Surface Treatment Enhancements

aPriori 2022 R1 provides these enhancements to the Surface Treatment cost model:

New Black Oxide Coating cost model

aPriori 2022 R1 introduces a new cost model for the Black Oxide surface treatment process.

Black Oxide is a surface treatment achieved as the result of a chemical conversion coating process when a ferrous material (or copper) is submerged in a black oxide solution bath. There are five distinct processing steps to achieve the Black Oxide surface treatment. The part is first cleaned, then rinsed, then submerged in a black oxide solution bath, after which the part is rinsed, and finally submerged in a supplementary finish such as an oil bath to protect the black oxide surface.

Black Oxide coating is used in many industries as it reduces light reflection, helps reduce corrosion and friction, and helps maintain the sharpness of components such as machine tools. It is ideal for small parts as the process can be done in large batch sizes and the impact on part dimensionality is minimal. In general, the process is cheaper than similar anti-corrosion surface treatments such as painting or electroplating.

There are seven process setup options that enable users to modify the default settings for the process. Number of Nested Parts, which computes the maximum number of parts that can be nested within the black oxide solution bath and is limited by either batch weight or part size. The Black Oxide Solution process setup option allows users to specify a branded black oxide solution with either low, medium, or high temperature applications. The Black Oxide process’s tool shop contains data for the branded solutions including the cost per liter, the soak time, and the solution temperature in the Digital Factory Manager. The remaining five process setup options all pertain to the cycle time of the five processing steps and enable users to override default cycle time values: Soak Time for the Part Cleaning Stage, Pre Black Oxide Rinse Time, Black Oxide Time, Post Black Oxide Rinse Time, Supplementary Finish Time.

By default, aPriori considers the Black Oxide surface treatment to be feasible for parts made from ferrous and copper materials and infeasible for other material types. Feasibility for a specific material type can be configured easily using the lookup table tblConversionCoating. If users apply the process to assemblies, aPriori does not consider the material of the assembly’s sub-components.

Updated Shot Blast cost model

aPriori 2022 R1 provides an updated Shot Blast process in the Surface Treatment process group.

Shot Blast is a mechanical cleaning process that uses small, typically spherically shaped media to abrasively clean part surfaces. Multiple updates were made to the existing Shot Blast cost model to make it more mechanistic and consistent with the Conveyer Abrasive Finishing process introduced in aPriori 2021 R1.

This cost model now offers two new process setup options.

The option Shot Blast Media allows the user to select one of six shot media: Aluminum Silicate, Calcium Silicate, Iron, Garnet, Glass Bead, or Steel. Each shot media is compatible with specific materials as defined in the lookup table tblShotBlast. aPriori accounts for the cost of periodically replacing the shot media, based on cost and attrition rate data provided in the Shot Blast tool shop in the Digital Factory Manager.
The option Number of Parts in the Batch allows the user to override aPriori's estimate of the number of parts in the batch (the greater of the specified scenario batch size or the number of parts that fit on the shot blast hanger, as limited by the machine’s batch weight limits).

The process cycle time was updated to account for a handling time as well as a non-handling time. The handling time includes loading parts onto a hanger, loading the hanger onto the machine and any reorientation time if required. The non-handling time includes the blast cycle time multiplied by the number of shot blast cycles within the machine blast chamber. Note that aPriori accounts for the complexity of the part geometry using a ratio of its surface area to volume; more complex parts require longer blast cycles to ensure that internal or partially obscured surfaces are accessed.

Two new machine selection criteria were added to ensure that the part(s) being shot blast can fit inside the machine blast chamber and the batch weight does not exceed the machine’s weight limits. The aPriori Regional Data Libraries 2022-02 include four new branded hangar-type shot blast machines alongside two virtual machines.

Finally, the Shot Blast process now supports including multiple instances of the shot blast process to account for situations where more than one shot blast media are required in order to abrasively clean the part surface -- for example, an initial shot blast using steel media followed by a second shot blast instance using glass bead. The default behavior is to include one shot blast instance when the process is added to the routing, but this can be configured using the shotBlastInstances lookup table. Users also can modify, on a part-by-part basis, the Number of Occurrences of the Abrasive Shot Blast node in the Routing Selection window.

