Prototype bobbins---3D printing!

[marku52]

I needed to make a proto bobbin for a bar magnet pickup I am working on. I decided to investigate 3D printing as a quick and easy way to make a prototype. I did the 3D model in Google Sketchup (freeware with not too high a learning curve), then sent it off for quotes to the top 5 or so 3D printers that showed up in a google search. I ened up up going with Xardas in San Diego, got 12 pcs to amortize down the $25 setup fee. They ended up costing about $10 each. Material was natural ABS.

Note: you have to be careful that your model is "watertight", that is, isn't missing any solid walls, and doesn't have any hidden interruptions that would confuse the printer and cause the bobbin to come out in 2 pieces. Like in my example, I made the bobbin bottom, added the center portion, copied the bottom and moved it up to make the top. If I had moved that piece up too far, I could have ended up with a 2 piece bobbin by mistake. Another freeware program, Meshlab, helps to test for these conditions.

Here is the xardas quote (and their picture of my model, to assure we see the same thing) and a picture of the completed bobbin. the quote is a pdf, and I don't know if it will come out in the post, whatever.

I think this is a useful proto technique!

xardas.PDF

[David Schwab]

Yes, it's a great way to have parts made. I did a set of custom pickups that way several years ago. Mine were two piece bobbins, and a friend of mine had the printer at work.

[StarryNight]

this is very cool. I didn't realize they came in so many colors. Great idea for prototypes! I wonder if these will ever be used for production?

[defaced]

I wonder if these will ever be used for production?

Doubtful for high volume production. It's a very slow process. We had one where I used to work. Cool things to have on hand. It was very helpful in selling and troubleshooting ideas.

[marku52]

yeah once you get up into volume (several 100's of pcs) then it makes sense to buy an aluminum molding tool and do the parts injection molded. I would guess a simple tool like a bobbin might cost $700-$1500 and piece price might be 50 cents to a buck, volume dependent. quite a bit of the cost is setup time on the injection machine.

There is an unfortunate gap in pricing/capabilities between the 3D printing and injection molding. we need something right inbetween that could do a 100 pcs at $5 per.

[Elias Graves]

That process is just way too cool for skool.

EG

[Tommorichards]

How do you guys do the bar magnet pickup?

Do you used a piece of metal and a magnet at the bottom, or the bar magnet itself for the slug?

[marku52]

you can do it either way, these will be an alnico bar mag inside the bobbin , and a metal plate across the bottom to help wrap the magnetic field around. It can also be done with a slug up the bobbin and magnets on either side on the bottom, kind of like a P90

[Tommorichards]

Cool. Where about do you get the bar mag? And please dont say stewmac.

[marku52]

one place is an ebayer named addiction-fx. he sells alnico 2,3, and 5 bar magnets and bobbins for making gibson style humbuckers, you can use the bar magnet to make this style of pickup. or any of the magnet sources listed in the archives here, magnetic hold is highly regarded.

[Tommorichards]

Well, im more interested in making bass pickups, as it is my preferred instrument, and i cant find bar magnets the right size.

[marku52]

a HB bar magnet from addiction-fx measures .125" X .5" X 2.5". It is a perfect size for a bass bar magnet pup. costs about $2.50, IIRC. want a fatter stronger magnet? stick 2 of them together!

[David Schwab]

a HB bar magnet from addiction-fx measures .125" X .5" X 2.5". It is a perfect size for a bass bar magnet pup.

That's a little narrow for some basses. My 4 string pickups use blades 2.75" wide. For five string basses you need about 3.4".

[marku52]

Good point, although they look wide enough for my P bass. Certainly won't do for a 5 string.

Here is an idea tho, why couldn't you cut a piece off another magnet to add to the 2.5" dimension ( I believe you could use a wet tile saw to do this), superglue it on to add to the length as needed, then magnetize the assembly? The flux path doesn't go through the axis of the cut. Anybody tried this? Way cheaper than a special order longer magnet.

[Tommorichards]

Im planning on trying a bass humbucker, like the '60's thunderbird pickup in the other thread. And i cant really buy off that seller, as the postage is outrageous to ship here in England.