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Understand the results

Butt trace and coefficient source

billet.butt_mm is physical thickness in the container. billet.butt_mass_kg is the mass of one such butt, while scrap.butt_kg is the order total. billet.butt_equivalent_billet_mm is its equivalent incoming-billet length. billet.kg_per_mm and billet.mass_coefficient_source identify the effective coefficient (geometric or user_plant_override).

Quantity-free ProcessResult exposes the same per-billet mass and equivalent length, with billet_mass_coefficient_source. Engine-generated results populate these fields even for a nonviable case; None is reserved for manually constructed legacy result objects without the new trace.

recommended_billet_length_mm is an operational ceil, not nearest-mm display rounding. Do not round before comparing billet limits. A changed loss-based productivity index is not necessarily a change in physical net kg/h.

PyExtrusion returns many fields because different users need different views. You do not need to read every field for every calculation.

This chapter explains the main result families in practical terms.

Trim and event scope

process.trim_total_per_billet_m is the incoming-billet total, not front-only scrap or predicted charge-weld extent. Each sequential contribution receives that total divided by p. process.trim_per_pull_m sums contributions for a full pull. It can therefore include several billets.

Use the four production event counters for an actual order, including its partial final group. For a quantity-free ProcessResult, the two *_per_pull counters describe full-pull configuration only. A kerf of zero does not remove the event, but its length/mass loss is zero.

1. Supported and viable

Read these first.

  • Supported: the scenario is covered by the current PyExtrusion model.
  • Viable: a supported configuration fits the selected press/process geometry.

A scenario can be supported but not viable.

This describes how billets and pulls are grouped by the calculation.

Common configurations include:

  • k_billets_1_profile;
  • 1_billet_2_profiles.

See the Glossary if these terms are unfamiliar.

3. Extrusion ratio (RE)

The extrusion ratio indicates how strongly the incoming material cross-section is reduced into the total outgoing profile cross-section.

PyExtrusion reports an extrusion-ratio value and an informational status. Treat it as one engineering indicator among several, not as a standalone accept/reject rule.

4. Exit speed and ram speed

  • Exit speed: speed of the extruded profile leaving the die.
  • Ram speed: forward speed of the press ram/stem.

You can supply one of these as the process speed input. PyExtrusion resolves the other from the geometry.

5. Cuts and table occupancy

These cuts are commercial positions, not total physical saw strokes. Inspect production.final_saw_events, internal_billet_transitions, puller_saw_events and billet_saw_events separately. See trim topology for partial-pull counting.

Important values include:

  • theoretical cuts;
  • cuts per billet;
  • cuts per pull;
  • table occupancy;
  • table margin.

These help you understand how efficiently the calculated pull uses the available runout table.

6. Billet length

PyExtrusion can expose:

  • calculated billet length;
  • recommended billet length rounded upward to a whole millimetre;
  • minimum and maximum billet margins.

The automatic calculation is designed around a billet-first principle: it prefers the longest valid billet for the process rather than shortening a valid billet only to increase the number of billets in one pull.

7. Bars, billets and pulls

Do not confuse these quantities:

  • bar: finished cut length requested/produced;
  • billet: cylindrical input material loaded into the press;
  • pull: continuous extrusion length handled as one pull on the runout table.

One pull can contain material from more than one billet in a multi-billet continuous configuration.

8. Scrap / process losses

PyExtrusion reports individual and grouped losses, including categories such as:

  • butt;
  • total trim/reject reserve (scrap.front_scrap_kg retains its compatibility name);
  • billet saw;
  • puller saw;
  • final saw;
  • startup allowance;
  • complexity allowance.

Two useful summary values are:

  • fixed scrap: fixed process-loss group;
  • total scrap: broader estimated loss group including startup and complexity allowances.

These are engineering estimates. Plant measurements remain the best reference when available.

9. Productivity

Useful productivity outputs include:

  • nominal gross kg/h;
  • real gross kg/h;
  • real net kg/h;
  • target/reference net kg/h when available.

For most practical production comparisons, real net kg/h is one of the most useful values because it relates good manufactured mass to the technical press time represented by the model.

10. Productivity index

PyExtrusion can report an orientative productivity/utilisation index.

Important:

The productivity index is not a physical quantity and must not be used alone to make the final industrial decision.

Always read it together with:

  • actual net productivity;
  • losses;
  • billet use;
  • table use;
  • configuration;
  • extrusion ratio;
  • warnings;
  • plant constraints that PyExtrusion does not model.

11. Timing

The current technical press time includes the extrusion time and the technical dead time modeled by PyExtrusion.

Additional downstream kerf increases physical extrusion length and time. It does not add a separate saw-operation duration or a new press dead-time event. The model also does not automatically include external delays between production orders.

12. Warnings

Warnings are there to draw attention to potentially weak or unusual process outcomes. They are not a substitute for engineering judgement.

When a case is completely non-viable or unsupported, focus first on the main reason instead of secondary indicators.