#1
So I took on this college project. The basic idea is to write a paper on a B plan for a guitar assembly line/workshop.

Now I have managed to gather data regarding parts, but I'm at a loss regarding machines used to cut the bodies.

Could you guys point out any book or site that could help?

I'm looking at a production run of around 200 or so guitars a year.
#2
Does this help?

https://www.youtube.com/watch?v=kbna8_JaTe8

Basically, multi-head CNC router.

Try looking for other guitar manufacturer factory tours on YouTube, but I suspect anything that isn't hand built is going to be a CNC router, whatever the production volume.
#3
Yeah it'll have to be CNC. I guess only assembly will be done by hand, assembly and paint and stuff.
On phone, watching the video once I get home.

Do you have anything regarding finishing of instruments? I intend them to be using a basic gloss finish, and a see through stain.
#4
For minimum machine time with minimal post-machining finishing, you'd ideally want a 5-axis machine. I can't remember the proper name, but one with a rotating/swivel head is what you'd want.
A 3-axis could be used, but you'd have slower cycle times, and still need quite a bit of finishing to get rid of the tooling step over marks on curved surfaces.

However, given your production target is 200 per year, that's only about 4 per week. More conventional methods, such as a copy jigs/routers may make more economical sense, given the high cost of CNC machines. At 4 a week, any reasonable CNC will knock them out in under an hour, so you'd have a high value machine doing next to nothing.
#5
Quote by GS LEAD 5

Do you have anything regarding finishing of instruments? I intend them to be using a basic gloss finish, and a see through stain.


Here in California, spraying lacquer runs afoul of the EPA, and it takes just one neighbor complaint to shut you down. Lacquer's also inefficient, requiring long drying time, etc. It's a nasty toxic stuff for your brain and nervous system, lungs and internal organs, as well as long term carcinogenic. And fires in lacquer spray booths are not unheard of and pretty nasty.

There are budget setups for doing UV-catalyzed Polyester finishes (same as the big boys), which will allow you to go dry-to-dry in under 24 hours, with your product ready for finish sanding.
#6
Quote by m_c
For minimum machine time with minimal post-machining finishing, you'd ideally want a 5-axis machine. I can't remember the proper name, but one with a rotating/swivel head is what you'd want.
A 3-axis could be used, but you'd have slower cycle times, and still need quite a bit of finishing to get rid of the tooling step over marks on curved surfaces.

However, given your production target is 200 per year, that's only about 4 per week. More conventional methods, such as a copy jigs/routers may make more economical sense, given the high cost of CNC machines. At 4 a week, any reasonable CNC will knock them out in under an hour, so you'd have a high value machine doing next to nothing.


Yes, the CNC machines will be expensive. However, they would be able to maintain levels of fit and finish comparable to bigger players in the market. Due to import tax regulations, an ESP MH401 would cost around Rs. 40-45000 here.

Using local wood, CNC machining, and cheap local labour, it should be possible to deliver a guitar of the same fit and finish and specifications (example, EMG pickups, Hipshot bridge, schaller tuning machines, tusq nut) within 25000-30000.

Quote by dspellman
Here in California, spraying lacquer runs afoul of the EPA, and it takes just one neighbor complaint to shut you down. Lacquer's also inefficient, requiring long drying time, etc. It's a nasty toxic stuff for your brain and nervous system, lungs and internal organs, as well as long term carcinogenic. And fires in lacquer spray booths are not unheard of and pretty nasty.

There are budget setups for doing UV-catalyzed Polyester finishes (same as the big boys), which will allow you to go dry-to-dry in under 24 hours, with your product ready for finish sanding.


Setup? You mean some sort of machine?
#7
Quote by dspellman
Here in California, spraying lacquer runs afoul of the EPA, and it takes just one neighbor complaint to shut you down. Lacquer's also inefficient, requiring long drying time, etc. It's a nasty toxic stuff for your brain and nervous system, lungs and internal organs, as well as long term carcinogenic. And fires in lacquer spray booths are not unheard of and pretty nasty.

