Rubber Injection Molding at Lake Erie Rubber

By definition, rubber injection molding refers to the process by which uncured rubber materials are transformed into a viable part, component, or product after raw rubber is injected into a metal mold cavity where applied pressure induces the chemical reaction known as vulcanization. While injection molding was originally developed to mold plastics into desirable shapes, it soon became a relevant process for fabricating rubber components.

Coincidentally, the advancement of injection molding for rubber and the founding of Lake Erie Rubber both took place in the early 1960s. Rubber injection molding is highly desirable for industrial applications especially projects that require immense throughput and repeatability. This specific article takes an in-depth look at the step-by-step procedures with the help of an informative video, the steadfast commitment to quality, and the many advantages of rubber injection molding at Lake Erie Rubber.

Steps & Procedures of Rubber Injection Molding

In the simplest of terms, rubber injection molding involves machinery that takes strips of raw rubber material and converts it into shaped vulcanized components through the addition of heat and pressure. The steps below are shown in detail in the “Rubber Injection Molding” video on our YouTube Channel (@lakeerierubbermanufacturin3285). Other videos are available to view on the channel that covers the specific advantages of different types of rubber, how to pick the correct rubber type, and a virtual tour of our facility located in Erie, PA. The infographic shown below also provides a clearer visual representation of the rubber injection molding process and how the selected rubber material is converted into a finished product.

Injection Molding Infographic

• Step 1: Close Mold
  • Both halves of the metal mold are brought together to create a tight seal that forces the rubber into the desired cavities without losing valuable material.

• Step 2: Inject Rubber to Fill Cavities
  • The rubber moves through the machine and is injected through the injection nozzle and sprue bushing to fill the hold cavities with rubber. The rubber is compressed and pushed through the sprue to fill the open space created by the hold cavities. The combination of heat and pressure forces rubber to fill the mold uniformly with some excess material overflowing into designed areas.

• Step 3: Cure/Vulcanize Rubber inside the mold
  • The combined heat and pressure initiate the process of vulcanization which is defined as the “curing of elastomers” or cross-linking rubber molecules to increase the strength and elasticity of the final product.

• Step 4: Screw pulls in a pre-measured amount of rubber for the next cycle
  • Each batch is carefully measured to avoid any wasted material or over-filling the mold cavities during operation.

• Step 5: Barrel fills with rubber pulled in by the screw.
  • This step improves the cycle time between product runs and helps the operator remain ahead of schedule.

• Step 6: Parts finish the vulcanization process with appropriate heat and time.
  • Now that the rubber has cured, the mold can be separated to reveal the mold cavities now filled with properly shaped rubber components.

• Step 7: Mold opens and parts are removed.
  • The equipment operator is careful when removing the hot rubber components from the mold. By design, these parts can be attached and require subsequent trimming noted in Step 9. The mold can now be closed and the rubber injection molding procedure repeated.

• Step 8: Operator completes visual inspection.
  • Each component is exhaustively inspected for any possible defects or structural deformities. Lake Erie Rubber prides itself on delivering only premium rubber products at the same immaculate quality from the first part to the very last of a product run.

• Step 9: Operator trims parts per work instruction.
  • Components are trimmed to meet specific measurements or design requirements specified by the customer.

• Step 10: Part Labeling & Inventory
  • All rubber injection molded parts are labeled with part number, and quantity, and are inventoried daily in our stockroom to maintain rigid documentation practices and quality control measures.

Keys to Quality Rubber Injection Molding

At Lake Erie Rubber we pride ourselves on delivering premium products that offer superior longevity and performance to our customers. As with most products, the final level of quality depends on the raw material. A substandard starting point will only serve to fabricate substandard components. The keys to quality rubber injection molding at Lake Erie Rubber can be found below.

Sourcing Quality Rubber for Injection Molding

Not all types of rubber share a uniform set of physical properties and the experienced team at Lake Erie Rubber works diligently to ensure that each shipment received meets our standards. By working closely with our suppliers and performing a battery of quality tests and proper storage practices we ensure that all rubber injection molded products are fabricated from the highest quality rubber.

• All rubber suppliers to Lake Erie Rubber are audited on an annual basis to ensure optimal quality of raw material.
• Each purchased and delivered batch of rubber must arrive with an attached lab report to verify the specific physical requirements are met.
• All shipment lab reports are comprehensively inspected and filed for a minimum of ten years to provide easy access should any concerns with that specific shipment arise.
• Any rubber shipments that do not meet quality standards are designated as “rejected materials” and transferred immediately to the quarantine area within our facility. This ensures that sub-standard materials are not accidentally used in any rubber injection molding projects.
• All approved rubber shipments that meet quality standards and moved to our cold storage room that maintains optimized levels of temperature and humidity to best protect the raw rubber material before use.
• FIFO (first in, first out) is always followed on raw material to guarantee that the oldest material is used first.
• Expiration dates on shelf-life raw material are listed by the manufacturer and stringently adhered to by Lake Erie Rubber.

