Fourslide vs. Punch-Press
What is a punch press? What can it do? What can’t it do? To put it as briefly as possible, it is a stamping plant in itself. Set in a progressive die, and it will blank out metal parts and stampings.
But, such a press has its limitations-because it has tool motion in only one direction it cannot, in itself, make certain forms or bends. These have to be taken care of by special cams and slides built into the die.
And that’s where the fourslide has the advantage, combining the features of the punch press, cams, slides; stock straightened and slide feed into one machine. A fourslide has all this and more.
Even a press head is available for fourslide, in 2 to 100 tons. The fourslides has four cams and slides, set 90 degrees apart, and each can be timed at any point in 360 degree of shaft rotation, with reference to the press head.
Yet the fourslide and its capabilities are not as well known as those of the punch press. Many shop men define it vaguely as one of those special machines that come tooled and ready to work on special long run jobs. They cost plenty? Of fourslide? It has something or other to do with forming wire or flat stock.
Let’s take a look at the fourslide and what it can do.
Take the slide feed, which can handle wire as well as flat stock. Here, the adjustable gripping jaws pressure on the material is positive and cam-controlled on the forward feed stroke, and it releases on the return stroke. A separate, cam-controlled adjustable stock checks jaw prevents the material from being dragged back, or from drifting.
Stock straightened? The fourslide has a two plane, 10 to 18-roll straightener that handles wire, as well as flat stock. And the fourslide has a variable speed drive to handle many different jobs.
And here is the “and more”: the fourslide also has two adjustable cam-controlled motions from above; a form lifter (for bending in the opposing plane, or for lifting the king-post form tool), and the stripper. The latter, as its name implies, strips the finished, formed stamping from the mandrel.
To round off the list of standard fourslide equipment, the machine has another slide, the primary cutoff, which is also cam-controlled and is laterally adjustable in either direction on the bed area, so that it can part the stamping from its strip before forming.
What do all these mechanisms accomplish? Just this: no more building of cams and dies for certain formed stampings – a job that involves a big dollar outlay for the press tools.
In addition to the standard equipment listed, there are many optional accessories. For instance, there is a secondary cutoff for notching, close control of length, and other operations. A nail-pointing attachment points stock or cuts material from above, instead of horizontally. Hoppers can be adapted for assembly operations, and holes can be tapped with tapping attachments. Spot or butt-welding can be done before, during, or after bending.
Does this mean you should sell your Punch Presses and buy Fourslides? By no means. Actually, both the punch press and fourslide are important in producing metal stampings. The fourslide, however, can produce a large number of formed stampings at lower costs with simpler tooling.
Fourslide tooling is designed and built to go on each slide as separate tool blocks for bending or forming, as required. For pushing off the formed stampings, a stripper is attached at the king post, where mandrels are located.
After the slide feed pulls the strip material off the stock reel and through the straightener, the material automatically feeds into the press area for piercing, after which it continues to the forming area, where it is cut off and formed to shape. Just before final forming by the slides, the blank is held by the front tool against forming mandrels.
The front tool finish forms the front portion of the stamping, as well as partially bending its ends. At the same time, the cut-off tool retracts, ready for the next cycle. The right and left tools can simultaneously advance to impart another 90 degree bending of the ends inward around the mandrels. Then the back tool advances to finish form the ends of the stamping around the mandrels. At this point, the tool slides retract. The stripper rod is attached to the stripper rod to push the formed stamping from the mandrel through an opening in the bed of the machine into a container.
The same basic knowledge that the tool and die maker and the tool designer have for tooling a punch press is sufficient for tooling the fourslide. In fact, the problems of building tooling are usually simple but perceptive skills are needed.
Our next installment will discuss why it’s better to make a music wire spring on a fourslide instead of using a punch press.
Many formed stampings, whether made of strip or wire, whether completed parts or just components can be produced by a fourslide as well as on a punch press. But if the job can be made on either of the machines, it is necessary to know the capabilities of each in order to choose which can do the job most efficiently and economically.
Today, increasing competition and a shortage of skilled labor have combined to put pressure on tool and die makers, tool designers, and plant engineers to produce parts faster and cheaper, and at the same time save on material.
