So, what is PVCu or uPVC as it is often referred to? PVCu is Poly Vinyl Chloride, which is a lightweight and yet robust type of plastic used in consumer goods. The “u” stands for un-plasticised, meaning that the plastic isn’t softened in the manufacturing process, thus ensuring its strength is maintained. So how do we go from a raw material powder to a fully formed and robust window or door profile?

Bulk tanker deliveries of lead-free raw materials arrive on site on a daily basis in the form of resins, stabilisers, impact modifiers etc. and are pumped into large storage silos and holding stations, where material is accurately weighed to Selectas formulation. Each raw material delivery is QC checked and tested to ensure that it is to our material specification, before acceptance.

The PVCu “ingredients” and ratios used in the extrusion of the Selecta window and door products are specific to a tried and tested Selecta formula and colour. The precise proportions of resin, stabilisers and modifiers are transferred in to what is effectively a large “mixing bowl”, a high speed mixer. The computerised system allocates the volumes and blends the various raw material ingredients to the Selecta formula. QC checks are carried out every two hours and automated monitoring ensures the consistency of the Selecta formulation. The blended mix is assigned to a silo and recorded for traceability purposes, with all the production processes controlled and managed via the ISO 9001 quality management system.

A window or door profile section tool consists of a main die and a sequence of tooling calibrators, whilst the extrusion machine is split in to sections, the die head, calibrator and cooling section, haul off, saw centre and tilt table, with each carrying out a particular process during the extrusion of profile. The start up of a new profile section run begins with the extrusion machine set to the specification of the master setting sheet for that specific profile section. Dependant on the extrusion machine there are approximately thirteen temperature zones within the head of the machine and die zone, each are set to a specific temperature to aid the gelation of the dry blend. Each profile section has specific settings for screw speeds, line speeds, pressure, vacuums etc. within the set up of a new run.

Once fine-tuned and set-up, the dry blend of PVCu material is pumped in to the head of the extrusion machine from the silo, which in turn via the heat in the machine head and die zones, softens the material in to a PVCu gel. This softened PVCu gel is then forced through the tooling die to form the profile shape. The warm and soft PVCu profile section then goes through a series of calibration dies to maintain the profile shape, whilst chilled water is sprayed over the profile during the cooling process.

An underground water chamber holding thousands of gallons of water, pumps water to the extrusion machines via large chillers, which ensures that the water is preserved to a set temperature. The water is regularly checked for bacterial growth and an automated system douses chemicals in to the water chamber to maintain a safe closed loop water system.

Once cooled inside the seven-metre-long calibrator and cooling chambers, the profile sections rubber gasket is co-extruded in to the gasket channel and the profile section is printed upon, every one metre, with the company name, reference to standard EN 12608-1, our climatic zone classification, our resistance to impact by falling mass classification, wall thickness classification, product code, date and shift identification. This aids traceability of the profile section throughout it’s journey.

The next stage is the haul off, which is reminiscent of two large tank tracks, that pulls the profile along the extrusion machine before the protective tape is applied and the computerised saw cuts the section at six metres before hitting the tilt table for packing.

During the profile sections journey along the thirty-metre-long extrusion machine, on-line dimensional, operational and visual QC checks are carried out and recorded every couple of lengths. QC lab checks are carried out every two hours of extrusion, with full dimensional, colour and operational checks with associated profiles, reinforcements, accessories and ancillaries.

A profile section and foil colour requirement is assigned to a particular lamination machine. There are three foiled section possibilities – foil on the bead side face, non-bead side face or both sides of the profile section. A single face profile section set-up on a machine, will very often follow with colour changes throughout the run. For instance, once set-up for a particular section has been completed it is far more efficient to run, let’s say, anthracite grey for the required stock run and then follow this with other stock colours or a special colour, than it is to change over to another section. This will happen even if stock is still available for that profile colour, but we will boost the stock levels further.

Lamination technology has improved considerably over the years with the new machines now all computerised in the respect of primer and adhesive application. The profile section face width is programmed in to the machines computer along with the adhesive weight and spread. The adhesive weight adjusts the thickness of the adhesive, whilst heater settings warm up the profile section and adhesive to make it ‘tackier’ and adjust its adhesiveness.

The set-up of the lamination machine takes on average between 30-45 minutes per side of a profile section. Each forming wheel, guide and cutter is manually adjusted and set to ensure that when the foil is fed on to the profile, each surface, chamfer, sculpture and lip is covered by the foil and formed in to the shape. The coloured foil is oversized to cover the face of the profile section, with the lamination machine cutters trimming the excess foil to the gasket and bead chamber. The correct size of protective tape is put on the feeding wheel, to cover the newly foiled profile section face. Profile section runners are used to fine tune the settings, before the required production quality is achieved and production is approved to continue.

The line speed is set accordingly to the profile section with an average of 15-16 metres per minute. However, this is sometimes determined by pack quantities, as we pack profiles on-line, whereas other lamination houses may pack offline and up line speeds. So, we effectively run, inspect and bag two and half lengths per minute of a one-sided coloured profile section. We see this as a more efficient and effective way of production and it also factors in on-line QC inspection as well as packing.

So, what is PAS 24:2016? Well, PAS 24 is the industry standard for Enhanced Security Performance Requirements for Doorsets and Windows. This is a product assessment specification and primarily referenced in the Building Regulations Approved Document Q. The manufacturer, or systems company in this case, submit a range of window or doors to a UK Accreditation Service (UKAS) accredited test house for testing to PAS 24 and the relevant ‘fit for purpose’ standards.

Rigorous testing methods for forcing entry are carried out to ensure that there can be no failure of components that make up that window or door. Testing also includes BS 6375 consisting of weathertightness, operational performance and strength, ensuring that the windows and doors serve their two main purposes of protecting the property from unwelcome visitors and keeping inclement weather at bay.

Test windows are generally made up of the largest side hung, next to the largest top hung over a fixed window, whereas French doors are made to the largest configuration, thus also covering single leaf doors as a worst-case scenario. Our patio and EASi-FOLD doors were again fabricated to the anticipated largest pane sizes to cover a number of configurations. These configurations and sizes provide the fabricator / installer with the opportunity of offering a vast range of multi-light window and door options, where PAS 24 is a requirement.

Let’s just say the PAS 24 mechanical and physical attacks leave windows and doors in a sorry state, but with the right hardware they will hold firm against the ruthless nature of the attacks. That’s why our research and development process is so important. From profile design and indicative testing through to collaboration with the supply team, to ensure the right components are used, and where required, profile specific.