Due to these enhancements to the Shot Blast cost model, there will be changes in estimated cycle time and cost for the process, compared to the previous release of aPriori. In a set of diverse test parts, the cycle time for every part reduced. The average reduction in cycle time was 78%. This reduction is explained by both the updated cycle time calculation logic and especially the batching of parts within a hanger shot blast machine, meaning that the amortized cycle time per part is significantly reduced. Additional Direct Cost increased very slightly (less than 1% on average) due to the accounting for the price of shot media. The Shot Blast piece part cost reduced for all parts by an average of 55%.

Updated Powder Coat Cart cost model

aPriori 2022 R1 provides an updated Powder Coat Cart cost model in the Surface Treatment process group.

Powder Coat Cart painting is a dry painting process in which an operator discharges powder paint through a gun nozzle and electrostatically coats a surface, after which the part is oven cured. Multiple enhancements were made to the previously-available Powder Coat Cart cost model, to model the various steps involved in this surface treatment process more explicitly and mechanistically. As part of these improvements, the Mask-Bench process also was updated, and a new Oven Cure process was created in the Surface Treatment process group.

Powder paint data and default properties are defined in the process's Tool Shop. Powder Coat Cart now provides nine process setup options to give users greater control over the specifics of their powder coat painting.

Top Coat Powder allows users to specify color options with different finishes: matte or gloss.
Top Coat Thickness allows users to specify the effective thickness of powder paint applied to the part prior to oven curing. By default, aPriori assumes a top coat thickness of 60 microns, which is stored in the process’s tool shop within the Digital Factory Manager alongside other powder paint data. Note that the paint thickness does not impact the oven cure times, but does affect the cost.
Top Coat Powder Flow Rate specifies the rate at which the top coat powder is discharged from the powder gun.
Clear Coat Powder is a clear coat application and is included by default. If users do not want a clear coat application then they can select the “Do Not Apply a Clear Coat” value for the process setup option. The default behavior can be modified by changing the default clear coat application in the tool shop.
Clear Coat Thickness and Clear Coat Powder Flow Rate work similarly to the analogous process setup options for top coat.
Fraction of Part Area that is Powder Coated is calculated as one minus the fraction of the part that is masked, which is calculated within the Mask-Bench process if included (and can be controlled by the process setup option Fraction Part Masked). Otherwise, the Fraction of Part Area that is Powder Coated defaults to the cost model variable defaultFractionOfSurfaceAreaPowderCoated, which is set to 1 in starting point Digital Factories.
Number of Parts Per Cart is calculated as the greater of the number of parts that fit on the cart as limited by either part size or weight; if the batch size is less than this number then the number of parts equals the batch size.
Number of Powder Guns by default is set to the number of guns available for the selected machine (booth). The machines in the starting point Digital Factories have either one, two, or three guns available based on the size of the booth, and the number of operators matches the number of guns. This option allows the user to change the number of powder guns on a part by part basis if desired. Note: If the user changes the number of powder guns he/she also should change the number of operators to the same value, using the Formula Dependencies capability.

The Mask-Bench process now is applied automatically to threaded holes, using either a silicone plug or masking tape depending on the hole diameter. Holes smaller than the starting point value of 65mm (as specified by the cost model variable maskBenchMaxPlugSize) are plugged with a silicone insert and threaded holes larger than 65mm are masked using tape. The masking method selected for a hole can be changed by the user if desired. Additionally, Mask-Bench has two new process setup options:

Number of Plugs Used displays the number of plugs used for all holes on the part and allows users to modify the value on a part by part basis.
Fraction Part Masked supports three modes:
- Manually Assigned calculates a percentage based on SimpleHole, ComplexHole, and surface GCDs that were explicitly assigned a Mask-Bench operation by the user.
- Non Painted Area (Assigned via Manual Paint) can be used if the user specifies a percentage of the part that is manually painted and is calculated as 1 – the fraction of the part that is manually painted. For example if 60% of the part was specified as manually painted, then 40% of the part is considered masked.
- The User Override mode accepts a value greater than 0 and less than or equal to 1.

Finally, a new Oven Cure process now is included automatically when Powder Coat Cart is included in the routing. The cost model assumes that parts are loaded onto the cart prior to powder coating and remain on the cart as it is moved between the Powder Coat Cart booth and the Oven. The Oven Cure cycle time drivers include the paint cure time, which considers whether both a top coat and clear coat were included, and the batch size, which represents the number of parts per cart. There are five new Oven Cure machines of varying internal dimensions to account for different part sizes and batch quantities.