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 firstname.lastname@example.org
Design for Manufacturing
At Alpha Die Cutting we have over 30 years experience in die cut manufacturing. We work diligently with our customers with the goals of producing a quality gasket and keeping costs to a minimum. We have developed the expertise to understand the main themes that contribute to the cost of manufacturing a custom gasket. We now want to share these experiences with you. Here are the seven main areas where customers could focus their gasket spec on to ensure the lowest possible cost. We have also included a Tip for each element so that you can make the best choice to keep your costs as low as possible.
We often see engineering drawings which have extremely tight radius or very small gaps between the diameters. The die cutting process involves bending and forming of hardened steel rule so there is a limit to how tight the bend can be. Here are photos showing the tightest radius bend possible.
Obviously a gasket has to fulfil its specific application needs but consider if the intricate shape is really a “must have”. We can form an alternative to the radius by using 2 straight rules joining at a point.
Tip – Review the gasket spec to see which dimensions are critical and which can be relaxed.
We see many drawings created in millimeters. While this is an acceptable protocol it sometimes reflects a design being extremely small with impossible dimensions. The dimensions seem larger in millimeters than if the drawing was produced in decimal inches.
Tip - If the drawing is drawn in MM (millimeters) convert into inches and you will see how some dimensions are extremely tight.
We have seen many drawings stating that the tolerances must be very tight. When we have discussed the gasket spec with the customer we have found that the engineer has used default tolerances and are much tighter than really required. Alternatively if the tolerances are true we will respond to the customer if they can be achieved or not.
Tip – Review the tolerances in the gasket spec to see which tolerances are critical and which can be relaxed.
The cost of the raw material is usually a significant portion of the total gasket cost. At around 50-75% it is important to get the material spec correct. We do not get to know the specifics of most of our customers applications but those that we do have details we find a significant number have the “top shelf” material specified when a less expensive material is all that is required.
Tip - Review the material spec for the specific application to see what is really required.
All materials are manufactured by the OEM’s in standard thicknesses. It is possible to purchase materials in thickness that do deviate from the standard but it is then considered a custom purchase. Any material which is custom made has an extremely high MOQ buy and a long delivery.
All raw materials have similar but sometimes slightly different standard thicknesses. For example Neoprene Rubber is available in 1/64, 1/32, 1/16, 3/32, 1/8, 3/16, ¼, 3/8, ½ inch thicknesses.
Tip – Where at all possible design the gasket using one of the standard material thicknesses.
The customers delivery requirement has a significant impact on the gasket price. If the delivery requirement is very short then we are forced to source the raw material from a national distributor. This supplier usually has inventory that can be delivered next day or sometimes with 1-2 days. But this service comes at a cost which is on average around 4 times higher than obtaining the material from one of our other suppliers.
If the delivery requirement is not so urgent then we source the material from 3 of our regular suppliers to find the best price and delivery quote. This material is less expensive but comes with longer delivery times of around 2 weeks.
Tip – Submit RFQ with a realistic delivery requirement.
We see many customer drawings which specify an adhesive backing (PSA – Pressure Sensitive Adhesive). This spec involves significant cost – the PSA is usually double the cost of the non PSA raw material.
Tip – Review if the gasket really needs the adhesive backing.
Overall – Design for Manufacturing
Each element in the design spec of a custom gasket has an influence on the cost of the gasket manufacturing cost. Where at all possible design the gasket spec for ease of manufacturing.
A gasket is a banal but essential element in a manufacturers product or assembly. Sometimes the design of the gasket is overlooked as being an inexpensive item.
At Alpha Die Cutting the manufacture of custom gaskets is central to our core capabilities – we have the experience and the expertise to help our customers control gasket costs.
Tip – if you need any help on any specific project please contact email@example.com
or call Martin at 8582793343 and we would be discuss how we can save you money.
Collaboration at the RFQ stage of gasket manufacture can save significant money and time. Recently a new customer, Swope Design Solutions a mechanical engineering and product design company; SwopeDesignSolutions.com sent a RFQ asking us to manufacture some custom gaskets.
