Mixers, Moisture Extraction and Dosing for WPC

Erk PVC Makine designs and installs mixing, moisture extraction, dosing and feeding systems for WPC (wood-plastic composite) production. The WPC extruder, the wood flour dryer and the downstream equipment come from other suppliers; we supply the raw material preparation line in front of the extruder and work with any extruder brand.

Why is WPC blending demanding?

WPC is made of PVC resin, wood flour (wood fibre), stabilisers, lubricants, coupling agents and colour additives. Wood flour makes the blend different from an ordinary PVC dry blend:

• Moisture: wood flour carries moisture and picks it up from the air. As the temperature rises in the heating mixer, this moisture is released as vapour. If it stays in the vessel it falls back into the batch, causing lumps, gas bubbles in the extruder and surface defects.
• Low bulk density: wood flour is light and bulky. Mixer charging and dosing must be set by weight, not by volume.
• Dust: fine wood flour raises dust easily. Open conveying and manual feeding mean material loss as well as cleaning and safety problems.
• Segregation: components with very different densities can separate on long, open routes.

So the real job in a WPC line is to make sure that the blend entering the extruder has the same proportions in every batch, is homogeneous and free of moisture.

Recommended line steps

1. Dosing: PVC resin, wood flour and powder additives are weighed to the recipe by automatic powder dosing.
2. Hot mixing: the heating turbo mixer warms the components by friction and spreads the additives over the resin and wood flour.
3. Moisture extraction: the EPM-JET filter and dehumidifier draws off the vapour and dust released during heating while the mixer runs.
4. Cooling: the blend cools down to storage temperature in the cooling mixer without lumping.
5. Check screening: a powder sieve removes lumps and foreign matter before they reach the extruder.
6. Feeding: a flexible screw conveyor carries the blend to the extruder hopper, closed and dust-free.

Recommended equipment

Mixer type and size depend on your recipe, the wood flour content and the hourly consumption of your extruder. The difference between horizontal and vertical coolers is explained in horizontal or vertical cooler mixer.

What matters for quality

• Wood flour moisture: moisture extraction in the mixer removes the moisture released during heating; it does not replace control of the wood flour’s moisture before it enters the mixer.
• Impeller and wear: wood flour and mineral fillers wear the blades. Blade geometry is chosen for the recipe, and balance and edge wear are checked regularly. See mixer blades.
• Temperature profile: wood flour is heat-sensitive; the heating mixer’s target temperature and discharge timing are set together with the recipe. General principles are in hot mixer temperature profile.
• Closed conveying: moving the blend in open containers after the mixer lets it pick up moisture and lose dust; closed feeding is preferable.

What Erk supplies and what other suppliers supply

Erk designs, builds in its own factory, installs and commissions the raw material preparation line: dosing, hot-cold mixing, in-mixer moisture extraction, screening and extruder feeding. The WPC extruder, die, wood flour drying and the downstream cutting, calibration and surface finishing equipment come from your line supplier. Installation, operator training, remote support and spare parts are part of our scope.

Request a line proposal

Tell us your WPC product (decking, panel, profile), the wood flour content of your recipe, your target output and your existing equipment, and we will prepare a line layout and quotation. Use the quote request form or Build Your Project.