CNC Router Productivity

      Shop owners evaluate the productivity advantage of CNC equipment, and discuss ways to adapt shop methods and processes to the machine's capabilities. October 2, 2007



Question
In Cabinet Maker Magazine there is a story about a CNC router. The owner said it used to take 4 to 5 days and now it takes 4 to 5 hours per kitchen! Wow, that's something. It took him 4 to 5 days per kitchen just to cut out. First, why so long? Maybe dull hand saw? Some people drive big trucks with a 454 who say they get around 20-25 mpg. My guess is they don't think you have a brain. How can you make the payment for a few hours per kitchen?

Forum Responses
(Cabinetmaking Forum)
From contributor T:
My experience with going to CNC router vs table saw. Before we set the router up, I timed myself cutting on the saw. I could cut 10 sheets per hour - that's pushing as hard as I could. I still had to drill for shelving, lazy susan hardware, pilot holes for drawer slide brackets, etc. The router does all that in the same time and does it all the time - I got real tired. The router also cut dados. End result - parts are ready in half the time, maybe less; cabinets are assembled way faster, close to half the time. All parts are perfect - no mistakes - everything perfectly square. I should have gotten one years ago.



From the original questioner:
Thanks for your response. Your time savings and quality makes sense. Hours saved, not days, but higher quality with less work.


From contributor A:
4 hours to machine, not only cut, all ready to assemble parts per kitchen is about right.


From contributor P:
I'm planning to go the CNC route in a year or so. After visiting a shop which cuts the majority of parts and does the majority of milling at the same time on the router, I'm sold. I think that a well set-up router with a competent operator will cut rings around any other method. It takes us about 90 or so man hours to completely cut and machine an average kitchen. (I don't have a slider, yet.) On the router, I believe it could be done in less than ten man hours and using dowels. The assembly time would be cut by at least 50% over our pocket screws. And if you use puzzle joints for frames, I think you knock at least a couple hours off of face frames.


From contributor L:
I'm sold too. We bought our 1st router 10 years ago. We were very busy and figured it paid for itself (80K) in 2 years. Since we've gone nested (on a bigger, faster router), it is better still. All the machining is complete in less time than our beam saw can just cut the parts. Complex curved casework is a snap.


From contributor M:
I have heard a lot of good things about CNC routers. Much down time with replacing bits and repairs? How hard is it to use? Is it hard on the back when removing the parts off of the bed of the CNC? Are the cheaper CNCs worth the while for a one or two man shop?


From contributor L:
I don't know about the cheapest routers but on a production machine, bit changes are done while the machine is working (bits are put in the tool holders at the bench, the tool holders are then just snapped into the tool changer magazine and you're off and running again). Repairs on our machines have been minimal, mostly clean and lube. The machines are easy to learn, the software is the key and that seems to vary greatly.

Removing the finished parts is easy; loading full sheets depends on how much attention you have paid to the process from the start. A jib crane and vacuum lift is a good investment. I wouldn't go deeply in debt as a very small shop, but I really do like the capabilities of a router. The machine can cut the parts while you are banding and assembling them. A cabinetmaker will cost you at least $40K/year; a good router is less than that and is more reliable.



From contributor B:
You asked: "Much down time with replacing bits and repairs?"

We typically change the main nesting bit every 80 to 120 sheets of material processed. Our machine is now 2 1/2 years old, and we have only changed the 8mm bit we use to groove for backs and drawer bottoms once. We are still using the original 8mm and 10mm drill bits, and have changed out the 5mm drill bit twice, and the 3mm drill bit approximately 4 times. It typically takes around 5 minutes at the most to change a bit, and a couple more minutes to recalibrate.

As for repairs, we have had to replace a switch that turns the vacuum pump on and off automatically twice now, and it needs to be replaced again, so we are looking for a better quality switch to replace it with. Early on, we had a couple problems with a gear for the servos, but the manufacturer upgraded (retro-fitted) the way it worked, and we have not had any other issues with those gears.

In the past 2 1/2 years, we have not had a single day that we could not produce parts (we were able to bypass the switch that failed, and the gear issue just made it noisy, not inoperable).

You asked: "How hard is it to use?"

I personally think that this has as much to do with how willing you are to match your products to its (the CNC machine) capabilities as to the machine's complexity. Too many of us still have this "gotta keep the machine working every hour of every day" mentality, which makes us want to do all sorts of crazy things to keep it working, which typically will require a lot of expertise and/or software that we do not currently posses. Both add additional time to the learning curve, and additional complexity that requires expertise that has to be transferable to be effective in the long run.