Correct Injection Molding Machine Setup

All rubber injection molding projects are unique and can require different machine setup configurations to create an optimized component. The experienced machine operators at Lake Erie Rubber take every precaution to dial in rubber injection molding equipment before operation and make sure it matches the exact specifications outlined on the provided setup sheets.  Each Lake Erie Rubber setup sheet has detailed instructions on the below settings.

• The first instruction on a setup sheet identifies the appropriate rubber compound for the specific project. With countless rubber compounds, each with a unique set of strengths or benefits, it is crucial for a machine operator to note and use the correct variant.
• Each machine setup sheet offers a detailed list of press setting instructions including things like pressure or temperature settings required to produce the desired component.
  • All press settings are developed and stored digitally in password-protected files.
  • The setup sheet is printed each time the job is run to ensure the correct revision number is available to the machine operator.
• Components fabricated by rubber injection molding will most likely have additional unwanted material attached to the part as a result of the molding process. The setup sheet will indicate the cutting or trim operations required to meet the intended product dimensions.
• All rubber injection molding projects undergo a final set of visual inspection requirements to guarantee there are no defects like missing rubber.
• Each machine setup sheet will outline the necessary boxing or packaging requirements for the manufactured part.

Quality Inspection Processes of Finished Products

After the raw material quality inspections and rubber injection molding process have finished, each component will undergo thorough quality inspection processes. Lake Erie Rubber has always prioritized expansive inspection procedures to maintain its reputation as a premium rubber molding company and to avoid sending customers a sub-standard product. While certain projects may dictate supplemental quality inspection processes, each rubber injection molding job will undergo the following criteria.

• A First Article Inspection (FAI) is completed for each job. This process involves a comprehensive inspection of all component dimensions to verify that the parts meet the exact specifications outlined on the setup sheet. If present, all discrepancies or differences will be corrected before Lake Erie Rubber proceeds with the complete product run.
• Each component may undergo a random inspection to check for proper vulcanization, dimensions, and finishing operations.
  • All random Inspections are tied directly to the specific project and stored digitally for a minimum of 10 years.
• Machine operators must record all data in Daily Production Sheets to allow for traceability for any quality issue that may occur.
  • Again, Daily Production Sheet data is digitally stored for a minimum of 10 years
• Internal audits are established in the Lake Erie Rubber QMS to ensure these processes are maintained.

Advantages of Rubber Injection Molding with Lake Erie Rubber

In addition to our decades of experience servicing countless industries with premium components, the actual process of rubber injection molding offers customers a distinct set of advantages over other rubber manufacturing techniques. Currently, the only significant drawback to rubber injection molding is the upfront cost of specialized tooling. However, as the product volume increases this tooling cost quickly pays for itself.

• Large Rubber Injection Presses: The availability of large-scale rubber injection presses at Lake Erie Rubber provides considerable flexibility to produce an assortment of products. These DESMA 968.560 ZO and DESMA 968.400 ZO presses allow for the production of all-sized components in higher cavitation molds that provide improved cost and reduced lead times to customers. The addition of these machines has helped us press larger and heavier components than previous machines allowed. In some instances, our abilities surpass most other companies offering rubber injection services.

• Localized Supply Chain: With supply chain interruptions and material shortages becoming more frequent, Lake Erie Rubber has worked hard to avoid future difficulties by working with localized suppliers. This has helped us offer customers expedited lead times over the competition without sacrificing the quality of their rubber injection molding requirements.

• High Precision Manufacturing & Over-Molding: Rubber injection molding offers impressive accuracy and precision on complex components. Furthermore, injection molding can be used to “over-mold” rubber onto pre-existing components made from metal and other materials.

• Reduced Cycle Times: Thanks to the overall efficiency and straightforward process of injection molding, components can be made in less time when compared to other methods. After working with Lake Erie Rubber most customers see tremendous savings in total project costs, increased throughput, and shortened lead times.

Contact for Quotes on Rubber Injection Molding Services

Since its inception, Lake Erie Rubber has worked with countless industries to develop and manufacture premium rubber injection molded components. Our diverse knowledge, modern equipment, and experienced staff help set us apart from the competition and we are always looking for new ways to advance the application of this molding procedure. From selecting the highest quality rubber compounds to implementing stringent quality control measures throughout the manufacturing process, the advantages of choosing Lake Erie Rubber are abundantly clear. If you are looking for superior products, industry-leading turnaround times, immaculate precision, and tremendous flexibility on your next rubber injection molding project please contact our team by email or phone to start the quoting process.

Contact Lake Erie Rubber

Video Transcription: https://www.youtube.com/watch?v=eggtPsiYy7c