Investment Casting Machine Selection

Investment Casting machine selection is covered in the following sections:

Conveyor Abrasive Finishing Machine Selection
Ceramic Core Making Machine Selection
Ceramic Leaching Machine Selection
Flash Fire De-Waxing Machine Selection
Metal Pouring Machine Selection
Mold Burnout Machine Selection
Mold Preheating Machine Selection
Primary Slurry Dipping Machine Selection
Secondary Slurry Dipping Machine Selection
Soluble Wax Core Making Machine Selection
Soluble Wax Leaching Machine Selection
Steam Autoclave De-Waxing Machine Selection
Wax Pattern Molding Machine Selection

Ceramic Core Firing Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per part. Overhead rate per part is the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.

A machine is considered feasible if its usable space is big enough to accommodate each of the part’s ceramic cores (that is, each of the part’s core’s that is assigned to Ceramic Core Making):

Core length fits: machine’s usable length is no less than the length of any ceramic core.
Core width fits: machine’s usable width is no less than the width of any ceramic core.
Core height fits: machine’s usable height is no less than the height of any ceramic core.

Machine usable length, width, and height are determined based on allowance (25.4mm in starting point Digital Factories) that is added all around the core:

Machine usable length: machine length minus twice the allowance
Machine usable width: machine width minus twice the allowance
Machine usable height: machine height minus twice the allowance

The allowance is specified by the cost model variable nestingAllowance_perimeter_ceramicCoreFireOven (25.4mm in starting point Digital Factories).

Machine length, width, and height are given by the largest, second largest, and smallest of the machine properties Bed Length, Bend Width, and Bed Height, respectively. Similarly, core length, width, and height are the largest, second largest, and smallest dimensions of the core, respectively.

aPriori selects only from preferred machines, if there is a feasible preferred machine and the cost model variable usePreferredMachines is set to true (the default in starting point Digital Factories). If there is no feasible preferred machine, or if the cost model variable usePreferredMachines is set to false, aPriori selects from all machines. A machine is preferred if the machine property isPreferred (typically displayed as Is Preferred) is true.

Ceramic Core Making Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per part. Overhead rate per part is the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.

A machine is considered feasible if it is big enough to accommodate the largest ceramic core mold, including providing enough clearance to allow removal of the core from the mold:

Platen length check: machine property Platen Length is no less than the larger of mold length for the longest core and mold width for the widest core (see the formulas for Mold Length and Mold Width in Ceramic Core).
Platen width check: machine property Platen Width is no less than the smaller of mold length for the longest core and mold width for the widest core (see the formulas for Mold Length and Mold Width in Ceramic Core).
Daylight distance check: machine property Maximum Daylight is no less than the required mold clearance for any ceramic core. The required mold clearance for a core is the mold height plus the product of the following:
- Core height (the smallest core dimension)
- Value of the cost model variable ceramicCoreMoldOpenStrokeFactor (1.25 in starting point Digital Factories).

The mold height is the core height plus twice the value of the cost model variable moldBaseHeightMargin_ceramicCore (38.1mm in starting point Digital Factories).

Note: aPriori assumes that if the machine can accommodate each core in this way, it has sufficient clamp force for each core.

Ceramic Leaching Machine Selection

aPriori selects a feasible machine with a mixture of low overhead rate and large load size. In particular, aPriori selects the feasible machine with the smallest value for the product of the following:

Overhead rate: this is sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.
Number of required batches: this is the production volume divided by the maximum load size, rounded up to the nearest whole number of loads. The maximum load size is determined based on the following assumptions:
- In starting point Digital Factories, no part occupies an area that is within one inch of the top or walls of the leach tank. Administrators can customize the allowance with the cost model variable ceramicLeachingTankEdgeNestingAllowance (25.4mm in starting point Digital Factories).
- In starting point Digital Factories, parts occupy 80% of the remaining (after-allowance) tank volume. Administrators can customize the occupied fraction of remaining space with the cost model variable defaultCeramicLeachTankSpaceAvailableFactor (0.8 in starting point Digital Factories).

A machine is considered feasible if its usable space is big enough to accommodate at least one part:

Length check: machine’s usable length is no less than the part’s longest dimension.
Width check: machine’s usable width is no less than the part’s second-longest dimension.
Height check: machine’s usable height is no less than the part’s shortest dimension.

Machine usable length, width, and height are determined based on allowance (25.4mm in starting point Digital Factories) along the top and walls of the tank:

Machine usable length: machine Bed Length minus twice the allowance
Machine usable width: machine Bed Width minus twice the allowance
Machine usable height: machine Bed Height minus the allowance

The allowance is specified by the cost model variable ceramicLeachingTankEdgeNestingAllowance (25.4mm in starting point Digital Factories).

