Extruder barrel bore

The instructions on the Wiki say to drill the extruder barrel with a 3mm drill. The spec for the filament is 3mm so that does not leave any clearance. I have purchased some 3mm HDPE welding filament but it measures about 3.1 - 3.2mm. The next size drill I have is 3.5mm. Will that work or will the clearance be too much? I suppose if it is too much the melted plastic may flow back up the barrel rather than out the small hole.

Can you not get a 1/8 inch drill bit over there any more? That one runs 3.175 mm.

yeah, either use a slightly bigger one or use a 1/8" one. thats what i use and it works great.

I do have an old 1/8th drill, it would need sharpening, but 3.2mm is bigger than 1/8th.

Maybe I have managed to find a poor supplier of filament, but I think the wiki instructions should be updated as 3mm hole for 3mm filament does not seem sound engineering.

I think you have a point there. :-)

I found a source of 3.1, 3.2 and 3.3mm drill bits here [www.toolfastdirect.co.uk]

They also have long 1/8th bits which would be good if your filament is not oversized like mine.

true... it should probably be update to say something like: 'start out with a 3mm hole. if your filament fits, then you're good to go. otherwise, step up the size until you have a bore that will comfortably fit the filament.)

But if your next batch of filament is bigger then you are in trouble. The filament needs to come with a stated tolerance and the hole needs to be a bit bigger. Does anybody know how much gap we can tolerate? We might need to have several interchangeable barrels.

Given how fragile the nichrome wire is it's probably more sensible to just have interchangeable Mk II's.

Forrest Higgs Wrote:
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> Given how fragile the nichrome wire is it's
> probably more sensible to just have
> interchangeable Mk II's.

Yes that bit has always looked fiddly and fragile to me. That is why I intend to have a go at making an induction heater. That way you use very thick wire and it does not need to be thermally coupled to the barrel as it is the barrel itself that is the heating element. I have all the parts to make one, just too many other things to do at the moment. Also it may be a sledgehammer to crack a nut so I will try nichrome and J-B weld to start with.

Perhaps we could make the connections a bit more durable. The bottom end of the coil could be connected to the barrel itself. The top connection could be attached to a metal ring round the top of the barrel. Two sprung contacts could then be used to connect the power.

Good bloody luck on "connecting nichrome to the barrel" It's easier to hang onto a greased pig than to get nichrome to stick to anything like solder, for example.

yeah, i'm using 30awg which is pretty sturdy. also, since 99% of it is encased in JB Weld, the only major issues would be with the connectors.

i was thinking you could solder jumper wires to those (or rather, twist splice some normal wire to them, then solder that wire, which would lock the two wires together) then... you could tack that down with a dab of jbweld, and leave the normal wires exposed for whatever connection you use.

true.

however, if you are using a barrel with an interchangeable nozzle, you could probably get away with taking the nozzle out, drilling out the filament hole, then replacing the nozzle.

my guess is if you go with your current filament + some small fudge factor you should be ok. also, with the design, the barrel + thermal barrier assembly are easily removed, so the above process would be super simple.