Too often “Activity” is confused with “Productivity”. Fabrication remains an evolving process; and manufacturers must continue to embrace best practices and leading technologies in order to ensure that day-to-day shop floor activities will have a direct and measurable impact on bottom-line productivity.
According to the National Bureau of Economic Research, the most recent recession began in December of 2007. Shortly thereafter, manufacturers of every size and type began scrutinizing nearly every aspect of the operation. As a result, terms like Responsiveness, Agility, and Lean Practices began taking on a whole new meaning. Within a few months there would become two types of manufacturers: those who would embrace change and those who wished they had.
Today, many fabricators who weathered the economic storm are reporting near record levels of activity with added shifts, rehired workers, investments in new machinery, and a backlog of orders waiting to be filled. But how does all of this activity translate into productivity? And why is it that these investments are not proportionately reflected in a growing bottom line?
The answer is non-value added rework that typically occurs well downstream. Efficiently nested parts on a sheet have a direct and positive impact on reducing material waste, accelerating cutting operations, and boosting shop floor productivity. Conversely inadequate nesting result in production bottlenecks and cost overrun as a substantial amount of a programmer’s time is spent re-nesting parts.
Part 2: Nesting
In its most simple form, nesting is a simple cookie-cutter concept: arrange shapes so that the most parts will fit on a given material size. However, moving from incremental to breakthrough levels of material savings and productivity requires a much deeper understanding of the factors that deliver measurable results.
Common-line cutting, for example, is the practice of arranging parts with shared edges so that multiple parts require only a single cut. When done properly the result is faster run time, maximum material usage, and often extended tool life as pierce points are greatly reduced. Common-line cutting is a tremendous time-saver when used with methodical processes such as cutting thick plate.
Sometimes less experienced programmers may get greedy when creating nests. In an attempt to get the absolute most out of every sheet of metal one may create a nest that is too tight. Skeleton management is another important metal fabrication consideration. Due to inadequate part positioning, material surrounding parts can be inadequate and will lack the strength to fully support a neighboring part once the cutting process has begun. This instability will have a direct and adverse effect on part quality. An effective work-around in this instance would be to add tabs for stability.
Other problematic issues are often related to placement of lead-in and lead-out, and heat distortion. Heat generated during the cutting process can create an expansion effect that shifts the part, creating an opportunity for errors. Again, being aware of these hazards and programming today’s advanced cutting machines requires knowledge that comes with experience.
Unfortunately for many manual nesters, or those employing less sophisticated nesting software, these lessons are too often learned through trial and error with a hefty price tag of scrapped parts and cost and time overruns.
Sophisticated fabrication software automates tasks and improves cutting machine performance. Whether purchasing a new machine or looking to improve operations, manufacturers should give the nesting software that drives costly and complex machinery careful consideration.
Part 3: Nesting Software
Manufacturers invest heavily to bring advanced cutting capability to the shop floor. Hundreds of thousands of dollars are spent to accelerate throughput and entice new business. Each feature is benchmarked and scrutinized with pain-staking due diligence to ensure that the best machine is purchased.
Unfortunately the same consideration does not generally go in to selecting the software to run these machines. Nesting software is too often an afterthought based solely on price. The scenario has been compared to spending many thousands of dollars on a high-performance sports car only to equip it retread tires. All laser, plasma, oxyfuel, waterjet, router and punch machines come with software that can nest parts; but few come with sophisticated software. And that difference makes all the difference.
Advanced CAD/CAM nesting software provides the ability to:
- Generate fast and accurate quotes based on known variables rather than best guesses
- Perform efficient automatic nesting
- Automatically import, unfold, and nest native CAD files
- Choose which parts are candidates for common-line cutting and nest them automatically to reduce scrap
- Properly generate efficient and safe tool paths for nested parts
- Perform previous cut pick-up for machine restarts
- Avoid areas of potential head crashing
- Extend beyond the shop floor to integrate with MRP/ERP, supply chain and other applications throughout the extended enterprise
Productivity = Profitability
Effective part nesting increases throughput and eliminates rework; but nesting is more than just arranging shapes on a sheet. There are many factors that can cause rework and waste and manual nesting requires a great deal of time and expertise. Fortunately an automated and advanced technology is available to drive the process. Robust nesting software goes well beyond manual nesting or “lite” nesting packages to optimize time and material while eliminating downstream rework. Developed by material optimization and nesting experts, these systems are driven by powerful nesting engines and employ experience-based problem-solving technology to put best nesting practices into practice.
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