Rotary Slitting Principles and Applications Part 3 - The Formtek Blog

THE MACHINES

Link to Lihao Machine

Although design details vary, slitting installations fall into either of two very distinct design styles. A good many lines for light gauge, small coils of narrow width (Fig. 17) have the slitter and recoiler assembled on a common base.  Some even have the uncoiler and scrap winder on that same base.  (Fig. 18)

These are the “package” type lines.  Several manufacturers make this style as pull-through, or drive machines, or as a combination of both. In general, the application of this type machine is restricted to maximums of 10,000 lb. coils, .095” gage, and, 36” wide.

In contrast, the “customized” or multi-unit lines (Fig. 19) find extensive application throughout the complete range of coil weights, metal widths, thicknesses, cutting capacities, and speeds.  These “customized” lines are likely to vary from 12” to 84” wide, for gauges as light at .005” to as heavy as ½”, for coils from 100 to 1,000 lbs. per inch of width or more, with slitter arbors from 2” to 12”, and for speeds up to possibly FRM.  Remembering the limits of this discussion, however, let us examine only the components of a typical multi-unit sheet coil installation.

UNCOILER

The expanding mandrel type of uncoiler (Fig. 20) is most common and employs a hydraulically expansible drum to grip the coil at its core.  The drum is carried on cantilevered shaft rotating in anti-friction bearings and supported in a welded or cast frame.  A feeding drive, a braking system, and a lateral adjustment complete the requirements.

For applications where the coil weight is too great for an overhanging mandrel, a cone or stub mandrel (Fig. 21) is used.

SLITTERS

There are about as many slitter designs as there are manufacturers, but common to all is a pair of arbors, a drive, a base, and an entry guide system; that is where the similarity stops. We will not develop or compare the merits of each, but, a quick look at fundamentals is certainly in order.

Precision is the key note.  The arbors must be amply proportioned for minimum deflection at maximum load.  The bearing fits and arbor tolerances must be established and maintained at an accurate level.  The machine design must readily accommodate cutter set-up changes and penetration adjustments, and provide for feeding and guiding the metal.  Figure 22 illustrates a design with arbor sizes up to 6” and for coil widths to 48”. Here, cutter penetration is adjusted by moving the top arbor with respect to the bottom one using a hand wheel on the operator’s side of the outboard housing.  The outboard housing is removable from the arbor ends so the tooling can be stripped.

A design that is somewhat unique but nevertheless a design gaining popularity in the heavier machine category is shown in (Fig. 23). On this slitter the upper arbor is stationary and the bottom arbor adjusts vertically for penetration.  The weight of the arbor and tooling assembly is supported from below by the screws instead of hanging from them.  The advantages of this arrangement is that the backlash of adjusting screws is taken up in the idle condition, and requires no further adjustment when loaded.

Anything that can be done to reduce cutter set-up time should be done if maximum out-put is to be obtained.  Powered penetration and outboard housing adjustments help somewhat on this score, but removable head type slitters go all the way. The arbor assembly can be lifted off a sub-base, leaving the drive and all other accessory equipment in place.  A spare arbor assembly that has been tooled “off line” is then set into position and the slitter is ready to run.  Usually a cutter set-up consumes from about 30 minutes to an hour, whereas, the interchange of a preset housing assembly requires on about 10 minutes. The savings are obvious.

The typical recoiler (Fig. 24) includes a drum, a drive train, and a stripper. Most generally it, like the uncoiler, is a cantilevered design with the drum carried on the extended low speed shaft of a gear reducer. The high speed shaft of the reducer is coupled to the drive motor.

The drum should present an unbroken cylindrical surface when expanded. It should be collapsible so the coil can be stripped off after winding and it must provide a means to grip the strand ends at start-up.  These two functions are usually performed manually because they consume very little time; but they too, in the interest of maximum output, can be powered.

RECOILER DRIVE

Since the recoiler drive in a pull-through installation governs line speed and has considerable bearing on over-all line performance, its design should certainly receive more than just casual attention. Characteristics should include smooth accelerations, smooth deceleration, speed adjustment, jogging, braking, stall tension, efficient use of power and, of course, minimum maintenance.

