Custom Rubber Molding

Inox Custom Rubber Molding

Inox Casting specialized in producing custom rubber molding and other molding products services. We own a product design and mold design and mold manufacture strong team which can provide the best solutions for custom rubber molding and for your product design.

We have advanced manufacturing equipment, experienced engineers, well-trained staff, and a strict quality control system. Our professional technology allows you to enjoy the best custom rubber molding service.

Inox Casting custom rubber molding is a method or process where raw rubber or elastomer is pressed or injected into heated molds, then cooled and cured to help the product retain its shape. This is one of the most popular methods in the industry.

The Inox casting custom rubber molding is used to create rubber seals, O-rings, gaskets, plugs, and other components used by numerous industries and for a variety of applications. This will bring a lot of benefits to include the following:

• Low cost and fast production time.
• Strength and durability.
• Can be formed into virtually any shape.
• Resistant to many chemicals.

Inox Casting custom rubber molding is perfect in a wide range of industries like medical, industrial, food processing, electronics, automotive, agriculture, and many more. Inox always uses the right component that truly meets different industry requirements.

Inox Casting is one of the trusted custom rubber molding providers and manufacturers. We are happy to provide the service you need to satisfy and gratify your inquiries. We are the most reachable company that can give you a quick response.

Please don’t hesitate to contact us for more information!

Custom Rubber Molding: Ultimate Guide

In this guide, you will find all information about custom rubber molding.

Whether you want to choose the best molding technique, material or rubber molding considerations – you will find all information right here.

Let’s dive right in.

1. Examples Of Custom Rubber Molded Parts

There are enormous uses of molded rubber products that are valuable in different industries like chemical, agriculture, food, electrical, oil, and gas, etc.

rubber molding

Rubber molded parts and products include:

They include:

• Casing pipes
• Joint replacements
• Medical tubing
• Catheters
• Grommets
• Automotive bushings
• Baby bottle teats
• Speaker surrounds
• Bottle closures
• Liners
• Diaphragms, pads, and rollers (for print)
• Anti-slip grips
• Wiper rings
• Slipper seals and flapper seals
• Tank straps
• Meal trays
• mushroom buffers
• Electric motor mounts
• Air spring bumpers
• Hydraulic seals
• Pneumatic seals
• O-rings
• Gaskets
• Fenders
• Cable covers
• Keyboard components
• Diving gear
• Surge arrestors

2. Choosing Rubber Molds

A rubber mold is a tool used to produce rubber parts or products.

rubber mold

The following variables will help you determine which rubber mold to choose:

• Choose one that produces parts and products precisely with minimal or no waste.
• One that can produce the design of rubber you desire. Whether simple or an intricate design
• Consider the production rates and know whether to choose a single cavity or one with several cavities.

Bearing in mind a single cavity handles one product a cycle while multiple cavities have a capacity of producing more than one product or part per cycle.

This applies to parts that work together and can use the same rubber.

• Rubber molds come in different sizes. Choose one according to the size of rubber product or mold you desire.
• Most rubber molds handle solid materials. Choose one that can work with materials in both solid and liquid states
• Choose one that is either made of plastic or rubber or engineering grade like Aluminium most common) zinc, magnesium, copper, brass, tungsten, etc.

3. Types Of Rubber Molding Techniques

There are processes that you should consider before starting the molding process. They include:

• Designing process- layouts are made on the rubber to produce the final product in the desired shape and design
• Production of the mold- the design is converted into a metal mold. Computer knowledge is required to produce molds that match the given design

There are 3 common rubber molding techniques.

Choose one according to the:

• Cost
• Desired look
• The nature of rubber in terms of weight, size, geometry, and volume of the parts

Rubber molding techniques include:

Compression Molding Custom Rubber Parts

Here a two-part slim mold is used to form the final part.

Rubber components are filled in the mold cavity, the mold is closed and heat is applied.

A hydraulic press is also used to apply pressure to the mold.

The rubber begins to heat up to fill the mold cavity.

