Injection Molding Cost Calculator Use Instructions

This cost calculator is provided to assist you in estimating the manufacturing costs for plastic injection molded parts. The estimated total cost can be used for budgetary purposes during your project planning and part design. It should be noted these plastic part costs are only estimates. Actual costs can only be obtained by submitting final CAD files and production control drawings to a molder. Determining accurate costs for Injection molding production technology is complicated by all the variables highlighted below:

This molding cost calculator is strictly limited to material cost and processing cost. The calculator has been specifically simplified so you can quickly determine a ballpark plastic part cost for an injection molded part. Actual production plastic molded costs will be affected by many other parameters, including:

• Number of inserts – inserts always increase the part cost. They can be inserted during the molding cycle or as a post-molding secondary operation. The added costs for inserts depend on the molder, insert, method of insertion, number of inserts, tolerances, and special requirements.
• Post decorating operations include silk screening, pad printing, laser etching, hot stamping, and application of labels. The added cost for these operations depends on many variables, including the number of colors, size, and complexity.
• CNC machining – Injection molded parts can require a post-molding machining operation. Added costs for post-machining depend on the material, part geometry, number of machining operations, tolerances, and overall time.
• Mold Pricing – Mold cost should also be a consideration in determining part cost. Tooling cost is typically amortized within a number of parts for a period of time. This cost has not been included in this cost estimator because of the wide ranges of mold cost, quality and lead time.
• Unique QC specifications – injection molded parts may require special post-molding inspection operations, testing and verification. The added costs of these operations can significantly increase part costs.
• Tolerances – Tight tolerance parts will always be more expensive than injection molded parts with less critical tolerances. Injection-molded plastic parts with tight tolerances are often molded in longer cycle times, more costly molds, and more expensive molding machines.
• Painting – Injection molded parts requiring a painted finish could cost more than twice that of an unpainted part. Paint costs are dependent on production order size, paint cost, method of application, and special masking.
• Your molder – Costs for all of the previously mentioned post-molding operations will significantly vary from one molder to the next. It is impossible to provide a “standardized” cost for any of these operations, which are highly dependent on the specific molder’s business model and infrastructure.

If all these additional line items were included in the calculator, it would be too complicated, time-consuming, and inaccurate. The estimated cost determined by this calculator will increase with additional specifications.

For example, paint could double the part cost. The addition of inserts could add as much as $1.00 per insert. Post decorating such as pad printing and post-machining operations will also increase the per-unit price.

Material Cost

• A limited list of standard resins has been included in our pull-down menu. If your resin is not listed, you can enter the material density manually.
• Since material prices are highly volatile, dependent on order size, color, and specific grade, an accurate cost per pound cannot be provided. You must, therefore, manually enter the material cost per pound.

Processing Cost

• Processing cost is essentially based on the hourly rate of the molding machine and the cycle time to mold each part. Hourly rates for larger presses are generally more expensive than smaller ones. As previously stated, many other manufacturing parameters will affect the final molded part cost. However, basic molding costs per part can be estimated based on the hourly rate divided by the number of parts molded per hour.
• Injection molding presses are sized according to shot size and clamping tonnage. This calculator is based on 3 tons/in2 of the projected area of the part. This is an average clamp force for most resins. Actual clamping force may vary between 2 to 5 tons/sq.in. based on material, wall thickness, and shot weight.

The projected area is determined based on a shadow of the part vs. the actual surface area of the part as shown in figure 1. Therefore, all that is required is a rough estimate of the projected area as shown.

• Estimating Cycle Time: Cycle time is dependent on many factors including wall thickness, cams in the mold, molded-in inserts, tool design, tolerances and material.
• Cycle times can range from 1/2 sec. to 5 mins for larger structural parts with thick wall sections. Most parts are molded within a 20 sec to 60 sec cycle time.
• You can experiment with different cycle times to see how it will affect your part cost or start with a 45 sec. cycle time to begin your estimate.