Nesting intelligence

A nest created using SigmaNEST. Image courtesy of SigmaTEK.

Every year the software that helps us manage fabricating processes gets more sophisticated. The most advanced programs allow you to manage the flow of parts from sheet storage straight through to weld assembly. Nevertheless, when parts are cut on the laser, unless you have automated part picking capabilities, it’s important that you have a nesting protocol that makes part sorting efficient and effective.

Manufacturing Execution Leaps Forward

At FABTECH® 2017 in Chicago, the sophistication of modern fabrication management products was on show at many booths. For instance, Bystronic introduced its Manufacturing Execution System (MES).

“The software enables you to monitor, plan, and track all of your production entities,” said Frank Arteaga, Bystronic’s head of product marketing for the NAFTA region. “This not only encompasses your jobs, but also the machines themselves, so you can see what work load each laser, for instance, has. If a part has to go through three or four operations, you can see the routing of that part.”

This sort of monitoring can help you flag delays in production or any necessary production changes.

“The system knows when the start dates of a job should be at each stage based on inputs you’ve given it,” Arteaga continued. “Therefore, if there is a delay in production, it will automatically readjust the start time because it has fallen out of the parameters initially set. Giving you advanced warning allows you to look at your entire production line and consider if you want to reroute that part to another machine to meet your delivery time or to take a load away from that machine.”

The MES essentially allows you to determine the flow of parts and assemblies through to shipment.

“The whole idea is to always be able to look at operations on the shop floor on both a part level and a job level, so that you understand the work flow of each machine, and you have a clear idea of how much capacity you have or do not have. I can look at the MES and say, ‘I have an urgent job, where can I fit it in? I can do it here and it will be done in x amount of time.’”

LVD Strippit’s CADMAN® software works similarly.

“The CADMAN software connects with your ERP system and will automatically locate the drawings associated with an order,” said Stefan Colle, laser product sales manager for LVD Strippit. “It will automatically create and sort the generated nests and send these to the queue of the selected laser system. We recently switched to 64-bit processing, which means all of these calculations are done that much quicker. Also, with the advent of fibre lasers, there is much less variability in that aspect of production, which also speeds things up. With CO2 lasers there were many variables that could impact the stability of the laser and the laser’s performance. Operators had to make changes on-the-fly to keep the laser operating well. With fibre lasers we can optimize for a specific material code very easily. That eliminates a lot of potential issues.”

One of the challenges in part sorting is ensuring parts are properly identified for the correct assembly. One method of managing this uses the laser cutter to etch a small QR code directly on each part. When scanned by a hand-held scanner at the press brake, for example, the small QR code can automatically select the correct program at the press brake. Image courtesy of Bystronic.

The company’s CADMAN-Job software, meanwhile, can follow the part through the rest of production as well, even gathering production information from non-LVD machines to maintain a view of production throughout the process.

Avoiding Remnants

The advanced manufacturing execution systems being developed by various machine suppliers all aim to support the just-in-time manufacturing philosophy heralded so often by shops in North America and abroad. The idea is to minimize material inventory and have cutting jobs maintain a flow that keeps parts moving through bending and assembly without creating unseemly bottlenecks along the way.

But the JIT philosophy does create challenges for a shop floor manager. For instance, does the shop care more about getting certain parts nested and in production than avoiding remnants?

“Each company must determine their own philosophy for managing the trade-off between nesting efficiency, production throughput, and the creation of remnants,” said Glenn Durham, vice president, engineering, at SigmaTEK Systems LLC. “For example, with three button clicks you can find out in our software what needs to be made from half-inch steel and sort it by due date. One company might autonest all the parts due in the next two weeks so that they maximize material usage and take advantage of economies of scale. But we can also tell the system not to use the last sheet of a nest unless the sheet is filled to a certain percentage. So, if that two-week window of parts fills a sheet plus another quarter sheet, the parts on that quarter sheet are not nested, but rather set aside for when there is enough work to fill another sheet. Perhaps that first sheet has production enough for eight days. This way, you are cutting a full sheet, not leaving a remnant, and by the time seven days go by, you are ready to cut more and you can backfill the other sheet with more orders.”

“Another strategy for ensuring maximum sheet utilization is to use filler parts as part of the sheet nesting strategy,” said Arteaga. “Filler parts are usually small parts which are often repeat orders and can be used to fill the empty spaces on the sheet after all parts have been nested. In this way, the material use can be kept to a maximum while still satisfying the order deadlines and also producing parts which will be required at a future date. Filler parts will be used to fill only the empty spaces of the sheet materials or can be used to fill the balance of a remnant sheet.”

