Where to get custom plastic bobbins made?

[peskywinnets]

Hi there,

I'm toying with designing a 'widget' in my spare time (actually, it's just my take on an existing theme!), but what's becoming quite apparent is that after I 'dip my toe in the marketplace water', that if it sells, I'm going to need a better way of making/sourcing bobbins!


At the minute I'm using a CNC machine to cut my own bobbins from acrylic sheet...it works, but it's very slow.

Now, while I'm reasonably adept at the techie side of things, I'm clueless as to the 'plastics' manafacturing process & just wondered if you knowledgeable fellas on here could give me some good input/leads?

The bobbin I require is the same basic shape as a Stratocaster single coil ...but where it differs from that is that the bobbin is only 6mm deep - nothing exists like this, so I need to establish a way of having these made cheaply!

What would be the best path? ...& what would the manafacturer need from me? (DXF file, a prototype etc)

What type of cost per unit would I be facing (for say a 500 piece first run)

[David Schwab]

Ah, welcome to my world!

Injection molding is very expensive to set up. For small runs, and cheap, you might want to consider making a mold of half of the bobbin, and then you could put the two halves together.

Also, Strat type bobbins are really only the top and bottom flat work, and held together by the magnets. So if you like it like that, it can be any depth you want.

I have some of my bobbin parts laser cut, and then the blade polepiece holes it together.

In the past I had a friend of mine make some on a 3D printer (SLA), but that's a nuisance to keep having to do that.

[peskywinnets]

Ok, it's a fair cop - my choice of 'example pickup' was bad ...I should have said, I'm after single coil bobbins like this...

Humbucker Bobbin Set at Stewart-MacDonald

(which are tantalisingly close to what I need in height, but still too high!)

Presently I'm cutting two halves of my bobbin design on a homemade CNC machine & then 'joining' them in the middle...I guess moulding them would be quicker (sigh, another new methodolgy to 'learn'!) ...but then again I'd imagine the resin mix isn't exactly cheap (whereas the acrylic sheet I use presently if all but free - ie it comes out of skips!)... I'd be curious to establish a ball park figure for having bespoke bobbins injection moulded though!

[Bruce Johnson]

Here's a link to a series of 6 pages showing the complete process of how I build the pickups for my Scroll Basses. I cast the bobbins in halves from polyurethane casting resin and do a few simple machining operations on them. For a low production rate, it's fast and consistent. Since you already have small CNC machining capability, you shouldn't have any problem making up the masters.

Building Scroll Basses- Pickups 1

[David Schwab]

Bruce, I was going to look for that thread, was too lazy!

[Spence]

That's very impressive Bruce.

[automan]

Here's a link to a series of 6 pages showing the complete process of how I build the pickups for my Scroll Basses. I cast the bobbins in halves from polyurethane casting resin and do a few simple machining operations on them. For a low production rate, it's fast and consistent. Since you already have small CNC machining capability, you shouldn't have any problem making up the masters.

Building Scroll Basses- Pickups 1

You are a true craftsman. I have a deep respect for people that dont just assemble things and dont just make things, but make the things that make things.

I don't know if that made any sense. I am trying to say I respect your work.

[the great waldo]

Hi Peskwinnets

Why not buy stewmac or mojotone bobbins and cut them through with a razor saw and glue them back together or make some moulds from silicone cast and cast them from polyeurathane resin.

Cheers

Andrew

[RedHouse]

Here's a link to a series of 6 pages showing the complete process of how I build the pickups for my Scroll Basses. I cast the bobbins in halves from polyurethane casting resin and do a few simple machining operations on them. For a low production rate, it's fast and consistent. Since you already have small CNC machining capability, you shouldn't have any problem making up the masters.

Building Scroll Basses- Pickups 1

Dang, I wish you were my neighbor Bruce!

I had a friend who runs a hotrod shop machine me some bobbin flanges for the newest hand-winder I'm building, it took him like 4 try's to get it close to what I wanted (I had detailed drawings) after try three I abandoned the removable plate idea (just like you have there) and just had him make a multi-use single face in the bobbin flange. By the time we were done he had 4 hours into it at $75/hr (his shop rate is $90/hr) so I got something short of what I wanted at twice the price I was hoping to pay.

[David Schwab]

Hi Peskwinnets

Why not buy stewmac or mojotone bobbins and cut them through with a razor saw and glue them back together or make some moulds from silicone cast and cast them from polyeurathane resin.

I was thinking the same thing.

But another thing to consider is with such shallow bobbins, the top and bottom flange of the regular humbucker bobbins might be too thick.

But they can always bee belt sanded.

[David Schwab]

Dang, I wish you were my neighbor!

Me too! I'd just like to hang around his shop for a day.

[Bruce Johnson]

Thanks, guys! If any of you need special parts for winders or bobbin tooling made up, let me know. I'm not really looking for work (because I'm very busy in general) but I'll help you out if I can. I charge $45 per hour for machined parts, and I can work from detailed drawings, or figure it out from rough sketches. I've made up parts for several guys' custom winder projects already.

I hadn't really thought about getting into the custom bobbin business, but I guess if anyone is interested, I could work out a price for making up small runs of your design parts.

[RedHouse]

...If any of you need special parts for winders or bobbin tooling made up, let me know. I'm not really looking for work (because I'm very busy in general) but I'll help you out if I can. I charge $45 per hour for machined parts, and I can work from detailed drawings, or figure it out from rough sketches. I've made up parts for several guys' custom winder projects already....

I will do that Bruce.

...I hadn't really thought about getting into the custom bobbin business, but I guess if anyone is interested, I could work out a price for making up small runs of your design parts.

What about making up those nice aluminum masters, is that something that you might do?

[Bruce Johnson]

What about making up those nice aluminum masters, is that something that you might do?

Sure, I can make those up for you. As an example, an aluminum master for something like my M-pickup bobbin (an oblong half-bobbin) would cost $100 to $150. A round spool-type bobbin would be less.

I make my masters from aluminum because I like the permanence, and I have the machine shop. But you can make up your own masters out of plastic, or even wood. For example, you could build up a master by starting with a block of MDF as the base, then glue up the shape of the bobbin from hobby store sheet styrene. Or chop up some existing bobbins. You just have to take the time to get it to the right dimensions, and smoothed out.

The silicone molds will accurately copy every little scratch and ding. So, the time you put into the master will be repeated in the quality of every part you make. If the bobbin gets completely hidden inside your pickup design, perfection may not matter. You do want the flanges to be smooth edged, so they don't snag wire during winding. On my masters, I put a slight radius on the outer edge of the inside surface of the flange, and polished them carefully, so that all of the cast parts come out of the mold like that. You want to minimize the amount of hand deburring that needs to be done on each part.

[Amplexus]

you can always build your own injection molder check out rhe hack a day link Home injection molding - Hack a Day A very nice machine