Flash Fire De-Waxing Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per tree. Overhead rate per tree is given by the machine overhead rate divided by the number of trees that fit in the furnace.

Machine overhead rate: sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate

Number of trees that fit in the furnace depends on the following:

Tree box footprint: product of tree box width and tree box depth; see Tree Box Dimensions.
Machine properties Bed Length and Bed Width.
Tree nesting allowance factor: fraction of the bed area (minus a perimeter allowance) occupied by trees, specified by the cost model variable nestingAllowanceFactor_tree_flashFireFurnace (0.85 in starting point Digital Factories). Higher values model tighter nesting.
Perimeter nesting allowance: space allowance all around the perimeter of the machine bed. No tree occupies space that is within the allowance of the perimeter. In starting point Digital Factories, this is set to 0, based on the assumption that the machine properties Bed Length and Bed Width reflect the dimensions of the usable bed area, and so already take into account the perimeter allowance required for proper airflow. Administrators can specify additional allowance with the cost model variable nestingAllowance_perimeter_flashFireFurnace (0mm in starting point Digital Factories).
Machine’s number of drainage cups: provides an upper bound on the number of trees in the furnace; the number of trees can be no greater than the value of the machine property Num Drainage Cups.

Note: A machine is feasible if at least one tree fits in the furnace.

Metal Pouring Machine Selection

Selects the smallest-capacity, feasible machine, where capacity is given by the machine property Furnace Capacity (specified in m3). A machine is feasible only if all the following hold:

Machine property Furnace Type matches the furnace type looked up by the material property Material Type in the lookup table tblFurnaceType.
Machine property Maximum Temperature is no less than the material property Pouring Temp.
Machine property Furnace Capacity can accommodate the material required for a single tree of parts (see below).

The mass of material required for a single tree of parts depends on the following:

Mass of material required for the parts in the tree: this is the product of the following: Number of Parts per Tree, part volume, and material density.
Gating efficiency: this is the fraction of the total material in the tree that is required for parts (as opposed to occupying the tree’s gating system). The mass of material required for a tree is the mass required for the parts in the tree (see previous bullet) divided by the gating efficiency. Gating efficiency is given by one of the following cost model variables:
- gatingEfficiency_small (0.5 in starting point Digital Factories): for parts with mass no greater than partMassThreshold_small (1.361kg in starting point Digital Factories).
- gatingEfficiency_medium (0.6 in starting point Digital Factories): for parts with mass greater than partMassThreshold_small (1.361kg in starting point Digital Factories) but no greater than partMassThreshold_medium (6.804kg in starting point Digital Factories).
- gatingEfficiency_large (0.7 in starting point Digital Factories): for parts with mass greater than partMassThreshold_medium (6.804kg in starting point Digital Factories).

Mold Burnout Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per tree. Overhead rate per tree is given by the machine overhead rate divided by the number of trees that fit in the furnace, where:

Overhead rate: sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate
Number of trees that fit in the furnace: depends on the following:
- Tree footprint: product of tree box width and tree box depth; see Tree Box Dimensions.
- Machine bed area: product of the machine properties Bed Length and Bed Width
- Perimeter allowance: specified by the cost model variable nestingAllowance_perimeter_burnoutFurnace (0.0 in starting point Digital Factories). This specifies the distance between the machine bed perimeter and its usable area. In starting point Digital Factories, this is set to 0, based on the assumption that the machine properties Bed Length and Bed Width reflect the dimensions of the usable bed area, and so already take into account the perimeter allowance required for proper airflow. Administrators can specify additional allowance with the cost model variable nestingAllowance_perimeter_burnoutFurnace (0mm in starting point Digital Factories).
- Nesting allowance factor: specified by the cost model variable nestingAllowanceFactor_tree_burnoutFurnace (0.85 in starting point Digital Factories). This specifies the fraction of the usable machine bed area that is assumed to be occupied by trees.

Note: A machine is feasible if at least one tree fits in the furnace.