And that’s where the fourslide comes in. Trouble is, even though this machine has been around for some 80 years, few shops know how to use it effectively. Admittedly, there are a number of knowledgeable job shops that use fourslides, but most other plants don’t seem to realize that they can produce complex parts on a fourslide with simple tooling at low cost, and on a short lead time.
Over the years, the fourslide has become a one-machine automated production line: raw stock is fed into it, and a completed part emerges with each stroke. It has a certain edge over the punch press in such operations as matching to bending, but that is not to say that generally the punch press is just as efficient as the fourslide when correctly tooled for a properly selected part.
Because of the fourslide’s versatility, the tooling designer is able to develop simple tooling for formed parts, whether they’re made of strip or of wire. Certainly, a music wire formed part would be a tough job for a punch press. But it’s a breeze for the fourslide.
Let’s put it another way: punch presses and fourslides can work side by side, if each is doing the work to which it is best suited.
Many job shops today have a wide range of fourslides, so as to give them a choice that is dictated by the size of the part to be made and the tonnage required.
In all fourslide models, however, basic operations are the same: a slide feed pulls the material off a stock reel, through a straightener, and into the press head area.
After the piece is punched, or goes through other stamping operations, it travels into the fourslide’s forming area, where it is parted and formed into shape by developed tool blocks that are arranged to suit conditions. And the positive feed is accurate in most cases within +- 0.002 in. In some cases, tolerances can be held with in +- 0.001 in. The tools in the four slides can be adjusted in any direction, while the tools of a progressive die cannot be cross adjusted. This also allows flexibility in any necessary deviations from design specifications after the tools are made. Such corrections in a die might be impossible.
Another quality and production consideration is that buckling of stock can be a serious problem with progressive dies. This can affect quality or cause undesirable machine downtime. Because forming takes place after the stamping operations buckling is reduced. Material cost, especially with strip stock, is usually lower with the fourslide. Because of the operating characteristics of the punch press, many times pilots are needed to insure accurate feeding and this means extra stock for pilot holes. Or again, added stock width might be necessary to prevent buckling. Then, to allow for possible variations in feed lengths in the punch press, material is provided between blanking in the strip. With the close tolerance control on feeding in the fourslide and because feed length usually equals blank length, less strip is consumed.
Some feel that the initial tooling cost for the fourslide is higher than the cost for a progressive die for the same part. NOT TRUE, fourslide tooling is significantly lower. Again, it is good to remember that one big advantage of the fourslide is that it can form complex shaped parts completely in one machine with out secondary handling. As was mentioned earlier, the tool life usually is longer in the fourslide, so the number of final parts required affects the tool cost, too. Even if the fourslide tooling cost 24% more initially than a progressive die. But the die life is half that of the fourslide tools. Then the actual tool cost for the progressive die is 60% higher than the fourslide tooling.
Other economies are realized because of the greater flexibility of the fourslide machines. Hourly production can be doubled in some cases by manufacturing two parts simultaneously. Or, complex parts can be partially formed at the same level as the die, then stripped to a lower level where a second set of tooling completes the forming operations. At other times, a third level and set of tools may be used again to complete the form in one machine without secondary operations. So many factors must be considered in determining which process is best. The modern stamping plant uses both kinds of machines for best results.
The fourslide have far more potential as a cost saver than has been indicated so far in this series of articles. Most people don’t set up more than single level operations with a combination of one or more of the four forming slides.
But this same machine can increase its output substantially with multiples of four operations in the forming section. Thus stampings requiring four, eight, or twelve forming steps can be produced at no more cost than if the operation were limited to four forming steps.
The trick here is to partially form the stamped part at one level, than strip it down to a lower level, where final forming is done with additional tools. This dual level tooling is known as multiple block tool design.
Stacked tool blocks, for example, are fastened together, and move together. The top tool performs part of the initial forming sequence, whereas the lower tool is the finisher. Multiple tool blocks, however, aren’t necessary for each slide, because tools are designed according to the requirements at each station.
Design and development of the tool blocks is the key to success with a fourslide, whose tools can sometimes be laid out completely by the tool engineer. In other cases, however, the toolmaker must make alterations to suit the forming characteristics of the metal.
When tooled for the fourslide, a formed sampling will generally require tools that are simpler and easier to make than those for a punch press. As a result, design is both practical and a better manufacturing method; and cost is low, because of simpler design.