There are budget setups for doing UV-catalyzed Polyester finishes (same as the big boys), which will allow you to go dry-to-dry in under 24 hours, with your product ready for finish sanding.
IIRC California has required "water based lacquers" for decades. (Keep in mind I haven't a clue how one might consider a water based paint a "lacquer" anyway).

Polyurethane finishes have typically been very dangerous to the technicians applying it also. Polyurethane contains a component called "poly-isocyanate" which basically destroys the lining of your lungs. It's purpose is to provide flexibility to the product.

Dupont's "Imron", ostensibly an "aircraft finish", at one time, contained the highest concentration of PIC on the market. (The more flex you needed, the more PIC required).

While I was at the auto repair/ body shop a while ago, I asked if OSHA had been successful in getting the PIC out of the finishing materials. The owner told me flatly, "no".

I'm not familiar with polyester's contributions to OSHA's "material data safety sheets", but I suspect they might be legion as well. Also, many makers use polyurethane for guitar finishes, (and I'm guessing here), in equal to or greater amounts than polyester.

The only reason I bring this up, is there seems to be a prevailing believe that lacquer is dangerous, while other types of finishing materials are, (relatively), "safe". They really aren't.

I think one primary objection to lacquer is the fact it's solid content is so low. It requires thinning to a viscosity far beyond that of poly finishes.

Again, (IIRC), even a low volume production facility dealing with paints, requires a hazardous waste disposal license of sorts. The operator being required to document the method of disposal for waste materials.

In fact, spraying poly was recommended to be done in a supplied air respiration suit, whereas with good old fashioned lacquers you could get away with a good old fashioned organic vapor respirator. (more or less)
Last edited by Captaincranky at Nov 29, 2015,
#8
Quote by GS LEAD 5
Yes, the CNC machines will be expensive. However, they would be able to maintain levels of fit and finish comparable to bigger players in the market.

There is no reason the fit/finish can't be achieved without CNC. Using a CNC machine just guarantees consistency, but that same consistency can be achieved using more manual methods. It's just that it takes more time.

Setup? You mean some sort of machine?

They mean everything required to do the job.
#9
Quote by m_c
There is no reason the fit/finish can't be achieved without CNC. Using a CNC machine just guarantees consistency, but that same consistency can be achieved using more manual methods. It's just that it takes more time.


They mean everything required to do the job.


More manual methods with skilled luthiers. My city has a shortage of those.

The guaranteed consistency of the CNC machine is needed. Thats the only way a product made by a local company can hope to compete with the big brands.
#10
Quote by GS LEAD 5
More manual methods with skilled luthiers. My city has a shortage of those.

The guaranteed consistency of the CNC machine is needed. Thats the only way a product made by a local company can hope to compete with the big brands.


A local company won't compete with the big brands. Not really. Large brands can buy materials and hardware far more cheaply than "local" companies can, and can amortize captial expenditures like CNC machines over a lot more guitars.

Any business plan that includes low-end guitars and/or designs that are minor modifications of existing designs is pretty much doomed to failure.

One local company (I'm in LA) that's doing well is Trussart, but they've got pricing from about $3500-6000, and their guitars are distinctive. Tom Anderson, Suhr and others that have been modestly successful are mostly building high end guitars. Carvin is building high-end guitars but has eliminated the retail market completely -- their business model is to sell a personally-built guitar directly from the factory to the end user. This largely eliminates the number of unsuccessful models that you'll find in larger builders' product lines. Their marketing was originally based on a mail order catalog (now both catalog and website). They maintain little or no inventory and don't wholesale to larger retail vendors such as GC. Their value to price ratio is very high, and they're able to control profit margins far more easily than can most.