Mold Preheating Machine Selection

Overhead rate: sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate
Number of trees that fit in the furnace: depends on the following:
- Tree footprint: product of tree box width and tree box depth; see Tree Box Dimensions.
- Machine bed area: product of the machine properties Bed Length and Bed Width
- Perimeter allowance: specified by the cost model variable nestingAllowance_perimeter_preheatFurnace (0.0 in starting point Digital Factories). This specifies the distance between the machine bed perimeter and its usable area. In starting point Digital Factories, this is set to 0, based on the assumption that the machine properties Bed Length and Bed Width reflect the dimensions of the usable bed area, and so already take into account the perimeter allowance required for proper airflow. Administrators can specify additional allowance with the cost model variable nestingAllowance_perimeter_preheatFurnace (0mm in starting point Digital Factories).
- Nesting allowance factor: specified by the cost model variable nestingAllowanceFactor_tree_preheatFurnace (0.85 in starting point Digital Factories). This specifies the fraction of the usable machine bed area that is assumed to be occupied by trees.

Note: A machine is feasible if at least one tree fits in the furnace.

Primary Slurry Dipping Machine Selection

aPriori selects the feasible machine that can accommodate the highest number of parts per tree (see Number of Parts per Tree). If two feasible machines can accommodate the highest number of parts per tree, the lower-overhead machine is selected, where overhead is the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.

A machine is feasible only if all the following hold:

Single pattern fits vertically: slurry tank working depth is no less than the sum of the following:
- Wax pattern dimension aligned with tree height--see Orientation of Wax Pattern in Tree)
- Cost Model variable runnerLengthAllowance (38.1mm in starting point Digital Factories). This is the length of the runner between the top of the wax pattern stack and the bottom of the pour cup.
- Twice the cost model variable singleGateHeigthAllowance (19.05mm in starting point Digital Factories), if the Pour Cup Orientation is centered and Gate Attach Location is top/bottom.
Slurry tank working depth is the product of cost model variable slurryTankSafetyMultiplier_depth (0.8 in starting point Digital Factories) and difference between machine property Tank Depth and machine property Horizontal Paddle Height.

Horizontal pattern fits widthwise: for panel trees (see Tree Type), slurry tank working radius is no less than the wax pattern dimension aligned with tree width--see Orientation of Wax Pattern in Tree.

For carousel trees (see Tree Type), slurry tank working radius is no less than the sum of the following:
- Wax pattern dimension aligned with tree width--see Orientation of Wax Pattern in Tree)
- Runner width (provided Pour Cup Orientation is adjacent): by default, this is the value of the cost model variable defaultRunnerWidth (38.1mm in starting point Digital Factories). Users can override default with the setup option Runner Width.
- Cost model variable gateLengthAllowance (25.4mm in starting point Digital Factories), provided Pour Cup Orientation is adjacent.
Slurry tank working radius is half the product of machine property Tank Diameter Less Vertical Paddle and cost model variable slurryTankSafetyMultiplier_diameter (0.8 in starting point Digital Factories).

Horizontal pattern fits depthwise: for panel trees (see Tree Type), slurry tank working radius is no less than the wax pattern dimension aligned with tree depth--see Orientation of Wax Pattern in Tree.

For carousel trees (see Tree Type), slurry tank working radius is no less than the sum of the following:
- Wax pattern dimension aligned with tree depth--see Orientation of Wax Pattern in Tree)
- Runner width (provided Pour Cup Orientation is adjacent): by default, this is the value of the cost model variable defaultRunnerWidth (38.1mm in starting point Digital Factories). Users can override default with the setup option Runner Width.
- Cost model variable gateLengthAllowance (25.4mm in starting point Digital Factories), provided Pour Cup Orientation is adjacent.
Slurry tank working radius: half the product of machine property Tank Diameter Less Vertical Paddle and cost model variable slurryTankSafetyMultiplier_diameter (0.8 in starting point Digital Factories).

Treebox fits depthwise: for panel trees, slurry tank working diameter is greater than tree box depth--see Tree Box Dimensions. Slurry tank working depth: product of cost model variable slurryTankSafetyMultiplier_depth (0.8 in starting point Digital Factories) and the difference between the machine property Tank Depth and the machine property Horizontal Paddle Height.
Tree box width (see Tree Box Dimensions) is greater than 0.
Tree box width (see Tree Box Dimensions) is less than slurry tank working radius. Slurry tank working radius is half the product of machine property Tank Diameter Less Vertical Paddle and cost model variable slurryTankSafetyMultiplier_diameter (0.8 in starting point Digital Factories).

Secondary Slurry Dipping Machine Selection

This process uses the machine selected by Primary Slurry Dipping Machine Selection.

Soluble Wax Core Making Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per part. Overhead rate per part is the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.

