When selecting materials in an operation, Microvellum's optimizer allows for users to assign an optimization priority to specific materials in their material file, to determine which materials should be used up first in the operation.

When using the optimizer, there are 2 sheet selection strategies available to users in the sawing processing station, under the Optimization Preference section: "Priority Selection" and "Weighted Selection". “Priority Selection” is the default selection strategy. This setting determines which sheet selection strategy will be used when processing a work order using the current processing station.

• If the setting is set to "Priority" then it will use the Priority Selection Strategy.

• If the setting is set to “Weighted” then it will use the Weighted Selection Strategy.

Fig. 1: Sheet Selection Type menu.

Priority Selection is the default sheet selection type and functions identically to the legacy optimizer. Priority is an integer value from 1-100 (any value is viable) assigned to a sheet or specific material in the material file. Sheets with the highest priority (lowest integer value) will be used before any sheets of lower priority (larger integer value). The optimizer will always use the highest priority of sheets with a quantity of 1 or more that are large enough to fit the current part being placed. If sheets have identical priority, the optimizer will determine which to use based on yield.

For example, say one has sheets of material with priorities of 1, 2, and 3. The optimizer will use priority 1 before priority 2 and priority 3. The optimizer will not select a priority 2 sheet until all priority 1 sheets have run out or the part being placed is too large to fit on any priority 1 sheet. The optimizer will not select a priority 3 sheet unless priority 1 and 2 sheets have run out or the part being placed is too large to fit on any priority 1 or 2 sheets, and so on.

This selection type and strategy also applies to scrap. Scrap material has the same priority value as a regular sheet and is treated as such by the optimizer.

A lower number means the sheet is used sooner. Priority 1 is consumed before priority 2, which is consumed before priority 3. This is a common source of confusion, because "lower priority number" and "lower priority" mean opposite things — the number is a queue position, not a ranking of importance.

A common goal is to stock a larger sheet for parts that will not fit the standard sheet, without the optimizer consuming that larger sheet on small parts for yield.

To do this, give the oversized sheet a higher integer than the standard sheet — not a lower one.

Setting the 12 ft sheet to priority 1 alongside the 10 ft sheet produces the opposite of the intended result. With equal priorities the optimizer falls back to yield, and the larger sheet is often the better yield choice for a batch of small parts — so it gets consumed first.

If your workflow requires both sheet sizes to share a priority value, switch the sawing processing station to Weighted Selection and lower the oversized sheet's Usage Chance so the optimizer prefers the standard sheet. See the section below.

The Weighted Selection strategy gives the optimizer more control over which sheets are used to allow for better yield by allowing users to apply percentage value to a specific material. This percentage represents the preference the optimizer will have when selecting a sheet to use. All values assigned to materials in the operation will be combined to equal 100.

A weighted selection strategy using two sizes of a material, each with equal “Usage Chance” will behave similarly to the Legacy optimizer when both sizes of the material have identical priorities- the one with the greater calculated yield will be prioritized first.

Figure 2: The new 'Usage Chance' column added to a sheet material in the material file.

When Weighted Selection is selected in the optimizer, the UI of materials in the material file will change to include the “Usage Chance(%)” cell. Clicking on the cell allows one to adjust values using a vertical arrow controller. This allows the user to easily increase or decrease the usage chance while looking at all sheets. When adjusting the usage chance, the UI will keep the resulting value of all percentages at 100 by adjusting the other values automatically.

Figure 3: The 'Usage Chance' column present in the Modify Work Order interface.

Figure 4: The 'Usage Chance' column present in the Scrap Inventory interface.

If Weighted Selection is enabled, the percentage value will also be displayed in the Modify Work Order and Scrap Management UIs, though the usage chance in these interfaces is not visually tallied up to 100 (as it is unnecessary in these two UIs).