Production

The raw materials are purchased from one of the leading spring steel producers in Europe and is 100% scrap-based. Separate springs and smaller batches are manually produced while the larger series takes place in a fully robot-driven production line.The important heat treatment of the individual parts, take place in an automated and controlled process for best performance and quality.

Spring Steel is an alloy of chrome, manganese and chrome-manganese-vanadium. The spring steel types used in the production on flat material are SAE 5160 and 50CrV4 these follows DIN 4620 and DIN 59145. It specifies the type of spring system that spring is best intend for. It is the same type of materials used on newer vehicles.

Rånäs use the Swedish spring steel, produced by Ovako. They are an eminent supplier to several spring manufacturers in Europe. The steel we buy is the

absolute best quality. Spring steel is a very flexible material that is available in hardness from 300 Hb up to 540Hb, with a tensile strength from 900 to 1700 N/mm2. This makes the material good for resilient as well for wear, depending on the hardness. This is controlled both in tempering process, but especially in the normalization (tempering) where the temperature and time is crucial for the hardness, so that the properties achieved. Rånäs, has a large warehouse with flat spring steel, about 240 tonnes over 100 different dimensions in width between 32-100mm and thicknesses between 5-26mm. The material is cuted from 6m lengths in a purpose-built line where the steel is cut in the length that are programmed into a computer. The computer listed a number of different parameters of thickness, width, length, number, cave display and podium place. Control of length and width is automatically done before punching the centerholes. Holes for the center screw and clamps punches automatically after point heating with gas at specified places in order to reduce the risk of cracks around the hole.

fjaderstål

Shapening
Forging line is a fully automatic, and it is unique in its kind. All leaves to be formed before tempering warmly processed here in a computerized production cell, containing end heating oven, two presses, two loop drawing machine, and a computer portal robot. To be able to forge the spring leaves ends, the temperature must reach 1000 -1100 degrees Celsius, we do it in a LPG-powered stove., Spring leaves are moved between the different elements of a sequence-driven portal robot with electromagnets.

smide

Light spring hardeningline

Tempering oven is LPG-powered and is manufactured according to our specifications with unique solutions. Hardening temperature should be between 840 – 870 degrees (C)and is governed by a special monitoring system. The leaves are fed into the oven by a sequence-driven robot which is controlled by a computer and transported through the oven by step beams. The output of the hot leaves is also specially designed. The last oven beam take the leaf outside the oven to the hardening process.

härdning

A piston put the leaves from the beam to the hardening maschine, which will form the leaves to the right radius, everything controlled by a computer. The leaf is hold in the span of a form fixture and the entire fixture will be lowered in the hardening oil to be cooled. After hardening the leaves are automatically moved in the electrical tempering furnace to be heated up to 500 degrees (C). This is to achieve both hardness and toughness. The leaves are cooled after tempering with a water shower down to manageable temperature.

härdning2

Hardening heavy line

Leaf to the tempering furnace is fed in by a portal robot with electromagnets and moved through the oven to step beams. Tempering temperature is 840-870 degrees and it is governed by a separate monitoring system to achieve the right temperature. Leaves brought out of the oven of the ejector to a conveyor which transports the leaves to the hardening.

härdugn1

A purpose-built robot moves, the warm leaves from conveyorbelt to hardening fixture. The fixture is motor-driven for quick conversions and the entire fixture tip down in the dumps core oil. The leaf is hold in the fixture and cooled. From there it goes directly from the oil bath to entry into the electric tempering furnace.

härdugn2

Hardness Test

After the leaves passed the tempering oven and cooled to manageable temperature, a hardness test is done on 10% of the produced leafs. This is done in a hardness tester (type Brinell), which reads the hardness.The results are documented by a print from the machine and stored along with the working order.

hårdhetsprov

Light assembly line

All leafs checked to ensure achievement of the right radius and that the leaves are completely straight sideways. Loops on the main leaves adapted to the tolerance and bushes pressed into loops. By assembling, also leaves including hoop, will be riveted. Plastic inserts will be pressed in the leaf ends, the center screw, clamp screw and tubes will also be fitted.

kontroll

Mounting heavy line

All main and second leaves for trucks are shot peening with steel balls to achieve a longer life. Leafs checked to the right radius achieved and that the leaves are completely straight sideways. Loops are reamed up and checked with interpreters before the bushing can be pressed into the loop. It is also important that the maximum stressed leaves have a larger radius to build up an internal tension in the multi leaf spring . Hoops will be fitted to the hoop leaves, center, clampscrews and tubes will also be fitted.

tungalinjen

Force testing

The spring will be exposed to an overload to build up a tension in the material and remove the uneven distribution of power. By this measure, the fatigue hold will improve a lot. We also control the spring force and that each spring has the right free arch. It will be documented by a printout which will be saved together with the production order.

provtryckning

Painting

The springs sprayed with a water based primer for minimum environmental impact. A label with the article and production numbers will be pasted on the finished product. Packaged on a pallet for delivery to the customer or our warehouse.

målning