A machine is considered feasible if it is big enough to accommodate the largest wax core mold, including providing enough clearance to allow removal of the core from the mold:

Platen length check: machine property Platen Length is no less than the larger of mold length for the longest core and mold width for the widest core (see the formulas for Mold Length and Mold Width in Soluble Wax Core).
Platen width check: machine property Platen Width is no less than the smaller of mold length for the longest core and mold width for the widest core (see the formulas for Mold Length and Mold Width in Soluble Wax Core).
Daylight distance check: machine property Maximum Daylight is no less than the required mold clearance for any ceramic core. The required mold clearance for a core is the mold height plus the product of the following:
- Core height (the smallest core dimension)
- Value of the cost model variable solubleWaxMoldOpenStrokeFactor (1.25 in starting point Digital Factories).

The mold height is the core height plus twice the value of the cost model variable moldBaseHeightMargin_solubleWaxCore (38.1mm in starting point Digital Factories).

Note: aPriori assumes that if the machine can accommodate each core in this way, it has sufficient clamp force for each core.

Soluble Wax Leaching Machine Selection

Overhead rate: this is sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.
Number of required batches: this is the production volume divided by the maximum load size, rounded up to the nearest whole number of loads. The maximum load size is determined based on the following assumptions:
- In starting point Digital Factories, no part occupies an area that is within one inch of the top or walls of the leach tank. Administrators can customize the allowance with the cost model variable solubleWaxLeachingTankEdgeNestingAllowance (25.4mm in starting point Digital Factories).
- In starting point Digital Factories, parts occupy 80% of the remaining (after-allowance) tank volume. Administrators can customize the occupied fraction of remaining space with the cost model variable defaultSolubleWaxLeachTankSpaceAvailableFactor (0.8 in starting point Digital Factories).

A machine is considered feasible if its usable space is big enough to accommodate at least one part:

Length check: machine’s usable length is no less than the part’s longest dimension.
Width check: machine’s usable width is no less than the part’s second-longest dimension.
Height check: machine’s usable height is no less than the part’s shortest dimension.

Machine usable length, width, and height are determined based on allowance (25.4mm in starting point Digital Factories) that is added all around the core:

Machine usable length: machine Bed Length minus twice the allowance
Machine usable width: machine Bed Width minus twice the allowance
Machine usable height: machine Bed Height minus the allowance

The allowance is specified by the cost model variable solubleWaxLeachingTankEdgeNestingAllowance (25.4mm in starting point Digital Factories).

Steam Autoclave De-Waxing Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per tree. Overhead rate per tree is given by the machine overhead rate divided by the number of trees that fit in the furnace.

Machine overhead rate: sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate

Number of trees that fit in the furnace: depends on the following:

Tree box footprint: product of tree box width and tree box depth; see Tree Box Dimensions.
Machine properties Bed Length and Bed Width.
Tree nesting allowance factor: fraction of the bed area (minus a perimeter allowance) occupied by trees, specified by the cost model variable nestingAllowanceFactor_tree_autoclave (0.85 in starting point Digital Factories). Higher values model tighter nesting.
Perimeter nesting allowance: space allowance all around the perimeter of the machine bed. No tree occupies space that is within the allowance of the perimeter. In starting point Digital Factories, this is set to 0, based on the assumption that the machine properties Bed Length and Bed Width reflect the dimensions of the usable bed area, and so already take into account the perimeter allowance required for proper airflow. Administrators can specify additional allowance with the cost model variable nestingAllowance_perimeter_autoclave (0mm in starting point Digital Factories).

Note: A machine is feasible if at least one tree fits in the furnace.

Wax Pattern Molding Machine Selection

aPriori selects the feasible machine with the lowest overhead rate per part. Overhead rate per part is the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate.

A machine is considered feasible if it is big enough to accommodate the wax pattern mold, including providing enough clearance to allow removal of the pattern from the mold:

Platen length check: machine property Platen Length is no less than the larger of mold length and mold width (see the formulas for Wax Pattern Mold Length and Wax Pattern Mold Width in Labor Cost and Cycle Time for Wax Pattern Molding).
Platen width check: machine property Platen Width is no less than the smaller of mold length and mold width (see the formulas for Wax Pattern Mold Length and Wax Pattern Mold Width in Labor Cost and Cycle Time for Wax Pattern Molding).
Daylight distance check: machine property Maximum Daylight is no less than the required mold clearance for any ceramic core. The required mold clearance for a core is the mold height plus the product of the following:
- Part Height
- Value of the cost model variable waxPatternMoldOpenStrokeFactor (1.25 in starting point Digital Factories).

The mold height is the part Height plus twice the value of the cost model variable moldBaseHeightMargin_patternWax (38.1mm in starting point Digital Factories).

Note: aPriori assumes that if the machine can accommodate the mold in this way, it has sufficient clamp force.