Welcome to ANDA
Welcome to ANDA
Co-extrusion is why a mature, highly demanded two-layer WPC decking line sells for more than a standard single-extruder line. Rather than producing a single-material board, the line runs two materials in one pass: the principal extruder drives out the core of WPC material and an additional smaller side extruder feeds a UV-resistant polymer cap into the same die. That additional layer is what helps preserve the shade and surface appearance of a deck located in direct sunlight over the years. Related WPC Decking Plank extrusion line: wpc deck plank manufacturing machine.
So if you are comparing a basic WPC deck line to a co-extrusion setup, it is not just what the extra machine costs but whether your segment of market actually pays for the cap. This article goes through the layer structure, and the die & vacuum table that contain it as well as how an extruded board becomes a wood-look deck via surface finishing.
Start at the raw end. The composite contains 50–60% wood powder, which is blended with recycled PE or PVC and the additive package in a high-speed mixer. Hot and cold mixing in an SRL-W mixer: The hot pass raises the batch temperature to 110–120°C, helping remove small amounts of residual moisture from the wood powder before the cold pass drops the temperature prior to feeding. Wood powder with high moisture content requires proper drying before mixing. If you skip moisture control, the board comes out with little pinholes on its surface — a problem no later finishing can easily cover up.
It goes into the main extruder, a conical twin screw, and from there it flows out through the mould as core. The thinner polymer compound is run through the parallel running co-extrusion extruder (SJ45 or SJ65 type single screw) which coats the core at the co-extrusion die, right there on an Anda Co-Extrusion WPC decking production line. The board that leaves the die is two materials joined together by heat, not a film applied afterwards. This is the very point of co-extrusion WPC decking: a cap with UV inhibitors offers surface protection and has colour built in, rather than fading as quickly as an uncapped board.
The die defines the board's cross-section and the gap through which the cap material flows, so rather than buying this generically you need to match it to your compound. At the back, a vacuum forming table which is composed of stainless steel and measures 4000 to 6000 mm long holds the profile against the calibrators while cooling takes place, so that the core and cap keep the required dimensions simultaneously.
The board leaves the table and has even tension maintained with a two- or three-claw caterpillar haul-off, speed-hold provided by variable-frequency drive. Even the way tension matters more here than asserted on a plain deck line, because uneven pulling can cause board deformation and visible marks along the board edge. Vacuum degassing on the extruder side, when equipped, removes any remaining moisture and volatile gases from the melt before reaching the die, which helps keep both layers clean. This is separate from the vacuum system on the calibration table.
As the board comes off the line, an embossing machine presses a deep 3D wood grain into the cap while its surface is still warm enough for embossing. But online is the bit that counts: the cap takes enough of a pattern to imprint on, and this grain lies in the UV layer — therefore it is not printed onto the board afterwards.
There is also a machine that runs over uncapped WPC surfaces with sanding and brushing tools to reduce the plastic reflection after cooling down. On capped decking, any sanding or brushing must avoid removing the protective cap. So what previously read as a glossy plastic board now reads natural wood. Auxiliary units such as a lamination machine, a hot stamping machine or printer take care of decorative profiles offline when an embossed grain is not required by the buyer, and if their own compatible scrap has been produced, it can be recycled in-house via crusher/pulverizer.
Main extruder | Main motor | Reference output |
SJSZ65/132 conical twin screw | 37 kW | 50–150 kg/h |
SJSZ80/156 conical twin screw | 55 kW | 150–200 kg/h |
The main difference between the two example sets is how many kilograms per hour the core can push. The co-extruder, vacuum table and cutter need to be matched to the selected profile and output. You size the line to be compared not against your top of brochure width but rather that which you actually sell, and against a cut length that is confirmed in your own compound at the trial run.
It has provided the whole thing in one turnkey solution from mixer, to main and co-extrusion extruders all the way through mould, vacuum table, haul-off, cutter and stacker, along with auxiliary units added when required by the buyer. Drives, low-voltage and temperature-control parts are sourced from brand-name providers so replacements remain available long after the line has been in plant. The equipment is CE certified, with installation, commissioning and operator training supported by a local service centre in India. Anda has produced and installed more than 1,000 production lines across its equipment range. Sizing starts with Anda Machinery.
Zhangjiagang Anda Machinery Co., Ltd. was founded in 2013 and focuses on plastic extrusion equipment and complete production lines, including WPC decking production lines. The factory area is more than 3,000 square metres, the equipment is CE certified and a local service centre in India caters to pre-sales as well as commissioning & after-sales support. Standard delivery is typically 30 to 40 days, depending on equipment and order requirements, with a one-year warranty from the time of installation. Before you sit down and try to size a decking project, watch this video of the Anda WPC Decking Production Line.
A co-extrusion line differs from a regular deck line mainly in the additional extruder and the double-layer structure formed at the die. The vacuum table and haul-off keep the profile stable during cooling, while embossing and optional surface finishing make it look like wood. Nail those three and the cap will earn its price within that market. Get in touch with Anda to compile a sheet that compares compound, board size and target output — before having the line sized against them.
Four questions come up most often while a buyer is weighing a co-extrusion line.
A main extruder forces the WPC core (commonly 50–60% wood powder in the compound) while a co-extruder wraps an online UV-resistant polymer cap around it. Both materials are bonded by heat at the die, so that the cap is a part of the board rather than a film added after cooling.
It helps remove small amounts of residual moisture in wood powder through high-speed hot mixing. Excess moisture can find its way to the extruder, leaving pinholes on board surfaces and defects in the cap. The cold pass then drops the batch to feeding temperature before it is introduced into the feeder.
The cap and the core take shape on this table. The vacuum holds the profile against the calibrators, while the longer table gives more time for cooling and helps keep the board flat and dimensionally stable before it reaches the cutter.
The automatic cutter runs a pneumatic lift blade or saw, and the cut length can be determined by limit switches. With proper setup, cutting accuracy can reach approximately ±2 mm, allowing a whole bundle of boards to come off with more consistent lengths and reducing the need for trimming before packing.
