When nesting, does it pay to be the early bird?

Is your company a bird or a mouse? Check the statement from each row that most applies to your company.

We have all been taught that to be early is to be on time. In fact, being on time is likely the most crucial component of any manufacturing business. Stakes are high, and manufacturing companies win loyal customers with their ability to deliver quickly and reliably ahead of their competition.

Being lean is likely the next most critical aspect. Lean businesses reduce waste and thereby cost to win orders with competitive prices. A key lean philosophy is just-in-time (JIT), whereby businesses reduce cost by avoiding the waste associated with overproduction, waiting, and excess inventory all while meeting delivery deadlines. Nesting finds itself at the crux of these two critical business practices.

When to Nest?
Nesting early does not necessarily mean that parts will be cut early, creating physical part inventory to manage. You can store CNC programs of nests for later use. Once you nest parts, you know the optimised material requirements. Being the early bird (nesting early), you know precise raw material requirements in advance.

With these optimised requirements, you can buy material needed in time for the work to be done, and be selective in shopping for a supplier. Your operation can consume these raw materials right away and eliminate the costs associated with warehousing raw material inventory. Money is then not tied up in stock materials, extensive warehouse space, or inventory management. In this manner, your operation can have the right material at the right time. In other words, you can be lean.

Nesting too early, though, or being the first mouse, can be lethal. The geometry of any part in a nest might change, as could the due date. Say you nest several jobs together, all with a due date three weeks away. Then you get a call from the salesperson; one customer needs his part sooner than expected. So you send that entire nest to the laser or punch. That customer’s part is cut on time, but all those other jobs aren’t needed for several weeks, so they are placed into inventory. The same thing can happen if the due date is postponed. Then, as your cut parts sit in inventory, one customer calls with a design change.

Design changes to a part already cut leads to out-of-process rework. If rework isn’t possible, those parts become scrap. So in essence, parts nested too soon can cause substantial waste as nests must be recalled, parts scrapped or reworked, nests reprogrammed, and CNC files remade.

Nesting too early can also waste material. You might decide to nest parts early on a certain day, because the shop workload seems to be a bit light, and the material yield may be acceptable. By getting a head start on this job, you keep the people and machines on the floor busy. So you cut the job early, and the parts sit in WIP as they wait several days to be formed in the press brake department.

The next day a small order comes in that requires the same material, but with a tight deadline. You have no choice but to buy another batch of the same material. Moreover, the material yield may be very poor.
Had you not nested those parts the previous day, you could have nested both jobs on the same sheet, increasing your yield. You also would have made just one raw material purchase, saving time in your purchasing, accounting, and administration departments. You also may have gotten a discount for purchasing material in bulk. This would have saved not only freight costs, but also your receivers’ time. Waiting to nest all the parts together certainly would have reduced programming time and the time required to load and unload machines.

Of course, nesting too late also can be a problem. You may nest at the last minute to avoid problems fAir Max 1 Ultra Essential