A madman with a blowtorch (problem soldering wire)

Hello!

Yesterday evening I had my first attemt to set the house on fire, thought the fire brigade might be more prepared during Xmas :-)

It seems quite possible to make the plumbing solder and fluss stick to the drive screw but I found it impossible to "wet" the 40mm wire part before torching it.

I feel a little confused, in the instructions for the extruder they warn you about going to heavy with the fluss, since that can make the flexible wire go stiff, but trying everything from a little heat to a red-glowing wire, the solder (silver-stannum I think) refused to stick.

I also used some fluss which caught fire if I used to much of it.

Maybe I'm using the wrong kind of wire, this was some $10 for 5 meter wire intended to use with boats.

Any suggestions? I obsiously need a wire that sucks the solder in.

Anyway it was quite fun yesterday. Today I bought a fire extinguisher...

I gave up on soldering and used the techinque below instead:

I cut a cross in the end of my screw thread.
I roughed up the inside surface with a small spherical grinder.
I stuck it with JB Weld and held it in alignment in my lathe.
After letting it cure at room temperature for 15 hours I then baked it in the oven for two hours at 200C.

I did this mid August and it is still holding up.

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[www.hydraraptor.blogspot.com]

I also had trouble with the drive screw. Finally had one of the shop profs braze it. He's pretty good so it went off well. Before that I was thinking about JB welding it like nophead. Though I hadn't thought of baking it. What does that add?

Demented

For some reason my JB Weld only sets fairly soft. I have to bake it to get it rock hard.

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[www.hydraraptor.blogspot.com]

Mystery solved!

I obviously had to luxurious taste for this project. I got a hot-zinked wire at half the price of my previous stainless one, much easier to solder!

Nophead,

Yeah, I noticed the same thing when I JBed the radiator--entire top of it!--on my girlfriend's old Mistubishi Montero. Worked well but was always a bit soft till we drove the piss out of it for a while. I've heard you can machine the stuff but I would definatly want to bake it before I tried to take one of the school's machines to the stuff!

Demented

I ended up using JB Weld too. All I managed to do with the torch was scorch the wire.

I did it the other night, what I did was to insert plumbers flux inside the drive screw and place a piece of solder wire in there so it could not escape.

Then just heated up the drive screw so the solder flussed nicely.

Then I took the wire with a lot of flux and this was a pain since the solder seemed to melt and then got blown away by the fire...

But anyway I managed to get some of the solder already inside the drive screw to stick so now it appears to work. Dunno about long-term though, but I have another 5 meters of wire to replace it with :-E

I also noted that making the ends soldered made the dremel cutting of the wire much more even!

... what's with a (silver- or tin-coated) crimp-shell around the wire (maybe soldered after crimping too) and then soldering the shell into?

Should work much better, then with the naked wire ...

Viktor

I had a heck of a time with my drive screw recently. I'll post pictures a bit later--I'm at work right now--but what happened in a few words is the cable wrapped itself up into a tight little ball and poped off of the gear motor.

I think my drive screw is a bit close to the hdpe and so binds a little more than it ought to. Whatever the cause, the crappy job done on soldering the cable to the screw held up very well. No problems there even with just a little bit holding it on.

I'm thinking this piece is a bit over done for what we are using it for. Maybe ABS will be harder to push and will need more strenght but HDPE doesn't and neither does CAPA. Does anyone have an alternate coupling idea to replace this clever but hard to fabricate design? Something simple.

I was fiddling with a direct drive setup like in a version one extruder and simply resigning myself to the fact that I won't be able to extrude stuff that wont bend. As far as I can tell there is no call fur such extrusion yet anyway.

Ideas anyone?

Demented

What about mounting the motor parallel to the drive screw and just use a worm gear to a normal gear to the drive screw. Short sweet to the point. Umm... I attached a drawing to demonstrate what I'm thinking. (Sorry about the crudeness, it was done in flash in 5 mins, but i think it gets the point across)

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Jay

You can drive a gear with a worm but I think you will find you can't drive a worm with a gear.

