You'll find them in mattresses, door handles – oh yes, and nuclear reactors. What would we do without the humble spring? "There's basically a spring in every mechanical product," says Stewart Lauder, quality manager of Glasgow-based Industrial Springs. "We manufacture springs that are the thickness of your hair, up to the thickness of your arm."
To make a spring, a coil of carbon spring or stainless steel is placed onto a former, which curves the wire into the correct shape. After that, the top and bottom of the spring is ground flat, so it can sit square on a flat surface. "They've got to be sitting straight so the force generated is linear," explains Lauder.
Next comes the tempering process, in which the springs are heated to 920°C, cooled rapidly in quenching oil, then heated again to 450°C to establish the appropriate level of ductility. Then there's painting, packing and finally transport – "We send a lot to Australia," says Lauder. Prices vary depending on size and weight, but the springs in these pictures cost around £80,000 for a batch of 2,000.
Competition from China – "We couldn't even buy the material for what people are finishing the job at, sometimes," says Lauder – has forced Industrial Springs to shrink from 50 to 12 people since it was started in 1964. But demand is still high, although for many people the process remains a mystery. "We have a joke," says Lauder, "about the spring trees that we just come in and water."
WIRED came across Industrial Springs through Make Works, an open access directory of fabricators, material suppliers, workshops and manufacturers designed to promote local manufacturing in Scotland. Make Works founder Fi Scott had the idea while she was studying Product Design at Glasgow School of Art.
"There are thousands of incredible manufacturers like Industrial Springs hidden away in industrial estates, all over the UK," says Scott, who is in the process of bringing Make Works from Scotland down to Birmingham. "We need to make sure these maker businesses are a part of our economy in the long term."
Spring coiler
The rollers on the left of this semi-automatic machine straighten the wire, which arrives at the factory in a round coil, before the points in the centre form it into a spring shape. This machine, which is for smaller wire diameters, churns out 1,000 springs an hour. Industrial Springs produces "five thousand a day", says Lauder.
Furnace
The forces required to bend a thicker spring are "massive", says Lauder, so to coil them safely Industrial Springs uses a softer material, such as chrome vanadium, then hardens it up in this 920°C furnace – from 12-15 up to 60 on the Rockwell hardness scale. Springs sit in for the furnace for half an hour as the temperature is regulated by two gas burners at either side.
Quenching oil
Once the springs have reached the right temperature – experienced spring-makers look for a pale orange colour in the metal – they are removed from the furnace and plunged into this pool of oil. Quenching transforms the grain structure of the metal, turning it from austensite to martensite, and making it very hard and brittle. It is then washed and tempered back to give it ductility.
Powder-coater
Before being sent out, the springs are powder-coated using an electrostatic gun, then cured at 230°C. (Here, a set of springs for a shale shaker are coming out of the curing oven). Powder-coating adds a rust-resistant hard finish, but it's also done for appearance. "A lot of customers like the springs to match the machine they're selling," says Lauder.
This article was originally published by WIRED UK
