Understanding the Cost of Injection Molding
MSI Mold
There is no universal answer to this question. A small and simple mold could cost you around $3,000 while a larger, more complex mold could cost over $100,000. What’s important to remember is that these numbers are not correct estimates.
When estimating the total cost of your plastic injection molding project, there are several factors you need to keep in mind.
In this comprehensive guide, we’ve broken down these various cost factors. Keep reading to learn more.
First, it’s important for you to know that the various costs involved in plastic injection molding can be broken down into two categories: 1) the one-time cost for injection mold tooling and 2) the cost of manufacturing your production parts.
The most significant factor that determines the initial mold tooling cost is the complexity of the part that is being produced. Plastic injection molded parts with a lot of sharp corners, thin ribs, or undercut features will generally be more expensive to make tooling for.
If the locations of sharp corners prevent the use of a round cutter for machining the mold features, they will require a secondary machining process called EDM machining (electrical discharge machining). Likewise, rib features that require machining deeper than 1/2 inch and thinner than 1/16 inch into the mold can also require secondary EDM machining.
Undercut features on plastic part designs will always increase the cost of the plastic injection molds. Undercuts force costs into the mold design time and machining time. They can also sometimes require the molds overall size to become larger to accommodate the space needed for the “side actions” (moving parts) that form the undercut features.
There is a wide variety of injection mold construction methods for different part shapes, and many different reasons why they all have a place at the table in the injection molding industry. But, you can simplify these methods into two groups: “Insert molds” and “free standing molds”. Click here to learn more about each type.
From a general cost point of view, insert style molds will cost significantly less than free standing molds.
Within a mold’s construction, there are many different styles of side actions that are used to release plastic parts with undercuts during the part ejection process. The lowest cost side action method, and used by many of our competitors, is frequently called a “hand load” in our industry. Hand loads are loose parts of the mold that get ejected from the mold along with the part, are manually removed from the part, then re-inserted into the mold every molding cycle.
Hand loads are a low-cost tooling option to deal with undercut part features in the mold, but they increase part cost and can lead to inconsistent part quality. At MSI. we prefer to use “automatic” side actions in our molds because they allow for a faster and more consistent injection molding process, which then gives our customers better parts for a lower cost.
Injection molds with automatic side actions do carry a higher cost to make than hand load molds, but for any production quantities higher than a few hundred pieces. the payback in part cost savings will generally wash out the added overhead cost.
The number of part cavities within the mold will directly affect the price of the mold. Parts that only require a low quantity of parts per customer order will be constructed as a one cavity mold to produce only one part per machine cycle, and parts with a high quantity of parts per customer order might be constructed as a two, four, or eight cavity mold producing several parts per machine cycle.
Multi-cavity molds will certainly cost more than single cavity molds, however, keep in mind that part pricing will have an inverse relationship to mold cost when considering mold cavitation and a projects total overall cost.
The size of a plastic part is directly related to the mold size that is required to produce the component. Larger molds require larger amounts of building space, larger and more expensive CNC machinery and equipment to work on them, etc.
However, in some cases there can be some crossover of the cost-to-size relationship. For example, a small injection mold with a very complex design can sometimes cost more than a larger injection mold with a very simple design.
So, when estimating the total tooling cost, keep in mind: the complexity of the part you want to create, whether you want an insert mold or free standing mold, how many cavities you need, and the size of your part. Please keep in mind that this is just one cost. As previously mentioned, there are two costs associated with plastic injection molding: the tooling cost and the actual production cost.
Now that you better understand tooling costs, let’s break down what’s involved in producing your component after the mold has been made.
The plastic material selection you make for your plastic part is not only critical to the part’s function, but also plays a huge role in its cost to manufacture. Raw plastic material cost can range in price from $1 per pound to $25 per pound. So, care should be taken in plastic part design to minimize weight when possible.
Choosing the correct plastic type can also help you achieve faster cycle times or production rates of your parts. For small parts, the cost of the material has a small effect on the unit price and the production rate has a large effect. On larger, heavier parts, the cost of the material has a large effect on the unit price along with the production rate.
When estimating this cost, keep this equation in mind:
Material Part Cost = Plastic Material Price x Part Weight (lbs)
“Cycle time” is a term used in our industry for both injection molding and CNC machining. In simple terms, it is the amount of time required for a machine to complete one production cycle. The total injection molding cycle time is made up of the following steps:
Let’s start with the machinery and equipment. Today’s high-tech servo driven injection molding machinery is very expensive. The tonnage size rating of the machine and its surrounding support equipment will determine the overall capital investment required to run production. Small tonnage machine sizes are used for running small molds and small parts, and large tonnage machines are needed to run large molds with large parts.
Even a small injection molding machine along with its support equipment will cost near $100,000 and very large machines will cost millions of dollars. It also follows that the machinery has a finite effective lifecycle because it wears out and also loses its advantage to newer technology over time. Knowing the cost being the capital investment in machinery divided by its effective lifecycle, it’s easy to understand that translates into an hourly operational cost of ownership of the equipment.
Secondary to the capital equipment costs discussed above would be a combination of fixed and variable costs, including the rent on manufacturing space, electrical power usage, etc. Through simple math, these costs are also very easy to drill down into an hourly operational cost.
The sum of all non-material related hourly costs combined and calculated out with a profit margin will become what is known as “machine rate” in our industry.
Finally, here is how the simple non-material related cost of an injection molded part is determined by cycle time:
The number of units produced per hour = (3600 sec / cycle time sec) x number of mold cavities
Non-Material Part Cost = Machine Rate per hour / # of units produced per hour
Since machine rates are all very competitive across the injection molding industry, cycle time and number of cavities in the mold are two significant determining factors in the total cost of a plastic molded part.
Commonly requested items like the following can increase the cost of injection molded parts:
To better estimate the total production costs, you must first understand what type of material you’re using and how much (in pounds) you need to produce your part. Next, you’ll need to factor in the cycle time, equipment costs, facility rental fees, electricity, and post-production packaging.
Are you looking for a plastic injection molding company in Michigan? Contact our experts at MSI Mold today! We offer free estimates and can help you better understand what type of materials are best suited for your specific component.
