User Inputs Affecting Overall Cost

The following process setup options affect overall cost:

Number of Operators (Piece Part Cost Driver)

This setup option affects cycle time, labor time, and labor cost – see Primary Direct Costs for Plastic Molding and Times for Plastic Molding.

This specifies the number of operators assigned to the Plastic Molding process (Compression Molding, Injection Molding, Reaction Injection Molding, or Structural Foam Molding).

By default, this value is specified by the Number of Operators machine property (located in the Digital Factory under Plastic Molding > Machines > [Plastic Molding process]). Typically, the default value is 0.5 for Injection Molding and Structural Foam Molding, 1.0 for Reaction Injection Molding, and 1.0-3.0 for Compression Molding.

With this setup option, users can override the default on a per-part basis. The minimum value must be greater than 0.1 (a value less than 1 indicates that an operator tends multiple parts of the process or multiple machines).

Colorant

(For Compression Molding, see Material Colorant.) Affects Addition Direct Costs in the cost taxonomy; see Other Direct Costs for Plastic Molding. Process Setup Options provide the following alternatives:

  • No colorant (default)

  • Colorant at standard rate (0.75 USD/kg, specified as a cost model variable)

  • Colorant at user-defined color charge

Material Regrind Allowance (%)

(Piece Part cost driver; not applicable to RIM or Compression Molding.) Specifies the percentage of melt using reground runners and scrap. The cost model assumes that no material cost is incurred for reground material. See Material Cost and Material Utilization.

The material property Can Regrind specifies which Plastic Molding materials can be reground. Digital Factory Managers can edit these values (under Plastic Molding > Materials) to restrict certain resins from applying regrind. This could be necessary, for example, because of the potential impact to part quality, or because of material properties that could cause damage to the regrinding machinery (for example, resins with a high glass fill percentage). It could also be necessary due to contractual restrictions.

This setup option provides the following alternatives:

  • Max regrind available in process (up to max default design allowable regrind): this is the default value. If ‘Max default design regrind allowable’ (described below) is less than ‘Max regrind available in process’ (described below), aPriori uses the ‘Max default design regrind allowable’ value. Otherwise, aPriori uses the ‘Max regrind available in process’ value (described below).

  • Max default design regrind allowable: specified by the cost model variable defaultRegrindAllowance * 100. In starting point Digital Factories, defaultRegrindAllowance is 0.25.

  • Max regrind available in process: calculated as (Aggregate Scrap Geometric Volume / Aggregate All Parts Geometric Volume) * 100.

    • Aggregate Scrap Geometric Volume: see formula below.

    • Aggregate All Parts Geometric Volume: see formula below.

  • User override regrind: users can enter a regrind percentage (0% to 100%).

Note: aPriori Design Guidance will alert the user via a Potential Manufacturing Issue if the selected regrind allowance is higher than the calculated amount available from the process. The part can still be manufactured if sufficient regrind material from outside the process is available.

Aggregate Scrap Geometric Volume = (Input Volume Include Startup - Output Volume) * Part Volume + Input Volume Include Startup * Runner Volume

  • Input Volume Include Startup: calculated as (Input Volume + Startup Scrap Number of Parts):

    • Input Volume: the total number of parts that need to enter the routing at this process in order to obtain the desired Production Volume. See formula below.

    • Startup Scrap Number of Parts: calculated as (Scrap Time / Cycle Time):

      • Scrap Time: the amount of time during initial batch setup during which test parts are produced (and scrapped). Specified by a cost model variable:

        For Injection Molding: scrapTimeInMinutes_IM (15 minutes in starting point Digital Factories).

        For RIM: scrapTimeInMinutes_RIM (30 minutes in starting point Digital Factories).

        For SFM: scrapTimeInMinutes_SFM (30 minutes in starting point Digital Factories).

      • Cycle Time: the time for one complete cycle of the applicable machine to make a single part. See Times for Plastic Molding.

  • Output Volume: the number of acceptable parts at the end of the entire part routing. It is calculated as (Annual Volume * Production Life), both of which are specified in the Production Scenario screen of the Cost Guide.

  • Part Volume: the part Volume property, extracted from geometry (visible in the Geometric Cost Drivers panel).

  • Runner Volume: see Runner System Model.

Input Volume = Total Production Volume + Number of Scrap Parts + Number of Scrap Parts Down Stream

  • Total Production Volume: as described above.

  • Number of Scrap Parts: the number of parts discarded as scrap during this process. Scrapped parts include damaged, broken, or out-of-tolerance parts. See formula below.

  • Number of Scrap Parts Down Stream: the number of parts (if any) scrapped by downstream processes (that is , by processes later in the routing than the current process). Scrapped parts include damaged, broken, or out-of-tolerance parts.

Number of Scrap Parts = ((Output Volume + Number Of Scrap Parts Down Stream) / Good Part Yield) - (Output Volume + Number Of Scrap Parts Down Stream)

  • Output Volume: as described above.

  • Number Of Scrap Parts Down Stream: as described above.

  • Good Part Yield: specified by the machine property Good Part Yield.

Aggregate All Parts Geometric Volume = (Part Volume + Runner Volume) * Input Volume Include Startup

  • Part Volume: as described above.

  • Runner Volume: see Runner System Model.

  • Input Volume Include Startup: as described above.

Part Eject Method

(For Compression Molding, see Part Ejection Method.) By default in starting point Digital Factories, the part eject method is Gravity. You can customize the default with the cost model variable gravityEject. You can override the default on a part-by-part basis with this setup option. Specify Gravity or Robotic. The eject method affects part removal time, as well as mold open and close time. See Times for Plastic Molding.

Local Mold Temperature Increase

Specifies an amount by which to increase the mold temperature for the purpose of calculating cool time – see Times for Plastic Molding. This can be used to account for localized temperature increases in mold regions that cannot accommodate cooling channels (for example, regions with closely-spaced ribs). Cooling channels are typically at least 6 mm in diameter.

By default, this increase is 0. Administrators can customize the default increase (0) with the cost model variable defaultMoldTemperatureIncrease. You can override the default on a part-by-part basis with this setup option.

Nominal Wall Thickness

(For Compression Molding, see Nominal Wall Thickness.) This specifies the nominal wall thickness of the part. It affects calculated cooling time (see Times for Plastic Molding). Process Setup Options provide the following alternatives:

  • Value derived from GCDs (default – see Nominal Wall Thickness).

  • User-defined value; the minimal value is 0.1 mm.