2 Differences by openthings
uploadet 3d file for body and 2d file for all pockets
- Added file WOOD_FINAL_newpocket_25_jnauary12_005_v4.3dm to the repository
- Added file all_pockets_DEF.AI to the repository
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uploadet 3d file for body and 2d file for all pockets
Can you produce a high quality electric bass guitar using the Fablab methodology?
Yes, you can. Like on fab foos, I like doing as much as I can from scratch, meaning winding my own pickups, milling the body on the Shopbot with a flip part set up, building the entire neck with a trussrod and a fingerboard with fret marks on the side at least.
My choices for wood were: Mahagony body, maple neck, palisander fingerboard.
You can buy special “tone wood” in Amsterdam at Fijnhout Houthandel.
A few components however I decided to buy:
The bridge, the tuners, the preamp, the nut, the trussrod
During my research I noticed a lot has happened in the guitar world in the past 20 years. You can now buy Xtenders, which is a tuner with a handle so you can drop the E to C if you want. There are Bass tremolos available and very terrific preamps that lift your output to about 12 DB. But the big mystery is, can I get that growl like a proper Fender Jazz bass, which I love so much.
Well, I will only know this when I have finished the project and plug it in.
My fretless Bass will be based on the Fender Jazz Bass.
Here is the original 1951 Fender Precision Bass, The first solid body electric Bass that changed modern music:
here is a deluxe version model of it from 2006, which has 24 frets, not 20 as the original version
And here is the “Shark Bass”
This is a very special Bass, featuring a tremolo, Xtenders of the E & G string and a kill switch. I am sure I can play pretty unusual cool stuff with it. I was inspired by Michael Manrings Hyperbass, a really crazy Bass. Listen to his tune Selene to get an idea.
Another inspiration I got was from a student who recently visited us to mill 3D textures: http://amsterdam.fablab.nl/node/3775()
So I asked him if he wants to share it, he agreed and so my Bass guitar will have a fantastic 3D texture on the body.
I am now in the process to prepare the cut files, and yes I will post the files so you can make your own…
As hard wood is somehow an expensive material, we decided to give life to the bass at first as a foam model. In this way we could check if size, proportions and holes dimensions were appropriate.
As the piece was a 3D one, I created in Rhino a supporting frame as big as the foam block, with bridges here and there to support the bass while being cut out.
In order to be able to flip it, the model had two holes placed on the central symmetry axes of the model. These holes were going all the way through the foam and also in the sacrificial layer (about 8 mm below the foam). After making the holes I used some wooden dowels to keep the model in place and to use when flipping it. The holes has to be slightly smaller than the the dowel, otherwise the piece will be loose (in this case the dowels diameter was about 8-8.2 mm while the hole was 7.8 mm).
Dealing with the flipping of the model has not been easy , especially because it is sometimes hard to do the finishing of the surface when the piece is too thick and the bottom part is still full. As the material thickness was too much to do the whole cut on each side, I did set the software to cut only halfway the thickness, but in this way the roughing did not cut away the inside leftover areas, that were creating a problem for the finishing step).
As an answer to this I decided to do the cut out of the empty areas before doing the finishing, after the roughing (although the Partworks 3D software suggests you to do it at last).
Milling bits for finishing often have the cutting part smaller (in terms of diameter) than the shank, which means that if the bit goes deeper than the cutting part lenght and there is not enough space, the shank will force the material by applying too much pressure on it. This means that if the material leftover is still part of the block after the roughing, the finishing bit will force the material.
For this foam experiment I have used a 1/4" flat end 4 flutes bit (roughing) and a 1/16" flat end 4 flutes for the finishing. The machine was driven quite fast during both operation, due to the fact that the foam is a soft material and that we did not want to be precise in this step, but just check shape, dimensions and proportions.
(By the way, I realized the the piece was too thick while the machine was already running, so, for the time it took me to realize it, the head of the shopbot pushed against the foam, trying to reach the bottom of the model..keep always in mind to check the thickness of the material and how much the milling bit is coming out from the shopboat head!!) (see pic below)
Here it comes the final result:
And here it comes the second episode of this ambitious project: the first wood sample!
To mill out this piece took quite some time. About 3 hours for the roughing of each side and about 6 hours for the finishing of only one side (the back side was quite flat, so we decided to save some time by skipping the finishing).
I had to use many tricks in order to accomplish the task and I have learnt more about the shopbot with this chop than with any other before.
So, talking about tools, we used a 1/4" 2 flutes flat end bit for the roughing and a 1/16" 4 flutes (both flat end and nose ball) bit for the finishing, four screws and two 8 mm dowels to keep the piece in place and let us flip it.