You'll notice that most guitar manufacturers don't have "skilled luthiers." They largely have task-oriented workstations populated with folks making a bit over minimum wage who are trained for and can perform one or two specific tasks.
Last edited by dspellman at Nov 29, 2015,
#11
Quote by Captaincranky

The only reason I bring this up, is there seems to be a prevailing believe that lacquer is dangerous, while other types of finishing materials are, (relatively), "safe". They really aren't.


Lacquers are toxic, carcinogenic, and injurious to the environment. A large part of that is associated with the solvents (acetone, etc.) that go along with it. You need a LOT of special permissions that are nearly impossible to attain if you're going to use anything more than a few rattle cans of lacquer. Lacquer continues to flash off those solvents for perhaps 30 days (and more) after initial spraying. Lacquer doesn't cure -- it dries, and slowly.

Polyester finishes can come close to 100% solids (Taylor puts the guitar on a robotic fixture and sprays the finish with a computerized arm that's claimed to produce a far more even (thickness) finish than any human. In addition, it largely eliminates any danger to workers by isolating the robotic components from the rest of the work area. Because it's not flashing off solvents, it has far lower effect on workers and the environment. Guitars finished this way are usually in the stores and/or sold before lacquer finished guitars are up for final sanding at the factory.
#12
Quote by dspellman
A local company won't compete with the big brands. Not really. Large brands can buy materials and hardware far more cheaply than "local" companies can, and can amortize captial expenditures like CNC machines over a lot more guitars.

Any business plan that includes low-end guitars and/or designs that are minor modifications of existing designs is pretty much doomed to failure.

One local company (I'm in LA) that's doing well is Trussart, but they've got pricing from about $3500-6000, and their guitars are distinctive. Tom Anderson, Suhr and others that have been modestly successful are mostly building high end guitars. Carvin is building high-end guitars but has eliminated the retail market completely -- their business model is to sell a personally-built guitar directly from the factory to the end user. This largely eliminates the number of unsuccessful models that you'll find in larger builders' product lines. Their marketing was originally based on a mail order catalog (now both catalog and website). They maintain little or no inventory and don't wholesale to larger retail vendors such as GC. Their value to price ratio is very high, and they're able to control profit margins far more easily than can most.

You'll notice that most guitar manufacturers don't have "skilled luthiers." They largely have task-oriented workstations populated with folks making a bit over minimum wage who are trained for and can perform one or two specific tasks.



You're forgetting that prices here are massively jacked up due to import taxes. Not only that, what in the west would be considered a low end guitar (say USD300 or R's 20000) here it is considered mid range. And that's before being hit by a 30% tax that sends it to usd 400 (around R's 26000).

We won't be having a huge or wide range of guitars. But they will have specs that will appeal to people who previously cannot afford more expensive guitars. Cheaper due to no import tax on the instruments, cheap labour, and the fact that theoretically at least you're producing an instrument at say 400 dollars that can match the features of one worth say 600.

An LTD MH400 series for instance while about USD 600 in the states, is closer to 900 here simply because of tax.
#13
Quote by GS LEAD 5
So I took on this college project. The basic idea is to write a paper on a B plan for a guitar assembly line/workshop.

Now I have managed to gather data regarding parts, but I'm at a loss regarding machines used to cut the bodies.

Could you guys point out any book or site that could help?

I'm looking at a production run of around 200 or so guitars a year.


so you're just writing a paper, not actually going to go through with this? so this is all theoretical?

i know it's pretty far from Calcutta, but if you can, check out the HMI factory in Chennai, get a tour -it might be helpful for you. i believe they handle Jackson.

https://www.youtube.com/watch?v=ImMbdFuHNlI
Last edited by ad_works at Nov 30, 2015,
#14
Quote by ad_works
so you're just writing a paper, not actually going to go through with this? so this is all theoretical?

check out the HMI factory in Chennai, get a tour -it might be helpful for you. i believe they handle Jackson.

https://www.youtube.com/watch?v=ImMbdFuHNlI


Theoretical for now.

One B Plan will be chosen from submissions, and that will be given funding as well as space in an incubation center.

