Many products rely on the strength and durability of springs but, as Capewell Springs warns, it is important to ensure high-quality springs are selected in order to avoid premature spring failure, which could prove disastrous.
The average mechanical watch movement for example – say, from a Swiss Rolex – contains around 135 individual parts. Whilst some of these parts – such as the main plates – are relatively large (at least in watchmaking terms), the majority are very small, often requiring magnification to see clearly. Expensive collectible watches like Rolex, valued more for their elaborate craftsmanship, aesthetic appeal and glamorous design than for simple timekeeping, often have purely mechanical movements and are powered by springs. Manufacturing components this small presents a set of unique challenges.
Capewell Springs, a member of the Kern-Liebers International Group of Companies, might not manufacture any components for Rolex but the list of industries it serves is impressive. The company manufactures high-tech springs and stamped parts from flat, round and profiled material meeting the exacting standards of their clients, complying with the ISO 9001:2008 quality accreditation.
Capewell Springs have recently invested in a new Mitsubishi MV1200S Wire EDM. The MV series is suitable for cutting applications for a diverse range of products, from product parts to those that require high-accuracy processing, including mould and die. The MV1200S, which was supplied by WD Hearn Machine Tools, has XYZ travels of 400 x 300 x 200mm and can accommodate a workpiece of 810 x 700 x 215mm. It has replaced a number of older EDM machines, and fits in with the Groups’ strategy of standardising on equipment
From its inception nearly 34 years ago, the company has grown to become a major supplier to the automotive, electronics, electromechanical, textile, lighting and consumer industries, to mention a few.
“All metal has a certain amount of spring-back. Spring-back, also known as elastic recovery is the tendency for the metal to want to return to its original flat blank shape after being bent. To fully understand why metal springs back, we first must understand that metal, when subjected to a bending operation, reacts in a similar fashion to Silly Putty. Silly Putty, known for its rubbery plastic consistency, is a special compound sold as a toy. Sheet metal, often viewed as a hard, semi-flexible medium, is in fact an elastic type of material. The extent of its elastic properties is controlled largely by the material’s mechanical properties,” explains Graham Montgomery, Managing Director of Capewell Springs.
“The metals industry typically does a great job of controlling metal specs. However, minor differences from coil to coil and from the beginning of the coil to the end are possible.”
Graham Montgomery, Managing Director of Capewell Springs with Sales Manager Emile Coetzee
“A spring is a device that changes its shape in response to an external force, returning to its original shape when the force is removed. The energy expended in deforming the spring is stored in it and can be recovered when the spring returns to its original shape. Generally, the amount of the shape change is directly related to the amount of force exerted. If too large a force is applied however, the spring will permanently deform and never return to its original shape.”
Background
There are several types of springs. One of the most common consists of wire wound into a cylindrical or conical shape. An extension spring is a coiled spring whose coils normally touch each other; as a force is applied to stretch the spring, the coils separate. In contrast, a compression spring is a coiled spring with space between successive coils; when a force is applied to shorten the spring, the coils are pushed closer together. A third type of coiled spring, called a torsion spring, is designed so the applied force twists the coil into a tighter spiral. Common examples of torsion springs are found in clipboards and butterfly hair clips.”
“Still another variation of coiled springs is the watch spring, which is coiled into a flat spiral rather than a cylinder or cone. One end of the spring is at the centre of the spiral, and the other is at its outer edge.”
“Some springs are fashioned without coils. The most common example is the leaf spring, which is shaped like a shallow arch. It is commonly used for automobile suspension systems. Another type is a disc spring, a washer-like device that is shaped like a truncated cone. Open-core cylinders of solid, elastic material can also act as springs. Non-coil springs generally function as compression springs.”
All of the wire Capewell Springs uses for manufacturing is locally produced, but for strip or coils the majority is from imported material
Capewell Springs has seven 25 ton presses, two 63 ton presses and six multispindle machines on the shopfloor
“For structures and equipment operating in harsh environments, springs and spring fasteners must be able to withstand different types of extreme conditions, including those found under water, outdoors and at very high or low temperatures. Challenging working conditions can be encountered across various industry sectors, such as aerospace, valve manufacturing, offshore and subsea, medical, power station and nuclear, turbine manufacture and general engineering. Springs and fasteners are often vital components and therefore must be designed to withstand the application-specific conditions.”
Controlling bend angles
“Bend angles are among the most frustrating geometric features to control in spring manufacture and metal stamping. This is due primarily to two factors – the inconsistency of the mechanical properties in the metal being bent and the die design.”
“The key to successful tight tolerance bend angle control is to design the die so that it can be easily, quickly, and safely adjusted within the boundaries of the press, for example.”
Toolroom – tool and die design and maintenance
“This is one of the reasons why the company has always had its own toolroom. We are processing 150 tons of material a year, which equates to between 50 and 65 million components. The mix could be made up of 400 different individual components, whether it is in the spring coiling department or the stamping area. The runs on each component vary but you are looking at between 1 and 1,000 000, depending on the client.”
“We manufacture power and constant force springs, compression springs, tension springs, torsion springs, bent wire parts, stamped bent parts, lawnmower blades and yes, brassiere under wires, to name a few.”