FANOUT & COIL SEPARATION

The slit strands are separated as they are wound on the recoiler drum by thin discs usually from 1/16” to 3/32” thick.  Thus, the overall width of the rewound coil on the drum is greater than the summation of cut widths.  This differential, when related to the distance between slitter and recoiler is known as “fan-out”. Obviously the drum face must be wide enough to accommodate the accumulation of separators and strands, but of more importance, the strands must be distributed equally to the right and left of center.  Also, the recoiler must be positioned far enough away from the slitter so “fan-out” does not tend to develop camber.

Separators may be discs slightly larger than the maximum coil diameter, (Fig. 25) or they may be small discs assembled on an overarm separating device (Fig. 26).  The overarm separating unit eliminates handling large discs for each coil, as they do get heavy and bulky. The unit also functions as a hold-down to retain the strands when they tail out of the slitter.

SCRAP DISPOSAL

The device to be used for scrap disposal depends on several factors, such as the gauge of metal, the relative value of balled, wound, and chopped scrap on the local market, and the established in-plant handling facilities.  A winder (Fig. 27) creates a relatively loose, level wound coil; a baller (Fig. 28), a solidly compacted bundle; and a chopper (Fig. 29), short pieces.  The typical sheet coil line, being limited to ¼” thick material would most likely have a winder or a baller, but heavier lines demand choppers. The noise level of the chopper type may not meet the recent standards set by the Labor Department.

Model No. 1 Scrap Chopper, for mild steel stock up to .095” thick.  The rotating cutter head and dual flywheel arrangement is driven by a high slip AC motor through a gear reducer.

The rotating head has four cutting edges, arranged to cut alternately on the two selvage edges.

The one shown is intended for a line in which one edge of the stock is always adjacent to the inboard housing.  Thus, as indicated by the arrows, the inboard cutting edges are relatively short, and long cutting edges are provided on the outboard side to accommodate various widths of coil.

Where stock is processed on centerline, the rotating head is made with equal lengths of cutting edges on each side of center.

COIL FEEDING AIDS

Once the coil is placed on the uncoiler and the circumferential band is removed, the outer wrap must be peeled and the end transported from the uncoiler to the slitter. When stiff material is involved, the coil should also be controlled to prevent it from “clock springing” and thereby endangering personnel.

If it is necessary to slit coils that consistently average thicker than .095” and wider than 36”, it is then important to consider the mechanical coil feeding aids available. Such aids are as follows:

1. The combination of a hold-down roll, a peeling spade, and a flattener unit, (Fig. 30) including a table from it to the slitter, and a table from the slitter to the recoiler.In this system the hold-down roll retains the outer wrap and thus prevents the coil firm “clock springing”. The holding roll is driven and, with the aid of the uncoiler threading drive, propels the leading end over the peeling spade.The spade opens the outer wrap, “breaks the strip’s back”, and serves as a threading apron to guide the coil end between the feed rolls of the flattener.  They in turn drive it beneath the top bending roll, which has been lifted, and over the bottom roll at the exit side of the machine. The top bending roll is then brought down to remove the coil set, thereby making it easier to insert the end into the slitter pinch rolls when it reaches that point.

2. A driven hold-down roll, cantilevered over the uncoiler, working with a combined peeler and entry threading table, (Fig. 31) and a table from slitter to recoiler represent an excellent compromise system for essentially the same purpo This unit is less expensive, roughly half the cost, but requires greater manipulation on the part of the operator, and does not remove the coil set. The peeler spade is pivoted from the end of a powered slide on the table.  Both actions are used in conjunction with the hold-down roll to peel, break, and thread. Successive manipulations of the peeler (Fig. 32), while the metal is being simultaneously driven forward, reduces the normal generous coil curvature into successive smaller scallops.

Without these devise, light gauges are threaded simply by a team of men, dependent on the coil width, supporting the end and walking with it to the slitter as it is paid off by the threading drive.  Heavy gauges, on the other hand, in addition to time, might very well require the use of crowbars, sledge hammers, and two to four men, plus the use of an overhead crane as a pulling force, or the recoiler as a winch, to open up the coil and thread it into the slitter.

This post is part of the series, “Rotary Slitting Principles and Applications.” Here are links to the other posts in the series:

Looking to automate your coil processing line?

Here are some points to ponder:

When Should You Automate?

