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Diecutting in a Clean Room Environment
Peter Bendell — Plant Manager,Pioneer-Dietecs
What is a Diecutting Clean Room?
A clean room is an environmentally controlled room typically used in manufacturing or scientific research that requires a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. More specifically, a clean room has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size.
A diecutting clean room contains a cutting press, cutting dies, material to be diecut and other equipment or furnishings required in the diecutting operations. These components comprise what is commonly referred to as the diecutting system.
Equipment inside the clean room is designed to generate minimal air contamination. Clean room equipment including the diecutting press and cutting dies are designed to produce a minimum of particles and should be easy to clean. These facilities are used extensively in biomedical, pharmaceutical and electronic companies that are very sensitive to environmental contamination.
The air entering a clean room from outside is filtered to exclude dust, and the air inside is constantly re-circulated through high efficiency particulate (HEPA) and/or ultra low particulate air (ULPA) filters to remove internally generated contaminants. Staff enter and leave through airlocks (sometimes including an air shower stage), and wear protective clothing such as hats, face masks, gloves, boots and coveralls.
Essential components of a diecutting clean room facility
Cutting Die Tooling
For many applications a standard steel rule die, clicker die or machined die will work fine, but in a clean room operation special factors must be considered. Cutting dies used in the clean room operations must be clean and sterilized to prevent contaminants from affecting diecut parts.
Sterilization can be accomplished by using an autoclave, which is a device that sterilizes equipment and supplies by subjecting them to high pressure steam at 121 °C or more, typically for 15 to 20 minutes depending on the size of the load and the contents.
Steel Rule Dies
Dieboards used in producing steel rule dies for clean room operations must be manufactured from manmade die substrates such as Rayform™, Lexan™, or aluminum that can withstand high pressure steam to sanitize the die and prevent any dust or splinters from being a potential contaminant. Normal wood based dieboards are not suitable for clean room operations since they are hydroscopic and absorb moisture that can change the dimensions of the die.
If the die-cut material is for biomedical use, it may be a requirement that the die be put in an autoclave for sterilization. This is particularly important with any cut parts to be implanted into the body or when die-cutting skin.
Stainless steel cutting blades must be used in these steel rule dies so that the blades will not rust in autoclave sterilization. Stainless steel rule may work well for these applications, but they have the inherent drawback that the joints may open up over time. The die blades may give snags and uncut areas in the material which could be problematic.
Alternative die types to steel rule dies
Consider using solid machined dies made from stainless steel. The advantage is that they are seamless, ensuring cleaner die cut parts and they can take the heat of the autoclave. This type of tooling tends to be more expensive than steel rule dies, but the added cost can often be justified in improved operations. However, there are not many die makers who machine dies from stainless steel. They do exist but may be difficult to find.
There are some coatings that can be applied to a standard machined dies such as Nickel and Teflon, but tests would need to be made for compatibility with the die-cut material. Also, the added cost of the coatings may outweigh the benefits.
Cutting Surfaces
Clean room cutting dies should cut against or onto a hard surface such as a hardened steel or stainless steel. Softer surfaces such as plastics or nylon must be FDA approved. Be aware that “into” cutting can create contamination from slivers or dusting from cutting surfaces.
Cutting Presses for Clean rooms
Size of the required cutting area
This is the size of the largest die you will be using plus a little extra for the material to be cut. Allow for future growth of the die sizes.
Tonnage requirements
Tonnage is usually based on the linear inches of blade to be cut. A large die with only an outside perimeter cut may require less tonnage than a small die with cutouts and punches. The pounds per lineal inch of blade may also be different for the various materials to be die cut.
Once the size and tonnage are determined, the next question is what kind of press will best suit the job?
Here are some questions to consider in selecting a press:
- Will your press manufacturer comply with all of your clean room requirements?
If not, you may want to seek a different press supplier. Many lower-cost presses do not hit flat and may give unacceptable parts or even damage the dies. A solidly built four-post press that can kiss-cut against stainless steel may be the best choice. Many standard presses are sold through distributors. You will need to find out who will service the press. - Is local service available?
- Will the work be guaranteed? Or will you be required to fly in a technician? If you plan on making in-house modifications you need to find out if this will void your warranty.
Custom Presses
A custom press should eliminate the above concerns as the diecutting system will be custom designed and engineered specifically for your application and be ready to run when you receive it. Your press and dies will be turn-key and guaranteed for the job.
It pays to find a die and press manufacturer who can supply both the stainless steel dies and press that best fit the application. You will be getting the correct die and press and know that the system has been engineered, tested and proven before it's shipped out.
Do your home work and make sure that any supplier you choose has a history of supplying clean room dies and presses. Give the supplier as much information as you can. Tell him the level of clean room you have and what you expect from his company.
Safety
Safety is always a major concern when diecutting. Most off-the-shelf presses come with two hand non-tie down buttons that are OSHA compliant. Still, they may or may not be as safe as you need. Think about who will be running the press and how safe it will be to others in the clean room. Will you need to add extra safety measures to the press? How much will that cost? Once again, a custom press can be tailored to your safety needs and concerns.
What’s better, a Hydraulic Press or a Pneumatic Press?
Hydraulic Diecutting Systems
Hydraulic Presses are widely used in diecutting operations. They are simple to operate and capable of lasting for generations. But serious thought should be given before deciding on any off-the-shelf press for clean room applications.
Many diecutting press systems that use hydraulic fluids can contribute to contamination in a clean room because the hydraulic fluids can leak or mist. Hydraulic fluid vapors can be a contaminant and hydraulic systems are also more difficult to keep clean. For these reasons hydraulic clicker presses are not usually recommended for high level clean room applications.
Pneumatic Presses
Pneumatic presses are the ideal solution for the clean room diecutting. There are many off the shelf pneumatic presses, but many of them may not work well because of their lack of close tolerances, so chose carefully. Custom presses can be tailored to the application and are a better choice.
Here are some important points to consider with all air presses:
Exhaust Ports
A high level clean room may require that all the exhaust ports be vented from the press to a location outside the clean room.
Lubrication Points
All grease and oil ports must be contained within airtight chambers.
Summary
There are many factors to consider when choosing die and press makers, so be diligent in your search and ask for recommendations from others in your industry. The final results can be well worth the extra effort you put into finding the right supplier. Sometimes the extra costs involved in having a custom system designed and built for your diecutting clean room operation are worthwhile. Trying to put together a system yourself from multiple suppliers may end up costing you more in the long run.
Download pdf of Diecutting in a Clean Room Environment.