It heats to a certain temperature where it hardens. Vulcanized rubber maintains its shape even after cooling down in the mold.

compression molding

Advantages Of Compression Molding

• It is the best method for producing large parts that require bulk materials
• Doesn’t require tooling features like gates, sprues, or runners
• It’s cost-effective for small production runs
• Requires a lower cost for tooling given the process doesn’t require an injection or transfer cycle.

Disadvantages Of Compression Molding

• Mould can undergo wear and tear due to the repetitive nature of the process
• Components of rubber can easily get contaminated
• It’s not the best method for intricate designs
• Has slower process times
• It’s a simple process but requires more manpower
• Produces great waste as it’s not as precise as injection molding

Transfer Molding Custom Rubber Molding

It is quite similar to compression molding although transfer molding has a transfer system located at the top of the mold to feed raw rubber into several mold cavities.

The mold cavity is placed on the pot (part of the mold).

Also, the components are then forced into the mold cavity by the heat plunger or piston through the sprue.

When the curing process is done, the mold tears, and the parts are released.

transfer molding

Advantages Of Transfer Molding Rubber

• Has short production cycles compared to compression molding
• Produces uniform results with fewer variables
• Has reduces lead time with less tooling
• Accurate and consistent
• Designing complex molds can be expensive

Disadvantages Of Transfer Molding Rubber

• It has slower cycles than injection molding
• Also, it needs to be handled by a professional

Injection Molding Rubber

Raw rubber is heated to form a liquid that flows freely into the mold cavity. Pre-heating is important as it shortens the curing process.

The mold should be tightly secured to avoid flashing during the process. The nozzle and barrel assembly are used to supply rubber to the mold.

Gum stock (consistency of rubber) gets to the mold cavity through the sprues and runners. Rubber in a liquid state fills the walls of the mold cavity where they form the desired shape.

injection molding

There are three branches of injection rubber molding.

They include:

Organic Rubber Injection

Here order in preparation of materials is required. Mixed rubber gets into the screw in estimated quantities.

When full, it’s injected into the cavities of the mold where it cures. There is no need to shape the rubber prior to the process.

Liquid Injection Molding Or LSR Injection

Liquid silicone is added to the mixture.

Once the mixture cures, it’s inserted into an injection unit. Runners and gates direct the flow of the rubber components.

The process is meant to speed up the process and limit contamination as it is closed.

Thermoplastic Rubber Injection

This process is the same as a plastic injection or plastic injection molding.

Thermoplastic elastomers are used in injection molding and can be colored and reused.

Advantages Of Injection Molding Rubber

It has:

• Fast cycle times of 5-30 seconds
• Lower production unit due to reduced cycle times
• High dimensional tolerance
• Low level of flash as the process doesn’t depend on over filing the molds
• Little waste as excess material can be recycled
• It requires less post-production work as most of the produced parts have a great finish

Disadvantages Of Injection Molding Rubber

• Machinery and tooling can be expensive
• The process can produce excess wastes
• Has high setup costs like the runners and ejector systems

rubber molding

Advantages Of Rubber Molding

Rubber molding is the process of producing, shaping, and forming rubber products and components.

Besides, the process replaced the manual shaping of rubber with chemicals that toughen the polymer chains of rubber.

Also, the reaction forces the polymer chain of rubber from expanding and contracting or moving on its own.

Here are the benefits of rubber molding:

i. Its eco-friendly- the rubber used in the process is recyclable and the process uses less energy.

ii. Low production cost- it’s a simple process that is cost-effective. There is little or no waste as sherds produced can be reused in other parts.

iii. Has no limitation whatsoever; different types of rubber materials can be used in the process.

iv. Rubber molding is an automatic process that needs one person to handle the machine hence saving on cost.

It also keeps the employees safe from getting involved in risky procedures. The end results are accurate with minimal variation.

4. Choosing Rubber Material For Injection Molding

Rubber injection molding is the most flexible molding method as the manufacturer can is different polymers to work with.

Rubber materials can either be natural or synthetic rubber:

Natural Rubber

It’s a common polymer in molding made from latex produced by a rubber tree.

