Many people purchase acoustics guitars but do they really know where they come from? I have read many books on building acoustics one at a time but to understand how they are produced in mass production is a completely different story.
Here is a factory tour of an Asian Acoustic Guitar Factory.
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Even with todays Cad software still the basic drawing is started by hand. Each detail of the guitars construction needs to be drawn out. The drawing usually starts by hand then after the layout is finished the final drawings are done with a Cad program and printed out on a plotter.
Acoustic guitars are not easy to mass produce you may look at one and feel it is not so difficult, however if every component is not exact than the guitar will not produce a good acoustic tone and also be not stable. |
| For example the top on an acoustic is not flat. They call them flat tops but really a properly constructed acoustic has a top and back radius to strengthen the guitar. This is done by shaping each brace to a certain radius
When the top or back is glued on the woods shape is controlled by the bracing. It is sort of like a bridge over a river, they never construct them flat because the bow makes it stronger. After the drawing is laid out it is time to produce a proto type. This allows them to understand what jigs will need to be made, what materials will need to be ordered, and if they will need to make any special equipment to manufacture the model. All of the proto types are hand constructed so that they can understand all the processes that are involved. Certain models in the factory will always need to be custom made even after the proto types are finished, this is because many of the high end models that are produced need more care and time to be spent producing the guitars detailed work such as inlays or hand scalloped bracing. Most guitars production designs are the standard dreadnought shapes, however it has been found that they can also adjust the sound that will be produced by changing the size, dimension, bracing pattern or the materials that are used. Certain woods retain different sound characters and this needs to be addressed during the initial design. After the basic layout and proto types are made it is time to order materials needed for production. they purchase woods from all over the world so they need to think ahead in ordering materials. The solid spruce nowadays usually comes from North America and is either Sitka or Engelman. Other materials like the rosewood backs and fretboard's comes from India, most mahogany is from Africa or Indonesia (Natoh) Most of the other materials are either produced in house or purchased from local suppliers. All the woods used must be properly dried before any production can begin. To check the moisture they have meters all over the factory to constantly monitor the moisture content of the woods before and during production. |
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In the start of production, after they have all the materials they start by gluing up the wood. Here is a picture of them joining a set of solid rosewood backs. They join the tops and backs the same was using side presses to hold the joint together and weights on the joint to keep the wood from buckling up during the drying process.
First the wood is bookmatched. Book matching is taking a piece of wood and splitting it down the center, then you open it up like a book and join the wood. The wood is laid flat on a table and two side clamps are closed on the wood, weights are laid on the joint to remove and flexing. The glue sets in about 30 minutes and takes 24 hours to completely dry before and production can begin. |
| After the woods are glued and dried its time to start production. The tops and backs are rough cut to shape and size. Next the sound hole is cut in the guitar as well as any fancy rosette routing. This is easier before the tops and backs get braced. |
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The sound hole is cut in the body using a large custom bit that has the exact shape and size of the of the sound hole. The placement of the sound hole is vital to the construction of the guitar so they designed a special machine that holds the top in the exact position so that the the hole is set to center. |
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The size of the sound hole is also important in the strength of the top. If the hole is too big you will get a louder guitar but a less stable top. |
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Before the back is braced they also inlay any materials like the backs center strip. The bodies will have a contoured shape after they are braced and glued. For this reason they do all the routs on a flat service. |
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Before they can start the bracing process the spruce braces need to be sanded and shaped to an exact radius. This process is started by machine but any fine adjustments must be made by hand. |
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After the braces are finished it is time to glue them in place. They use a polyvinyl glue and a glue wheel. Basically the wheel spins and keeps a constant amount of glue on the wheel at all times.
The braces are passed over the wheel and the exact amount of glued needed is applied evenly over the braces. |
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For placing of the actual braces on the tops and backs, they have a jig that has the exact placement laid out on it. Each brace is a different size so they are pieced together on the top using the jig. They are then placed in a heated press until the glue sets. The press is designed to allow even pressure all over the tops and backs so all the braces are glued tight.
While the tops and back are drying it is time to start on the sides. They bend the sides in heated presses that have the side shapes molded in the press. The pieces of wood for the sides are thickness sanded and cut to size,then pressed to their shape. |
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The sides are then placed in molded side templates to control their exact shape while they prepare to glue the top and back on.
