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Industrial extruder machine with yellow safety guard, control panel, and Bonnot logo on the frame; features large motors on both ends and a protective cover over the central section.

Bulk Molding Compound Extruders

The Bonnot Company manufactures single-screw extruders specifically configured for processing bulk molding compound (BMC), a fiber-reinforced thermoset material used in compression and injection molding. These extruders deliver a consistent weight and density profile that optimizes downstream thermoset molding while minimizing voids, excess flash, and glass-fiber degradation. Bonnot has built BMC extrusion equipment for approximately 50 years and tests customer formulations in-house before specifying a machine.

What Bulk Molding Compound Extruders Do

Bulk molding compound is a viscous, fiber-filled thermoset putty containing resin, fillers, and chopped glass fiber. It is sensitive to shear: excessive mechanical work shortens the glass fibers and degrades the mechanical properties of the finished molded part. A BMC extruder’s job is to ingest this stiff, sticky material, convey it gently, and form it into uniform charges (slugs) of consistent weight for compression or injection molding presses. Bonnot configures each single-screw extruder for this duty specifically, prioritizing positive feed and low shear over throughput speed.

The design centers on controlled, low-degradation material handling:

  1. Large-Capacity Feed Section

    Large feed section to accept stiff, high-viscosity BMC without bridging or starving the screw.

  2. Single Counter-Rotating Packer

    Single counter-rotating packer that forces material positively into the screw, ensuring consistent feed while minimizing the working that breaks down glass fibers.

  3. Chrome-Plated Contact Components

    Carbon steel construction with chrome-plated contact components to reduce drag, resist wear, and ease material release.

  4. Tapered Auger (Application-Dependent)

    Tapered auger (application-dependent) used in some configurations to accommodate a larger feed batch while producing a smaller-diameter extrudate.

  5. Jacket and Auger Cooling with TCU

    Jacket and auger cooling with a temperature control unit (TCU) to hold the compound within its processing window and prevent premature cure.

  6. Single-Orifice Forming Dies

    Single-orifice forming dies in a range of sizes to set extrudate diameter.

  7. Easy-Clean Hoppers, Packer, and Barrels

    Easy-clean hoppers, packer, and barrels (optional) for faster material changeovers between formulations.

Extruder Design Features

  1. Single packer for positive material ingestion and low fiber degradation

  2. Jacket and auger cooling

  3. Chrome-plated contact components

  4. Customizable dimensions, configured to the specific application

  5. Integrated temperature control unit (TCU)

  6. Guillotine cutter with integrated conveyor (TCU)

More information
Forming and Cutting The extruder pairs with a guillotine cutter and integrated conveyor to produce cut-to-length charges. The turnkey system uses a photo eye to control cut length precisely, delivering repeatable slug weights for consistent press loading. Formulation Testing Bonnot maintains a test room where customers worldwide can run trials on their own BMC formulations before committing to a machine configuration, including harder-to-process compounds. This lets the extruder geometry, packer, cooling, and die be matched to the actual material rather than estimated from specification sheets. Applications Bulk molding compound is used to mold components that require dimensional stability, electrical insulation, and heat or flame resistance — common in electrical enclosures, automotive components, appliance parts, and lighting housings. Bonnot's BMC extruders prepare and form the compound charges that feed the molding presses producing these parts.
A close-up view of an industrial machine with yellow safety covers and metal components, including a conveyor belt and ventilation grills, likely used for processing or manufacturing tasks.

Bulk Moulding Extruder with Guillotine Cutter

Our turnkey system incorporates a photo eye for precisely controlled cut lengths.

Our team testing Bulk Moulding Compound processing

In our test room we welcome customers from all over the world to test bulk moulding compound formulations. In this case, we were testing a tougher to process material.

Four men wearing masks and gloves stand around a metal table in a lab, handling white material and using trays. Industrial equipment and storage shelves are visible in the background.

Trusted by the Best

  • The image shows the 3M logo in large, bold red letters on a light gray background, suggesting a connection to innovative technologies such as the vacuum extruder.
  • BASF logo with a black geometric symbol and the company name in bold letters. Below, the tagline reads, “We create chemistry,” all on a light background.
  • The image shows the blue P&G logo, with the letters “P” and “G” connected by an ampersand, on a light gray background. This sleek design could easily represent innovation in industries like Custom Extruder manufacturing.

FREE FEASIBILITY TESTING

WANT TO PROVE IT OUT?

The Bonnot test facility offers free feasibility trials for bulk molding compound extrusion — different weight profiles, formulations, and full material testing.

  • EARLY RESEARCH

    EXPLORE BMC EXTRUSION OPTIONS

    Not sure which configuration fits your formulation? We'll help you match your material to the right setup.

    VIEW SPECIFICATION RANGES

  • TECHNICAL EVALUATION

    BOOK A TECHNICAL CONSULTATION

    Discuss web width, uniformity, and medical-grade requirements directly with a Bonnot process engineer.

    SCHEDULE A CONSULTATION

  • READY TO TRIAL

    BOOK A FREE TRIAL RUN

    Bring your formulation to our facility. We'll run a trial, measure key parameters, and send you samples.

Relevant Ancillary Equipment

A metal mechanical assembly with an open rectangular housing, an attached motor, precision screws, and a circular plate featuring multiple holes—resembling the core of an advanced extruder cutter. The internal components and mounting brackets are visible, highlighting its robust design for precise material handling.

Extruder Cutter

A white rectangular industrial device with a display screen, red button, side nozzle, and a blue “B BONNOT” logo on the front panel. The unit features advanced extruder controls, connection ports, and a gray handle on the bottom.

Extruder Controls

Frequently Asked Questions

What is a bulk molding compound extruder?
It is a single-screw extruder configured to convey fiber-reinforced thermoset BMC at low shear and form it into uniform, repeatable charges for compression or injection molding. The Bonnot Company has manufactured this equipment for approximately 50 years.
Why does low shear matter when processing BMC?
BMC contains chopped glass fiber that reinforces the molded part. Aggressive screw working shortens those fibers, reducing the strength of the finished product. Bonnot's single counter-rotating packer and feed geometry are designed to move material positively while minimizing fiber breakage.
How does the extruder ensure consistent part quality?
A consistent extrudate weight and density profile produces uniform molding charges, which reduces voids and excess flash in the molded part and improves press-to-press repeatability.
Can the extruder handle different BMC formulations?
Yes. Bonnot offers easy-clean hoppers, packer, and barrel options for faster changeovers, and tests customer formulations in its test room — including tougher-to-process materials — to match the configuration to the compound.
What is the tapered auger option for?
In some configurations a tapered auger accommodates a larger feed batch while producing a smaller-diameter extrudate, matching feed capacity to the required charge size.
How is the extrudate cut to length?
The system integrates a guillotine cutter with a conveyor and a photo eye, which controls cut length precisely for repeatable charge weights.