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Multi-Spindle 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.

  • Load Balancing Improvement: Operation Splitting (can impact cycle time): In the previous release, aPriori assumed a single rough turning operation on a single GCD must occur entirely on a single spindle. For parts that include GCDs with relatively high-cycle-time roughing operations, this prevented an approximately even distribution of operation cycle times across spindles, resulting in an overestimation of part cycle time. In this release, aPriori automatically splits some types of operations into multiple distinct, shorter-cycle-time operations which can be assigned to different spindles in order to balance the load.

    As a result of this change, cycle time estimates decrease for parts with operations that have long cycle times and are of the following types:

    • Pecking and Drilling of SimpleHole GCDs
    • Rough Turning of Ring GCDs

    The amount of decrease depends on the specific feature geometry and the number of spindles on the selected machine. In a set of test parts, over 70% had GCDs whose roughing operation is now subdivided among multiple spindles. Cycle time decreases ranged between 25% up to 44% for these test parts, with the largest decreases observed on 8-spindle machines.

    Note:

    To restore the behavior of the previous release and disable operation splitting, modify the lookup table tblMultiSpindleOpSplittingThresholds in the Machining process group: Change the value of each cell in the column Enable Operation Splitting to false.

  • Number of Operators(affects labor time and labor cost): In the previous release, aPriori assumed one operator per CNC Multi-Spindle machine or CNC Turning Center machine. In this release, aPriori assumes 0.25 operators per machine for 6- and 8-spindle machines, and to 0.5 operators per machine for 2-spindle machines. As a result, labor costs decrease by 75% and 50% respectively, compared to the previous, early-adopter release. Fully burdened cost decreases by between 5% and 10%.

  • Part-size Limits for Large Virtual CNC Multi-Spindle Machines (can affect machine selection, labor costs, and overhead costs): This release updates the Large size virtual CNC Multi-Spindle machines in the aPriori RDLs to reflect the fact that this class of machines can make somewhat larger parts than previously reflected.

    The maximum part length limit for the Large Virtual 6- and 8-spindle machines has been increased to 205 mm (about 8 inches) from the previous value of 120mm (4.72 inches). The maximum workpiece diameter limit for the Large Virtual 6 and 8 spindle machines has been increased to 90 mm (about 3.5 inches) from the previous value of 50 mm (about 2 inches)

    As a result, these machines may now be selected for some parts that were previously assigned a Virtual CNC Turning Center machine. Labor and overhead costs may change as a result.

  • Feasible Recommended Spindle Speeds for Simultaneous Operations: In the previous release, aPriori allowed two operations with fairly disparate recommended spindle speeds to occur at the same time, on the same spindle. In some cases, this resulted in assumed spindle speeds that were too high. In this release, by default, two operations are allowed to occur at the same time and on the same spindle only if their recommended spindle speeds differ by no more than 10%. This is true for both automatically computed and user-specified spindle speed values. Administrators can customize the threshold with the cost model variable spindleRPMPercentageDifferenceLimit in the Machining Process Group.

    Since there are now tighter constraints on simultaneous operations, part cycle times may increase compared to the previous release. In a set of test parts, cycle time increases were modest for the majority of parts; only 15% of parts had increases of more than 10% on 6-spindle and 8-spindle machines and 23% of parts had increases of more than 10% on 2-spindle machines. For the parts with larger increases, average increases were on the order of 25% or less, but in isolated cases larger increases were seen, especially for 2-spindle machines.

See also changes in the Machining process group.