When thinking about how to produce a gasket the main issues the customers engineer usually asks about are focused on understanding how the die cutting process works. To help with this concern I have outlined the die cutting process which we follow. I have also addressed some of the most common questions.
At Alpha Die Cutting we use a steel rule die cutting manufacturing process which cuts uniform shapes out of various types of materials to create standard gaskets, custom gaskets, O Rings and other final products for a wide variety of industries. This is a low cost, accurate, high repeatable and high accuracy option for the manufacturing of flat non-metallic parts.
The die cutting process
After we receive a RFQ or PO the first step in our process is a “design for manufacturing review”. This is a crucial step where we review the specifics included on the customers engineering drawing - the material called out, thickness, type, hardness, the required tolerances, the design complexity along with the demand quantity and delivery need.
Based on our expertise we then determine if we could add value by suggesting any change to make the manufacture of the part easier, quicker or less expensive. If we find anything during this review we contact the customer for their approval. This positive interaction only takes a short time but can result in significant cost and time savings for our customers.
The die cutting machines
We use flat-bed die cutting machines where a die is carefully positioned into the machine chase. The machine holds the die in the correct position to allow the raw material to be pressed between two plates. The die hits the raw material with enough pressure to be cut and penetrated through. When the press is reversed the cut material is exposed and pulled out.
Steel Rule Dies
The dies are specific tooling that are used to cut the material. The simplest analogy for this type of die is a household cookie-cutter. The die is customized to the required part design. The part can range from a simple circle or square to a complex design with tight tolerances.
Die costs are kept to a minimum. Based on the size and design complexity of the part most dies vary in price from around $100 to $300. The die itself is a pattern of specially hardened steel rule set in a plywood base. The steel is shaped into specific positions and sizes and inserted into the slits that have been cut into the plywood. After the steel “blade” is inserted we then add an ejection rubber pad which is adhered to the die base. This material helps to eject the materials from the die after the cut is made.
The actual type and thickness of the steel rule is specifically selected for the thickness of the material being cut and the complexity of the part features. As there are different lengths, thicknesses, profiles and cutting patterns of steel rule to choose from it is vital to use the best die cutting practice.
We purchase the raw material in either sheet or roll format and then trim the material to the size required for the specific die cutting machine being used. Because the rule in the die is steel this process is not really suitable for cutting metal although thin and soft metal like foil can be cut.
We can cut most non-metallic materials with a plain backing or if it has an adhesive (PSA).
The raw materials we can cut include:
Rubber – EPDM, Neoprene, Silicone, Poron, SBR, Viton, Nitrite, Buna.
Plastic – Polyethylene, Polypropylene, Polycarbonate.
Paper – Nomex, Vegetable Fiber, Cardboard.
Fibers, Felt, Cork, Vinyl, Sponge, Films, Felt, Leather, Tapes.
The thickness of the material we can cut varies from very thin, 1/64” to over 2” but it becomes difficult to cut very thick material when the part has an intricate design or very tight tolerances and dimensions.
What is the accuracy of die cutting?
It depends on the part being die cut but as a general rule +/- 0.015” tolerances are achievable. To ensure the best quality possible we always produce a FAIR (First Article Inspection Report) to demonstrate that the part can be produced per the drawing. After our Quality Manager has approved the FAIR then we continue with the complete PO quantity.
How long does a die last?
It depends on the number of hits, the material type, thickness, hardness and the complexity of the part design. As a general rule a die lasts hundreds and thousands of hits.
We manufacture our dies in 2 sections which allows us to just replace the steel rule in the die. When the knifes get dull and not producing a clean cut we re-knife the die at 50% of the cost of the new die.
What is the size of the part you can die cut?
We can cut parts up to 40” X 28” on our largest die cutting machine. We can produce larger parts if the design can be made in sections and then dovetailed or put together on assembly.
We can cut very small parts, in the range of < 1” X 1” on our smaller die cutting machines.
How complex a design can be die cut?
The steel rule has to be bent so there is a limit to how tight a radius is possible. As a general rule around 1/8” is about the tightest possible radius.
The biggest issue we encounter is when the part is designed with holes and other dimensions which are too near the edge of the part. When the cuts are too tight to the edge then it leaves no room for the thickness of the steel rule to be located in the die. It is important to note that bolt/fastener holes are made using a pre-made punch and so the holes in the part design must take account of the bay thickness of the punch. As a general rule the gap between the edge of the part and the dimension should be at least 0.050”.
If you have a die cutting project and want to utilize our extensive expertise and experience, please call Martin (858) 279 3343 or e mail email@example.com
About the Author
With over 25 years of experience in the manufacturing industry, Martin Chell brings a wealth of knowledge to his client projects. He has worked with large companies including Qualcomm and completed projects in a variety of aerospace, biotech and other applications.
“The die cut samples look great.” ~ Aquapail
“Thanks so much for the great service.” ~ Robert, Hat Fitness
“The gaskets worked out just fine. Thanks for your help.” ~ Chong, Redpoint Engineering