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Panel Optimization & Labor Allocation2/22/15
I just thought of an interesting test for panel optimization. CutList Plus has the option to record fall down scraps as inventory similar to full sheets. When it does the parts layout you can ask it to include those pieces in the optimization.
What I am wondering about is the overall efficiency of cutting parts for just one cabinet vs all the cabinets. I would guess that the optimization yield goes down when cutting just one cabinet but I am curious about by how much it goes down? Is this a 3 sheet increase in materials over a job or 6 sheets? What are the implications for overall labor costs if you could manage just one cabinet at a time.
Not much in our product line takes more than about 30 minutes to produce. We can generally build any face frame, box, door etc takes 20 - 30 minutes max. It will take more than 30 minutes to build 4 drawers but the remaining 2 drawers can be machined and assembled while the face frame is being mounted to the box and doors are being fitted.
What I am wondering about is how succinct we could be with targeting labor where it is needed if there was only two cabinets in play at any time. We could call these the now & next cabinet.
A kitchen with 30 cabinets is a pretty overwhelming process. It's hard really to figure out just where to start so you start something with the justification that it will be needed later. Why is it that a 30 cabinet kitchen is so hard to build but you can spank out a 3 cabinet bathroom vanity combination? What would it take to break that 30 box kitchen into 10 bathroom vanities?
It's easy with Cutlist Plus to evaluate material yield at varying batch sizes. The next frontier would be to see how obvious decision making becomes at lower batch size. With enough choreography could you build cabinets one at a time but as a river of one at a time? It would certainly be easy enough to identify which operation was the hang up. If boxes were waiting for face frames then this tells you to start boxes sooner in the process.
How would you communicate status with such a system? Could this be something like an abacus?
Bob Buckley was a one man shop who determined an ideal batch size for his operation. It was something like 4-6 cabinets at a time or the number of cabinets he could produce in a day. Bob's software was able to sequence cabinets in the material optimization.
Producing closet organizers, my processing was determined by how the truck was loaded. The truck was loaded in the reverse order of the in home assembly process.
A couple of years ago, I asked CutList Plus if it would be possible to optimize based on production sequence. Todd thought it was an interesting concept to consider. I never pursued it afterwards, nor heard anything about it.
Gains and losses are often trade offs. I took material yield to an extreme for a while. Inventorying and handling every offcut was obviously more trouble than it was worth, but I determined minimum sizes and developed streamlined processes for that.
I was surprised at how many times I was told how compact and efficient my flow was. I think Bob had it best. There are advantages to batch processing and advantages to one piece flow. It will take a long time and the benefits will shrink as you approach it, but the ideal production flow is dependent on your product, equipment, people, suppliers, and management style.
These are just thoughts, but a little playing with the software and it would be pretty easy to see the extra material.
On a typical job, we average about 1 cabinet per sheet. We do nest the entire job together though. Some playing with the software so the cabinets came out in order, would show us how many extra sheets would be required. I have never done this though.
Another interesting thing to consider would be what kind of systems you would need to have in place to support and sustain this approach. It's kind of like the shiny shoes theory. If a guy's shoes are shined then his pants are probably pressed. If his pants are pressed then his shirt is probably tucked in.
One of things that is interesting about Todd's software is that you can pretty much parse out the inventory as you like. We, for example, buy a certain amount of our material ripped to custom width. We inventory 12 & 24 inch wide pre-finished maple plywood with PVC on one edge. We also keep a stack of 51/8 inch wide rips of un-finished 3/4 ply.
We've pretty much beat the PVC out of our cabinets. We used to own a Brandt bander but keeping it running properly turned out to be much more expensive than just buying it banded. It also takes less time to build the cabinet because as soon as the part was cut it could be assembled. There were are no engraving issues because we already know which edge is visible.
The 5 1/8 inch rips get used as stretchers within the box, or they get ripped in half to produce toe kick ladders or they end up as cosmetic faces in front of toe kicks. It's kind of like using all the buffalo.
One of the advantages of starting with 12 & 24 inch rips is that you can immediately understand what you have in scrap inventory. Since everything is the same depth you only have to track the vertical axis. It's real easy to rank material by dimension if you only have to compare one denominator.
This also has implication for how you could integrate inexperienced people into the work flow. Breaking down 4x8 sheets on the slider is pretty much a one man job. Crosscutting 2 x 8's produces a perfect harmony for a sawyer and a catcher. You'll get through the cutting faster and the apprentice won't be spending as much time polishing the floor to seem productive.
