Extrusions / Bar & Tube Fabrication Cost Model Enhancements
aPriori 2019 R2 provides a new Extrusions cost model for estimating the cost of parts made from custom aluminum extrusion profiles. It accounts for the cost of manufacturing the custom extrudates themselves, as well as the sawing, punching, and machining operations needed to remove material and any bending operations needed to produce the finished part. This initial release is intended for parts which have light-to-moderate amounts of material removal.
The Extrusions cost model is available from within the Bar & Tube Fabrication process group but is separately licensed. If you have licensed the Extrusions cost model, aPriori will recognize the part is made from extruded stock with a custom cross-section profile. (Specifically, the CrossSection GCD will have a Shape property value of “GENERIC_EXTRUSION.”) Without the license, aPriori simply will try to match the part against the various commodity bar & tube stock forms available in the Bar & Tube process group and will not recognize the part as being made from a custom extrusion profile.
The Extrusion routings in the aPriori baseline cost models include the following processes:
• Billet Preheat and Die Preheat – ovens for heating the billet and die respectively, before they are placed into the extrusion press
• Extrusion – this process includes all the operations and equipment sold with an Extrusions work center:
o Release Agent application – an acetylene torch is applied to the billet end to form a soot which helps prevent billet from sticking to the ram of the press
o Pressing of the raw billet stock through the extrusion die, via a traditional extrusion press
o Cooling of the extrudates as they emerge from the press, via either Standing Wave, Water Spray, or Air Spray quench tank
o Rough Cutoff – long sections of the cooled extrudates are cut off and then pulled down to the opposite end of a runout table to make way for more extrudates emerging from the press
o Clamping and Straightening – the long sections and clamped and pulled in order to straighten them and remove stress introduced by the forming or subsequent cooling operations
o Semi-Finish Cutoff – the extrudates are cut into shorter lengths (but not necessarily finished part length), to enable Racking of extrudates in preparation for Aging
• Aging – for strengthening the raw extrudates
• Secondary processing of the raw extrudate, including
o Band Saw, Circular Saw, and Reciprocating Saw processes for cutting extrudate to finished part length,
o Tube Punch, 3-Axis Router and 5-Axis Router for material removal
o Rotary Draw Bending, Compression Bending, and Bar Bend Brake processes if finished part is bent
o Optional surface treatment processes which may be included manually if desired
The cost model estimates Material, Tooling, and Process costs for producing the extrudates as well as secondary processing to produce the finished part from the extrudates.
• Material costs are computed based on the unit costs of round billet stock and account for three types of scrap produced by the extrusion process.
• Tooling cost is estimated based on the size and type of die required for the part (solid or hollow profile). Tooling Cost estimates also account for expected tool life; the cost of multiple dies will be included if the die is expected to fatigue before the specified production volume is produced.
• Extrusion process costs are based on extrusion process cycle time. The extrusion process cycle time is computed by determining a billet size, number of cavities, and ram speed which will result in the extrudates exiting the die within a recommended speed range for the selected material and maximizes material throughput for the various viable solutions.
A new Cutout GCD has been introduced for parts made from custom extrusion profiles. The Cutout GCD represents a volume of material which is removed either interior to the part or adjacent to an end of the part. This GCD was introduced in order to support more accurate estimates of the cycle time and cost of material removal operations, as it provides more information about the the accessibility of the geometry and applicable tool sizes than the ComplexHole GCD. Cutout GCDs may either be machined with a 3-Axis or 5-Axis CNC Router, or may be punched with a Tube Laser, depending on the size and location of the feature and various preference settings available as process setup options.
Note: for parts made from the standard commodity Bar & Tube stock forms, GCD extraction and routing assignments generally are unchanged in aPriori 2019 R2. Specifically, for parts made from standard commodity stock forms, Cutout GCDs will not be extracted and ComplexHole GCD still will be extracted. However, some small improvements were made and are described in the section
Issues Resolved in aPriori Professional below.
Note: Parts which have heavy amounts of material removal may be estimated more accurately by using the Extrusion cost model in conjunction with the 2-Model-Machining cost model. In particular, if the finished part is made from a custom extrusion such that the entire perimeter of the extruded profile has been machined away, aPriori will not be able to determine what the original extruded stock looks like by costing the finished part in isolation. Both the extrusion and machining cost estimates likely will be inaccurate in this case. To handle this case, you can cost a CAD model of the custom extrusion profile in the Bar & Tube process group, then use 2-Model Machining to cost the finished part, specifying the custom extrusion profile scenario as the “Source” scenario.
Please refer to the Known Issues and Workarounds section below for a description of some limitations in the initial release of the Extrusions cost model and workarounds. For more information about the extrusion cost model, please refer to Version 2019 R2 of the aPriori Cost Model Guide.