Their engineer, Stephanie Whalen linkedin.com/in/sawhalen/ had a good idea of the gasket need for the application but wanted to use our expertise and open to any suggestions we had for finding a better solution.
Over the next couple of days we developed a very effective communication interchange on various questions, issues and clarifications. We discussed and agreed on some minor drawing changes regarding material thickness and material hardness. Even with this dialogue we were able to issue a quote within 3 business days of the original request.
This collaborative style of working allowed us to utilize our die cutting expertise resulting in a custom gasket which fit their exact application but was also less expensive than anticipated and delivered earlier than the initial quote.
An additional change was that we added a second gasket which was nested inside the initial gasket.
This change had the double benefit of reducing the material waste and as both gaskets could be produced on the same die enabled us to produce double the parts per hit. We love to save the customer money and at the same time reduce waste.
As the customer wanted an initial demand of only 100 parts we sourced the Silicone Rubber, 40 duro, red color, 0.062” thickness material from a national distributor. We find McMaster Carr a good source of material if the customer has a low demand quantity and requires a quick delivery.
Because the customer provided a forecast future demand of around 1000 over the next year we are able to source the equivalent material as we purchased from McMaster Carr but at a lower price. We could use one of our strategic suppliers quote on a higher amount of material. This practice has a down side in that the material delivery is usually 2-3 weeks and has a higher MOQ than McMaster Carr. But the big advantage is that the manufactured piece part cost is much lower. Using the McMaster Carr material the piece part cost for qty 100 = $4.70 each. Using the strategic suppliers material the piece part cost for qty 100 = $3.50 each and for an order of qty 1000 the price would decrease to $2.25 each.
A common customer dilemma is when they cannot find a washer to fit their application because only standard parts are available. They ask us if we can manufacture a custom washer type gasket – the answer is YES.
Many customers don’t think of talking to a gasket company when they need washers manufactured. In fact, washers are just small gaskets that can be cut using our die cutting capabilities. A washer is a thin plate, usually round with a hole that is used to distribute the load of a threaded fastener such as a screw or nut.
The shape and size of your washer can be customized to suit your application. Washers can save you money - instead of adapting your design to washers that are available as standard, use a custom washer to decrease your costs. You can use exactly the parts that you need instead of working your design around a washer that doesn’t fit correctly. This can be critical for an end users experience, especially for pre-assembled products.
We produce washers in a range of non-metallic materials, such as rubbers, foams and plastics and in a wide range of dimensions and thicknesses. We can add an adhesive (PSA) backing to help with product assembly.
Rubber Washers and Plastic Washers
Rubber and Plastic is available in various grades, thickness, hardness and colors. Material selection can be critical depending upon your specific application. Different materials are better suited for different applications. This is determined by factors such as temperature resistance, fluid resistance, chemical resistance, ozone resistance and abrasion resistance.
Some of the washers we have previously manufactured include:
Send your drawing in Pdf format to firstname.lastname@example.org and we will source the spec material and die cut manufacture the custom washer. We can manufacture from prototype quantities to full production volumes.
We were recently asked about die cutting a SAE F-13 felt at ¾” thickness. The customer wanted a part made for their Battery application. We had no prior experience with this material before, but we were confident we could cut the material to produce the OD of the part but not so sure about the small dimensional slots. Die cutting the part would be a challenge because of the combination of the material thickness, the material density and the narrow dimensions of the slots.
Our initial response to the customer was to be completely transparent and say that we were not sure we could make the part but would be willing to conduct some R&D to determine if this project was possible. The R&D effort involved purchasing the F-13 felt material, to make a custom die and a few different die cutting attempts. We have now successfully produced the required part.
Industrial S.A.E (Society of Automotive Engineers) Wool Felt.
This is a felt used where resistance to abrasion, durability and wear are not so important. Applications such as spacing strips, sound deafening, fuel oil filters, anti-rattle, grease and oil retention.
The felt varies in thicknesses, colors, densities and composites specified by the SAE designation i.e. F-X.
If you want to know more about this capability or send a RFQ please 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