Because of the variety of work that is handled in many shops, these basic goals can’t be achieved with a punch press alone. This is especially true of some formed stampings and wire parts. Therefore, an up to date stamping shop should have fourslides, as well as punch presses, so it’s possible to choose a better manufacturing method, not just one that will make the part.
Because the fourslide machine has a press head (ram), or can have a press attachment, as well as the four slides, plus stripper and vertical form, the part can be completed in one machine. Two types enhance versatility and flexibility of the fourslides: first, a wire machine, and second, a flat stock or strip machine.
The wire machine handles material up to ½ in. in diameter and feed lengths to 36in. Four shafts surround its horizontal bed with power transmitted through miter gears from the variable speed motor. The machine incorporates its own roll straightened, feed mechanism, stock check, cut off, four cam actuated slides operating at 90 degrees apart, a stripping mechanism to eject the finished part, and, when required, a vertical form lifter.
The cut off unit can be removed and a light press attachment substituted for use in light flat stock jobs. Cutting off is then accomplished with the press attachment or front tool. A standard secondary cut off attachment can be used for cutting the right hand end of wire or ribbon stock for extreme accuracy in length. The device also is used to cut an irregular contour on the end of the stock different from that made by the primary cut off, or to perform operations on the fight hand end of the stock.
The feed is accomplished in 180 degree of the cycle. It is accurate in most cases to within +- 0.002 in. and in some cases to +- 0.001 in. Special feeding can be accomplished in 90 degrees, allowing 270 degrees for forming. While the feed stroke, the stock check grips the stock positively to eliminate slippage. The cut off mechanism has adjustable timing and is cam actuated. Cams also actuate the fourslide. Camming is made to suit each job, but standard cams are used in many cases.
Then, the fourslide flat stock machine has all the features just mentioned, plus a crank or cam actuated ram located between the check and cut off. This provides a horizontal press head or ram, so the stock rests vertically on edge. Design of dies is the same as for progressive dies. Pilots can be employed and vertical ram actuated holders hold strip against the wear strip in the die, which is made in sections. If additional piercing is required, the press attachment ca is used in place of the cut off mechanism.
There are some models of the fourslide that have two rams where the stroke of the first die is 35 degrees of the second. Although the tonnage of each ram might be 12 tons, machine rigidity is required only for 12 tons instead of 24. This out of phase operation of the stock lengthwise, in an operation such as coining, without affecting piercing, trimming or drawing in the second die set 35 degrees later. With the stock coming through the fourslide in a vertical position, slugs from the stamping operation are pushed out the back. The completed parts are made from stock up to 4 in. wide and feed lengths to 15 in.
It is important to select the right size fourslide machine for the wire or strip job. Fourslides are rated for thickness and width, or diameter, length of feed, and tonnage required for the press operations. Feed rates for simple jobs approximate 100fpm/ Actual speed is determined by strokes of cams, feed length and intricacy of the tooling involved.
By forming on two levels, as described in Part 3, a large number of operations can be performed on one fourslide machine. Therefore, there is a strong chance that a rather completed piece can be completed on one machine, rather than requiring second operation.
The two or three level capability of the fourslide should also be kept in mind. And to extend the usefulness of the fourslide, try to think in terms of making two parts at once, and splitting them apart.
It is this sort of versatility and resourcefulness that keeps a stamping shop competitive. The company that has capable tool designers, toolmakers and methods engineers can come up with economies that supply the essential “edge” in obtaining new work. With both presses and fourslides in several sizes on hand, the capable production man can decide which will give the best efficiency and delivery on a job.
Final cost and delivery depend heavily on the time it takes to design, make, and set up tooling. By having both presses and fourslides in the shop, the advantages of each can be obtained in respect to tooling and production. But to show where the fourslide fits in, we must explain an example.
The job is a formed stamping that is required in large quantities and, as usual, at low production costs. First, the choice must be made between the punch press and the fourslide. Since this part is complex, tooling costs mount in unrealistic proportion with the punch press to produce this part economically. But an acquaintance with the versatility of the fourslide is needed to see how to double production.
The obvious approach with the fourslide is to think of producing one part at each machine cycle. But, without any increase in tooling costs, there is a method of producing two identical piece parts at each cycle to double the output. For the job with the machine operating at 190 strokes per minute. 380 parts are produced.
After the piercing operations, the double piece part is formed on the upper. Then it is transferred to the lower level for final forming and parting of the final form into two stampings.
