To nest or not to nest?
Is nesting appropriate for all shops? June 4, 2003
How many of you nest? It seems to me that when the idea of nesting came out a few years back it was the "thing of the future." My take is either it fits your shop or it doesn't. I feel that our shop would not benefit from it since we have a beam saw, a Point to Point, and a CNC with a 59x51 table.
This topic has resurfaced lately from people who don't pay attention to the CNC industry as much as I do. I feel that we would have to change our product flow and scheduling as well as invest in a new router and software if we were to pursue nesting. I try to be open minded, but I believe our system of "cut it, then route whatever needs it" isn't broke, so why fix it.
We are a large cabinet shop that does 99% face framed cabinets.
Anyone else have a take on this?
Production managers deeply involved throughout the world in the calculation of unit cost of the panel are in agreement with you: nesting is not the benefit that most of the software houses (and linked CNC manufacturers) have promoted for years. Spend a few minutes thinking about the following concept, which is one of the basics for the mechanical class at the high school: always rough shape, then finish... i.e. cut down with a beam saw then trim with a router. This is what the routers are for. To fit the performances required by a massive cabinet maker, most of the CNC manufacturers are over spec-ing the machines in order to get closer to the cutting speed of a beam saw. Can someone explain if it really makes any sense? Non-nesting benefits are larger, even if you need a saw and a CNC instead of a single machine tool and (of course) a bit more skill in organizing the production. It has been proven up to 30% cheaper with much better finished and accurate products.
The answer to your question depends on a number of factors. Nesting really pays off if you are a volume producer and have your production needs changing on a daily basis. You can save material, time and confusion. On the other hand, if you have same layouts that you have been routing for months, obviously nesting will not be as important. In addition, communication needs two different processes and automation of some of these processes may determine how far you want to go with nesting/software integration.
I don't see anybody arguing that NBM can compete in a production environment with a PBM cell.
However, let's look at a different angle. Say I'm two guys in a 3000 sqft building and I produce a kitchen a week. Should I still be looking at a Saw/P2P combo? At 20-30 cabinets a week, what's my ROI on that investment vs. a router? Either way you go in this scenario will easily produce the amount of parts I need in less than a day. So why would I want the additional payment of the PBM cell? Why would I want to give up the space required by a saw? Why would I want to deal with the additional software headaches by throwing another machine (saw) into the mix? Either way I go I'll have excess capacity to grow into.
Don't misunderstand what I'm saying here. I'm not pro or con one way or the other, but neither solution is a one-size-fits-all fix.
Brian Personett, forum technical advisor
Brian is correct; there is really no argument in a situation where you have a manufacturing and engineering requirement that the NBM solution will cover, and you have a product that lends itself to NBM.
The bottom line is to ask yourself which system is the best reflection of your current information gathering and processing system and which will integrate with your product and construction requirements to give you a better return.
You all have mentioned the scheduling aspect in high production. Here is a twist. If you nest parts from the same cabinet on a panel to the router, you can be down to only scheduling the program, not the cabinet. Let alone you can eliminate material handling time from loading the saw, unloading the saw, moving parts away from the saw, finding the parts after this, moving them to the router, loading the router and unloading the router. Nesting allows you to leave the material raw and stacked and handle it twice (on and off the router) before it is complete. Also, I think you must include the fact that the more times you handle the parts, the more scratches and chances for damage or error. Piece setup of the router takes longer having to create stops or locations for parts on the bed. Also consider the fact that someone has to bring all these parts back together again so they can be assembled. Brian had a good point about space needed for the equipment. I think you also have to include the space to handle the work in process. Our shop has a saw and a router and have tried both ways and nesting is the way to go for us. I have been doing it for 15 years now. I would also agree with the others that it would depend on your product line. There are two systems for a reason.
From the original questioner:
We cut 100-200 sheets of sheet stock a day, so we would need a beam saw no matter what. And we already barcode with the PTP, so it would be an extensive and expensive project to convert to NBM. I didn't mean to start a "my system is better" argument. I will stick with my first opinion... Either it works for your shop or it doesn't.
You just answered your own question. NBM is at its best in a low to medium volume/high product diversity shop. An example is a custom kitchen where each job has a lot of unique parts. Also, a single nesting cell is pretty much limited to about 50 sheets per day based on cutting and material handling times.
Another way to make the analysis is to look at the achievable stack height on your beam saw. If it doesn't average more than two or three sheets you are an NBM candidate. More than that and stick with the beam saw/P2P.
We have a beam saw as well as a CNC router. It would have been our intention initially to nest as much of our work as possible when we first got our router. It took us a while to get familiar with all the issues like holddown loading and unloading, feeds and speeds, dust collection, etc. I have to say, having spent almost a year "trying to get there," the one issue that the router does not perform well in is the quality of cut compared to the beam saw. Nesting melamine chipboard most of the time we have found that we have to give the edges a light sanding before edgebanding because of tear out. If there is someone out there that is achieving a good quality cut on melamine chipboard, please tell us how you do it, as this for us is the one disappointing aspect of nesting.
The biggest problem that we have faced was poor "core" edge quality (never the faces... except some nasty lams/wood end grain... another whole topic).
I was using 1/2" compression with chip breaker. Turned out the chip breakers were misaligned and would leave grooves. We went to plain compression (up/down) as 1/2" lowered our feedrate to about 400-450ipm @ 16krpm and have not heard any complaints for a while.