“I would say it’s based on volume. The more the volume increases, the easier to justify the investment. It’s not a rule of thumb that fits every manufacturer, however. A million parts per month to one company might be mere hours of production to others. Anything that is consumer driven, such as beverage cans, has extremely high volumes thus requiring the utmost in automation to remain competitive,” says Robert Allred, Beaufort, SC-based general manager, marketing and sales, for the automation division of the Minster Machine Company (itself headquartered in Minster, Ohio).

Fine, but what if a firm has a relatively low volume of production and wants to expand; should the owner automate his coil processing line in the hope of drumming up more business? Or should companies only automate when production volumes are high?

According to Jeff Norman, vice-president of Mecon Industries Limited in Scarborough, Ontario, these are the wrong questions to ask.

The real question should be, “’How often are setups changed?’ not, ‘High or Low volume’. More business may mean more setup changes to keep a system fully booked. Adding automatic features that reduce setup time will payback in greater uptime, will lead to lower costs per part and in turn allow the work to be sold at a lower price with similar profit,” he states.

Norman offers the following example: “Consider a company that has eight hours per shift, runs the same process all the time. Coil run time is 50 minutes while coil reload time is 10 minutes. Assuming no other waiting time then the system will process eight coils per shift.

“Now consider a situation where the company has mixed production and must change the setup every third coil. In a manual system, the operator would thread the new coil, tune the straightener or other process settings during the beginning of the run. Let’s say the tuning takes 10 minutes before the production is up-to-speed. So, three coils [times] 60 minutes equals 180 minutes plus 10 minutes for setup, for 190 minutes in total. Time to run three coils is 190 divided by three or 63.3 minutes, which is a little more that 5.5 percent longer than the first system. If settings are preloaded and the machine changes automatically when the new job is loaded, then the tuning time should be reduced or eliminated,” he continues.

Retrofit/refurbish/upgrade

When times are tight, it’s sometimes a better idea to make do with what you have than to purchase new. “Refurbishment” (a fancy term for retrofitting or upgrading) is the key concept here.

“I would say in a recession people look to retrofit, upgrade their equipment a little more” rather than purchase new equipment, says John Cauffiel, president of Galaxie Corporation in Detroit.

Galaxie specializes in buying and selling used coil processing and tube equipment. Top selling systems include slitting and cut-to-length lines. The company doesn’t do retrofits but offers referrals to contractors and rebuilders who do.

“Refurbishment is a valid choice in some instances. In others, new is better as it allows the user to get what they really need,” adds Norman.

New, Noteworthy, or Both

Red Bud Industries of Red Bud, Illinois, is a major manufacturer of coil processing equipment with some innovative products for companies looking to automate their line.

If you are looking for more details, kindly visit Coil Slitting Line.

Take the recently released Auto Slitter for example, a fully automated CNC programmable slitting head designed for use on multi-blanking or slitting lines.

“Historically, if you’re into slitting lines or multi-blanking, the most tedious, time consuming part of the process is setting up the slitting head ... it’s not uncommon on a traditional slitting head to take a minimum of half-hour, sometimes 45 minutes to an hour, to set that particular piece of equipment up,” says Dean Linders, vice-president of marketing and sales, at Red Bud.

“So, what we’ve done is [invent] our first automated slitter that sets up in two minutes flat. The operator inputs the width of the strip and the thickness of the part into the computer and it takes over and completely sets up all the slitting knives to [do] the job,” continues Linders.

The Auto Slitter can support up to 10 cuts at one time. It has a maximum width capacity of 72” ( mm), maximum thickness capacity of .250” (6.3 mm) and a minimum slit width of 5” (127 mm).

“If required, complete jobs can be downloaded directly from the customer’s in-house computer system directly to the line for the Slitting Head,” adds Red Bud literature.

Red Bud has also introduced the fully automated Coil Prestage and Load System for heavy gauge coil processing lines. This automatic coil loading system is a fairly unique creation.

“It’s not a typical thing you see on the marketplace,” boasts Linders.

The Coil Prestage and Load System consists of an Inline Coil Prestaging System, integrated Coil Car and Dual Stub Arbor Uncoiler. The operator hits a button and “the Coil Prestage and Load System’s integrated Coil Car retrieves the coil to be processed. The system will then measure the outside and inside diameters of the coil. After measuring, the Coil Car will position and raise the coil as required automatically for loading onto the line’s uncoiler. The Dual Mandrel Uncoiler will then spear the coil and center it automatically on the line,” explains Red Bud literature.

