Define a press

A Press represents one direct extrusion press and its relevant physical/operational limits.

Minimum information

The simplest practical definition is:

from pyextrusion import Press

press = Press(
    name="Example 8-inch press",
    nominal_size_in=8,
    table_length_m=54,
)

table_length_m is mandatory. PyExtrusion does not infer table length from nominal press size because two presses with the same nominal size may have very different runout tables.

Use real plant values whenever possible

press = Press(
    name="Production line",
    nominal_size_in=9,
    billet_diameter_mm=228,
    container_diameter_mm=236,
    billet_min_length_mm=500,
    billet_max_length_mm=1300,
    table_length_m=64,
    dead_time_sec=14,
    target_net_productivity_kg_h=2250,
    press_force_t=3500,
)

If you supply real plant dimensions, they take priority over PyExtrusion defaults.

Important public input ranges

Input	Supported range / rule
Nominal press size	6 to 16 inches, whole integer
Billet minimum length	100 to 3000 mm
Billet maximum length	100 to 3000 mm
Table length	10 to 100 m
Technical dead time	5 to 30 s
Saw kerf	0 mm, or 3 to 10 mm

The billet minimum must not be greater than the billet maximum.

Saw kerfs

The three saw-related values are independent:

• billet saw;
• puller saw;
• final saw.

A value of 0 is allowed and means that the corresponding operation contributes no length or mass loss from kerf. Physical event counters retain the selected topology; this does not add or remove a separate saw-operation time.

Example:

from pyextrusion import Press, SawSpec

press = Press(
    name="Press with billet shear",
    nominal_size_in=8,
    table_length_m=54,
    saws=SawSpec(
        billet_mm=0,
        puller_mm=5,
        final_mm=5,
    ),
)

Incoming-billet mass coefficient

billet_kg_per_mm_override remains available for a measured mass per mm of original incoming billet. Without it, the coefficient is density_kg_m3 * billet_area_m2 / 1000. Results identify the source as geometric or user_plant_override.

The override applies to incoming-billet length and billet-saw loss. Butt mass is instead density_kg_m3 * container_area_m2 * butt_mm / 1000; its incoming-billet equivalent is obtained by dividing that mass by the effective coefficient. A measured coefficient does not redefine container density. See Geometry for the geometric upsetting limitation.

Defaults versus real values

PyExtrusion can infer several practical defaults from nominal press size when real values are unavailable. These defaults are intended to make preliminary calculations possible; they are not universal press-design laws.

For engineering or production use, prefer measured/known plant values whenever they are available.

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