Guest Editorial

Decoding punch programming

By Mike Boggs

Assess current methods to further automate processing

FFJ 0917 guest leadSeptember 2017 - Although laser cutting’s versatility has made it a prevalent technology for sheet metal fabricators, CNC punching continues to excel in applications where it can produce parts cheaper and faster and wherever secondary operations can be eliminated. Fabricators who rely on punching technology often struggle with programming operations because punch machines are inherently more involved to program than laser machines. This stems from myriad tooling options that introduce placement, ordering and tool path considerations.

Machine and tooling manufacturers continue to advance punching technology to broaden its applicability, and these advancements often increase the complexity of CNC punch programming. This leaves many fabricators questioning whether punch programming can ever move beyond interactive methods. The level of punch programming automation that can actually be achieved depends upon many factors, but at a minimum, existing programming processes can often be improved.

Tool placement

How automated CNC punch programming can become depends on how effectively the programming software applies tools to parts. This is the software operation that we most commonly think of as “punching.” If the software punches every part optimally, then a high degree of automation is likely to be achieved.

But, as anyone who has ever programmed a punch machine knows, this can be quite challenging except with the simplest of parts. The following punching operations should be considered:

• Standard tool placement—Your programming software should be able to accurately place standard tools, such as rounds, obrounds, squares, rectangles, ‘D’ tools and polygons. But if your parts contain complex geometric configurations, such as involved bend reliefs, even the placement of standard tools can be challenging. Ideally your programming software will also memorize desired tooling patterns for a selected geometric configuration and repeat that tooling pattern as that geometric configuration is encountered in subsequent operations. This allows your punching software to adapt to your programming requirements and become more automated over time.

• Shaker tab (micro-joint) placement—Automatic placement of shaker tabs requires accurate calculation of tab locations and tab size, which can be both part and material dependent. Tabbing specific tools could require consideration.

• Special tool placement—Perhaps the most challenging punching operation to automate is the placement of special tools. Forming tools, tapping tools, rolling tools, cluster tools, bending tools, character tools, deburring tools and others can require extensive part analysis for accurate feature identification and tool placement.

In addition to automatic punching, programming software should quickly modify tooling on punched parts to override automatic tooling results and address engineering changes.

Pre-tooling vs. dynamic tooling

Punch programming software should provide the option to pre-tool parts, dynamically tool parts or some combination of the two. A pre-tooled part is one where the punch tooling is applied prior to the part being positioned on the sheet. The part is then maintained in a library with the tooling already in place. This is ideal for standard parts that are run repeatedly in varying quantities because it guarantees tooling accuracy and consistency.

Alternatively, parts can be dynamically tooled. This refers to parts being tooled on demand after, or in conjunction with, being placed on the sheet. A separate tooled instance of the part is not maintained. This is more suited to custom parts that are not likely to run again. Determining which approach to implement depends on such factors as production style, complexity of parts and punch machine features.

Extensive analysis

Accurately tooled parts are key to programming automation, but your programming software must also optimally process the tooled parts and take advantage of advanced punch machine capabilities. This can include tool sorting, tool path optimization, sheet repositioning, programmable clamp processing and drop door support. Each of these operations requires extensive analysis to automate, and each can introduce exceptions that must be managed.

Automating punch programming begins with an assessment of current programming methods. Each point of user intervention should be evaluated against programming software capability and process requirements. As software products continually advance, this should be an ongoing process with periodic reviews to ensure best practices. The end result may be significant reductions in punch programming time. FFJ

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