Here are my quality tips tensioning production lines
Steel coil slitting processing lines have reached a level where they operate with such high reliability, within such tight tolerances that we have come to think of the process as always having been completely under control and easily managed.
Nothing could be further from the truth. The quality products we enjoy today, everything from our shiny new appliances, to the gleaming car doors, to the perfectly proportioned soda cans, and literally 1 million other products, have all become routine. This being made possible by improvements in slit coil processing technology.
In this article we dive into some of these improvements along the way to make sure that the quality expected by all levels in the manufacturing process are easily met by a steel coil slitting processing operation.
Multiple Coils from One Coil
The main remarkable achievement was going from coil to coil with a series of slitters creating a new product for industrial America with several narrow slit coils out of one master coil. This was easy task.
Taking a coil that weighed at least five tons and converting it into a thickness of under 1/32 of an inch, and then carefully producing narrower coils that met tight tolerances was the silent beginning of a revolution in manufacturing.
That was nearly 80 years ago. There have been major advances in controlling each step of the process, but the main function remains the same. In order to produce the same high quality product time after time, one of the critical components is using slit coil tensioning appropriately and in a controlled fashion throughout the entire slit coil processing line.
The early days of steel coil processing were bare-bones simple lines using only an uncoiler, a gang slitter, and then a recoiler, all powered with general service alternating current motors.
As basic as the setup was, it not only got the job done for World War II, but in many places it continues to get the job done with the old system known as pull through slitting. The coil products that pull through slitting produced could not meet tight tolerances, but were good enough for the demands of the time.
Coil Lines Meeting Higher Standards
Lines must meet higher quality standards in today's competitive environment. Quality is generally considered to be meeting the specifications required for acceptance by the customer.
The specifications could include surface quality, deformation tolerances, width tolerances, tightness of the coil, thickness of the material, and a host of other potential quality factors.
Some of the newer means of maintaining quality include using slit separator discs at the recoiler, plus turning the entire line with servomotors and controllers that link from the uncoiler through the recoiler.
These carefully coordinated rotary velocity links ensure that the proper tension continues throughout the processing. This in turn produces a more uniform final product.
Though these slits separators, or doughnuts as they are sometimes called, can be important for straight wall recoiling, they also can introduce deformation if the edge of the coil is off even slightly.
The doughnuts will then impart a bending force on the slit material. Maintaining quality while; using doughnuts or slitting separators, laser alignment of the entire process and confirming the edge to the coil straightness, is critical in order to avoid any edge deformation or quality impact.
Post loop slitting is another type of coil slitting operation that is more advanced than the pull through format of slitting. Post loop slitting uses an uncoiler plus the slitter and a tensioning device prior to the recoiler.
The slitter and the recoiler will all have their component drive systems, whether they are servos, or alternating current motors. Unlike the pull through slitting method, post loop slitting has driven slitters and motors which must be sized so that they are capable of withdrawing the strip off of the uncoiler. Then have enough horsepower left over for consistently slitting the material and passing it through to the next phase.
Choosing Loop Methods for Coil Management
By necessity, the post loop method requires; a tension device, two drive motors and a looping pit that gathers material before the tension device and after the slitter.
There are a host of issues that this operation can develop with this setup. One of them is strand length differential which is supposedly handled with the loop and tensioner. The other one is edge problems with more loose edges, which will also contribute to strand length differential.
If a coil does not have the problems of either loose edges or loose centers, and the coil has been leveled, then the strand length differential will generally not exist. Most of the reason for a loop can be attributed to a crowned strip of material.
Maintaining the quality of a strip coil tensioning system requires primarily ensuring correct tension at each phase of the process without inducing any deformation on the material along with correct alignment from the uncoiler through the slitting heads and to the recoiler.
Paying attention to these key details will ensure a quality product from a coil strip processing line.To return from this Quality Production Tips page to the Strip Metal Coil Processing Home page, click here.
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