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The True Cost Of A Plastic Injection Mold

10May

Asking for the cost of a plastic injection mold isn’t an easy question to answer, but it’s the most important one when starting the manufacturing process. It’s a lot like asking “How much is a house?”  Are you looking for a starter home with 1 bedroom and 1 bathroom for you and your cat or are you looking for a 4 bedroom, 3 bathroom, split level house on 2 acres with a detached 3 car garage, in ground swimming pool and room to roam for a growing family.

Just like there are homes for different stages in your life, there are different molds for parts and the costs are just as different.  Depending on what you are molding and how many parts you are planning to make will decrease or increase the cost of the mold.  But there is good news, the mold will be the biggest cost out of the process, with very low per product costs for many years to come!

The differences between that 1 bedroom home vs the luxury home on 2 acres are the same for molds which can start low and accelerate very quickly.   Generally molds are crafted out of either aluminum or steel. Aluminum molds are cheaper and a perfectly reasonable choice if you don’t need the mold to perform long-term or produce many pieces. However, if your project requires that a mold lasts for several years, an aluminum mold may cost more in the long-run.  Steel molds last longer and produce higher quality pieces.  Hardened steel molds lasts the longest and have a long production life, however the initial upfront cost is higher. It’s like that old saying goes “You get what you pay for”.

If your part is semi to very complex then the mold itself is going to be expensive. You wouldn’t expect a Rolex watch to be made with anything less than pristine tools and parts and by a trained Watch Engineer now would you? If you want to put out a high quality product with a great reputation why would you opt to save a little bit of money for a cheap mold which will only harm your product and your future profits?

Building an amortization schedule for your mold can help you see the perspective of how much you are actually spending. For example, if your mold is going to cost $45,000, made out of steel and expected to make 500,000 parts over the next three years think of it this way, the cost per year for 3 years is only $15,000 and your cost per part is only $0.09! The cost of the mold and what you are getting from it suddenly makes a lot of sense.

Another consideration in determining what a mold will cost is the material selection.  Material costs will change depending on what type of plastic you are working with and the quality of the material.  For instance, if your product requires a fiberglass filled material it will cause a lot of wear when it is injected under high pressure so the mold will need to be made from hardened steel, which will cost more.

Additionally, where you have your mold made is another consideration for cost.  It’s no secret that molds are generally 40% cheaper from China.  But that cost is quickly added back on to correct the issues that arise with those molds.  China is not required to meet strict tolerances or prove the quality of their steel. This causes quality issues, shortens the life of the mold and harms the production of the parts.  We recommend and educate our customers that it’s worth spending the extra money to have their mold made in the United States where we use the best steel available for the mold base and cavities and utilize the latest technology in CNC machining which meet the highest performance standards.  

There are other variables that impact the cost of a plastic injection mold such as the number of cavities required. A fewer cavity mold requires less tooling work and time which costs less. An experienced molder may maximize cavitations by making a “family” mold in order to maintain the highest level of productivity.  Family molds are created with various cavities for assorted parts so your production is much higher.

The mold base, core/cavity machining and part complexity also play a large role in the cost of a mold.  The cost of the mold base, which holds all of the mold cavities, inserts and components together, is estimated based on the size of the mold, the type of steel and the core/cavity customization.  Most mold bases come in standard sizes and are machined to meet the requirements of a specific project. All molds must be customized which includes the placement of cores, cavities, ejectors, cooling lines, etc. Just as the number of cavities plays a role in determining the cost of the mold, so does part complexity. This includes the surface finish of the final part as well as the number of undercuts required. Parts that demand tight tolerances also contribute to the molds cost.

However, there are ways you can save on the cost of a mold. If you have a target price for your part the mold can be built with that in mind and will help to determine the right number of cavities needed to achieve your price. The more cavities required the less expensive the parts will be and will allow for a higher output.

Providing the mold maker with as much up front information is key. Without seeing the part design it’s difficult to give a cost or even an estimate for a mold. Sometimes even small design features can add thousands to the cost of the mold. Supplying CAD files for your part will provide the mold maker with all the details needed to prepare a quote with accurate costs. Formats generally accepted are: .stp, .step, .x_t, .igs, .mcx, .sldprt, .dwg, .sat

If you work with a mold builder who is also a parts manufacture it can help defray the mold building cost by subsidizing a portion or all of the cost of the mold based on the full term and value of the manufacturing contract.  It is easier to amortize the cost of the mold so they can maintain profit margins while providing the lowest possible per piece cost to the customer. 

The cost of a mold is a major expense, however, tight-tolerance, precision molds that are made from the best steel available will last for years to come. Questions you should ask yourself before starting the quoting process:

  • Will your part be in production for several years or several months?
  • Does your part require high-volumes? 
  • Are faster cycle times required? 

Depending on how you answered these questions an investment in a quality steel mold made in the US will lower you’re per part cost and you will end up saving a lot of money in the long-run.  Armed with these key cost factors will help you in obtaining and comparing quotes.   

PM Plastics is a US Manufacturer with 70 years of experience specializing in injection mold design and building and high volume manufacturing of custom plastic components. With 4 facilities located in Wisconsin, 53 Presses Ranging 30T -1,000T, 2-80 oz. Shot Repeatability, 24 Hours A Day, 7 Days A Week, ISO 9001 and UL Registered we proudly offer services from A to Z!  From prototyping to production, assembly and fulfillment we are YOUR ONE STOP CUSTOM INJECTION MOLDING SUPPLIER! www.pmplastic.com

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