This might be relevant.
The nesting stuff that I've used (never used a cut list program 'cause I use CNC, but I assume it's similar) starts with the largest parts and ends with the smallest.
Since I can't get my nesting to keep all the parts for one cabinet within a specific number of sheets of material I ended up with this process.
I take the nested sheets and cut from the second last to the first and then the last.
The later sheets tend to have more small parts, therefore impact more cabinets per sheet of material cut.
Once cut, the parts are end drilled and edgbanded and put on a shelf that has numbered slots. Could be put in slots before drilling and banding too.
As the slots start to fill up, it becomes apparent when there are enough parts in any given slot to build that cabinet.
The obvious question is why start with the second last? That is because the last sheet is usually not completely used up and any damaged parts can be added to that sheet. I don't cut the last sheet until I have built all the cabinets that I can without it.
This seems to allow the best use of material and least amount of labour.
I don't keep any waste.
I started out using CutListPlus using ripped and banded stock. I was using a scoring radial arm saw to cross cut melamine. I was stocking 12/16/24 widths but carrying too much inventory, because a wider range of colors had to be offered. Lead time was 2-3 weeks and I had to order 2 - 3 units at a time. I banded the lengths as the material came in but often swore at the poor quality of cut. I would have to inspect each piece to edge the better edge, and plan usage to hide the chipping when both edges were bad. Got stuck with colors that went out of style. Always battled a balance of inventory.
The combination of incorporating a Striebig and CLP transformed the business. I was able to order a unit of material in mixed colors and sizes that was already sold.
I will say the weakness of the vertical was in ripping long lengths. Did not need a catcher since the carriage was not in the way. I learned to crosscut as much as possible first and minimize ripping long lengths. CLP did allow to maximize cross cutting. A vertical is ideal for cross cutting, and is much easier. Also, I would regularly stack cut too, especially for drawer sides and bottoms.
Rich & Dropout,
You both bring up some really good points.
I would have taken me a million years to come up with the cutting sequence of 2nd to last first. It makes perfect sense when you think about it. I also like the parts rack that can signal when you are ready to install. Bill Norlin in his book "The business of Woodworking" made a similar statement about coping and sticking. If you rest your parts on the bandsaw table prior to coping them and your bandsaw can hold seven parts then seven is the batch size.
Larry does something like this with conveyors. If you set up your work flow such that there is a buffer between each work station then you can only work on a maximum of two things before you have to stop and go figure out what the hang up is that's keeping your buffer zone jammed up. In a way it is like bringing your boat into dry dock so you can the water level and look for defects.
I did like working from largest to smallest, because a miscut large part could be substituted for smaller parts later in the process. Because I ran so tight, I pretty much had to reoptimize after figuring out what was cut and taking it out of the parts list. Again, I had to have different colors.
Dropout offers good points. I essentially sorted cut parts onto carts destined for different processes. For example, I had shelves separated from partitions, and I would sort the shelves by size. Different widths were loaded onto different shelves in the truck. My ultimate goal was to handle each part as little as possible. But I was not assembling cabinets in house.
Having a buffer of an extra sheet or two means the miscut part could be entered into inventory for a future job.
I think you have a lot of options to consider now, to see what you can apply to your situation. Your results should be interesting.
I had a tremendous opportunity recently to spend about four hours in an auto assembly plant producing three distinct vehicles concurrently based on sold orders. No batch processing and a finished vehicle off the line about every minute. The choreography and the ballet was truly amazing, Inventory on hand of various stampings, components, and assemblies was about four hours worth.
When the vehicle comes off the line, the shipping company pays the manufacturer for the vehicle and ownership is transferred to the shipper. The amount of buffers throughout the process was amazing. My escort accidentally shut down the line in one area for about 10 minutes. Thanks to the built in buffers, no harm was done.
Toyota builds their cars in Japan on a line like you describe. They build them in the sequence that the orders come in. It might be a yellow sedan then a green pickup then a blue pickup then a blue station wagon. They don't set aside a portion of each day or week to just build pickups or station wagons.
To make this happen they need to have buffers like you describe but they also need to have robust communication systems. Sometimes the communication is done with a computer. Sometimes it's just a colored clothes pin tied to the work order to signal the guy building seat belts that the next vehicle is yellow. I don't mean to hijack my own thread here but your comment on buffers stood out. In a way Dropout processing the last nest last is also a buffer.
