Keeping pace in sheet metal manufacturing
To stay ahead of the competition, fabricators need to apply best practices or risk falling behind
To remain competitive, a shop must be willing to embrace both innovation and change together. To get the most out of that commitment, a shop needs to understand just how the introduction of any new technology will affect the entire process chain, not just one part.
Innovation is the driving force for new fabricating technologies, which help to resolve shop floor inefficiencies. Concurrently, however, fabricators also are challenged by these same innovations, because they place new demands on other processes.
That’s why fabricators must not only look at the addition of new technology in isolation, but also how it affects the entire production process chain. This is very important because technological innovation is a continual process, forcing fabricators to embrace change on a constant basis. To remain competitive, a shop must be willing to embrace both innovation and change together.
Defining the Process Chain
To understand how the introduction of new fabricating technology can affect operations, a fabricator needs to take a holistic view. They need to understand the process chain.
In simplest terms, the process chain is everything that occurs from the time an order is received until the time metal parts or final assemblies are delivered. The constant challenge for manufacturers is to shorten this process chain and reduce the cost per part in the process. While fabricators can find many ways to shorten process times without adding new technology, they also often discover that new machine technologies can catapult existing processes to more productive levels more quickly.
Of course, that machinery investment results in a marked improvement for one segment of production, but how will it affect the process chain? Will it result in more parts per hour ready for delivery? Does it create more capacity? Where is the capacity located in the process chain? Many fabricators quickly find out by answering such questions that they have more productivity at one link in the chain but unknowingly create a bottleneck at another part of the process chain.
Software’s Contribution to the Process Chain
For a clearer picture of how a fabricator can eliminate unforeseen bottlenecks with the introduction of new technology, let’s look at a hypothetical sheet metal shop that employs laser cutting machines, automated material handling, and press brakes.
The entire process begins when the order is received. Front-office processes and IT systems determine just how fast the front end of the manufacturing chain can derive work instructions to fulfill the order. Best practice: Employing an enterprise resource planning (ERP) system can prepare the order and break it down quickly into its corresponding raw materials and manufacturing processes.
Once the order reaches engineering, CAD operators create the single part program either from 3-D models or 2-D drawings. Best practice: Companies can use an order management system to streamline the entire process. By having such software interface with their existing ERP system or activating a job order management module of an existing shop management software package, a shop can guide the work automatically from incoming orders to finished parts.
How does this work? A good order management system can take incoming orders, search for the correct DXF part files, automatically program the parts, nest, and schedule the job for the appropriate machine. Scheduling can be defined by the due date or job priority. In some instances, the triggering of a job can be delayed until a clearly defined point late in the delivery window—guaranteeing assured delivery deadlines without clogging up the shop floor with unneeded work-in-process.
An order management system also maximizes part production and efficiently distributes all the orders that the ERP system has released to the various cutting equipment. Best practice: The cutting plans can be released automatically to the machines based on the equipment’s ability to achieve required material yields. This results in more parts per sheet and helps the fabricator forecast material utilization and delivery more accurately.
Automation’s Contribution to the Process Chain
At this point it is easy to see the impact of software technology on the process chain. How fast can an order be processed and released to production? If the front office is too slow, then it risks starving the rest of the process chain.
This is where automated equipment can help pick up the slack. Production officially takes control of the order when the finished program is uploaded to the laser cutting machine and subsequently to the automated material handling system. It is at this point that the part designs are being turned into real fabrications. Every aspect of speed is quite critical to subsequent operations.
The automated material handling system now must load the raw material onto the shuttle table before the machine has finished cutting the previous program. At this point it is obvious that the automated material handling system needs to keep up with the speed of the machine. Can the automation complete the cycle of unloading the previously cut sheet in a staging area or in a dedicated shelf and loading a raw sheet onto the shuttle in the time it takes to cut the sheet on the cutting bed?
With the recent incorporation of fiber lasers (see Figure 1) into sheet metal processing, this is even more of a challenge for automated material handling systems because of the significant increases in laser-cutting speed when compared to CO2 laser cutting machines. A fiber laser’s focused beam produces more than five-times the power density at the focal point and nearly two-times more absorption characteristics than that of a CO2 laser. The higher absorption capability of the fiber beam is due to its shorter wavelength located in the near infrared range; a CO2, laser is 10-times further away in the far infrared range. Because of the higher power density and the higher absorption, processing of materials such as copper and brass are not a problem for the fiber laser. With fiber lasers typically cutting as much as 300 percent faster than CO2 lasers in thin materials under 11 gauge, shorter sheet cycle times have made it a necessity to employ high-speed automation (see Figure 2). This is especially true with fiber lasers are used to cut large parts in thin gage material. Best practice: These high-speed automation units are capable of unloading the cut sheet to loading a new raw material sheet within a 60-second time frame.
Braking for Increased Speed
In the next step, the laser-cut parts move to the press brake. If a shop is using a fiber laser, it likely will have produced more parts to bend. It is easy to see how this creates the next downstream challenge in the process chain. Just how quickly the parts can be formed will determine how quickly the parts can move on to the next process. Not matching the production speed of the fiber laser could create a major bottleneck.
An easy solution is to just add another press brake. But what other opportunities are there with the press brakes? Press brake setup is where a fabricator typically finds a lot of opportunities for reducing production times. Best practice: Quick-change tooling can be used. Bending programs can be created and simulated offline and then loaded into the bend control via a bar code scanner, keeping the press brake operator focused on bending parts.
If the setup issues have already been addressed, what’s next? It’s time to take a look at the speed of the press brake itself (see Figure 3). How fast can the press brake approach the bend part safely? How fast can each bend be completed safely? How fast can the ram return after each bend? Best practice: Electric press brakes employ exactly this high-speed bending capability. Just as the fastest of laser cutting is relegated to thin materials under 11 gauge, such is the case with high-speed bending. Electric brakes can bend 2.5-times faster than hydraulic press brakes; this provides for more bends per unit of time. Electric press brakes bend faster because of ram acceleration; they do not rely on the assistance of gravity as hydraulic brakes do. Gravity is limited at best to 1 g of acceleration, but that’s without considering any resistance. Electric brakes use the full acceleration capabilities of the twin electric motors to engage the ram quickly and accelerate it to levels that are much higher than 1 g. Another significant benefit of the electric brake is that during the time between full-speed approach and the actual bending, the deceleration transitions are much smoother and almost blend together seamlessly. No hydraulic braking or hydraulic lag times associated with conventional hydraulic brakes exist.
More throughput in the bending process chain now enables parts to move downstream to the next process and avoid the bottleneck at the press brake. It reinforces the cause and effect of adding new technology.
Technology continues to raise the expectations of what can be achieved. While fabricators must continue to improve their processes to remain competitive, new technology can propel them to the next level of productivity. Keeping pace in the process chain is crucial if a fabricator wants to realize the potential productivity gains of new technology, lower their overall part costs, and remain competitive in the constantly evolving environment of manufacturing.
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.