Another big one is the software, and again, our desire to make it do what we want to do rather than do what it does best. We are seldom willing to re-evaluate/re-engineer what we do (our products and our processes), and see if there is not a better way to do it, capitalizing on the machine, and the software strengths. I think a lot of the current learning curve length is due to our insistence that the machine do things the way we want to do them rather than for us to find the best way to achieve our objectives without complicating and/or compromising the software and the machine.

This has been true for most technology breakthroughs - we just want to do what we have always done faster, not look for new ways of doing things, which many times will provide huge dividends by providing significant breakthroughs in overall productivity. We have to be very careful to not allow technology to rule us, or to be blinded by technology, but we also have to be creative and open minded to be able to exploit it. Daniel Boorstin once said "Technology is so much fun we can drown in our technology. The fog of information can drive out knowledge."

A couple examples for me would be when I converted from face frame construction to frameless, I had to completely re-evaluate our material handling methods, and the effort was rewarded by multiples of increased productivity. Had I insisted on handling the cut parts the same way we had done it in the face frame environment, I would have prevented the break-though in productivity we were able to achieve. When we switched to CNC, we again had to completely change the way we handled the parts, but again, the change added enough additional production capacity to allow us to either lay off two people, or bring our installation back in house, but maintain the same level of sales. I chose to bring the installation back in-house, and I still have the option of outsourcing installation again if we choose to take on an even larger workload.

I also think a lot of this comes from not looking at our global objectives, but focusing on local objectives that do not produce the best returns on the time and money invested (insisting that the machine run parts for 20 cabinets a day, even though we can only finish, and/or install 8 to 10 cabinets a day), which only draws down our cash flow, fills every square inch of floor space with WIP (work in process) and carts to hold the WIP, extends our lead times, makes scheduling impossible, and confuses our workforce.

You asked: "Is it hard on the back when removing the parts off of the bed of the CNC?"
Not if you get a machine that utilizes the gantry (we call ours a parts pusher, some call it a parts sweep) to push the entire sheet of parts off all at once.

You asked: "Are the cheaper CNC's worthwhile for a one or two man shop?"
I am not sure what price range you consider to be cheaper, but I feel like all of the CNC routers have their place. I do think that most of the larger machines are overkill for the majority of small shops, and that there are a really good group of machines that are under $100,000.00 that are ideal for smaller shops, even down to the one man shop.



From contributor G:
I, like the questioner, wonder why that shop was even in business if it took them 4-5 days or more to process sheet stock for one job. If they were that inefficient, how could they get financing in the first place for a router? I take those claims with a grain of salt if it is an advertisement. When it is a magazine article and there is no bias, I really wonder. We build face frame cabinets. Over the last 10 jobs we averaged 14 sheets of 3/4 material per job. Averaged .84 hours per sheet to cut to size (panelsaw), dado and rabbet (dedicated tablesaw and feeder), drill shelf/drawer slide mount holes (46 hole double line drill), and edgeband (tabletop bander trimmed by hand). Pocket holes are drilled during assembly so are not recorded as panel processing. Accuracy is not a problem. .84 hrs x 14 sheets x 3 jobs per month averages = 35.28 hours/month processing sheet stock. Cut that time in half with a CNC saves about 18 hours per month x $50/hr shop rate equals $900/month. I realize there are other things we could do with the router, but at this time I don't think they would add a lot to my bottom line. Considering the floor space, mechanicals and learning curve involved, I don't think a router is a wise investment for me yet. I am a sucker for a new tool purchase, so if anyone can see a flaw in my thoughts, please let me know.


From contributor D:
You are off a bit on your panel process times. It takes my shop about 12 - 15 minutes per sheet on my router; about 6 minutes to machine the sheet and the rest to label, clean the table, and reload the machine. Labeling parts is the biggest waste of time, though it must be done.

So the 14 sheets can be totally processed in about 3.5 hours, and the whole job assembled by the end of the day. But let's just say it takes 2 days to complete a job. That means you get 2 1/2 jobs done a week, or 10 a month. The router allows you to take on more work with less people. Which adds up to additional savings. How many guys would you need to get 2 1/2 jobs out per week with the old school methods? What kind of labor savings would that be in a year? How much space does a slider, a couple table saws, a line borer, the extra employees to run these, take? There is a lot more than panel process times to take into consideration when purchasing one of these machines, which most of is not realized until you get it and get familiar with its abilities.

As contributor B stated, tools do last a long time on these machines, though I get closer to 4 - 5 hundred sheets with my cut out bit. It took some trial and error to get there, though, and that is what I can achieve as a regular average. It all comes down to getting to know the abilities of your machine and making it work for you, not you working for it.



From contributor I:
You also don't need to pay workers comp, health insurance, or vacation pay to the router.

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