The turret punch press has been used to punch holes into blank sheets for three-quarters of a century. For processing a small volume of parts in a short amount of time, the punch press always has been more efficient than a conventional stamping press. In the last 20 years, laser cutting technology has addressed the tooling requirement with even faster setups, eliminating punches and dies completely. For the turret punch press market to survive, manufacturers had to reinvent the machine.
Today punching is only half of what a new turret punch press can do. Adding secondary operations is key to cutting process time, and adding automation reduces handling time. These capabilities have been incorporated into modern machines.
There are many options for metal parts manufacturing, and each offers a set of unique pros and cons. Efficiency, the detail and delicacy of the finished product, and the type of metal used all influence what the best metal manufacturing tool to use is.
If you are looking for a production method that improves your production speed and versatility, then consider turret punching. Turret punching is a good fit for anyone looking to have flexibility in the size of their production runs and their designs, and who need a method with a shorter turnaround time from design to the final product. It offers more dynamic manufacturing than other methods, making it a great option for anyone seeking faster, cost-effective manufacturing solutions. Read on to find out more about turret punching and its benefits.
What is turret punching?
A turret punch is a type of press punch, used to manufacture metal parts by punching the shapes out of large blanks. The machine operates by using two turrets that function as a die and punch, with one below the blank and one above. They move in perfect sync with each other to punch the shapes from the metal.
Turret punches address the greatest restraints of punch presses: the cost of the machine itself and the creation of custom press tools. While punch presses are good for mass production, they inhibit presses from being used for smaller orders or prototype manufacturing. Turret punches work by using a set of standard punch tools, usually around 60, to create shapes. Instead of a single punch, turret punches work in a series of strokes, using standard shapes like squares, hexagons, and circles, moving around the blank to create specific pieces.
Punch Tool Basics
Tooling for a punch press consists of a punch, die and stripper. The punch is located in a guide mechanism that fits in the turret on a turret punch press. Turrets hold a variety of tools and index to bring different punch tools into the work zone of the machine.
Each punch tool has a corresponding die that is located under the machine tool’s worktable. The geometry of the punch determines the size and shape of the hole created in the sheet metal. Clearance between the punch and die is adjusted to reflect the material thickness.
When the punch press is actuated, a ram descends, causing the punch to knock out the material creating a slug. The die is designed to allow the slug to fall through. The stripper holds the sheet metal in place until the punch is fully withdrawn from the sheet.
Most sheet metal punch tools used in shops today are self-stripping. Instead of using the ram to push the punch through the material and pull it out, these tools are built with an internal spring that automatically retracts the punch. The ram then only needs to work in one direction. This saves cycle time and wears on the turret punch press.
Most of the more recent improvements in CNC punching technology have been focused around the need to improve productivity. While much effort has been directed to making the machines go faster, thereby reducing cycle time, additional consideration has been directed to looking at time savings across the entire sheet metal fabrication process.
Job shops have demanded these innovations, and original equipment manufacturers are responding to their customers’ demands for shorter order turn around, tighter tolerance specifications and delivery that coordinates with just-in-time inventory control systems.
Moreover, advancements in the simplification of sheet metal manufacturing, with the use of CNC and user-friendly programming systems, has helped shops respond to the shortage of qualified workers. Many of the skills traditionally required to set up and operate punch presses are being incorporated in software and hardware that is designed to simplify the operation.
Push Button Setup
In the area of setup, tooling innovations have provided significant throughput improvements for fab shops by reducing the complexity of setting tools. Simplified punch length control is a technical improvement in tooling design that has had an impact on punch tool setup.
Part of the setup procedure for turret punch press tooling involves setting the stroke of the punch. This is especially critical when installing a punch that has been re-sharpened.
Grinding the punch removes metal and therefore affects overall length of the punch. To compensate, shims were used in the punch guide assembly to bring the tool back to its optimum length. That process is time-consuming.
Current tool design has made compensating the punch a much simpler job. These new tools use a push-button adjusting system. Fine increments of 0.0001 inch eliminate the need for shims and make the tool setup consistent and fast.
In the stripper plate, rather than requiring screws or other fasteners to hold it in the guide, a push-button locking system is used to secure the plate in the guide assembly. This system eliminates the need for installation tools, and together with seamless adjustment, can reduce setup by 15 minutes per tool. For a 30-tool capacity machine, that’s significant.
The punching process generates heat. There is friction between the punch and the guide assembly as the punch reciprocates within its bushings. Modern turret punch presses are capable of 1,000 strokes per minute.
Most punch presses are equipped with, or have available, an automatic oil lubrication system. It supplies an air-oil mist through ports in the guide assembly to lubricate the moving parts in the tool. This significantly extends the life of wear parts within the punch tool.
Coating the punch is another method used by tool manufacturers to get more life from a tool grind. Hardness and smoothness are key to longer tool life, and currently, titanium carbo-nitride (TiCN) is used for this property.
Punch hardness of 90 Rc is available using this coating. Because of their geometry, coated tools can be reground without losing hardness.
Another property of the TiCN coating is that its smoothness helps with lubricity. This is well applied to jobs where oil is considered a contaminant. Shops making parts for food processing or parts that will be painted or coated are better left without an oil film.
Shops are always on the lookout for more and better ways to increase the productivity of their sheet metal fabrication operations. Combination tools, made possible by the application of CNC technology, are one tooling technology that has extended the productivity of the turret punch press.
A turret within the turret, these tool clusters can be programmed to the index to punch position, and they can be set up to provide 360 degrees of freedom for orientation of the punch tooltip. A single tool station on the turret can effectively bring several tools into the operation without indexing the turret.
Working in three dimensions is another application advancement being made in sheet metal fabrications. Increasingly shops are using the turret punch press to create 3D shapes in the workpiece that traditionally would be stamped in a secondary operation.
