CNC Equipment, Beam Saws, and Cabinet Shop Effiiency

      Cabinetmakers discuss one shop owner's real experience, as compared to the promised efficiency boost of his new CNC. October 14, 2009

Question
Last year we purchased a CNC router with a plan to switch to nested manufacturing. Here is our experience with that project to date. When shopping for a router we were especially anxious to improve our through put in our shop. The process at that time was cut list from software to CNC beam saw, process parts through a CNC point to point, edge band and on to next tasks. Although we were batching kitchens by wood veneer species to a maximum of three kitchens per batch we realized that the first step in our process, the beam saw was most often cutting one sheet at a time (capable of cutting five sheets). This limited our through put to the maximum number of sheets that an operator could cut in one eight hour shift - approximately 67 sheets daily. The sales people for the CNC routers (regardless of brand) boasted that their machines would cut about 100 sheets daily. Our thoughts were that we could improve the through put and eliminate the point to point position.

Here is what really happened. The CNC router is possibly capable of cutting near 100 sheets daily under the following conditions. There can be no time allowed for spoil board maintenance, no tool changes because of dull cutters, one type of material being cut (stacked beside the machine) no labeling of parts and no sorting of parts for the next task. Our real world processes require that we cut varying veneer species, sometimes veneer is down white melamine is up (finished exterior cabinet), sometimes veneer is up melamine is down (finished interior cabinet).

Sometimes the material is veneer/veneer (cabinets finished inside and outside). Our cutting tools on our router provide clean cuts for approximately 100 sheets. We then have to change out the tool. We have bought extra collets and spindles to speed up this task (simple plug in new tool into tool changer) but the machine must still perform a tool length measurement program. Our most common material (white melamine is stacked by the machine and the operator has a panel lifter to assist in loading material). All other material is nearby but with five veneer species it must be retrieved from racking that holds all of our veneers. Normally we only have to dress our spoil boardsí once every seven working days. All parts are labeled to identify the job, the cabinet description, the part description and the part size in millimeters. Real through-put is 47 sheets daily.

Nested manufacturing produces irregular sizes cut offs. These initially increased our waste and caused handling and storage issues. We have most recently changed our programming in our cut lists so that only parts that require milling (shelf holes, hinge hole, drawer rail holes etc.) are cut on the CNC router. All parts that do not require any machining are produced on a second cut list that is processed at our beam saw. We first use all cut offs from the router to produce these parts so that waste is reduced to almost zero.

Since only the parts that require milling are going to the router we are cutting 45% of our total cabinet parts on the router and 65% of our total cabinet parts on the saw. This effectively changes our through put capacity to approximately where it was before. There is more that I could add if any specific questions come to mind. We are still looking for opportunities and wonder what other shops have experienced in the changeover to nested?

Forum Responses
(Business and Management Forum)
From contributor R:
Is your router capable of pendulum processing or is a single sheet machine?



From the original questioner:
Two 5x10 tables.


From contributor R:
At an average of five minutes per nest, thatís 12 sheets an hour or 96 sheets in an 8 hour day. Thatís not including all the variables that you mentioned. In the shop I use to work at we averaged around 80 sheets a day, that were labeled, sorted and staged for the next process. While one sheet was running the labeling, sorting, and next sheet prep was done. As far as material staging our software (CadCode) gave us a detailed report for the material handler to preload for the day, and all programs were loaded to the machine from barcodes on cut patterns. Now this is all in a perfect world. I guess where we really saw the value was in assembly as all the parts fit as they should.


From the original questioner:
We used to prepare a book for our rear load panel saw. This book had all of our veneers on top and whites under. The book was loaded into the back of the panel saw and the cut list was in the same order as the book. We could do something similar for the router, but for the same the orientation of the material (veneer up/white down or white up/veneer down would slightly complicate the book making process. We did test once but saw little advantage. We also sometimes will have a kitchen nest where one last piece or a few pieces will be nested and not required a whole sheet. We like to use some of our off cuts for these single parts and that also slows our process but reduces waste.


From contributor B:
To the original questioner: what are your feedrates and spindles speeds, and what construction methods are you using?


From contributor N:
Well, as I see it, you went from 68 panels a day cut on a beam saw, but did all the parts get machined on the point to point that day as well? The thing about nesting is you are moving material less. You donít have to pay a guy to run the beam saw and the point to point. No paying someone to roll a cart from one part of the shop to the other. They can go from nest strait to edgebander. If you use 3/4" backs, I have seen people nest a whole cabinet on a sheet, so it can then go to the endgebander, this way your first cabinet may be built and be loading on the truck before you finish cutting the last one.


From contributor J:
If there is enough volume, it does because cutting parts with a router is not faster or more efficient than NBM. And if there's enough volume, the saw is cutting parts while the previously cut parts are being bored and grooved on a CNC processing center. NBM is for shops, not production facilities. It doesn't make any sense to cut one sheet at a time with a router when you can be cutting three to five sheets at a time with a saw.


From the original questioner:
What I maybe didnít explain well in my first post was that do to the custom nature of our business our optimization program rarely had enough similar parts in a three kitchen batch (even in white melamine) to produce multiple sheets with the same pattern. Thatís why we were cutting single sheets on the saw.


From contributor E:
Material handling is the key. You need to have the material ready for the operator to load, not go find it, and loading time is critical. We use an automatic loader and it really pays off. The tooling needs to be measured off line, ready to just drop in the tool carousel when needed, and change length and tool comp. We use a manual conveyor; our operator separates the material to go to the bander on one rail and on another rail to a horizontal drill. We found that using shop carts was really a waste of time. Also did the beam saw and point to point. That works really great if you are making a lot of the same parts. Our operator is a girl that likes to work and she has done over 100 sheets per day, not lately.
When busy we have the materials stacked in front of the loader waiting.


From contributor K:
If you are doing lots of the same thing, then a beam saw and PtP will be faster than a router. But it sounds like you are doing lots of custom stuff- maybe that's why you only had single sheets being cut on your beam saw.

I would suggest three things to speed up the process. I don't know if you mentioned it, but do you have a push off device for the router? If you have to manually take parts off a machine and stack or sort them prior to starting the next sheet, you are wasting lots of time. My router pushes off the sheet onto a panel cart and vacuums the table at the same time, plus I set it up to leave the pop up pins down and the gantry out of the way so I can immediately load the next sheet. After I start the next sheet, I can label and edgeband the parts I just cut while the second sheet is being processed. There is very little down time for the router. The next would be to print labels at the machine so you could just stick them on the correct part. Most labels will have a bar code that has all necessary info for further processing, thereby eliminating the opportunity for a mistake.

Lastly, I would organize my software to optimize the sheets by cabinet. I set it up so that parts from no more than three cabinets can be on a single sheet. All parts from cabinet # 1 must be cut before any parts from cabinet #4 show up. This way you will be sending complete cabinets through the system. I am a one man shop with a sometime part time helper, and I can process about 40 sheets a day depending on how complicated the sheet layout is.



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