want to know is how much pressure in the cavity will cause the platens to push part.

I.e. what pressure defeats the clamp tonnage.

And that calculation starts what pressure you need in the cavity to achieve the job, (times the presented area).

You are approaching it the wrong way around.

And if you don't know what the pressure for the process is - well you're fuc[not in a good position]ked

If the specific pressure in the cavity =30 kg/sq cm..

"The surface area of cavity=8750 sq cm"

"If the specific pressure in the cavity =30 kg/sq cm..

Then; 8750 x 30 = 262500 kg = 262.5 tons.

If you are compression molding rubber, you must be using rubber gum stock.

Since you can squeeze rubber gum stock and shape it with your hands, why are you worried about compression pressure?

"That injecting pressure times"

There is NO injection pressure involved in the compression molding process.

The material is put into the cavity prior to closure of the mold. The only pressure required is the pressure needed to close the mold and squeeze the excess material out of the mold. Did you not bother to read my initial response?

You don't have a clue and have completely misguided the OP. Butt out.

Calm down! There's no need for this

To nobody in particular

Vulcanization methods

A variety of methods exist for vulcanization. The economically most important method (vulcanization of tires) uses high pressure and temperature. A typical vulcanization temperature for a passenger tire is 10 minutes at 170 °C. This type of vulcanization is called compression molding.

This might be helpful. Again it was a case of googling the OP's question.

PDF] Compression Molding of XIAMETER® High Consistency Silicone RubberFile Format: PDF/Adobe Acrobat - Quick View
In compression molding, a preform is placed on one half of a heated mold. ... The figures given in Table I are typical; but for each specific molding job ... Molding Pressure. Enough pressure should be applied to obtain sufficiently ...

https://www.xiameter.com/en/.../95-562-01%20Compression.pdf

Guide
Compression Molding of
XIAMETER® High Consistency
Silicone Rubber
In compression molding, a preform is placed on one half of a
heated mold. When the mold is closed and put under pressure
(in a press), the rubber is forced into all parts of the mold
cavity, and excess rubber flows into a flash groove around
the mold cavity.
Silicone rubber is compression-molded to form gaskets, seals,
0-rings, flat sheets, fabric reinforced laminates, and many
other types of industrial rubber goods, of almost any size
desired.
AV1065 AV01203
COMPRESSION MOLDING OF XIAMETER® HIGH CONSISTENCY SILICONE RUBBER
Fig. 1. Typical compression mold
Loading the Mold
Single cavity molds are loaded by hand. With some multiple
cavity molds, loading boards may provide faster mold
loading, which helps prevent scorching of the preforms.
Loading boards are devices on which the preforms are placed
in position for simultaneously loading all of the mold
cavities.
1
Molding Time
Molding time and temperature vary with the vulcanizing
agent used, the thickness of the part being molded, and other
production conditions discussed under "Molding Problems"
The figures given in Table I are typical; but for each specific
molding job, the most favourable values of time and
temperature can only be determined by experimentation.
Molding Pressure
Enough pressure should be applied to obtain sufficiently
rapid flow of rubber in the mold. Most XIAMETER® silicone
rubber products flow well at about 200 psi (1.4 MPa).
Unloading
Silicone rubber parts are usually unloaded hot. However,
when molding thick sections or fabric reinforced parts, it may
be necessary to cool the mold before releasing the pressure to
help prevent backrinding, porosity, and delamination.
TABLE I: SUGGESTED CONDITIONS FOR COMPRESSION
MOLDING WITH VARIOUS VULCANIZING AGENTS
Molding Time, minutes
Vulcanizing agents Molding Temperature 1.5mm 3mm 6mm 10mm
mm
12mm
2,4-dichlorobenzoyl peroxide 116°C 5 5 10 15 20
Benzoyl peroxide 127°C 5 5 10 15 20
Dicumyl peroxide 150°C 10 10 15 18 20
Tertiary-butyl perbenzoate 150°C 10 10 15 18 20
2,5-dimethyl-2,5-di (t-butyl peroxy) hexane 171°C 10 10 15 18 20
Tertiary butyl peroxy isopropyl carbonate 140°C 5 5 10 13 15