HMI factory? Wait, Jackson builds guitars in India? Wut?
#15
yep. the x series. i have one. look closely at the video and you will see jackson headstocks.
#16
Quote by dspellman
Lacquers are toxic, carcinogenic, and injurious to the environment. A large part of that is associated with the solvents (acetone, etc.) that go along with it. You need a LOT of special permissions that are nearly impossible to attain if you're going to use anything more than a few rattle cans of lacquer. Lacquer continues to flash off those solvents for perhaps 30 days (and more) after initial spraying. Lacquer doesn't cure -- it dries, and slowly.
As someone who has worked with many types of paint, and been employed in the auto refinishing industry, I have to point out there's very little in the above captioned paragraph I'm unfamiliar with.

Quote by dspellman
Polyester finishes can come close to 100% solids (Taylor puts the guitar on a robotic fixture and sprays the finish with a computerized arm that's claimed to produce a far more even (thickness) finish than any human. In addition, it largely eliminates any danger to workers by isolating the robotic components from the rest of the work area. Because it's not flashing off solvents, it has far lower effect on workers and the environment. Guitars finished this way are usually in the stores and/or sold before lacquer finished guitars are up for final sanding at the factory.
Bob Taylor is a shining star in the field of environmentally friendly procedures and production techniques. When the opportunity arises, he will tell you the same thing, at some length.

Not every small shop would be guitar builder has the means to purchase a robotic spray booth. That having been said, the guy at the corner body shop isn't going to be spraying your dented fender with a robot either.

So, after visiting DuPont's rebranded finishing web site, I'd be happy to provide to you with a laundry list of PDF material safety data sheets, to reinforce my point that other finishes have dangerous compounds in them as well.

As far as the horrors of acetone go, as long as you don't load nail polish remover in a spray gun and shoot it without a respirator while locked ion a closet, you'll most likely survive it.

Here's some light reading on product safety: http://www.axaltacs.com/us/en_US/products-services/liquid-coatings/nason/products/safety-data-sheets.html
Last edited by Captaincranky at Dec 1, 2015,
#17
Quote by Captaincranky
As someone who has worked with many types of paint, and been employed in the auto refinishing industry, I have to point out there's very little in the above captioned paragraph I'm unfamiliar with.


Congratulations. This information was not, then, directed at you, but at the OP.

Quote by Captaincranky
Bob Taylor is a shining star in the field of environmentally friendly procedures and production techniques. When the opportunity arises, he will tell you the same thing, at some length.


He does indeed promote whatever he's passionate about. Many of his production techniques are innovative and they do promote a lot of consistency in his guitars. And he's one of the few guitar manufacturers to put his money where his mouth is when it comes to funding, using and promoting sustainable tone woods.

Quote by Captaincranky
Not every small shop would be guitar builder has the means to purchase a robotic spray booth. That having been said, the guy at the corner body shop isn't going to be spraying your dented fender with a robot either.


And the point of mentioning all that was more that it was possible to set up a worker-health-friendly paint system that offered dry-to-dry in 24 hours. Carvin, just down the road from Taylor, has been spraying conventionally but producing outstanding finish results using these same materials. I have acquaintances in Hawaii who produce high-end ukes in relatively low volume that have switched from lacquer to UV-cat materials with a relatively economic spray booth and curing station designed specifically for low-volume use.

Quote by Captaincranky
So, after visiting DuPont's rebranded finishing web site, I'd be happy to provide to you with a laundry list of PDF material safety data sheets, to reinforce my point that other finishes have dangerous compounds in them as well.


Noted. OTOH, high solids volume spraying and quick curing eliminates a lot of the exposure.

Quote by Captaincranky
As far as the horrors of acetone go, as long as you don't load nail polish remover in a spray gun and shoot it without a respirator while locked ion a closet, you'll most likely survive it.


