At Zhejiang Huasheng Machinery Equipment we build the EPS pre expander machine as the first process step in an EPS foam production line. The machine takes a weighed batch of raw EPS beads, heats it with steam in a sealed barrel, and releases the pressure so the beads expand to several times their original volume. The pre-expanded beads then go to silos for aging before molding, and the consistency of this step decides how the finished block or shape looks.

How the Batch Process Works

The cycle starts with batch loading, when a precise weight of raw beads is fed into the insulated expansion vessel. Steam is injected to heat and pressurize the chamber, which softens the beads and activates the blowing agent inside them. Rapid depressurization then lets the beads expand, and the expanded material is discharged to storage for aging and stabilization. Each of these stages is controlled from the PLC and touch screen, which manage barrel temperature, pressure and material level so the machine can run automatically.

Density Control and Barrel Design

Bead density is the number that matters most in pre-expansion, and the machine controls it with a material weighing system plus photoelectric control of the material level. That combination reduces the density error between batches, which keeps the molding stage predictable and cuts scrap. The inner barrel is made of stainless steel plate with a closed structure and high thermal efficiency, so the steam heat stays in the material rather than escaping through the wall. A steam reducing valve and angle seat valves hold a steady steam pressure, and the electrical and pneumatic components are well-known brands.

Models and Capacity

Two models cover the common production sizes. The HS-YF-1100 has a 1100 mm barrel diameter, a 1500 mm height and 1.4 cubic metres of volume, while the HS-YF-1500 has a 1500 mm diameter, an 1800 mm height and 3.2 cubic metres. Both use a 50 mm steam inlet at 0.6 to 0.8 MPa working pressure, a 40 or 50 mm compressed air inlet at the same pressure range, and an expanding density of 12 to 30 grams per litre. Capacity at 18 grams per litre is 450 kg per hour for the smaller machine and 800 kg per hour for the larger one, rising to 800 and 1300 kg per hour at 30 grams per litre.

The installed power is 15.5 kW for the HS-YF-1100 and 26.5 kW for the HS-YF-1500, and both need a workshop height of 6000 mm. The overall size is 6300 by 3300 by 4500 mm for the smaller model and 6500 by 3300 by 4800 mm for the larger one, with weights of 2500 kg and 3500 kg. The main body includes the feeding device, weighing system and bed dryer, so the line does not need a separate dryer for the pre-expanded beads.

Choosing the Right Model

The model should follow the molding line rather than stand alone. A block molding line that runs at a steady rate needs enough pre-expanded bead inventory to cover the aging time, so the capacity of the pre-expander is usually set a little above the molding consumption. Tell us the target density, the molding cycle and the number of shifts, and we can check whether one HS-YF-1100, one HS-YF-1500 or a pair of machines fits the plan. Steam supply, compressed air and workshop height are the three site conditions to confirm before the order is placed.

Steam quality matters as much as steam quantity. Wet steam delivers less heat per kilogram and makes the batch time harder to repeat, so the boiler and the pipe layout should be checked together with the machine. The bed dryer uses its own 25 mm steam inlet, and the dried beads flow better in the silo and in the molding machine. For a new factory, we recommend a site visit or a layout drawing before shipment, because the space around the barrel and the access to the discharge point decide how easily the line can be serviced.

Service and Contact

Zhejiang Huasheng Machinery Equipment Co., Ltd. supplies EPS machines, EPS molds, auxiliary equipment for EPS foam factories and spare parts, and our team supports the line from layout to commissioning. For a quotation on the EPS pre expander machine, send the target density, the required output, the steam and air conditions and the destination. Contact us on +86-571-69961788 or at info@zjhssb.com, or visit the plant at No. 88, Guanting, Baiqian, Luzhu, Fuyang District, Hangzhou City, Zhejiang Province.