Strategies For Successful Punching

Particularly sophisticated machining problems can often no longer be solved with standard tools. Strategies for successful punching include

special tools and using the right tooling for manufacturing of highly complex components in shorter and shorter amounts of time. Contributed by Trumpf.

The Right Tooling

For punching there exists different tooling options. The Classic punching tool system is the leading tool system for punching and punch laser machines. Due to the broad range of forms, shears, coatings, and accessories, you can use it with flexibility. Another tooling option is the MultiTool that integrates up to ten different punching and die inserts in one tool.

Using the MultiTool increases productivity as different punching operations can be carried out by one tool. Additionally, forming and embossing can be carried out. The MultiTool possesses up to ten different inserts in one tool adapter, which increases flexibility and high efficiency. Another benefit is the reduction of non-productive times due to reduced setup and tool change times.

The Right Process

Scratch free processing

When it comes to punching, the end result heavily depends on the right process and it is crucial that the products are scratch free at the end of the process.

• Support tables for scratch-free workpieces: The basis for scratch-free processing is the use of brush tables, which provide soft support to the sheet and thereby preventing scratches and reduces noise. During positioning, the sheet slides over the brushes, which, due to their length, bend in the direction of movement.

Also, through raising brush field and laser cutting support plates around dies, the contact between sheet and die will be reduced leading to less scratches during the punching, forming and laser cutting.

• Solutions for punching-tools: Adhesive pads are pre-formed, self-stick polyethylene film and can be attached to dies, strippers and intermediate rings to prevent scratches on the workpiece. To avoid imprints and scratches on the sheet surface, a specially coated stripper can be used. The coating is also is wear-resistant and keeps material abrasion chips from sticking to it.
• Special die solutions: To reduce scratches for intermediate rings and dies, brushes or Ampco can be used. Ampco is a soft alloy that avoids scratches on the bottom of the sheet because of its softness and lubricant effect. Another option are descending dies that by moving downwards during the positioning of the sheet, eliminate the contact of metal between workpiece and processing station. Active dies additionally operate a second punching head able to perform an active forming stroke from below, broadening the rage of processing strategies and tool usage and enabling new forming sizes and heights.
• Gentle material handling through intelligent automation: By using different automation solutions, scratches can be easily prevented before and after production. A conveyor belt with soft surface, where finished parts are ejected from the punching machine, ensures gentle handling. Loading, unloading, stacking can be automated as well and by using a vacuum technology during these steps, scratches during part pick up, transport and deposit can be eliminated.

Material Usage Optimisation

Scratch Free processing | Image Source: Trumpf

Skeleton free processing

Material usage optimisation not only boosts your production but also helps you save – a lot. By implementing skeleton free processing companies can increase their sheet utilisation by 10 percent on average which reduces material costs. Additionally, smaller bits of residual material simplify logistics and yield higher scrap prices. Another advantage is the enhanced process-reliability achieved through the safe unloading of finished parts and small parts even when the part chute is open and through the automatic cut up and removal of residual pieces of sheet metal. Working without a scar skeleton also increases safety and is operator-friendly. Residual pieces of sheet metal can be sorted by material and good parts and scrap are sorted to different containers.

Other benefits of implementing skeleton free processing are savings in operational time by 14 percent on average and energy needed for the process itself: Operating a punching machine instead of manufacturing a metal sheet, consumes about 30-80 times less power which in turn leads to energy savings equal to the power needed to operate a punching machine for 40 years. Simultaneously, companies increase output rate through smaller workpieces and enhance their production and hence significantly boost their return on investment.

Skeleton-free processing relies on common slit cuts, which enable the sheet layout to be optimised, so parts are initially processed in sequence and then freely punched prior to discharge and removal. Parts or scrap are rotated using a separating tool with a bi-level stripper for ejection via the parts chute.  The remaining strips are then crushed.

Automation

Automation can save costs and boost production but it has to be reliable and safe to do so.

Automation can be applied to the loading of raw sheets or blanks and or pre-cut parts and the consequent unloading of finished parts, micro-joint sheets and scrap skeletons. Also disposal of scrap skeletons and remainder strips and sorting of small parts and punching slugs can be automated with the right machinery.

There are plenty benefits that automation in punching operation offers for example the increase in productivity due to high machine utilisation and reduced factory lead times. Additionally, automation increases process reliability, enhances efficiency and improves safety during the punching process.  Automated systems typically perform the manufacturing process with less variability than human workers, resulting in greater control and consistency of product quality

Integrated Tool Management

Automation can come into play even before the punching process is carried out. Before punching, suitable tools have to be selected and set up in the machine. Tool availability, proper assembly and accuracy of tool data in the machine control have to be checked, which is all very time consuming. With integrated tool management these steps can be automated which reduces search times and setup times. The central data management make data available—anytime and anywhere- and enables direct data transfer between machines. Tool management automation also increases efficiency of inventory management, productivity and process reliability, as the tools and tools lengths and changes are recorded and punch-stripper and –die combinations and tool suitability are checked by system automatically.

Programming

The software used to execute punching operations has a great impact on success and efficiency. Technology offers many different processing options and the right software should support users to make use of all these possibilities. A good software should simplify the nestling process and thereby optimise material utilisation and save costs. It should also reduce the effort required to generate the NC program for example by applying automatic repositioning and trimming.

Choosing a software that has the option for offline programming can reduce machine down time as programmer can prepare the next programs already while the machine is running. Additionally, settings can be predefined and adjusted to the specific needs of the company. If industry 4.0 is a topic for your company, a software with the ability to automate processes and integrate systems to make use of IoT should be chosen.

Skeleton Free Processing | Image Source: Trumpf

The Right Machine

A successful punching operation obviously depends on the selection of the right machine. To determine which machine is “right”, it is important to look at the nature, complexity and material of the items that will be processed. The type of material and sheet thickness play the dominant role in determining the punching force that is needed for future operations and therefore influence the decision on which machine should be purchased.

Another important factor that can influence which machine is right for you is the productivity needed. If speed and efficiency are of high importance in your production, a high-end machine that offers these benefits may be the best solution.

Additionally, it needs to be considered whether automation is of significance in your company or will be in the future. Not all machines offer the possibility to add on automation options and equipment, whereas other machines are especially well equipped and adapted to support automation functions and add-ons.

Lastly it is important to keep in mind that the purchase of a punching machine is a long-term investment and its functionality can affect your business success. When deciding which punching machine to buy, not only the differences in options and quality of the machine should be considered but also the supplier that you purchase the machine from.

The supplier should be reliable and trustworthy. A good supplier will support you with expertise and knowhow and provide proper consultation to find the optimal solution for you. It is essential to choose a supplier that provides after-sales services to ensure that your machine will be well maintained and to avoid downtimes and malfunctions in the future.

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