We are looking @ off fall as a constant revolving inventory and we have to keep it neat as to not waste time looking through it. Because it not being done quickly and efficiently, is a waste in itself. Software is great with "Materials Managers" built in is wonderful but the data has to checked and inventory verified before a cultist can be executed.
Whether we are running Corian, solid wood or nesting laminated panels, it has to be up to the discretion of the fabricator/operator to make a judgement to cut into another 1200 dollar sheet of Corain , or book matched veneer or use the scraps and cut out what is needed from that. Luckily we justify this in terms of "How will this effect my bonus ?" How will the overall health of the shop be effected ?
I think the inventorying of just what is needed is great and I pay the money to have cherry for S4S'd for us for JIT work also. It is important to track what has been used to justify what is to be bought or execute the purchase with software such as Cutlist or any software that is plug and play to make a decision. When it comes to deciding to shut off the edgebander and sell it, puts you at the mercy of a vendor of processed materials and that is ok, but most of our work is custom and we charge for it- versatility and trained staff on the machines, does have benefits
Yes, someone and not a cnc needs to make a decision to cut around a defect, and longest to shortest truly entails using up off fall as you go, but it takes training to identify that pre-cut material from an existing job has labor in it and it should be viewed as a durable product in the rack for our end product and not just waste, or scrap.
As for the "Now and Next cabinet" analogy, along with the 30 kitchen cabinets and where to- "starting point," it's the same as a reception wall or 44 dorm rooms. Pick a starting point and move forward. It's important to have all the information and materials @ hand to execute the production of the product efficiently, whether its 4-6 cabinets a day, or 120 for the week. Either way, from the perspective of the shop fabricators, it does a lot more for moral to execute completed projects every few days and mock up the work to justify the exerted labor and examine what is efficient and what is not in the process, therefore allowing the fabricators to tweak what is right and get rid of what is wrong in the process from examining the completed work. No software can do this for your shop.
Gosh Tim, I 'm all Leaned and softwared out.
This is a great thread. To me, there is nothing to disagree with here, but rather a variety of valid perspectives to mull over and find what may fit for each individual situation. I can see this thread showing up in the biweekly recap.
I got hung up with Dropout's description of the parts sorted by cabinets on the parts rack. It is the movement of completed collections of cabinet parts. Do you unload them from the rack onto another cart? No value added labor. Or do you move the entire cart to the next processing area? If you move the cart, then you stop that process or disrupt the sorting. It is a minor point, but that is where I was in my processing, splitting hairs like that, considering pros and cons.
The auto plant I visited is one of the oldest in North America, (began operation over 90 years ago) and yes the vehicles were interweaved not only among 3 distinct models, but also by unique police and retail packages for two of the models. I was there on a very unique day when not only did I observe regular production but I also watched assembly of a new 2016 model to judge assembly process and quality in between regular production units. Puts what I did in a very small perspective. On the other hand, I saw a LOT of wasted manpower devoted to that one vehicle with about 20 different engineers imported for the event from other locations.
There are settings in our software that will force it to get all the parts for successive cabinets as close together on different sheets as it can. Helps. But the biggest help is just running smaller batches. If you've got 50 cases to make breaking it down into 3 groups makes for better flow. If you are running a CNC router using true shape nesting it is quite easy to gain a sheet by trying different batches. But how much time are you willing to spend to save a sheet?
My shop is laid out like this:
CNC next to end boring machine. Parts from the CNC go on a table between the 2. I'd rather not, but the CNC is an expensive table.
The edgebander is beside the end borer. Parts are end bored and fed through the edgebander. I have pallet racking with numbered slots in case I am nesting a job that requires more than one colour edgetape.
From the outfeed of the edgebander the parts go into the numbered slots on pallet racking. Once the slot has enough pieces to build a cabinet the cabinet is built on the assembly table which is 3 feet from the racking.
I learned long ago not to touch anything unless adding value.
This is in a rough C shape starting by the door and ending at the door.
Just for clarification, I have 2 sets of slots on two different pallet racks. One as a buffer before the edgebander in case of multiple edgeband colours and one between the outfeed of the bander and the assembly table.
There is an interesting book called "The New Manufacturing Challenge"by Kiyoshi Suzaki. It talks about how to configure machinery layout so that one person can efficiently staff all stations or you could one person on each station.
A typical shop might have someone add value, stack it on a cart, shove the cart to the next station add value. There are three things happening here but only one of them is making you any money. To add insult to injury you often have commit massive portions of your floor space to aisle ways to drive and store these carts. This is space that could dedicated shapers etc.