As in the first test we did set the software to cut until half of the material’s thickness, because the bit wasn’t long enough to cover the whole wood block. We therefore also did the cutout before the finishing (for more details about this take a look at the previous episode: Foam Test).
In the next screenshot it is possible to see which settings we used for the roughing.
For the finishing we decided to reduce the milling surface, in order to save time by avoiding passing over the supports over and over again. In order to do so, we reduced the Machining margins in the Material Size and Margins menu, setting negatove numbers. This is the only way to avoid milling useless areas. I decided to do this in the finishing but not in the roughing because, by milling the whole piece back then, I avoided surfacing the wood block and I had then a perfectly flat surface for the flipping (that is also why when roughing the second surface I reduced the milling area again). Remeber that perfectly flat wood is something very unlikely to happen.
In the screenshot below it is visible how these parameters were set before starting the finishing.
In order to decide which finishing to go for we did different test, with 10% 20% and 40% stepover and using first a nose ball and then a flat end bit. Below is a screenshot from the 40% setting.
The ball nose seems to be more appropriate and below it is possible to see the difference between the stepovers:
As the texture of the bass is very soft, we decided to adopt for the future the 10% steover so that we won’t need to sand the wood afterwards, risking to scratch away also the waves. Unfortunately this means that the finishing of the front side of the final bass will take between 15 and 20 hours..which means that somebody will have to sleep with the Shopbot =)
Something that created problems again was making pockets deeper that half of the material thickness, as the software wouldn’t see them. Furthermore when finishing the piece the machine lost a lot of time finishing the inside of holes and pockets, which is absolutely unnecessary. In order to solve both issues we decided to do all pockets and holes with the 2d software instead of including them in the 3D model in Rhino.
In order to better understand if size and dimension were right I did assemble the main knobs, which were quite well fitting!
Bass neck wood test
Here comes the neck!
Same procedure as the body, just a different wood (harder) which forced us to go slower with the machine (speed 30 instead of 40). 1/4" flat end 2 flutes bit for roughing and 1/16" nose ball 4 flutes bit for finishing.
I decided to place the piece of wood horizontally, in order to facilitate the machine and create less noise (when the shopbot moves on the y axis is smoother than on the×axis).
The roughing took about 3 hours on the first side and only 1 hour on the second side. Althought the front side is almost flat and therefore wouldn’t need almost any machining I decided to place the model in the middle of the wooden block, otherwise the finishing bit would have not reached the deepest part of the back curve.
Finishing took about 5 hours with xy speed on 30.
At the end of the chop we made a profiling outline on the bottom part of the bass, the part that we will glue on the main bass body. In this way we got rid of the bridges with a perfect flat surface ready to be glue.
After that we could finally make an ergonomic test!
Winding the pickups
Since the Shark bass is custom made, the electronics should also be made at Fablab!
We started working with the Jazz Bass Pickup kit from Stewart MacDonald and the instructions.
According to Vintage Guitars Info, the wire specs differ per type of pickup. Since we wanted to create a Fender Jazz-like sound, the specs for a vintage Fender Jazz pickup were used: an average of 9000 windings of 42’ Gauge wire (also from Stewart MacDonald).
To precisely measure the number of windings, we used an old milling machine. The revolutions of this milling machine were counted by using a Hall sensor connected to an Arduino, by using this tutorial: http://www.zipfelmaus.com/blog/arduino-with-hall-sensor/. Below you can see the Hall sensor connected to the Arduino UNO.
A magnet was attached to the rotating head of the machine. The Hall sensor sensed when the magnet was close and this way, the Arduino counted the number of windings of the pickup.You can see the setup below.
After winding, the resistance was measured to check if the wire was not broken and sanded properly.
According to the instructions from StewMax, the resistance of each pickup should be around 8k?.
The pickups were put in there casing and they were ready for use. When the bassmodel is done, it is time to install the electronics. I wonder what it will sound like!
As Alice was preparing the roughing and finishing files beforehand, I was able to start the jobs instantly. A important aspect when milling a time consuming piece is the X Y Z reference. The Shopbot should ideally have been setup with absolute “home” table coordinates, based on the proximity end switches. This allows you to reset the machine if it happen you had a com error and the machine stops and lost the coordinates.
The finishing job for the front texture took 19,5 hours, which forced me to stay in the lab all night ;-). This was caused by a 10% step overrunning on 12000u, 30mm/sec using a 1/16 end ball nose milling bit. (=0.15mm per pass resolution).
Now the reason why I managed to drill a simple hole on the wrong spot after this marathon job is, that I didn’t reset the X & Y axis to 0 after moving from absolute 0 to 3d bass 0. Lesson learned. Always reset X + Y axes after moving from home to your object’s home. Do this on the top menu “reset”, or press z key and then 2, enter = done.
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