All holes, notching and blanking are handled in the built in press head section of the fourslide ahead of the forming area. The developed double length blank is fed into the forming area. Here the cut off tool parts the blank. At this instant, the front tool is holding the double length blank against the forming mandrel. Form this point, the front tool continues forward, to bend the four legs of the blank. The cut off tool is retracted and ready for the next cycle.
Next the left and right tools advance to form the double blank. The back tool, advances to complete forming the four legs on the upper level. As all tools retract, the stripper pushes the finished double form from the upper to the lower level.
As the front tool starts a new cycle at the upper level, the tool on it lower level serves as a pressure pad to hold the preformed stamping. This lower level front tool presents a slitting die section, to receive the slitting punch on the back tool, lower level.
A secondary cut off attachment provides the tooling action, under the front tools, to make the final form on both parts of the double form. Then the back tool, advances to cut out the center divider between the two parts. Thus, two identical stampings are completed. The two side tools were not used on the lower level.
In addition to the production advantages of getting two finished parts at a time on the fourslide, material cost are less than they would be with the punch press. Savings in material can be substantial. Also, handling of excessive scrap is eliminated.
Then, too, the simplicity of the form tools is seen. The separate tool blocks for each bend or form are not complex nor are they confined to one area as in the die shoe of a punch press. Also, they use the built-in fourslide cam system, so that no special cam slides are required.
There are many other jobs where a decision as to which method to use is determined by the versatility of the fourslide process and simplicity of tooling. Example: one wire form, with a center bend and a bend on each end, is produced by the thousands in eighteen different sizes. All bends are identical, but the length in the two legs varies. The final tool design enables the production of all sizes with one set of tools impossible by any method other than the fourslide. Simple spacers for each length are inserted into the front tool as needed. Then the stock feed and the strokes of the left and right tools are adjusted as required with each new size.
If the modern stamping plant has fourslides, many jobs can be accepted that formerly were turned away. For instance, a part is wanted in large volumes, and is to be produced from 0.125 in. brass tubing 3¼ in. long before forming. A hole is to be pierced in one wall, one end is to be swaged watertight and the tubing formed into an eye. Without the fourslide’s versatility, the job probably would not otherwise come out of the shop.
Some thinking precedes turning up a solution. In the cited case one must decide to take the tubing off a coil or use stock cut to length. The latter is the right answer. However, this means a new type of feed. And here a simply designed gravity magazine feed is the answer. Since the primary cut off isn’t needed with stock cut to length, the secondary cut off attachment replaces the primary and is used to hold the magazine feed. Then a feeding finger is designed to push the tubing lengths from the magazine over a grooved guide rail that is attached to the secondary cut off. All the operator must do is to keep the magazines filled on three machines, remove filled tote pans. Our records show that he can turn out 345,000 pieces per eight-hour shift.
At other times, the fourslide can eliminate special machines. One such job requires dual coils on the ends of No. 10 round wire, with different lengths between the coils which always require the same 2 ¼ turns. In this case, the long feed length of the fourslide comes in handy because the lengths run to 26 in.
One must not forget that various types of treatments can be put on wire. In addition to a square cut off, chamfered ends can be obtained. Then simple swaging operations can provide parts swaged on the ends, swaged in the middle or items with swaged ears. Other wire parts may require swaging, piercing the swaged section and trimming.
Further flexibility of the fourslide process will be described in Part 5. A detailed account will be given of how a fourslide machine can handle both wire and strip at the same time. The strip is punched, the wire is inserted into holes in the strip, and both parts are formed into one completed part…all in one machine cycle.
Stampings costs come down when you can eliminate a second operation. And especially so, if you keep the tools simple. But these truisms are annoying when you are confronted with a part that consists of a wire form assembled to a flat stamping. However, if you have a fourslide, it is frequently possible to do the whole job in one operation.
Our case study, was a flat stamping with a wire form assembled through its legs. This assembly can be produced on a fourslide by feeding the strip and the wire from opposite directions. The standard stock straightener and feed mechanism built into the fourslide will handle the strip. And, an inexpensive, air operated slide feed is added on the right side of the machine to draw the wire through a set of roll straighteners. A Nilson S1-F fourslide provides the die space for the piercing or punching operation in the flat stock.