With more advanced automation, remnants may not be an issue, but avoiding them in a mid-sized shop can be a big concern.

Part Identification to Improve Flow

Managing removal of parts from a flatbed laser table is also a concern. In an ideal future, pick-and-place automation will take care of this onerous task, but in the meantime, that process is another critical potential bottleneck. The right nesting approach can help.

“Tracking parts and connecting them to the correct order can be handled in a variety of ways – again, depending on the needs of each company,” said Durham. “If material use isn’t the biggest concern for a shop, and instead it’s more important that all parts for one assembly are grouped together, you can nest these parts by work order name. All the parts associated with one order are automatically nested together and separated by a crop line. That crop line can identify a discrete assembly and make unloading the parts more straightforward.”

Software for shop floor management is becoming more advanced all the time. Here is a screen capture of SigmaNEST’s Load Manager, designed for cutting machine scheduling and workload management. However, without the right nesting and part sorting process in place, this and other software of its kind can’t be efficiently employed.

If separating parts that way in the nesting program is too wasteful for a shop, there are other ways of simplifying part identification to speed part sorting.

“SigmaNEST can also automatically etch the part number or other identification information on each part to allow that part to be tracked,” said Durham. “In some industries, this method is critical for traceability – enabling a defective part to be traced all the way back to the piece of steel from which it was cut.”

Another option is to generate a report that labels each part on the nest. “This can be a printout that is given to employees on the shop floor, but more and more often companies assign employees tablets or have flat-screen monitors that allow employees to see the colour-coded parts right on the screen,” said Durham. “Colour coding can be done by part name or any other sorting method you want. For instance, one colour could indicate all parts that are required to go to sandblasting, another colour could be for parts going to the press brake, or one colour could indicate one assembly.”

Another option is to print labels that can be placed directly on the part.

The main thing is that however you manage part nesting and sorting, it needs to make this one human bottleneck in the increasingly automated fabricating process run smoothly to feed press brake and assembly operations as efficiently as possible.

The advantage of advanced part identification processes on the shop floor is that if a part is scrapped at this or any other stage, you can alert the system of this scrapped part and it will reintroduce a replacement immediately into a nest being prepared.

“Another efficient method of part tracking uses the laser cutter to etch a small QR code directly on each part,” said Arteaga. “When scanned by a hand-held scanner at the press brake, for example, the small QR code can automatically select the correct program at the press brake. When scanned by a smartphone QR code reader, the QR code can provide critical information such as part number, revision levels, production run ID or date, or any other type of information text that is required for quality and tracking, even years later.”

Take Your Time

Most shops aren’t yet using the most advanced manufacturing execution systems, of course, but it’s important to pave the way to understanding how to best use them. Durham recommends that shops take a step-by-step approach to creating the best JIT process for their operations.

“We encourage people to bite off a little at a time,” said Durham. “Get to know the basics of the software you are using and then add to that knowledge gradually. Maybe the first thing you do is to take a more dynamic approach to your nesting. Then look at your inventory, your remnants. I go to factories where there are stacks of remnants around the shop. We then say, ‘Let’s get this inventory into the software so it can be managed, start managing full work orders, start doing just-in-time nesting. Once this becomes possible, consider how more automation can be added to the process.’”

The saying “You can’t improve what you don’t measure” is very appropriate for justifying the addition of software automation to the front end of the process, said Arteaga. “With monitoring software in place to measure efficiencies of the machine, one can justify machine and software automation,” he said. “For example, if the monitoring software indicates that the machine is idle because cutting programs are missing, this may indicate that programs are not being created in a timely manner. Are their enough programs to keep the machine operating on multiple shifts? Are programmers only on first shift and need to produce enough programs for the entire 24-hour cycle? With fibre lasers producing up to four times more parts per unit of time compared to CO2 lasers, what used to be feasible for one programmer is now out of reach. When machines sit idle, they don’t generate revenue and so adding software automation becomes justifiable. The same goes for justifying material automation. When the monitoring software detects that the machine has finished cutting but cannot process the next sheet, either because the first sheet was not unloaded or the material is not ready on a consistent basis, adding material automation becomes justifiable. The monitoring software provides the data to justify software automation and material automation based on machine efficiency levels.”

The value of advanced tracking and management systems now in the market is that, with data coming in from each stage of production, you can better understand the time and effort associated with each phase of production. This may help you make the case for further investments in automation. At the very least it can pinpoint how processes can be adapted to create better workflow.

Editor Robert Colman can be reached at rcolman@canadianfabweld.com.

Bystronic Inc., www.bystronicusa.com

LVD Strippit, www.lvdgroup.com

SigmaTEK Systems, LLC, www.sigmanest.com