When is a PVCu bi-fold not a PVCu bi-fold?

“One of the most satisfying things is to see the look on new customers’ faces when they try the ModLok™ bi-fold for the first time!”

So says Design and Development Manager Chris Armes, who has more reason than most to be happy with this reaction – he was an integral part of the ModLok’s innovative design.

Clearview took time out to find out what makes this bi-fold completely different from the other uPVC systems on the market, and exactly why Liniar customers are so delighted with the door.

Historic problems with uPVC

When uPVC bi-folds first appeared, they seemed to offer a cost effective way of meeting the demand for this new must-have door system. However, it didn’t take long for problems to arise, with the new systems falling foul of expansion and contraction issues, size and weight stresses and hardware failures – resulting in expensive call-backs and repairs.

Any installer experiencing these problems first-hand might be forgiven for steering well clear of uPVC bi-folding doors ever since. But uPVC is still a great material to use, not only for its thermal properties but to match fully with the rest of the installation.

Fresh, new approach to a patented design

By taking a fresh new approach, looking at the inherent issues with uPVC and testing ways to overcome problems, Chris and the Liniar team were able to launch a brand new patented concept, as he explains:

“The sheer size of a bi-fold door meant uPVC frames needed steel reinforcement to support the weight of the glazed units. But by adding steel, the doors lost thermal efficiency, with cold air being transferred – so U-values were poor.

“In addition, and in spite of the steel reinforcement, early uPVC doors were unable to span large heights or widths. The weakness of uPVC meant that the continued opening and closing of bi-folding doors eventually led to faults with hinges, rollers and other moving parts, due to the movement that the profiles allowed.”

Turning it inside out

“We wanted to put the reinforcement on the outside of the uPVC, rather than the inside,” continues Chris, “but this hadn’t been done before, as it interfered with the positioning of the locks.

“So we designed our own unique locking system and embedded it into an aluminium exoskeleton which encased the uPVC (hence the name, as it’s literally a modular locking system).  This not only bypassed the problem but led to a much improved and more secure bi-fold.

“It’s not usually possible for hinges to be secured directly to the doors’ reinforcement; however the ModLok™ concept enabled this innovation to become reality, which was beneficial for PAS:24 testing. This means we’ve achieved both PAS:24 and Secured by Design compliance with ease.”

Thermally efficient

“The other benefit to using aluminium on the exterior meant that additional uPVC webs could be added inside the profile, or frames. This results in multiple chambers of air inside each profile, improving energy performance and making U-values of 1.0 achievable with triple glazing.”

Cycle testing

“All the indications showed the aluminium exoskeleton would give the doors unparalleled stability and durability – however this needed to be cycle tested,” says Chris. “So we purchased an ABB articulated robot and tested a full-size 3-pane ModLok™ bifold on a custom-built rig.”

“Our robot eventually reached hit 128,700 full ‘open and close’ cycles before we stopped it to test our next product – with the ModLok bi-fold still fully operational. This was more than 12 times the British Standard required for a door of this type, so we knew it worked!”

High strength and large sizes

“The ModLok™ categorically isn’t a hybrid – it has a core of uPVC profiles with an aluminium surround – so it’s very straightforward for Liniar fabricators to manufacture,” continues Chris.

“Its strength and rigidity are almost equivalent to that of an aluminium bi-folding door, giving us confidence in the maximum sizes of 2.1m high by 1.0m wide sashes and up to 7 panes wide.”

Issues solved!

Best of all, the ModLok™ has put to rest the previous issues with uPVC bi-folds; we haven’t had a single fault reported since its launch. When new customers see it in our showroom, they often don’t realise it’s made from uPVC, as it operates so smoothly.”

“ModLok™ has a choice of thresholds, a clever folding key system and is available in all stocked Liniar colours and foils to perfectly match the window system,” concludes Chris. “And even now, I still love seeing that look of surprise when someone experiences a ModLok bi-fold for the first time!”

To experience ModLok™ for yourself, ask for your nearest showroom at www.liniar.co.uk.