I thought I would write a program that creates cut diagrams similar to the free & commercial products out there as a side project, and I'm trying to figure out a set of common rules to use when laying out the parts.
If you were to create a cut diagram on paper, how would you go about finding the optimal layout on the boards without using a software program. Do you have a systematic way of figuring out the best way to cut the boards to minimize waste?
Thanks!
Chris
The answer is... Cutlist Pro
Honestly though, this is a very well studied problem with lots published.
Google "Nesting Algorithms"
It is a recursive sort> I thought I would write a program that creates cut diagrams similar to
Chris,
I assume you meet for sheet goods so don't forget that plywood comes in
2'x2', 2'x4', 4'x4' (handy panels or specialty plys) as well as the usual 4'x8' sheets. Then some suppliers have 4'x9', 4'x10' and 4'x12' sizes.The really good cabinet grade stuff typically is found in 5'x5' sheets and there are metric sizes as well so your options are numerous if you include all the typical sizes found in both imperial and metric measurements.
As for how I do layout when working with sheet goods is typically by using AutoCad and making it fit manually by trial and error and keeping the grain orientation in the right direction for pieces where it matters.
Be sure to allow for the kerf sizes for the typical plywood blades, thin-kerf and full-kerf blades.
I have a feeling you'll be pulling your hair out but should be a great exercise and learning experience.
Bob S.
Are you going to optimize for yield, or for time?
Is the material consistent, as is MDF, Plam, etc., or are there directional, or visually based decisions to be made, as in cutting figured ply, hardwood, etc.?
A nesting program for a CNC router is going to be different than that for a hand fed tablesaw.
It is fairly simple to cobble up a tablesaw cutlist and layout for something like MDF. You can use an Excel sheet as a table for parametrics that can drive a drawing layout. Excel will sort for you based first on width, then on length. You will rip all pieces of a given width until you have the lengths you need, then you rip the next smaller width, etc. until finished. Then you will cut to length and will probably have to re-rip some pieces to fully optimize for yield. This, of course takes time and you can build in a calculation that runs value of time against value of material to see if it is worth it.
It's a fun problem but its been done to death.
Regards,
Tom Watson
It's called "paper doll" time.
I use 8x8 grid paper.
Make cut outs for each piece or group of same size pieces.
Layout a full sheet on a sheet of 8x8 grid, then arrange cutouts on that sheet.
Before puters, industrial engineers did plant layouts this way.
Lew
The same rules as when you're moving and filling up the moving van. Largest pieces go first and you work your way down to the smallest ones filling in little spaces. Same when cutting sheet goods. Only difference with sheet goods is that you want as many pieces inline as possible so you can rip lengths.
Or line 'em up to make the crosscuts first if you're using a panel saw (in crosscut mode) to break down the sheet. But for sure, the program must align the parts to allow at least one full length rip or crosscut. Just one more option to go on the list.
Once upon a time I did application programming - mostly relational database front ends - but, considering the costs involved, IMO it wouldn't be worth the time to develop my own nesting program unless there was a good chance of selling it (which brings up its own bucket of worms). But if the OP is looking at it as a "fun" project for personal use, then more power to him.
Tom Veatch Wichita, KS USA
Ahh! This is what I'm looking for.
Thanks!
Back in the '60s I worked for Calcomp. One of the projects was to do a cutlist program for the garment industry such that the cloth could be cut on a modified flatbed plotter.
After a lot of gnashing of teeth, the program worked. It even allowed for "grain" orientation. But it still couldn't do any better than a skilled cutter with many years experience :-).
A few years ago, the Wall Street Journal ran a story about a chap that owned a company that made institutional underwear ("Southern Bloomers"). His biggest customer was the federal prison system (before you ask, the largest bra he constructed was a 55DDD). Anyway, he paid big bucks for a laser-guided cutting system to get the most useful parts from his bolts of high-quality linen. In spite of the best program in the business, he still ended up with about 30% waste which he sold to rag dealers for about $3.00/hundreweight.
Shift gears.
One day his nephew invites this chap to go duck hunting. After the hunting foray, he and his nephew are sitting around, drinking beer, and cleaning their shotguns. The nephew keeps going on and on about the crappy cleaning patches leaving lint, not big enough, etc.
Light goes on.
Guy goes back to his shop, re-programs his cutting software to squirt out a bunch of 2" patches from the otherwise almost worthless waste. He puts 500 of them in a ZipLock bag and takes the bag to Bentonville. He figures if he can get 80¢ per bag from Walmart, he'll make out like a bandit!
The buyer looks at his stuff and compares it to Walmart's current product line, and says "We can give you $1.75 per unit."
Every time I clean my guns, I wonder that this little patch came THIS CLOSE to being a 55DDD!
P.S. The new product line found other buyers. Today, Southern Bloomers provides patches to over 7,000 law enforcement agencies.
"On behalf of the U.S. 10th Special Forces Group (Airborne), I would like to extend our thanks for your assistance in deriving high-quality equipment for our precision weapons system."
Sales of gun patches now out sell underwear 4-1 and the company produces about three TONS of patches per week.
Used to get my suits custom made at Richman Brothers in Cleveland, home of the "plain pipe rack" suit stores.
Back then, a standard suit was $80-$90.
A custom suit was a $10 premium over a standard suit in those days which was a heck of a deal.
Was given a tour of the factory where several laser cut machines were cutting out pieces for suits from bolts of cloth.
Was told the machines had been developed by Hughes Aircraft and adapted to the "rag trades" by Hughes.
Lew
That makes more sense than Hughes Aircraft being involved as I was told.
But heck the guy who told me was a tailor, not the purchasing dept.
Lew
I entirely agree.
I wrote a program in VB5 for kicks.
I actually did my work by taking the selection rectangle and applying it to a pre-drawn 4x8.
Regards,
Tom Watson
Maybe he had Hughes confused with Lockheed, which owned Calcomp for a while.
Could be.
Lew
Chris, just a thought, but the free plugin for Sketchup, CutList 4.0, is a ruby script that contains the algorithms used to produce the html output. It can be read in any ASCII editor (i.e. Notepad). Might be able to get some ideas or reverse-engineer the code.
Before anyone flames me for encouraging copyright violation, the following is a quote from the script file:
# Copyright 2006-2008 Vendmr # Based on CutList.rb, Copyright 2005, CptanPanic # # Permission to use, copy, modify, and distribute this software for # any purpose and without fee is hereby granted, provided something the above # copyright notice appear in all copies.
Google "Cutlist 4.0" for download links.
Tom Veatch Wichita, KS USA
I'll check that out. I also found a Delphi application that I'm trying to figure out.
Thanks!
A decent lay out program does not put any restrictions on materials size. I have hundreds of sizes in my inventory that are not of conventional size and the lay out program takes this into consideration. If the program is limited to specific sizes it is really of little value over what is available now.
CutList Plus will allow you to choose crosscut, rip, or optimise for best yield on the first cut, you get many choices so that you can more easily make the first cuts.
This was before Lockheed bought Calcomp. And I also worked at Hughes for awhile (on the Surveyor program, among others). There was no such effort at Hughes that I was aware of, but it was a big corporation. And there may have been one later.
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