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Plastics Injection Molding 101: Part 3

Plastics Injection Molding 101:  Lowering Costs and Cash Flow

This blog series is for inventors and new businesses looking at creating a new product using the process of plastics injection molding.  It’s aimed at anyone with limited experience in launching a new injection molded product.

Here we go Part 3:  How to Lower Initial Costs and Ensure Sufficient Cash Flow

In this last installment we will go over some specifics on lowering initial costs and creating cash flow to support your start-up:


There are 3 main areas for cost savings at the start of a project:

  1. Design and Prototyping
  2. Making a Mold
  3. Production of Parts


Design and Prototyping –

        A good design will be a key factor in maximizing the profit margin of your parts.  The key to ensuring a good design will be to employ a designer with experience designing parts for injection molding.  Industrial and Mechanical Designers have the training to design parts that will meet the necessary qualities of your project while meeting the manufacturing demands and lowering the price of producing parts.  Accurate works with a specific group of local designers that we can count on to ensure ensuring our clients’ parts can be molded efficiently and meet all critical dimensions and mechanical specifications are met.

        Prototyping at the early stages of design is great for proof of concept.  At the final design stage, prototyping can be an effective form of presentation and testing.  3D printing is a cost and time-effective method for prototyping a limited number of parts.  In general 3D printing is great for parts 8” x 8” x 8” or less in size, or parts that can be divided into an assembly of parts within these dimensions.  The reason for this is that most printer beds are around this size and therefore cannot print anything larger.  Accurate offers two methods of 3D printing; Polyjet and FDM, and we can recommend which process best suits the needs of your parts.

        The key to costs savings during the design and prototyping stage is to find the right designer from the start and to minimize the number of prototype iterations.  Being flexible to sacrifice areas of minimal importance in your design in order to allow for a part design that will be easier to manufacture will also be important.  Finding an experienced industrial designer who also has mechanical design expertise will ensure that you get the right design from the start. 

Making a Mold –

        Good part design is the key to saving on the cost of a mold.  Certain features on a part can require additional mechanisms in a mold in order to make them.  These mechanisms such as slides and cylinders can in themselves cost thousands of dollars to make.  Often these features on the part can be removed or adjusted to eliminate the cost of these additional mechanisms without impacting the overall utility of the part.

  • Aluminum vs Steel – an aluminum mold can be a great option for your project especially if you plan on lower volumes and less rigid materials.  Aluminum molds usually do not last as long as a steel mold. However, they are less expensive to make as tooling is quicker.
  • Know Your Steel – most of the time you want a steel mold as your final production mold, know which steel you want:  P-20 is for mid to high production and Hardened steel is for high production volume.
  • Know Your Plastic – harder and abrasive materials will result in the need for hardened steel molds and possible protective coatings which increase costs.
  • Design  Simple – Reduce undercuts and part dimensions or features that require some type of side action.  Often simple changes to a part can result in significant savings.
  • Know the Trade-Off – more cavities and automated features in a mold can significantly increase the mold cost, but can also significantly decrease the per part cost for high production parts.
  • Identify what is Critical – Know what dimensions are truly critical and try not to over-specify.
  • Get a Good Design – finding a designer with experience in creating parts for injection molding is the key to ensuring your mold and part costs are as low as possible.


Parts Production –

Parts that have thick walls can be hard to produce without secondary processes to ensure cooling without warping and have long cycle times.  In most cases, a part walls can be adapted to have the same mechanical strength without the same wall thickness. 

  • Blanket Orders – When you order this way you are giving your molder the ability to mold parts whenever is convenient for them; this usually means discounts or even no setup fees which can save greatly especially if you usually pick up small batches.
  • Know Your Yearly Volume – When ordering parts if you can give the molder your yearly volume of parts and not just the order batch volume, then the molder will usually discount your order batch getting closer to the cost per part of running your yearly volume in one production run. 
  • Make it Black – avoiding custom colors, which are really anything other than black, white, and natural, will save a good bit on material costs.  In addition, for products with a selection of colors, limit the number of colors you offer to ensure larger volume orders and lower materials costs which both lead to lower part costs.
  • Multi-Cavity Tools – If you will have a large production you can save extensively on per part costs by having a multi-cavity mold.  This will have similar cycle times to a single cavity mold but mold multiple parts, thus decreasing the machine hours dramatically.
  • Minimize Slides and Side Action – Just as side actions and slides for undercuts increase the cost of a mold they also mean longer cycle times and more expensive parts.
  • Minimize Labor – Make a mold that runs automatically and does not require an operator.  Have a mold designed that will eliminate labor involved in secondary operations or by requiring 100% operator time at the machine. 
  • Go Generic – Use generic materials vs specific material grades for projects which do not require specific mechanical or chemical resistance requirements.
  • Don’t be so Picky – What aspects of your part really need cosmetic requirements?  Which dimensions are actually critical?  The more dimensions defined as critical and the more aspects of your part requiring a cosmetic finish the more expensive production will be.
  • Sub Gate or Try a Hot Runner System – edge gated parts need a secondary separation of the runner from the part.  Hot runner systems save this same secondary operation and material as they don’t produce a runner meaning less waste and lower material costs.
  • Avoid Thick Walls – one of the main areas to decrease cycle times is to ensure that your wall thickness is fairly constant and does not have any points where the walls thicken greatly.  Cooling is more than 50% of cycle time and thus thick walls mean long cycle times in order to allow the thicker walls to solidify.



If there is anything we have learned from our clients it is that cash flow during the initial stages of a project will most likely determine its success.  We have seen a few very successful methods for ensuring you will have the finances available to launch your product and we are going to list a few of our favorites here:

  1. Go Ahead and Start Taking Orders – the first successful method has been to go ahead and market your product and take pre-orders to adequately gauge interest.  There is no better way to prove there is a market for your product than to go ahead and sell them. Usually, pre-orders are offered to end consumers vs wholesalers or retailers, however, in some cases, retailers and wholesalers may offer you a limited trial. Usually, this means setting up some type of storefront either at a physical location or online.
  2. Don’t Forget Sales and Marketing – while design, prototyping, mold making, and parts production are very obvious and tangible costs of a new project, they will not bring cash flow nor will they create income on their own.  One of the forgotten costs of funding a new project is sales and marketing.  You will need to create a budget and put in a lot of sweat equity to get your project off the ground.  Be prepared for this investment and don’t assume your hard work will make up for a lack of a financial budget for marketing your product.  You will have significant costs in ensuring your parts are unique, and that they are selling.
  3. Secure some Outside Investment – one great way to obtain some early cash flow is to present your project to investors.  Having proof of sales and final iteration prototypes as well as all applicable patent documentation will help significantly.  In addition, have a plan as to how their investment in your product will pay off.  Any investor will want to know and may even define for you how they will receive a return on their investment.  Be flexible, but don’t give your business away.  Know the value of your product and project, not your dream numbers, know the actual value of your business in its current state.  Have a detailed account of your assets, your expenses, and your budgets for sales and marketing as well as parts production.  Know your market and the legitimate resale value of your product to a wholesaler and to a retailer, not just the price to the final consumer.


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