Production rate for the complete assembly is 165 units per minute, using the tooling setup. Because the strip must be pierced and formed first, the wire is fed through the punched holes, at a second, or lower level of the tool.
Additionally the cut off quill and cut off tool for the wire are mounted in the standard secondary cut off attachment that finds so many good applications in fourslide setups.
After the holes are punched in the flat stock at the press head area, the developed blank is fed into the forming area. Here, the primary cut off tool parts the blank. At the moment of cut off the front tool clamps the blank against the king post tool on the upper level. Then, the front tool continues to advance to form the first portion of the stamping into a double 90-degree bend.
The left and right side tools now advance to finish form the stamping. (Note that the back tool is not used on the upper level.) After this, the tools retract and the stripper transfers the formed stamping to the lower level of the king post tool. At this second level, the developed length of the wire is inserted through the slot in the king post tool.
While the upper level tools start a new cycle, the secondary cut off attachment on the lower levels cuts the developed length of wire. Now, the front tool (lower level) acts as a pressure pad on the wire, and also presents a forming area for the wire to be shaped.
At this point in the cycle, the back tool advances to finish form the wire as a two-piece assembled part. As the cycle repeats, the first level form strips off the completed assembly when it is pushed into position on the second level. Again, it is to be noted that the side tools on the second level are not used. If more complicated forms were needed on the wire, these tools would be available.
All stock fed into the fourslide forming tools should be as free as possible of bends, kinks, spirals or twists. But the wire, unless straightened, will have coil curvature, and may have additional spiral twist or cast, especially if it is high tensile or music wire. Uniform straightness is essential of uniform parts.
Straightening is accomplished by bending the wire past its elastic limit in two planes, so that it lays flat. For this purpose, one uses a standard wire roll straightener. This device has the usual two banks of slide-able tools mounted in antifriction bearings. The two banks operate at 90 degrees to each other to straighten in two planes. Each bank shown has five rolls, three above and two below the wire line. The roll positions are staggered.
Screws all on the rolls to be moved against the wire line. All rolls have grooves to guide the wire.
To set a wire straightener for a new stock size, the rolls are backed off so a hand-straightened length easily passes through the rolls. Now you set the rolls against the straight length. As the wire extends from the first plane, the furthermost roll to the right is moved toward the wire line to turn the wire from A to X. The opposite occurs to move from B to X. When these movements do not rectify the wire, so it points straight out to X, adjustments must be made on other rolls. This is true in both planes. After adjustments are made on the test wire, production wire can be inserted through the rolls to start the coil. For heavy gage wire of ¼ in. diameter or larger, a quick release type straightener is used for starting new coils.
During the last decade, miniaturization has required closer tolerances for straightness of small gage wires in various alloy materials. This occasionally calls for the use of rotary straighteners, wherein grooved blocks rotate around the wire. The blocks must straighten the wire without spiral scratches or barber poling.
With some types of small diameter wire, a counter rotating straightener might be required. In this unit, two heads turn in opposite directions at up to 12,000 rpm, so that wire down to 0.004 inches in diameter can be safely straightened.
As has been said repeatedly in this series, the fourslide is as important as the power press in the manufacture of metal parts at high production rates yet it seems that few press room have both types of equipment.
It stands to reason that any shop, which possesses both kinds of machines, is more flexible, and can handle a greater variety of jobs than a shop with just one type.
And the fourslide and the power press need not be competitive there are many instances when they are compatible.
With such a combination of machines, a shop’s versatility is greatly increased, secondary operations can be eliminated, and handling and assembly costs reduced.
Tooling flexibility on fourslide machines is maintained without a complex, sophisticated approach. In the production of formed stampings, one of the big advantages of the fourslide process is the simplicity of the form tools used in conjunction with a separate die area for stamping operations. And, when comparing this process with the punch press, the avoidance of intricate camming, as in a progressive die, is an attractive advantage. Moreover, the many different approaches in fourslide tooling make it possible to select a simple one.
Metco Fourslide manufactures a complete range of fourslide stampings: custom metal stamping, fourslide products, miniature stampings, punch press stampings,
stamped flat springs and stamped wire forms, located in the Los Angeles, California area. • 17540 S Denver Avenue, Gardena, CA 90248
Toll Free: (800) 582-3476 • Tel: (310) 516-6547 • Fax: (310) 323-6365 • Send e-mail • www.metcofourslide.com