“99% of the components we manufacture are supplied into other production facilities that are generally producing the end product. Each component can have many different varieties as well. For example the brake caliper springs have 45 different varieties. Sorry, but I can’t give numbers on the under wires!”
“The toolroom staff don’t merely look for better ways to design the tools they build and keep the dies in good repair, they are also building our fixtures so that we have the ability to hold closer tolerances when forming the components.”
The company has a number of spring coiling and wire forming machinery
Capewell Springs processes 150 tons of material a year, which equates to between 50 and 65 million components. The mix could be made up of 400 different individual components, whether it is in the spring coiling department or the stamping area
“We also offer design services, feasibility studies, tool design, manufacture of prototypes, design of the manufacturing process and secondary finishing operations.”
“We have embraced the TASA initiative in the toolroom and currently we have three interns.”
“Industry experts like to stress the pace of modern metal fabricating. Lead times are tight as customers look for just-in-time deliveries, and fabricators hope to minimize the order-to-cash cycle to maximize the cash available for reinvestment in the company. Cutting-edge machine tool technology is used as a competitive advantage and keeps the shop floor filled with work-in-process.”
“When an operator is running presses at around 6,000 strokes per hour, shop floor personnel have to keep track of a lot of parts. For stamped components, customers demand these parts in a couple of weeks—even days in some instances—instead of six to eight weeks, is not a new phenomenon.”
“A stamping die is a special, one-of-a-kind precision tool that cuts and forms metal into a desired shape or profile. The die’s cutting and forming sections are typically made from special types of hardenable steel called tool steel. Dies can also contain cutting and forming sections made from carbide or various other hard, wear-resistant materials.”
“Stamping is a cold-forming operation, which means that no heat is introduced into the die or the sheet material intentionally. However, because heat is generated from friction during the cutting and forming process, stamped parts often exit the dies very hot.”
“We have seven 25 ton presses, two 63 ton presses and six multispindle machines on the shopfloor, in addition to all our spring coiling and wire forming machinery. They are hungry and we cannot afford any breakdowns.”
Capewell Springs manufactures power and constant force springs, compression springs, tension springs, torsion springs, bent wire parts, stamped bent parts and lawnmower blades to name a few
The runs on each component vary but you are looking at between 1 and 1,000 000, depending on the client
To ensure the company keeps heading in the right direction, Capewell Springs has undertaken initiatives to increase the flexibility of its manufacturing processes so that series production of both new and established designs is better supported.
New Mitsubishi MV1200S Wire EDM
“This is precisely the reason why we have invested in a new Mitsubishi MV1200S Wire EDM. The MV series is suitable for cutting applications for a diverse range of products, from product parts to those that require high-accuracy processing, including mould and die.”
“The MV1200S, which was supplied by WD Hearn Machine Tools, has XYZ travels of 400 x 300 x 200mm and can accommodate a workpiece of 810 x 700 x 215mm. It has replaced a number of our older EDM machines, and fits in with the Groups’ strategy of standardising on equipment.”
“Although the machine was installed a few months ago it has helped the toolroom reach new heights of efficiency and performance. I’m very impressed; it’s a fun machine to run. Processing speeds are so much more advanced than even five years ago, and it has made a big difference for us.”
“Kern-Liebers, with its headquarters in Germany, is a worldwide supplier for systems vendors to the automotive, textile and consumer goods industries. Our group of companies develops and manufactures precision products made from steel strip and wire at over 50 locations around the world, with over 6 000 people employed.”
Capewell Springs are a cold forming operation offering design and zinc plating as extras
Heat treatment (stress relieving) is another service the company offers
“We have been part of the Group since 1999 and we regard ourselves as a second-tier supplier. To put our number into perspective, one of the sister companies will manufacture 10 million components in one day. Another will manufacture 20,000 springs from as small as one gram of material.”
“Our expertise in precision engineering is also recognised in the medical engineering industry. We offer an extensive range of guidewires for many different applications, including minimising invasive surgery. Here you are looking at wire diameters from 0,08 – 0,2mm.”
“We are a cold forming operation offering design, heat treatment (stress relieving) and zinc plating as extras. All of the wire we use in our manufacturing is locally produced, but for our strip or coils the majority is from imported material. In some cases the client will provide his own material. Most of the material is either carbon spring steel or stainless steel.”
“We moved into our current location, which is 2500m², in 1994 and we employ 55 staff. The mix of product is made up of 40% on the wire side and 60% on stamped parts.”
Another component Capewell Springs manufactures is brassiere under wires
Brassiere under wires come in many different sizes
Wire components ready for delivery
“We process strip spring with dimensions between 0.20mm and 4mm thickness and a width of between 5.0mm – 150mm. The material used is texturised carbon and stainless steels, with applications in the automotive, mechanical, electrical and consumer industries.”
“The wire spring we process ranges between 0.25mm and 6mm and is made up of compression, tension, torsion springs and bent wire products with spring bodies being cylindrical, conical and barrel-shaped, and spring ends squared, reduced, unformed, ground and special forms that are used in the automotive, electro-mechanical, lighting, furniture, textile and consumer industries.”
For further details contact Capewell Springs on TEL: 021 505 9400, email sales@capewell.co.za or visit www.capewell.co.za