Again, it contains high tensile strength, high abrasion, and surface friction properties.

Besides, it is used for diaphragms, seals, o- rings, etc. it can be used for coating as it blends well with metal.

Benefits of natural rubber include:

• Excellent elastomer hence able to bond to the metal in combination with other adhesive
• Has a high tensile strength
• Can withstand chipping, cutting, and tearing better than synthetic rubber and is highly resilient

Some of the disadvantages of rubber are:

• Hard to produce natural rubber compared to synthetic
• Doesn’t react well when exposed to UV rays and heat

Synthetic Rubber

It is artificially produced by turning monomers into polymers.

Again, it is more economical, easier, and malleable hence can be used for more applications.

They include:

a. Nitrile or Buna-N (NBR) – from acrylonitrile and butadiene through the emulsifier process.

It is one of the most commonly used synthetic rubber due to its ability to resist water, oil, some fluid, and solvents.

It also has incredible mechanical properties and is resistant to abrasion and tearing.

b. Silicone rubber is made up of silicon, carbon-oxygen, and hydrogen.

There are various silicone rubbers differentiated by chemical structure and organic groupings like methyl, methyl phenyl, methyl vinyl, methyl phenyl vinyl, and fluoro vinyl methyl.

It’s known for its resistance to temperature weather and its flexibility

c. Fluorosilicone (FVMQ) – is a type of silicone that has trifluoropropyl which helps in chemical, oil, acids,non-polar solvents, fuels, oils, alkaline, and acids resistance.

It is highly versatile like silicone

d. Neoprene™- it resistance properties to weather, temperature, fire, and abrasion. Its versatile hence can be used in any rubber molding process

e. Styrene Butadiene (SBR) – has great aging and crack resistance. It’s mostly used in the rubber molding of seals, gaskets, and diaphragms

f. Fluorocarbon (FKM)-materials are crosslinked with different types of copolymer. Crosslinking materials include diamine, dihydroxy, and peroxide.

These qualities make FKM resistant to chemicals and high temperature

g. Butyl or Isobutylene Isoprene (IIR)-IIR rubber is made by copolymerizing isobutylene with isoprene.

It’s used to manufacture seals and vacuum applications as it’s not permeable to gas

h. Urethane- is manufactured from the reaction of polyol with a diisocyanate.

Different urethane rubber materials can be made from different combinations of components.

Urethane rubber has high abrasion and excellent tensile strength

i. Hydrogenated Nitrile Butadiene (HNBR) – this rubber is highly strong and resistant to heat.

It is also resistant to water, dilute acids, bases, salt solution oil and fuel, vegetable oils, silicone oils, and greases hence it’s highly used in the automotive industry

j. Ethylene Propylene Diene Monomer (EPDM) – its strong structure makes it able to withstand 150° temperature, and resist heat, light, and ozone.

It is very long-lasting and hence used for steam systems, panels, cars, etc

5. Rubber Injection Molding Vs Rubber Extrusion

Injection molding of rubber is one of the most common molding processes used by manufacturers to create standard or custom-made rubber.

Heated rubber compounds or materials are injected into a closed mold under high pressure.

Rubber Extrusion on the other hand is where extruded parts under high pressure are emitted through the cross-section die.

rubber extrusion

Soft unvulcanized rubber components are used to make rubber products hence extruded parts are soft and malleable in nature.

End products of extrusion must be hardened using different curing methods.

The main difference between the two is rubber injection molding is more complex and is used to produce 3- dimensional parts.

However, rubber extrusion is a simple process that produces 2- dimensional parts that need to be hardened.

6. 3D Printing Rubber Vs Injection Molding Rubber

Both techniques are used to produce rubber components but each process is different:

3D printing– here layers of materials buildup to create an object.

Its best used for prototyping as it has fast turnarounds.

Besides, it is a flexible process that can be used if constant changes in the design are required.

Also, it can be used to create both small, large parts and products in complex designs

Injection rubber molding on the other side of the coin- a mold is filled with molten rubber that cools down and hardens to form parts or products.

