The Model M Guitar was a personal research project in seeking the feasibility of building the first acoustic guitar totally printed in 3D with almost no support material. The design was inspired by Devin Montes' The Bodysnatcher design, an Australian Youtuber, to make the acoustic body of the guitar independent of the arm, what makes the design modular and allow you to create your own body. The Project was accomplished through the support of MakerLab FACAMP that made available the space and 3D filament for the construction of this project. I would like to thank the support and enthusiasm of my friends Ana Beatriz Linardi and Rafael Coelho who believed and helped in this project.
Step 1: The Project
This project passed through a series of digital failures to arrive at the model printed in 3D and documented in this Instructables. This first version went through challenges and adaptations throughout the assembly. I am giving you the STL model for free for non-commercial purposes. It was readjusted after the completion of the assembly of the first prototype and also with the correct corrections. If you want the CAD file and the technical drawings you can buy soon for a buddy price. The goal is to continue doing these types of project and make it available to you.
Step 2: Material and Time Consumed
Most, if not all, of the materials used for the development of this project are listed below. Keep in mind that you can use alternative solutions and materials that are available to you.
It is important to say that this project takes around 3 to 4 weeks of work, you will hardly be able to buy, print and build before this period of time. So also take this into consideration in case you want to make a guitar for you.
Frets 2m R$ 50,00
Turning Keys R $ 47,00
Tensor R$ 46,00
Guitar string R$ 40,00
Epoxy Glue R$ 25,00
Aluminum Bar 9mm 2m R$ 30,00
Neodymium Magnet 8x4mm 10 und R$ 12,00
Body Filler R$ 12,00
Super Glue R$ 10,00
Spray Paint R$ 20,00
Spray Varnish R$ 20.00
Latex Glove R$ 20,00
Mask x5 R$ 10,00
Protective goggles R $ 20,00
Sandpaper R$ 30,00
Filament PLA 1Kg R$ 148,00
Filament PETG 2Kg R$ 316,00
Total Materials Cost: R$ 856,00
The approximate value in reais should serve as a basis for you to decide on whether you are willing or not willing to bear the costs of such a project.
3D printer with print area greater than 27x27x32 mm
Step 3: Validation
This is the most important step in the whole project. In it we must validate the critical points of the project to avoid future reworking with great losses of material and time. Therefore, validating the gaps of the fittings in small parts is essential to move forward with peace of mind.
The main points to be validated are:
Fit between arm parts
String passage on bridge
String passage on nut
Turning Keys fitting
Below are the SLT files to perform the tests. Probably the turning keys may not fit if they are from a different model. I will try to make available, over time, the fittings for the main models available in the market, if the model you are trying to use is not available leave a comment.
Tip: For accuracy of validation, the samples should be printed in the orientation of the final part.
Step 4: 3D Printing
The total design has a forecast of more than 100 hours of continuous printing. Relying on the total of 11 printed pieces. A little more than 2kg of plastic material (2230g) were used in the whole project. The arm uses 962g of PLA, and the body uses 1267 g of PETG. You can choose whatever material you wish but, following the logic of the luthier in the choice of wood (harder wood for the arm and softer wood for the body), I prefered, among the material I had at my disposal, to use these two because PLA has the greater resistance to tension and PETG is the most pliable plastic material. Fell free to try others materials and leave a comment about your tests.
The settings used for slicing in Simplify3D were:
Arm Shell :4
Support : Fron Build Platform Only
Support Infiill: 10%
Dense Support : 55%
Dense Support Layers: 5
Attention: Some parts of the arm that undergo a greater force request were reinforced with a 100% fill: Fit between parts A-B, B-C, bridge and nut as shown in the pictures.
Support: Normal Only
Support Infiill: 10%
Dense Support: 55%
Dense Support Layers: 5
Attention: It is important that the edges are solid so there is no gap between the walls so the Shell value is high.
Step 5: Assembly
With the pieces in hand came the long-awaited assembly time. Try to keep the pieces as clean as possible until the end. You will use glues and sticky masses, if you are not too careful you can be left with your poorly finished project.
The assembly is for the most part quite simple. I intend to pass here some important tips, so that you will have a good final finish. Remember to use the information recommended by the manufacturers of each product used as well as the safety equipment if necessary.
Always wear gloves when handling epoxy or plastic. Glue the body parts with epoxy glue, but remember to use a piece of paper between your desk and the pieces to avoid gluing the piece to the table. A glue with a cure of 10 minutes is enough, try to keep the pieces in contact and aligned to the paste. A good tip is to glue two pieces at a time and then go pasting the other pieces to form the guitar. Gluing all at once will result in a large glaze of glue and misaligned parts.
On the arm it is not necessary to glue any of the parts for assembly all the parts (A, B and C) are only properly fitted. If necessary just sanding the inserts and using a rubber mallet to fit, use several soft beats to not crack the material, make sure that the parts fit properly so as not to compromise the loudness.
You may prefer to place the frets with super glue before attaching the parts of the arm, as the frets are mostly sold in rolled spools, and for this reason they tend to be arched when cut, which compromises the snap fit. So sometimes it is necessary to use glue since the adhesion of the fret in the piece printed in 3d is not as good as in the wood. Always keep in mind that any loose piece will vibrate when the guitar is played causing an unpleasant noise, so it is important that everything is firm. That way, it's also important to keep the frets straight and well seated on the arm to avoid unwanted contact with the strings.
I will release a version with the arm where the frets are printed together, I do not recommend this option because with the vibration of the strings the plastic will be eaten reducing the life of the instrument and the metal frets are visually much more attractive. Either way it stands as a possibility.
To fit the turning keys, simply screw and thread them. In the upper fret you may need to sanding to adjust the height of the strings as desired. And do not forget to put the magnets using epoxy glue, and with the poles properly oriented to be able to hold the arm and body more firmly.
Before placing the strings you must insert the tensioner inside the guitar arm, just slide it in and adjust the tension. If you try to use the guitar without the tensioner the arm will flex and possibly break. I even did a test without the tensioner and quickly the arm flexed.
Step 6: Finishing
Now it is almost all ready just pass a little body filler sanding with much affection, repeat this cycle if necessary, a little paint and varnish and we are ready.
Apply the plastic mass according to the recommendations of your manufacturer expect to dry and go sanding with increasingly thin sanding and seek to achieve the smoothest surface possible, any imperfection is visible in the final result.
To further improve the final result it is important to pass primer before applying the paint and then the varnish. Be patient, the paints on average take from 24 to 72 hours for a complete drying, and handling the piece before it can ruin your work.
Step 7: Time to Play!
Now, just fit your arm on the body, put on the strings and have fun :)
I hope you enjoyed it, I plan to bring more projects like this! If you have any doubts about the project or its construction just comment below. If you want to follow me on Instagram.
Second Prize in the