CNC does have a dirty little secret. It is a lousy production tool. Everything you make with a CNC machine requires that you write a program, plan a cutting path, test that the machine will really go where you intend it to go, decide cutting parameters based on the cutting tool and material being cut and set up the cutting stock. This is not a high speed process. It is wonderful for prototyping and one off type production, but not for mass production.
It is much faster to just use a pattern cutting bit in a router and do it by hand following a template. The setup is faster, it is just as precise and a whole lot cheaper. Have a set of complex cuts? Make a set of templates. If you want to ramp up production to mass produce some pieces, just grab a few routers and some pairs of willing hands and you can multiply productivity to pretty much unlimited production rates.
Many times, it is faster and easier to do things manually. If you want to cut out a simple shape, just measure and mark, clamp down a cutting guide, and have the piece done much more quickly than even booting the computer. You really don't need a program to cut a piece of plywood into a 1' square.
I feel better. There are many techniques available that will beat CNC routing in a production setting. Stamping, casting, injection molding, pattern routing... The list goes on. It is from this standpoint that I can say that I really don't care how fast my CNC machine will cut. It doesn't make any difference. Why would I care if I can get "1500 in/min Rapids" or some such nonsense. I am not routing a path from Seattle to Miami. For a one off piece, it doesn't really matter whether it takes 5 minutes or even 2 hours longer to cut something out. If I am using an expensive CNC machine to do what a $2 piece of plywood template could do faster and easier, throwing more money at the CNC machine to make it faster doesn't make it less silly.
While it's true that there are a lot of things that are better done non-cnc, you couldn't be more wrong about CNC not being a production tool.
ReplyDeleteI've been doing high production CNC routing for about 15 years. It's all about the software you use. The right software will automatically do all the steps you mentioned in seconds.
It really is a niche production technique. There is a break point for how many units you will be making, depending on the product. Once you get beyond that break point, it will lose every time.
ReplyDeleteIt also works in CNC's favor. If you use mass production techniques, you have to have a pretty large number of minimum number of units to make before you can realize any profit. Make fewer and you lose money. Makes it real hard to stay in business unless you are doing charity work or happen to have a lot of slave labor you want to keep under control. The threshold for making a profit in CNC is a lot lower.
It just is not up to the speed of mass production that you can do with other techniques. You just cannot compare an automated CNC router to the speed of full on automated material handling and dedicated machines that you would have in a production line.
I am not dissuading people from using CNC. There is potentially a lot more money to be made for small runs that are not cost effective to set up for real high speed production techniques.
Sorry, but you're wrong. Go to any high production cabinet shop, and they all use CNC routers. It's just faster. Especially for mass production, where multiple operations can be done to a part at one time, where doing it other ways would require multiple operations, and the additional handling time those operations require.
ReplyDeleteAnd yes, while efficiency goes up while quantities go up, it's still far more efficient to do one off jobs, provided you have the correct software to automate the programing process.
Someone can walk into my office, tell me to cut a cabinet, and it can be ready to assemble in 10 minutes. Regardless of the type, or size.
Labor is the most expensive part of most woodworking projects. CNC's do the labor, reducing cost.
Sure, you can choose certain products that wouldn't benefit from CNC, so this discussion is somewhat pointless unless you're talking about a specific product.
My area of expertise is high volume cabinet manufacturing (several million dollars/year).
You won't find any shops in this market that doesn't rely heavily on CNC. And it's been that way for 20 years.
Ok, we seem to be having a difference in the definition of high production.
ReplyDeleteA high production cabinet shop is not anywhere near the scale of a factory. I am talking about the the kind of production levels for that stuff you can pick up at IKEA, HON, Walmart or Office Depot where their daily output is measured in shipping containers. The fact that their tooling costs are so high is what allows you to do so well with small scale of production. In the big places, it can cost several million dollars just to tool up and train for a new product run.
I worked for a while with a small sized high production facility where their "small production runs" were starting in the range of 5 or 10 thousands of units. They were taking the "small jobs" that the big places wouldn't touch. Not being argumentative, it is just a different world and not comparable.
CNC is creating a new paradigm for small to middle sized volume production runs because the kinds of things that they produce in a factory setting don't fit every need and they are not able to adapt to customization. You can't walk into IKEA and say, "I like that table. Could I have 15 of them 10" longer." They couldn't touch the job if you asked for 1000 of them. They probably would not get out their calculators and think about it below 10,000 units.
Last post. Maybe.
ReplyDeleteAre you saying IKEA doesn't use CNC? Never been in an IKEA plant, but my guess is that all their parts are cut on CNC beam saws, that can cut up to 5 sheets at a time, and all the holes for all the knockdown hardware are done on CNC Point to point routers with multiple drilling heads.
I can't believe that IKEA is not using CNC for at least 95% of the machining done on their products.
Anyway, good luck with your project. I'll be keeping an eye on it.
Generally, they have fixed machines with multiple spindles that drill simultaneously. Line boring machines. Grabs the piece off the line. Clamps it down. Bores all holes at the same time (or in sets, depending on the spacing) and spits it out. 5 or 10 seconds max. Gang saws. Vacuum lifts and clamps. High speed computerized quality control cameras. Fascinating stuff. Generally, though, the cutting tools are in fixed positions. It is just faster and less chance for positioning errors. You can't cut wrong if the cutter doesn't go anywhere else.
ReplyDeleteI would never want to work in that type of facility again but I still enjoy watching "How It's Made" on TV. Magical to watch all the stuff fly past and all the specialized machinery. Unfortunately, it is mind numbing once the novelty wears off.
Thanks for chiming in. I don't claim to be an expert and getting other people's input is why I am doing this online. I just think that there is a lot of room for improvement on the basic designs I have seen for CNC machines. They are just now getting to the point where people can bypass the way over priced stuff that is commercially available.