To make 3D shapes on a turret punch press, the raised form must be created up or away from the worktable. Since the sheet is manipulated under the turret, a 3D feature would create interference.
Therefore, when creating 3D forms on a punch press, the relationship of the die and punch is reversed. A hydraulic lift located under the die is actuated to raise it toward the punch. The total forming height is generally around 0.5 inch as measured from the top of the sheet metal to the top of the form.
Although the height of forms that can be produced on a turret punch press is limited, the ability provided by the machine and tool is a boon to shopping productivity. If relatively high, complex forms can be done on the punch press, and that’s one less manufacturing step the fab shop needs to consider.
A Wheel Of An Idea
In recent years, the wheel tool has proven to be a versatile addition to the fabricator’s arsenal of tools. It’s designed to work in a turret punch press, but unlike other tools, it’s not a punch.
Instead, a rolling knife, not unlike a pizza cutter, mounts in the machine turret and is held down in position by the hydraulic ram. A die is also used and locates in its usual position under the sheet metal.
This tool cuts sheet metal at the machine’s highest traverse rate. For shearing operations, the wheel tool cuts as fast as the sheet metal can be pulled under the cutter by the punch press.
In addition to shearing, the wheel has been developed into a variety of other application uses that can score a sheet for breaking, roll an integral rib for stiffening and roll an offset. Used in conjunction with an auto-indexing tool station, the wheel can be used to shear forms and contours.
Up to the wheel’s operating thickness limit of 0.092 inches in aluminium, it can cut large diameter holes without the need for nibbling. A new design for these tools allows their use on mechanical punch presses. Like the clicker on a ball-point pen, the ram lowers the tool with a stroke and raises it with another when the cut is finished.
The punch press continues to evolve in terms of speed and power. Tooling development is moving in tandem with these machine tool innovations. Higher tonnage machines allow shops to punch thicker sheets. Heavy-duty tools with more punch travel can be used in sheet metal material up to 0.5 inches thick.
Speed too is a consideration for the shop, and innovations such as Wilson’s slug hugger dies to allow shops to go faster. In this die, small bumps on the inside edge of the dying act to keep a punched slug from pulling out of the die at high speed.
Progressive tooling is an innovation that takes advantage of the punch press turret capacity. A single combination tool station can be used to perform a multiple-step punching operation that traditionally would have been done on a stamping press.
In general, innovations and advancements in machine technology and tooling application are creating a better fabricator. That’s good for the shop and good for the industry.
Types of turret punches
A CNC turret press can have up to 60 press tools to choose from. With this controller, we can rotate the tool holder quickly and conveniently, and move the required punching tools, whether square, circular or other shapes, to the punching position. If you use a press, there will be a turntable on the bed, one for the press and one for the mould. In order for the press to work effectively, the two turntables must be fully aligned and rotated synchronously.
State of the state-of-the-art art machines may also add forming and bending equipment, as well as punch cutting. Although it is unlikely to replace the pressure mechanism actuator used for box making, even the forming ability of small lugs may change the two machine process into one machine process, so as to shorten the material processing time.
When to use a turret punch?
If you want to cut many repeating shapes in succession, you can use a turret punch. If you need more complex, composite shapes, the laser cutter may be a better choice.
A typical CNC turret punch has up to 60 tools to choose from in a turret that can be rotated to bring any tool to the punch position. A simple shape, such as a square, circle, or hexagon, is cut directly from the sheet. A complex shape can be cut by making many squares or circular cuts around the circumference. Since the stamping tool needs a matching punch and dies set, there are two corresponding tool holders above and below the bed for punch and die. The two turrets must be rotated precisely in sync and carefully aligned. Several punches of the same shape can be used in the turret, each of which has a different angle because there is usually no function of rotating the sheet workpiece relative to the tool.
Why a turret punch?
Turret punching is a very fast and economical way to make holes on the metal plate, so people who need a fast and economical way to make holes on the metal plate often expect turret punching. Turret presses are so cost-effective because they contain multiple tools in one device, which means manufacturers avoid the cost of creating multiple, work-specific press tools.
Since each tool in the turret press is relatively small, the power required for the press is smaller than for a press with a press stroke to make similar parts. This makes the tools lighter and sometimes cheaper, although this is offset by the increased turret and paper positioning complexity. Each stroke of the turret punch is heavier. The tool press works fast, although of course, it needs many strokes. A turret punch can reach 600 strokes per minute.
Punching and general stamping work is a very suitable process for large-scale production. However, the initial processing cost of the machine and a special press is very high. This limits the use of punch work for small volume and prototype work. Turret punch is a way to solve this cost. A large number of standard punch tools are used in the mould of turret punch: holes of various sizes, straight edges, commonly used notches or mounting holes. By using a large number of strokes and several different tools, in turn, the turret press can make a variety of parts without first making a special press tool for the task. This saves time and money, allowing rapid prototyping or small batch production without mould delays.
Punches are less flexible than lasers used to cut composite shapes, but faster for repetitive shapes such as grilles for air conditioning units. Some units combine the features of laser and punch in one machine.
CNC turret punching creates shapes in sheet material by successively punching a series of basic shapes such as circles and rectangles. The basic shapes are selected from a rotating turret under CNC control. Edges are usually very good due to the shearing action. CNC turret punching can produce 2D shapes, including cutouts. It is best suited for custom enclosures, Metal Brackets, front panels, boxes, etc.
CNC turret punching is a cost-effective method for cutting sheet steel in moderate to long runs. It has vast tooling potential for increased versatility. This means the ability to produce a variety of components without re-tooling. This results in a significant saving in production cost and a noticeable increase in productivity. This has a great impact on job work cost, and so we are able to do job work with excellent quality at an affordable cost.