Bass guitar wood test
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!