3D printing rubber

 Its best for high volume production as it has minimal or no wastage.

7. Properties Of Rubber For Injection Molding

Rubber is a versatile material compared to metal or wood.

It has a higher tolerance rate hence used in the manufacturing industry. Some of its properties include:

• Heat aging– molded rubber expands and contracts. If it’s exposed to varying amounts of temperature, it still maintains its qualities
• Elasticity– rubber is elastic and hence very effective when applied in an area of motion as it provides flexibility and protection to the surface.
• Compression– rubber compresses when pressure is applied. You should select the right size for your product.
• The hardness of rubber is measured with a durometer. High numbers on the scale indicate the rate of hardness the rubber has.

8. Rubber Metal Bonding Vs Injection Molding Rubber

Rubber metal bonding is also referred to as rubber to metal bonding. Metal is bonded to rubber to become stronger and more durable.

A heat-activated paste is sprinkled on the metal before being inserted into the mold.

Rubber and metal mix in the mold to form a stronger bond than the one the rubber initially had.

The final product has as strong as a metal but flexible as a rubber.

rubber metal bonding

Metals that can be used for the bond include:

• Aluminum
• Copper
• Brass
• Steel
• Beryllium

Choose a metal according to the function and the properties you want your rubber to maintain after the process.

Injection molding of rubber is one of the most common molding process where heated rubber compounds or material is injected into a closed mold under high pressure.

Different rubber materials discussed above can be used in the process. It’s the best method for high volume production and for complex design.

rubber injection molding

9. Considerations For Customs Rubber Molding

Rubber molding materials are selected according to the industry the rubber will be used.

For example, the rubber used in food processing is totally different from the one used in mechanical applications or aerospace.

Contemplate the following points while considering rubber molding materials:

• Choose quality materials that can withstand minimum and maximum temperature without losing their qualities
• Require a low cost of production
• They are resistant to oil, gas, and fuels to avoid damage during production
• These materials are functional and meet the industrial requirements
• Materials whose eco-friendly such that they will not harm people or pollute the surrounding environment.

10. Customs Rubber Molding Problems And Defects

Unfortunately, some defects can be seen in the final product on the molded products or parts. Here are some of the reasons for defects:

• Inaccurate process parameters
• Poor quality rubber was used in the process
• Inadequate material supply
• If the process was handled by inexperienced personnel.

Shrinkage

This is a common problem in rubber molding. Molded rubber tends to be smaller than the mold cavity used to create them.

Possible Solutions:

• Increase the size of the mold cavity. Ensure its slightly larger than the size of rubber you want such that when the rubber shrinks you still get the desired size
• Have a suitable cushion in the mold cavity
• Slow down the process of gate sealing to allow it to fill
• Increase cavity pressure

Too Much Flashing

It’s common with injection molding where rubber materials drip between the mold surfaces.

This interferes with the surface finish of the rubber.

Possible Solutions:

• Improve the clamping force
• Reduce the peak cavity pressure
• Use a larger press

Brittleness

It originates from shorter molecular chain lengths.

Possible solutions:

• Eradicate rubber from other polymers to avoid contamination
• Increase the rate of filling the mold cavity
• Improve the mold temperature and cool time to ensure the desired results are achieved

Short Shot

This occurs when you fail to fill the required amount of rubber material in the mold cavity which leads to insufficient molded rubber parts.

Possible solutions include:

• Improve the temperature of melting and molding rubber materials
• Increase shot size
• Check the filling speed, pack pressure, or injection time. If it’s slow consider improving
• Use materials that melt faster to make the process faster

Warpage

This defect molded rubber is produced in the intended shape.

However during the cooling process, it gets distorted, it either warps, twists, bends, or bows.

It changes the whole design of rubber. As a result, it may or may not be used in that state or shape.

Possible solutions:

• Reduce hot spots in the mold
• Incorporate cycles in the process
• Reduce the injection fill rate
• During the molding process consider high temperature and low pressures

For all your custom rubber molding needs and requirements, contact us now.