The kerfed lining that holds the top and back on is installed using modified clips that work like cloth pins. Before gluing the top on they cut the ends of the bracing. This could be done before they installed the braces but because it is much easier to keep accurate the length of the braces so they are flush with the sides of the body, this is important for the sound transfer to the top. After the body sides are placed in the jig, they use a contoured belt sanding machine that has the exact shape of the body molded in it. |
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The body top and back are sanded on this machine. Acoustic guitars are thicker in the back and get thinner up in the neck area. The contouring machine controls this while also placing a arch in the bodies tops and backs.Once the bodies sides are shaped, the tops and backs are installed on the side jigs and put in a press till the glue sets. |
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The neck is rough shaped out on a band saw before it is final shaped using cutters, The main reason for rouging it is that to keep the cutters sharp and accurate it is better to cut the least amount of wood possible. By rouging the neck they are actually saving the cutters from becoming dull to early.
They have many different cutters and jigs for shaping all the parts of the neck. To keep the neck production consistent they have specially made cutters that have the shapes for the back of the neck and heel area, these machines are very high speed so they make large jigs to safely hold the material without standing too close to the blades. |
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After shaping the neck they laminate and trim and headstock veneers and cut the binding channel on the necks using a modified shaper table and bit. The neck is then bound by hand using Ducco cement and ABS materials.
After the body is dry and removed from the side presses the binding channel is cut around the body using a modified router table. The body is then bound. |
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Multiple bindings are made during the installation, If the binding is 5 ply they use 5 different pieces of binding and install all five at once, The Ducco cement bonds the binding strips together as it bonds it to the body. They use a low tack masking tape to hold the bindings in place while they dry. |
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After the body and neck are final sanded they will be matched and joined together. A machine was designed that actually sets the neck and body to the perfect neck angle using a belt sander, after the the body and neck are shaped to each other a multiple drill press drill the exact joint location on the body and neck so that a perfect match is made. This body and neck are now joined as one. |
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Once the neck and body are joined and dried a truss rod is installed and the fretboard is glued on. The guitar is starting to take its final shape and the craftsman make the final neck shaping contours by hand. They do this so that the necks heel shape and body are smooth with no high or low spots. |
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The preparation for finishing is started and scratches or dents from production are sanded out. The binding is final scraped to bring out its true color. This area is very critical because after the guitar is finished any imperfections in the woods or bindings can be seen. |
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Just before the finish is applied, the body is stained to the color by hand and then the decal's are installed. If there is any color or sunburst on the model, it is sprayed before the logo is installed.
The guitar is moved to a dust free paint area where it is cleaned one more time and the final finish coat is applied. The thickness of the finish is controlled by hand. The painters are very experienced in spraying and each coat is applied in the same amount to control the sound after the guitar will be finished. From the spray room the guitars are moved into the heated drying area where they will sit for a few days until the finish is hard enough to sand and buff. This is the longest amount of time in production they can't stress enough how important drying is. |
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After the finish is dry it is time to start the fretting. The fretboard is shaped and sanded to the proper radius. First using a cutter that controls the neck set angle, and then on a sander to final sand the radius and get any imperfections out of the wood.
Once the fretboard is ready the frets are first hammered in, They use a fret press to make sure the frets are seated properly and final adjust the frets by hand. After the frets are seated, they level the frets using a straight block. This assures that all the frets are the same height and no fret buzz will occur. The frets are final sanded and polished to remove and scratches in the fret finish that can cause the the strings to feel scratchy on the frets. |
| Time for the final finish sanding and getting the guitar ready for final assembly. Depending on the finish of the guitar they take different steps if the guitar is going to have a gloss finish is will need to be sanded and buffed. Matte finish guitars are sanded and a thin clear matte finish is applied, Sanding is not recommended after this is applied because they don't want the finish to have any shinny spots.
Gloss guitars are sanded to #1000 before they use a polishing compound and buffing wheels to remove any finish scratches and bring a high gloss finish to the guitar. The tops and backs are first buffed by a automatic buffing machine and then hand buffed to there final finish. Once the guitar is final buffed it is time to place the bridge on the guitar. They use a jig that centers the bridge and also places the exact intonation points for each string, The area is roughed and then they use and air-press to glue the bridge down. The bar going in the sound hole is support for under the bridge at the bridge plate so that the pressure does not crush the top of the guitar. |
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Now the hardware and any electronics are installed. The slot is final adjusted and the nut is seated into the slot. Machine heads are installed using an pneumatic socket to control the torque of the nuts.
Finally it is time to string the guitar. Just before stringing the guitar is checked once more for any defects. After the guitar is inspected the strings are installed and it's time for the guitar to move to the final setup area. |
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The guitar is set-up by their final inspectors by hand using jigs and templates to assure the exact specification for each model. The nut is cut to its height, and the action is set at the bridge.
The guitar is tuned to 440 pitch and then the necks truss rod is set and the guitar is played by the inspector to make sure there is no fret buzz or other problems. If there are electronics such as an EQ or Piezo it is tested at this point to make sure that there is even string response for all six strings. |
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After the inspection and setup the guitar is polished and packed for shipping. |