As you are probably aware, then, it's not *just* the exposure during spraying that counts, but the exposure to flashing solvents during the drying process that can cause issues. Furniture plants here in Southern California are using water-base finishing supplies, but just south of the border you'll find lacquer still used, and a high incidence of cancer, nervous system and liver disorders among those workers.
#18
Quote by GS LEAD 5
The guaranteed consistency of the CNC machine is needed. Thats the only way a product made by a local company can hope to compete with the big brands.


That statement tells me you don't have much experience in manufacturing.
Yes, a CNC will have consistency, but you can also have the same consistency using manual methods, by creating a range of jigs/templates.

Main body outline can be handled via a bandsaw, followed by a template and router table.
Main body contours, a copy jig will manage, and then finished with suitable sanders, which you'll most likely need to do anyway.
Neck's are going to involve quite a bit of manual work anyway, but the same processes will work.

To put the CNC costs into perspective, here in the UK, for a 3axis machine for doing body outline/profile, a good estimate would be upwards of 40'000GBP by the time you include all the needed accessories.
Assuming you finance the machine over 5 years, each guitar is going to cost you £40 to pay for the machine, that's not including finance cost, operator, or consumables, so £50 is probably a better cost for estimating. Now that is just for the cost of the machine.
Now even if you made all the main parts on the CNC, I'd guess you'd be looking at a very minimum of 1hour machining time, excluding setup changing. And then you'd still need to sand everything to the required finish level, but then that is the same regardless of the main process.

Now if you were to make a series of jigs/machines for the main parts, I'd say a reasonably worker should manage all the main parts in 2-3 hrs.
Yes the Jigs/machines will have a cost attached, but I'd say in the UK I could manage them for under £10'000, so using the same 5 years, that's only £10 per guitar cost.

Comparing the two using those basic figures, the CNC option is going to cost £50, whereas the jigs are going to cost £10 plus 2-3 hours labour.

If you want an idea of the processes/jigs involved, search for BigDGuitars over on youtube to see how he uses jigs, and also have a search for other videos showing factory tours. Some of BigD's processes will take hours, but he's not doing batches, he's setting up to do single items at a time, so he's continually changing setups, after which the actual machining is relatively quick.

If you really want to put together a viable business plan, you have to understand the full process, and the cost of all options for each step of that process.
#19
Quote by dspellman
....[ ]....He does indeed promote whatever he's passionate about. Many of his production techniques are innovative and they do promote a lot of consistency in his guitars. And he's one of the few guitar manufacturers to put his money where his mouth is when it comes to funding, using and promoting sustainable tone woods.
True, although I don't think his, "streaky ebony chat', was received as well as it should have been by the acoustic guitar "elite"..

Quote by dspellman
And the point of mentioning all that was more that it was possible to set up a worker-health-friendly paint system that offered dry-to-dry in 24 hours. Carvin, just down the road from Taylor, has been spraying conventionally but producing outstanding finish results using these same materials. I have acquaintances in Hawaii who produce high-end ukes in relatively low volume that have switched from lacquer to UV-cat materials with a relatively economic spray booth and curing station designed specifically for low-volume use.
Admittedly finishing techniques have changed greatly since I was involved in the trade. I guess a point I failed to get across was the polyurethanes were more dangerous than lacquer at the application stage.

Quote by dspellman
As you are probably aware, then, it's not *just* the exposure during spraying that counts, but the exposure to flashing solvents during the drying process that can cause issues. Furniture plants here in Southern California are using water-base finishing supplies, but just south of the border you'll find lacquer still used, and a high incidence of cancer, nervous system and liver disorders among those workers.
The central nervous system warning was right on the sides of the cans! Part of the origins of that convention, I expect, was experience gained through the glue sniffing era. (I thankfully missed that one). Although I have to admit, most of the organic solvents involved with lacquer spraying, smell as good as, or better than roses to me...

If you were to move lacquer at 68 degrees F, 30% RH, it wouldn't "blush". Some of the prolonged solvent venting would be reduced. It's when you start using "******ers", with the heavier solvents they contain such as xylene, the problem is exacerbated.