Norwalk Innovation of Springfield, Missouri, meanwhile, is renowned for a piece of equipment called “the Un-Coiler” which allows for speedy coil changes, thus reducing handling time and allowing more efficient use of labour. Like the coil Prestage and Load System, the Un-Coiler isn’t new, but it is inventive.

The Un-Coiler “works in automatic mode off of a loop control system,” explains Norwalk sales manager Steve Cox.

Trends to Consider

“Equipment related to energy seems to be doing pretty good ... like hot rolled steel processing equipment,” notes Cauffiel.

Another trend to bear in mind is the move towards heavier coils.

Bigger coils can improve productivity: “Larger coils result in less change-over,” says Cox.

However, if you’re buying used equipment, massive coils can limit what you can acquire.

“Mills would like to sell you bigger coils ... 30 – 40 ton easily ... some of the older equipment doesn’t have that coil weight capacity,” warns Cauffiel.

What’s the best way to get the most out of your coil processing line?

“Provide proper training, be sure to use the equipment within design limits, inspect and maintain equipment regularly,” advises Norman.

“First, completely understand its capabilities and operation. Don’t do like me and not read the manual until it breaks!” adds Allred.

The Philosophy of Automation

“In terms of automation ... what we’re doing on our equipment is continual improvement of the process. Identifying the machine in terms of how they function, what can you do to automate the process to make it easier to run, quicker to set up and change-over, fewer people needed to run the machine to keep costs down,” says Linders.

A Warning: Don’t get carried away

“You still need people to man these big lines ... you still need a human being there to monitor the automation ... maybe you can eliminate a person here or there but the human element is still essential,” says Cauffiel.

“Where you see big production loss is not so much the machinery itself doing the processes, it’s the handling of the material, either the entry side or the exit side ... the material handling is more essential than doubling the speed of the machine. I see more time lost handling the coil,” he states.

Norman advises company owners to “focus less on ‘automation’ and more on which machine features are needed to achieve best production efficiency, to be operator friendly and maintainable.”

Next Steps

Once a shop owner has their automated coil processing line in place, what kind of upgrades should they be looking at?

“It depends on the goal … often greater benefit is found by improving the mechanical features of the system. Feature upgrades depend on the starting point. Most systems have a simple manual mode and automatic mode with a start button. Setting the machine for the next job will require the operator to manually set speeds, heights, or other parameters,” states Norman.

He ticks off a list of possible system upgrades for shop owners to consider:

“One: provide accurate position indicators for mechanically set devices, so the operator can repeat the setup.

Two: motorize manual mechanical settings so that they may be done from a control console.

Three: install a controller that will store electronic parameters by job number.

Four: Connect the electronic parameter list to the devices to change, so that the new setup can be done by a single button pressing.

Five: convert the motorized mechanical setup to servo motor setup and command the servomotor from the electronic parameter list.”

For his part, Allred says, “If the control is not equipped with a modem look into that. We have saved a lot of money for warranty repair and customer service charges by being able to “plug into” the control and diagnose the problem through a line or better Ethernet. This gets the customer up and running quicker and eliminates costly travel expenses. It can also be utilized to install software updates as required.”

Look South for Bargains

While the Canadian dollar has been slipping a bit recently, it’s still far stronger than it was a decade ago, when it plummeted to 60 cents against the U.S. greenback.

Given the dollar’s notorious volatility it might be a good idea for Canadian firms to scoop up coil processing equipment in the U.S. before the loonie fades again.

“The strength of the Canadian dollar makes us more competitive in Canada. However, the trend of manufacturing moving to Asia reduces the volume [we sell to Canada],” says Cox.

A Final Thought

Given the above point, is automation a good way for North American firms doing coil processing to compete with low-cost, off-shore companies?

“Absolutely. You beat them by being more efficient and producing a better quality product and you do that through automation,” says Linders.  CM

Nate Hendley is a regular contributor and freelance writer based in Toronto.

www.mecon.com

www.redbudindustries.com

www.galaxiecorp.com

Contact us to discuss your requirements of Cut to Length Line. Our experienced sales team can help you identify the options that best suit your needs.