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Machining

Geometry or Cost Engine Changes that Could Impact Configured Digital Factories

The following changes might impact costing, even for Digital Factories that use earlier cost model versions.

  • NO IMPACT

Bug Fixes or Small Improvements to Prior Cost Model Versions

The following changes might impact costing for Digital Factories that use earlier cost model versions.

  • NO IMPACT

Cost Model Changes that don't Affect Configured Digital Factories

The following changes do not affect costings with Digital Factories that use earlier cost model versions. The changes are available only in the latest cost model version.

  • Tool Reach (impacts feeds, cut depths, and cycle times): In the previous release, aPriori determined tool length based on the length (along the tool axis) of the GCD being machined. In this release, for various milling operations, aPriori also takes into account the presence of obstructions near the GCD, and selects a tool length large enough to ensure that such features do not interfere with the tool holder. This applies to the following operations:

    • Side Milling of PlanarFaces and CurvedWalls
    • Rough Milling of Pockets, Slots, and SimpleHoles
    • Slot Milling of Slots
    • Perimeter Milling of Perimeters

    In addition, for these operations, aPriori now adjusts tool feed and cut depth based on the rigidity of the tool, in order to ensure that tool deflection is not too great (excessive tool deflection increases the risk of chatter vibration). Tool deflection is determined using a static-force model and is based on tool length, tool diameter, tool material, part material, and cutting parameters.

    Note:

    You can restore behavior of the previous release by setting the cost model variable defaultToolDeflectionAndHolderClearanceOverride to true. You can restore the previous behavior on a per-part basis with the setup option Tool Deflection And Tool Holder Clearance Override, provided by the Machining node in the Process Options Editor. These disable both consideration of tool holder clearance in the determination of tool length and the adjustment of material removal rates based on tool deflection.

    In a set of test parts, fully-burdened cost generally changed by between 0% and +5%. Across all parts, the average change in fully-burdened cost was around +1%. Among parts with increased cost (about half the parts), the average change in cycle time was around +4% and the average change in fully-burdened cost was around +2%. The maximum cost change observed (an outlier) was around +15%. In very rare cases, fully-burdened cost decreased slightly (by less than 1%), because operation assignment changed from Side Milling to Facing.

  • Maximum Length to Diameter Ratio for Side Milling (impacts feasibility and operation assignment): In the previous release, Side Milling was considered infeasible if the tool's length-to-diameter ratio exceeded 8, by default in starting point Digital Factories. This release changes the default ratio in starting point Digital Factories to 12. Administrators can customize the default with the cost model variable difficultL2DRatio. Users can override the default on a per-part basis with the setup option Specify Maximum Side Milling Length to Diameter Ratio on the Machining node in the Process Options editor.

    As a result of this change, some surfaces that were previously infeasible for Side Milling may now be assigned to Side Milling. Note however that a separate change increases tool length for some surfaces in order to provide tool holder clearance (see Tool Reach, above); the result may be that some surfaces remain or become infeasible for side milling, even with the increase in feasible length-to-diameter ratio.

    In a set of test parts, cycle time increased for about half the parts and decreased for about half the parts. On average, cycle time increased by around 5%. Note that the separate change that increases tool length sometimes decreases material removal rate (see Tool Reach, above), which may account for some cases of increased cycle time.

  • Grinding Operations (impacts operation assignment): In the previous release, if all other grinding operations were infeasible for a GCD, a General Grinding operation was assigned. In this release, General Grinding operations have been removed. In addition, for other grinding operations, feasibility rules have been strengthened to ensure that the GCD is accessible to the operation. As a result, some GCDs that previously were assigned grinding operations may now fail to cost.

    If a GCD fails grinding feasibility, you can check the Design Guidance tab to see why, and override feasibility checks if you think grinding should be considered feasible.

  • Number of Grinding Setups (impacts labor and overhead costs): In the previous release, aPriori assumed, by default, that each grinding process required only a single setup for a given part. Users could override the default and specify a number of setups with a process setup option.

    In this release, aPriori determines the required number of setups based on the part geometry and the types of tool access required for the assigned operations. A Grinding Setup node appears in the Manufacturing Process pane for each required setup; the children of each Grinding Setup node are the operations that use the corresponding setup. This applies to the following processes:

    • Cylindrical Grinder
    • Internal Grinder
    • Jig Grind
    • Reciprocating Surface Grinder
    • Rotary Surface Grinder For each process, the process-level setup option Number of Part Setups has been removed, and its setting is now ignored in scenarios from prior releases.

  • Grinding Setup Times (impacts labor and overhead costs): In the previous release, for the grinding processes mentioned above (see Number of Grinding Setups), time for part setup was based on part weight by default, and users could override the default with setup options that specified the time for the first setup and the time for each subsequent setup: First Part Setup Time and Subsequent Part Setup Time.

    In this release, time for part setup is still weight-based by default in starting point Digital Factories, but customizing or overriding the default has changed. By setting the new cost model variable partSetupTimeMethod to machineBased, administrators can customize the default and direct aPriori to use the time specified by the machine property Base Part Setup Time. Users can override the default on a per-part basis with the setup option Total Part Setup Time provided by each Grinding Setup node. Users can also specify the number of repetitions of a given setup with the setup option Repetitions of Part Setup.

    For each process, the process-level setup options First Part Setup Time and Subsequent Part Setup Time have been removed, and their settings are now ignored in scenarios from prior releases.