Automated systems and cells continue to gain ground in job shops, particularly around bending and laser cutting operations. However, equally automatable is the punching operation. The modern, standalone punch press is fast, often multi-process (think forming, tapping, scribing) and, depending on the application, can produce more parts in less time than a laser cutting machine.
Side note: A punch press punching 530 holes per min. delivers 8.83 holes per sec. on single hits at a 25.4-mm pitch. Using a cluster tool (nine holes per hit), even at a 50 percent hit rate, the result is 4 hits per sec., 36 holes or 2,160 holes per min. – faster than laser cutting.
Automating punched part removal will add a few seconds to process time, but the overall benefits are significant, including reduced overall operating cost, reduced cost per part, organized material flow and a step forward in building a smart factory. In the most fundamental measurement, an automated system is typically 1.5 times more efficient than one worker.
There are different ways to automate punched part removal – from taking basic steps to adding fully autonomous material load/unload and warehousing systems individually or in combination.
Using micro-joints
Punching micro-jointed parts within a large sheet of material is a simple improvement from using blanks cut to the size of the finished piece and is an effective way to produce and remove parts. Combine this method with an automatic material load/unload system and/or automation tower to handle a large volume of parts in an interrupted process.
In this scenario, the automation unit loads the material, pulls the sheets of tabbed parts off and places them on a pallet. A second operation is required to shake and break the parts and stack them.
Pick and place
The punch press can be equipped with automation that includes part picking and stacking for 2-D and part sorting for 3-D. This is an advantage of the punch press. In comparison, the laser offers automation on a sheet level only – with no part picking or sorting ability.
Robotic pick-and-place options offer even more versatility. A robot that individually picks parts off a worksheet allows automatic offload of different size parts. The robot neatly stacks parts ready for the next operation – no operator involvement needed.
Vacuum cups and/or magnets on the robotic arm reach into the punch press to pick an individual part as it is punched free from the sheet. The cups and magnets are programmed and activated for picking according to part geometry and nest location.
Magnets will pick any part configuration, but are limited to ferrous stock. Cups will pick parts from any material, but their use may be limited when offloading small or hole-intensive parts.
Note that automating the offloading of punched parts is easier on a single-head-style of punch press (versus a turret punch press). A large feed clearance makes it possible to pick both small and large parts as well as a broader range of part sizes. The automation device has more space between the tool magazine and the table to access parts. A turret-style punch press has less feed clearance. Because of this, the turret can interfere with the part picking operation with a higher likelihood of the automated device colliding with the turret. Therefore, part picking on a turret is restricted to larger sized parts.
Drop door, scrap bin
The drop door or work chute, standard on most punch presses, is a hinged door used to offload parts that are punched free of the sheet. It can be used to remove parts that can’t be tabbed because of edge quality, radius corners or aesthetic reasons. Parts drop into a bin on a conveyor system and are available for the next operation. Alternatively, parts can drop into a bin and then be fed into a sorting system that deposits similar parts into designated bins.
The workpiece skeleton can also be completely deconstructed on the machine: The sheet is punched and the skeleton is offloaded via the scrap bin. All scrap is offloaded into one contained bin, reducing material handling and making it easy and convenient to recycle scrap.
Automation digitization
An automated material load/unload, tower or warehouse system advances smart manufacturing. Such a system can track jobs electronically for a lean manufacturing flow. The system places jobs in a specific order sequence, allows the job list to be paused to run a “hot” job, tracks and monitors progress with a real-time display of job status, and oversees sheet inventory for material usage.
This intelligent operation allows users to confidently manufacture lights-out whether for day-to-day operations or for when extra capacity is needed, maximizing output without adding labor.
System options
There is a lot of choice in the type of system to use for punched part removal. Most systems are modular and offer a flexible configuration.
The modern material load/unload material system requires about 25 percent less floor space than systems designed just a decade ago. A punch press with a single-sided material load/unload system can be combined with a warehousing unit within the same footprint required for the punch press and a single-sided load/unload system (approximately 30 ft. by 20 ft.).
Loading devices generally have material input stack capacities of up to 10 in. and 10,000 lbs., allowing high throughput volume without operator intervention. Adding an automatic tower or multiple towers to a punch press with a large turret and tool capacity (i.e., 48 stations) further increases the autonomy of a system.
A tower system with a 30-shelf capacity allows the flexibility to work with different material types, grades and thicknesses, often a requirement for job shops. The tower unit also provides storage capacity to free floor space from pallets of material.
The bottom line: Shops are in search of operations that add value. A punch press that is able to counter sink and tap eliminates hundreds of hours of secondary processing time a year. Adding some form of automated punched part removal to keep material flow continuous and uninterrupted and sheets and parts organized provides even more savings and advantages for the fabricator.