As for Mexican furniture makers there may be two factors involved. The first is the old saw, "you can lead a horse to water", of workers possibly being unwilling to adhere to safety guidelines. Second the companies being unwilling to provide those aforementioned conditions.

I saw some strange things in the paint shop. We had a helper who was apparently addicted to lacquer solvents of the most heinous kind. He used to station himself between the vehicle being painted and the exhaust fan, to soak up as much of the fumes as possible. He particularly seemed to relish the flash off from DuPont 222, "bonding clear", which no one else in the shop would even walk by an open can of it,without a respirator.

And now we move to Gibson, whose customers can't live without nitro finishes, and their employees you insist can't live with them. (Not saying you're wrong here).

In any case, (pun intended), like all things today the risks of lacquer may be exaggerated. That from the interpolation of data gained at the most severe levels of exposure, and applied to someone walking by a guitar sprayed with lacquer two months prior.

Granted, you don't bring a freshly painted car into your living room with you. But second, I am a bit cynical that one nitro finished guitar sprayed a month previously, is going to wipe out everyone within a city block radius.

Just some points to consider.

The website wouldn't let me post the legitimate name of this product so:
Last edited by Captaincranky at Dec 1, 2015,
#20
Quote by m_c
That statement tells me you don't have much experience in manufacturing.
Yes, a CNC will have consistency, but you can also have the same consistency using manual methods, by creating a range of jigs/templates.

Main body outline can be handled via a bandsaw, followed by a template and router table.
Main body contours, a copy jig will manage, and then finished with suitable sanders, which you'll most likely need to do anyway.
Neck's are going to involve quite a bit of manual work anyway, but the same processes will work.

To put the CNC costs into perspective, here in the UK, for a 3axis machine for doing body outline/profile, a good estimate would be upwards of 40'000GBP by the time you include all the needed accessories.
Assuming you finance the machine over 5 years, each guitar is going to cost you £40 to pay for the machine, that's not including finance cost, operator, or consumables, so £50 is probably a better cost for estimating. Now that is just for the cost of the machine.
Now even if you made all the main parts on the CNC, I'd guess you'd be looking at a very minimum of 1hour machining time, excluding setup changing. And then you'd still need to sand everything to the required finish level, but then that is the same regardless of the main process.

Now if you were to make a series of jigs/machines for the main parts, I'd say a reasonably worker should manage all the main parts in 2-3 hrs.
Yes the Jigs/machines will have a cost attached, but I'd say in the UK I could manage them for under £10'000, so using the same 5 years, that's only £10 per guitar cost.

Comparing the two using those basic figures, the CNC option is going to cost £50, whereas the jigs are going to cost £10 plus 2-3 hours labour.

If you want an idea of the processes/jigs involved, search for BigDGuitars over on youtube to see how he uses jigs, and also have a search for other videos showing factory tours. Some of BigD's processes will take hours, but he's not doing batches, he's setting up to do single items at a time, so he's continually changing setups, after which the actual machining is relatively quick.

If you really want to put together a viable business plan, you have to understand the full process, and the cost of all options for each step of that process.



40000 gbp?
whoa, that's massive.

I thought a 5 axis CNC would come in at under 20,000 dollars? That's what I
based my calculations on. 40k GBP converted to rupees is 4 times the cost :/

I look him up, and I'll post here if I have any more questions.
#21
Quote by GS LEAD 5
40000 gbp?
whoa, that's massive.

