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What is the difference between Heat. Cured Rubber (HCE/HCR) and Liquid Silicone Rubber?

Heat cured rubber is a high consistency product that can be molded, extruded or calendered using conventional rubber processing equipment to meet a wide range of cost, durability and performance standards. Liquid silicone rubber is a flow-able, pumpable material that can be injection molded with minimal manual labor and fast curing times. Liquid silicone rubber technology combines the speed, cost efficiency and versatility of plastic injection molding with the outstanding properties of silicone rubber. Both HCE and liquid silicone rubber are thermally cured and require heat to crosslink the uncured materials to obtain the final cured rubber part. What does post-cure mean? Post-cure of the material brings about an improvement in the mechanical properties (such as compression set) of the finished part. The content of volatile components is reduced. During post-curing, it is mainly volatile siloxane that evaporates, leading to a loss of weight. Since no decomposition products are formed, this weight loss is naturally less than in the case of peroxide-vulcanized silicone rubbers.

Does CST have any standard parts I can buy off the shelf?

No. CST is strictly a custom rubber molder producing molded parts to the customers furnished blueprints and specifications.  All the tooling in our possession belongs to our customers and we cannot manufacture products for any customer out of another customers tooling.

Does CST have any minimum order requirements?

Yes.  Our minimum order varies based upon mold, process and operations being performed, therefore, each item is reviewed individually.

What are molds made from?

Most injection molds are machined from pre-hardened “tool steel” or Stainless Steel.  Depending upon part size and configuration, the cavity area may be Tool Steel inserted into a mold base.  Transfer and Compression molds can be pre-hardened but are sometimes made at a lower cost from E-45 or J-45 steel, depending upon anticipated production volume.  Prototype molds are normally E-45 or J-45 Steel.

How much is it going to cost for a mold and parts?

That is difficult to answer because each part is quoted individually and based on a customer furnished blueprint and specifications.  No two parts are alike in weight, size, shape, function, complexity of design, material, etc.  All parts require either the customer to furnish an existing mold to CST or to have us manufacture a new mold.  We can produce single cavity molds for prototyping or small run production and/or multi-cavity production molds.  We will normally quote a wide variety of mold sizes.

What is LIM™?

LIM™  stands for “[glossary id='205' slug='lim']Liquid Injection Molding[/glossary]”.  It utilizes L.S.R. or Liquid Silicone Rubber to produce the part.  This is a relatively new process of injecting Silicone developed over the last 20 years.  It uses equipment similar to plastic injection presses with the exception that the injection barrel is cooled and the platen or mold is heated to accomplish the “cure” of the polymer.  There are several advantages to LIM™.  In large quantities, the economies of scale are such that injection molding yields a much lower part price using fewer cavities.  The process is relatively flash-free and clean making it ideal for many Medical, Food Grade, electronic and aerospace applications.

How do I choose a rubber type (Polymer/Elastomer)?

We have years of experience in recommending a particular polymer or type of rubber to customers.  It is always based upon their specific application.  Let us know the environment, including temperature, media exposure and other applicable characteristics required. We will be happy to make our best recommendation of a material from one of hundreds of formulas or develop a specific formulation for your particular application.

What is the standard lead-time on parts and molds?

Lead times for parts vary upon the size of the order, availability of raw materials, and production scheduling.  Normally, we are able to produce a product within 4 to 5 weeks and can sometimes produce partials much sooner to get customers out of scheduling conflicts.  Again, this is based on our production scheduling.  When new molds are made, the time to produce the mold and First Article Samples varies from a minimum of 3 to 5 weeks for a simple prototype mold up to 10 to 12 weeks for high cavitation hardened steel complex production molds.  Typically, 6 to 8 weeks covers most mold order lead times and production can be scheduled to commence as soon as the customer has approved the First Article Samples.

Who owns the mold?

All of the molds used by CST to produce parts for specific customers are owned by those customers.  If you do not already have an existing mold, we will work with you in creating a mold type for your particular application.

Do you mold Food, Healthcare or Medical Grade rubber parts?

Yes.  We mold these materials on a daily basis and specialize in them.  We have a Cleanroom for high cleanliness sensitive products and mold U.S.P. Class VI Medical and Food Grade materials.

What is an Elastomer?

An Elastomer is a material that has the property of being elastic with resilience or memory sufficient to return to its initial shape after major or minor distortion within a reasonably short period of time.  This property makes rubber materials excellent for sealing applications where its flexibility is highly important. 

What types of files do you need to quote?

Native Solidworks, IGES file and a dimensional 2d drawing will get you the fastest quote possible.