Casting Cost Model Enhancements
aPriori 2021 R1 provides various enhancements to the Investment Casting and Die Casting cost model:
Casting cost model now supports Titanium materials
The Investment Casting cost model now supports estimating the costs of parts made from Titanium materials and provides a new Chemical Etching process required for these part types.
For titanium materials, an additional process Chemical Etching is required to remove the hard, brittle alpha case layer which forms during the casting process. This process is included automatically in the Investment Casting routing for titanium parts. In this process, parts first are cleaned, then loaded into baskets which are submerged in chemical etching tanks for a sufficient time to remove the calculated or specified depth of the alpha case layer. Parts are rinsed in the tank, then removed from the basket and dried. Finally, the part depths are inspected to ensure that the alpha case layer has been sufficiently removed.
The part cleaning, drying, and depth inspection are modelled as bench operations. The chemical etching process machine selection criteria includes ensuring that the parts will fit inside the selected tank. The size of the bench required for cleaning, drying, and depth inspecting is determined dynamically based on the part size and is accounted for in determining indirect overhead charges for the bench space.
The depth of the alpha case layer is calculated based on the part’s average thickness. The chemical etching cycle time is computed based on an etching rate (depth of material removed per unit time). Process setup options Alpha Case Layer Depth and Chemical Etch Rate are provided to override the calculated values for the case layer depth and the etching rate, respectively.
The Regional Data Libraries for the Casting - Investment process group now include two titanium materials ‘Titanium, Cast, Ti-6Al-4V’ and ‘Titanium, Cast, Titanium Grade 2’.
Investment Casting Tooling cost estimates account for Tool Life
Tool Life calculations were added to the Wax Pattern Molding, Ceramic Coring, and Soluble Wax Coring processes in the Investment Casting routing, accounting for the cost of replacing tools due to wear when needed.
The Tool Life is defined as the number of parts that can be produced with the tool before it needs replacing due to wear. Previously one tool always was assumed to be sufficient for each of these processes. Tooling cost estimates for Wax Pattern Molding, Ceramic Coring, and Soluble Wax Coring now each include the cost of multiple tools if needed to manufacture the specified production volume. For each process, Tool Life is determined by assuming a default value for the number of shots per tool, then adjusting this value based on the tool material type, the tool coating type, and the number of cavities. Due to this enhancement, the estimated number of tools required to produce a given part at a given production value may increase, compared to the previous release of aPriori. If this occurs, Tooling Cost and Fully Burdened Cost will increase as a result.
Improved extraction of Inner Diameter (“RingedHole”) geometry for Castings, Forgings, Machined parts and more
aPriori has updated how it extracts GCDs which represent the “inner diameter” (ID) features of parts made by near-net-shape and/or machining processes, to improve how that geometry is displayed in the aPriori viewer and to more accurately calculate the material volume removed, cycle time, and cost for machining that ID geometry.
Some similar work was done previously in the aPriori 2020 R1 release for just the Stock Machining, 2-Model Machining, and Bar and Tube Fabrication process groups. This newer enhancement extends and replaces that earlier work, and applies also to the Casting-Die, Casting-Sand, Casting-Investment, Forging, Powder Metal, and Additive Manufacturing process groups. As a result, the assigned operations and computed cycle time for ID geometry may differ somewhat from previous releases. There are several aspects to this enhancement:
• For castings and forgings, the RingedHole GCD now better represents the ID volume. Previously for these commodities, the walls of RingedHoles did not completely follow interior walls which were slanted (conical) or curved (toroidal) and instead were approximated as cylinders. For large parts with large features, this could result in the volume of the RingedHole GCD being significantly different than the corresponding removed volume on the actual part, resulting in inaccurate cycle time estimates for machining operations assigned to those volumes. (Note that this aspect of the enhancement already was implemented in aPriori 2020 R1 for parts cost in the Stock Machining, 2-Model Machining, and Bar & Tube Fabrication process groups).
• By default, for all process groups, ID geometry now is extracted consistently. The way the ID geometry is extracted depends on the primary or secondary machining process included in the routing:
o If machining is performed with a turning (lathe-based) process, A RingedHole is used to represent rotationally symmetric, interior volumes of the part. A RingedHole is a compound GCD which consists of a central through-hole or blind hole (extracted as a SimpleHole GCD), surrounded by one or more Ring GCDs which represent enlargement of the central hole.
o If machining is performed with a milling process, the interior geometry will be extracted as a set of MultiStepHole and/or SimpleHole GCDs
The site variable createRingedHoleMCD can be used to extract ID geometry differently by process group, if desired. See following paragraph.
• The site variables available for controlling how ID geometry is extracted were updated. The process group site variable createRingedHole has been deprecated. (It was introduced in aPriori 2020 R1 for the Stock Machining, 2-Model Machining, and Bar & Tube Fabrication process groups only). Instead, customers should use the site variable createRingedHoleMCD in the Machining process group. This site variable existed in previous releases (but had no impact in aPriori 2020 R1). Now this site variable is once again used to control ID geometry extraction, and the names of the possible values have been updated for clarity, as this table shows:
| | |
ALL (Default in aPriori baselines) | For all process groups, ID geometry will be extracted as a RingedHole GCD – which contains a central SimpleHole and one or more Ring GCDs which surround it | For all process groups, ID geometry will be extracted as a series of SimpleHole and/or MultiStepHole GCDs |
NONE | For all process groups, for both turning and milling routings, ID geometry will be extracted as a central SimpleHole with and optionally one or more RingGCDs which surround it; these are top-level GCDs and do not have a parent RingedHole |
Net Shape Only | For “net shape process groups” (Casting, Forging, Additive Manufacturing), result is same as that for “ALL” above. For non-net shape process groups (Stock Machining, 2-Model Machining, Bar & Tube), result is same as that for “NONE” above |
(Improved Display of Part Thickness via Design to Cost Thickness Dialog
Based on customer feedback, aPriori has improved how it displays Design to Cost feedback about the thickness of plastic injection molded parts and castings to make it easier to identify where part thickness violates recommended minimum or maximum values.
Accessibility Visualization for Undercut Features
For plastic injection molded parts, die castings, and investment castings, aPriori now provides visual feedback concerning the accessibility of undercut features, to help expert users better understand aPriori’s automated tooling and side-action determination.
For castings, tooling side actions (slides and cores) are required to make geometry which is undercut with respect to the draw direction.
For more information about this enhancement, please refer to
Accessibility Visualization for Undercut Features.