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[www.hydraraptor.blogspot.com]

How about a conical screw, mounted offset to the axis of the feedstock? Tip against the heater, wide end on top.
The screw would have to change in pitch from "base" to "tip".
By doing this, you'd be able to mount the motor at an angle other than in line with the feedstock, without relying on a flexible shaft.

I can see making one by wrapping a cone in a string, and making a sandcasting of it. I can also see soldering, lightly, a wire to a cone, then using a dremel to carve the cone between the wraps of the wire, before peeling the wire off the cone.

What about altering my previous design, and just have the drive screw mounted directly to the gear, and feed the plastic filament through the middle of the gear?

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Jay

Workable, but the gear needs to be smaller than the screw. Otherwise, it blocks the feedstock anyway. Since the driving gear needs to make up the difference, it means your screw drive motor will be significantly geared up.
Alternately, you can use a belt between the two.

personally, i'd like to see a return to the direct drive anyway... the only reason we switched was so that we could extrude PLA and eventually Fields Metal. The offset drive shaft has caused way more problems than it has solved, so i think that it would be a smart move to switch back.

i'm going to see if adrian will print me off some of the old designed parts and get molds of them for the store. we an even use the same drive screw... instead of soldering the steel wire to the screw, then a nut to the wire, we can just solder a nut directly onto the end of the drive screw. nice, easy, simple.

i'll let you guys know when its ready, and i may even be able to offer just the mounting part for the drive itself if there is interest.

I think it's just down to having an OK soldering iron and ensuring it's all mild steel no stainless, I soldered it all in 5 mins using regular soldering iron and pre-fluxed electronic solder (normal leaded solder) and ensuring the soldering tip is always well wetted with solder. It's also easier to cut the cable if you tin it first as the grinder does not then splay the end

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Ian
[www.bitsfrombytes.com]

Yes I expect you can solder it if you don't have stainless steel but it seems most people end up with either the wire or the threaded rod that is stainless.

The JB weld option works fine so why not change the wiki instructions to that?

I would recommend the direct drive except for the fact that to me PLA seems the only hope of room temp FDM working.

HDPE filament is available but shrinks too much.

CAPA or PCL is is the recommended plastic but my experience with hand molded PolyMorph is that it shrinks a lot when it cools, perhaps as much or even more than HDPE. I can't find mold shrinkage figures for it on the web.

So PLA looks like it might work from Vic's pics but I can't find mold shrinkage figures for that either.

Commercial FDM machines use ABS which has low mold shrinkage but even with that they feel the need to put it in an oven.

Does room temperature FDM work with any known plastic?

Edited 1 time(s). Last edit at 12/22/2007 05:04AM by nophead.

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[www.hydraraptor.blogspot.com]

Hi Nophead

It looked to me like you virtually had HDPE sorted I guess when you get to overhangs the problem returns but i for one am very impressed with the result you've got.

Back to the original I think it's simply a case of which ever is easier for the individual and I suggest the wiki has both methods as I know for some getting JB weld is a problem, all down to local conditions

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Ian
[www.bitsfrombytes.com]

And Now I wait.



I'll do what nophead says..."After letting it cure at room temperature for 15 hours I then baked it in the oven for two hours at 200C."

So Friday after dinner (tomorrow), the oven is mine!

I found myself silver-soldering the cable in the RepRap in FoAM.. killed all springiness in the wire.

I abandoned the flexible drive shaft. If the filament has a low bend radius, the answer is simple; use a longer feed screw and mount the motor further away from the extruder barrel. The longer the screw is to the motor, the lower the curvature required of the filament. Direct drive lowers friction and motor heat. It should be possible to mount bearings away from the filament contact area of the feed screw.

[www.flickr.com]

Our version is in lasercut ply but you see the idea.

Maplin stock a couple of universal joint/couplings.

Universal Couplings Order Code
4mm - 4mm N12BQ
6mm - 6mm N13BQ

Which may/may-not be worth considering.

I think they are supplied to maplin by MFA COMO DRILLS who interestingly enough are usualy cheap and cheerful and now stock Timing Belts and Gears.......

[www.mfacomodrills.com]

Cheers

aka47

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Necessity hopefully becomes the absentee parent of successfully invented children.