I thought a 5 axis CNC would come in at under 20,000 dollars? That's what I
based my calculations on. 40k GBP converted to rupees is 4 times the cost :/

I look him up, and I'll post here if I have any more questions.


why do you think you need a 5 axis cnc machining center? in the states for a quality new machine that'll run you around 200k USD. you'll need software for it (around 20k), you'll need to program it, you'll need a tool pre-setter and support equipment, etc.. also, if you buy a machine tool from the US, 5 axis tech is still export controlled.

you can certainly source from elsewhere, but again why?

you can get a 5 axis router for much less but you don't even need that. you can get something used and try to get it to work right but you don't need that either.

bottom line is that you don't need 3 or 5 axis cnc machine tools for small quantity guitar production. basically the 3 most important areas concerning accuracy on a guitar are the neck pocket, the bridge position, and the fret spacing. easy +/-.002"~.005" tolerances with competent, conventional fixturing.

respectfully, you're way off base. i suggest that you study that video that i linked for you -all of your answers are there if you know where to look.
Last edited by ad_works at Dec 1, 2015,
#22
You probably could get a 5-axis cnc for 20'000usd, however I certainly wouldn't expect it to be production capable, or accurate, which would defeat the purpose of having a CNC.
Industrial CNC's, even second hand, cost lots of money.

ad_works, it was me who originally mentioned the 5-axis. It would let you machine contoured bodies and other parts which would require minimal post machining sanding, however suitable jigs/fixtures would be just as quick (probably quicker for some parts) and more cost effective.
I was just highlighting the possible methods to achieve the same thing, which for anybody doing a business plan, they should be investigating all the possible options.
#23
Quote by m_c
You probably could get a 5-axis cnc for 20'000usd, however I certainly wouldn't expect it to be production capable, or accurate, which would defeat the purpose of having a CNC.
Industrial CNC's, even second hand, cost lots of money.

ad_works, it was me who originally mentioned the 5-axis. It would let you machine contoured bodies and other parts which would require minimal post machining sanding, however suitable jigs/fixtures would be just as quick (probably quicker for some parts) and more cost effective.
I was just highlighting the possible methods to achieve the same thing, which for anybody doing a business plan, they should be investigating all the possible options.


of course.

let's clarify "cnc machine" here for a second. when discussing woodworking, one generally is referring to a "router". in the used market one could certainly purchase a Thermwood Cartesian for under the 20K amount. When discussing a "5 axis cnc machine" in the metalworking world, it's an entirely different thing and 20k will get you laughed at.

regardless of the machine being used for woodworking, you will have to sand -period. since the cycle time to machine surfaces is driven by the cutter size, the stepover amount, and feeds and speeds, as well as the tool overhang and overall part set-up, a fine stepover and scallop height on the order of say .003"~.005", will create a ridiculously long and unprofitable cycle time (on the order of many hours for a strat body for example) and you will still have to sand to remove imperfections and to provide "tooth" for the finishing process. if you increase the stepover to say .062~.093" you will shorten the cycle time drastically and the required sanding is still there. you only have to bring the raw wood down to 220 -no finer.

Carvin demonstrates on a funky old 3 axis Fadal (probably a 4020) machining center (not a router):

https://www.youtube.com/watch?v=fnUKqRqQbao


i love cnc's, they're fun to use and program and investigating all the possible options is fine, but in the manufacturing world quantity is one of the initial front end drivers of the technology chosen to make the product. ime, a quantity of 200 guitars per year doesn't warrant the investment in 3 or 5 axis tech. kick that number up to 200 per month, and now the investment becomes much more reasonable.
Last edited by ad_works at Dec 2, 2015,
#24
For the purpose of this thread, I was making the assumption by CNC machine, people would know we were talking about wood working machines i.e. routers.

5 axis would let you machine contours to near finished at full stepover far quicker than a 3 axis having to do a partial stepover. and need less finish sanding.
But as has been said, it all comes down to cost, and for 200 guitars a year, a CNC just doesn't make economic sense. Jigs/fixturing will get the job done almost as quick, and probably quicker for some jobs, and cost a fraction of the initial outlay.

I like CNC machines as well, and is why I have a small CNC mill and a reasonable sized CNC lathe in my workshop. I also have a bigger mill that I'm retrofitting as time allows, but spare time for that is lacking just now :-/