The first compression spring coilers machine were developed in the United states of America by the end of the 19th century. Their basic technical principle has not changed a lot. A spring coiler built by Wafios around the century 1900. It already has all basic elements of a modern compression Machine. In 1912, Wafios built the first adjustable spring coiler that could produce springs with a different number of coils as well as with closed ends on both spring heads.
Mechanical spring coilers
A notable characteristic of mechanical spring coilers is the limited wire feeding length and the one-motor instructor that all tool control by one shaft as well as their synchronization gear were based by means of mechanical solutions. The accuracy and repeatability of the processes was extremely aggravated by material stress and mechanical clearances. These machines could only be operated by highly experienced spring makers; cam discs for pitch and spring shape had to be adjusted individually.
The high maintenance costs, long set-up times and low flexibility were the main problem of these machines. Therefore, the production of small amounts was very expensive. These machines would not meet the requirements of modern spring manufacturers.
mechanical spring coilers with Clutch-control
The progress and spread out of electric motors after 1945, enabled the construction of electrically driven machines. A clutch connected feed rollers pitch axis, up/Down cutting axis and OD cam with the motor that ran continuously. Cams on the main shaft controlled the clutch and let the feed rollers rotate for a certain revolution. As soon as a specific feeding length had been reached, the main shaft was disconnected from the drive motor. When the feed axes is stopped, the cutting shaft could be rotated by means of a clutch. During this time, all other tool motions are stopped. Larger machines had a hydralike clutch installed. In this system Cams engaged with mechanical system so quickly which made loud sounds. In this case there was a very great physical forces on clutch system parts and they are extremely stressed. All smaller spring coilers were equipped with friction clutches. With these clutches, the motor could be engaged slowly with the gear. Sudden shocks were avoided and the machines ran quietly. The essential problem of these machines was, however, that the feeding length was not stable.
The feeding length varied depending on the time the clutch needed to engage completely. Depending on the condition of the clutch, the springs were longer or shorter.
Another common problem of all clutch machines was a continuous feed speed. The adjustment of the coiling speed of a spring with a big spring index, was not possible.
controlling mechanical spring coilers different axes
The feeding axis by an oscillating link block connected to the continuously running motor. The part drove the feed rollers in one direction (forwards movement). During the return stroke, a freewheel disengaged the feed rollers from the link blick and interrupted the wire feeding action. At the same time, a mechanical brake stopped the feeding rollers while the cut action was made. The amplitude of the oscillating segment corresponded to the wire feeding length, the amplitude of the segment (the swinging motion of the pendulum) could be adjusted through the eccentricity of the link block.
Toothed rack control for mechanical spring coilers
One version of the segment control was the toothed-rack-controlled spring coiler which aimed at a high output. A spring coiler driven by toothed racks produced two springs during one 360°-revolution of the control shaft. This was possible because the second spring was produced on the return stroke of the toothed rack.
Multi-axes Electronic spring coilers
The spring production with mechanical spring coilers was rather expensive due to the cam discs employed, smaller batch sizes could not be produced anymore with acceptable set-up times.
By rapid developments in technology and be able to producing low-cost machine controls and powerful computers, design and manufacture of multi-axes machines become possible.
A computer in electronic spring coilers can synchronize the five axes. In addition to the control of axes movements, the computers enabled the processing of input data, the multi forming operations and measuring devices.
For high-quality springs, enough motor power for the wire feeding and forming is required. Furthermore, hard and more strength machine body is necessary to avoid vibrations and also compensate temperature fluctuations.
By using rotary cut system, the quality of springs increased dramatically. In this new cut system, the creation of burrs reduced. even though, burrs can not be completely avoided, they were reduced to a minimum.
Other mechanical deveopments such as separate coiling plate and modular design for tool carriers, increased machine advantages flexibility to produce different spring shape with short set up time.
Two-axes Electro-mechanic spring coilers
Besides developed solutions for the flexible production of small batches, there are even today machines needed for economical mass production. This is where two-axes electro-mechanic spring coilers are the solution. One axis is used for feeding in any length of wire and the second motor controls the tool motions of the cut, pitch and coiling. This compromise between conventional mechanic machine and fully electronic machine is even today a powerful and economical alternative.
Fully electronic spring coilers
Modern CNC spring coilers are more and more subject to economic aspects. The integration in networked production systems, which enable open communication on production level, workshop management and e.g. job control, plays an important role. It serves for the reduction of downtimes and the ideal use of the available machinery also when producing very small batches.
When acquiring new machines, not only the costs per unit based on output and material costs are considered, but the machine’s lifetime has become a crucial factor. Criteria like energy efficiency, machine availability and zero-error production gain more importance in the catalog of requirements. The decision for or a against the acquisition of a new machine is not merely based on its price but rather on the total cost of ownership (TCO) which include the required floor space, the fees for demolition and recycling and the machine’s running time. Therefore, questions about increasing the energy efficiency by means of the materials used, by means of energy recovery (intermediate circuit/energetic recovery system), by an optimized design of energy consumers like air-conditioning units and axes etc. play an important role in the development of new machines.
In the future, the main challenge will be to increase the machine capability and not to reduce downtimes or to maximize the output. The efficiency of the employed machine can be improved, e.g. by testing systems in combination with monitoring and measuring technology for achieving a zero-error production or by monitoring the production process for determining the ideal machine speed to minimize the production of defective parts. Increasing the machine capability may also mean to process different materials and thus increase the flexibility of the machine.