Process Cycle Time

For most machining processes, cycle time is the sum of the cycle times of the process’s child operations, together with tool indexing time and tool replacement time. VPE administrators can globally adjust process cycle times by specifying a value for the cost model variable cycleTimeAdjustmentFactor.

Cycle Time = Process Time * Cycle Time Adjustment Factor

Cycle time is the product of the following:

• Process time: unadjusted cycle time for the current process. See the formula below.

• Cycle Time Adjustment Factor: value of the cost model variable cycleTimeAdjustmentFactor. This is set to 1 in aPriori starting point VPEs. VPE administrators can change the cost model variable to globally adjust cycle times for machining.

Process Time = Child Operation Cycle Times + Tool Indexing Time + Tool Replacement Time

Process time is the sum of the following:

• Child operation cycle times: sum of the cycle times of all child operations (including setup operations) of the process. See Operation Cycle Time and Cut Time Calculations.

• Tool indexing time: total time required for tool indexing for all operations of the process. See the formula below.

• Tool replacement time: total time required for replacing worn out tools for all operations of the process. See the formula below.

Tool Replacement Time = Number of Worn Out Tools * Single Tool Replacement Time

Tool replacement time is the product of the following:

• Number of worn out tools: sum over all operations in the process (that use tools) of the tool life fraction for that operation—see Expendable Tooling Costs. For example, suppose a process has two child operations, and in one operation the tool is used for 10% of its associated tool life, while in the other operation the tool is used for 5% of its associated tool life; in this case the number of worn out tools is considered to be 0.1 + 0.05 = 0.15.

• Single tool replacement time: time required to replace a single worn out tool. This is the value of the machine property Time to Replace Dull Tool.

To remove tool replacement time from the cycle time calculation, set the cost model variable toolReplacementTimeSwitch to 0.

Tool Indexing Time = Number of Times a Tool Must Be Indexed * Single Tool Indexing Time /

Number of Parts in Pallet

Tool indexing time depends on the following:

• Number of times a tool must be indexed: sum of the tool counts of all the process’s setups. A setup’s tool count is the number of distinct tools used by the operations that use that setup. Tools are considered distinct if they differ with regard to either tool family or tool diameter. Note that this can sum to more than the process’s total number of distinct tools, since more than one setup might use the same tool. Indexing occurs for each use of a distinct tool by a setup.

• Single tool indexing time: time required for the current machine to index a single tool. This is the value of the machine property Index Time.

• Number of parts in pallet: see the PSO Parts in Pallet in Machining Process-level Options. aPriori assumes that once a tool is loaded into the spindle, the operations involving that tool will be performed on each part in the pallet before switching to the next tool, so the total tool indexing time is amortized across the total number of parts in the pallet.