Extruder drive screw soldering instructions

Just made the extruder drive screw. The instructions in the wiki say to use a small blowtorch and plumber's flux. I bought these and found both were unnecessary. It is much easier to use a soldering iron and electrical solder with built in flux. I used a 50W temperature controlled iron but it did not struggle at all so I think 25W would probably be OK too. It might save somebody some money if the instructions were amended.

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[www.hydraraptor.blogspot.com]

That is BEAUTIFUL! Is that 5mm threads or standard? Did you turn that yourself?

It is M5 threaded stainless steel. Here in the UK metric is standard! Yes I turned the lands and bored the hole using a watchmaker's lathe which is actually too small for the job but I added a home made "three point steady" which allows it to handle parts this size. I believe other people have managed with a drill.

The steel cable is only 2.5mm rather than the 3mm specified. I don't know if it moves plastic yet but it certainly rotates ok. Video here [hydraraptor.blogspot.com]

Edited 1 time(s). Last edit at 07/23/2007 04:08AM by nophead.

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[www.hydraraptor.blogspot.com]

I found that solder doesn't stick to stainless steel properly. My joint failed after a few minutes use. I re-soldered it but I don't have a lot of confidence. Eric has shown that JB Weld does not work so if it fails again I will drill a small hole and put a pin through it I think.

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[www.hydraraptor.blogspot.com]

LOL! Almost nothing sticks to stainless steel properly... except eggs over easy.

I think I've found a way for JB Weld to at least be 'good enough' to last you a little while - if you drill out the main shaft as normal, but instead of using a small piece chopped off the end along with a nut, use a small hex-head bolt (drilled through) with the hex head the same size as the nut you would use otherwise, and the thread size the same or similar to the main shaft size - this makes the cable run straight for the length of the bolt, and seems to reduce the bending stresses that pull it apart. If this is unclear, let me know and I'll try to post a pic. So far this has worked for me a good bit longer than simply replacing the solder with JB Weld as I had it before.

Eric,
I didn't use a 5mm section from the main shaft, I substituted 5mm cut from a bolt so I had no trouble soldering that end.

Are you saying that you have your main shaft 5mm longer, hence the hole 5mm deeper?

I did think of reducing the main shaft by 5mm and screwing it into a brass rod with a hole to take the cable in the other end. That would solder nicely and I could secure it with a lock nut. The only problem is that it turns anti-clockwise so it would always try to unscrew itself. A shake proof washer or some super glue would hold it I think.

Of course its probably easiest to avoid stainless steel in the first place.

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[www.hydraraptor.blogspot.com]

No, I originally had the 5mm section cnnected to a nut like in the directions, but the cable kept bending at the end of that section, and this was causing the JB Weld to take a lot of lateral stress that it did not handle well. The second time it broke, I just tossed the 5mm piece and nut and replaced them both with a drilled bolt of about 1cm length, and got the cable inserted just right so that the bend of the cable is at a midpoint between the bolt and the main shaft. This makes the JB Weld a lot happier, since it isn't trying to flex - it is just holding the cable in the bolt and main screw.

Ah, I see. My cable does not bend near the ends because the solder wicks up it a bit making the ends stiff. Also the cable I had to hand (left over from a garage door opener) is 2.5mm rather than 3mm so perhaps a bit more flexible in the middle.

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[www.hydraraptor.blogspot.com]

Just a sugestion, I would slot the top of the main threaded body and resolder. This would allow the solder to form a cross "X" gripping the whole rod better than a smooth hole. You could also slot the braided wire once "-" accross for even more grip.

Edited 1 time(s). Last edit at 08/01/2007 12:54AM by Richard.

Good idea Richard, I will try that first when / if it breaks again.

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[www.hydraraptor.blogspot.com]

Well no surprise it did break again after extruding about 300mm of HDPE at 200C. I switched the motor off and left the heater on. When I switched the motor back on the filament would not move so I tightened the springs and the joint broke.

I will try Richards idea of cutting a cross in the top of the screw next. I read that it is possible to solder stainless steel with ordinary tin lead solder but you need the right flux. It can also be braised which might be better in this application.

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[www.hydraraptor.blogspot.com]

Well the crossed version lasted about 20 mins before it broke. The solder didn't really penetrate into the castellations much as it doesn't wet the SS it's probably a surface tension thing.

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[www.hydraraptor.blogspot.com]

You all may want to go back to the previous version of the Mk II that doesn't have that piece of ss cable in it but a direct connection from the gearmotor to the threaded rod polymer pump. I've got a 12v motor driving my GM3 gearmotor and it takes every bit of torque that that thing can put out (close to 60 oz-in) and the tightest spring settings I can get to happen to pump HDPE.

If you are breaking that soldered joint before the clutch on your gearmotor engages you've got a real problem and maybe ought to think about braising.

By the way, was there some special reason that you all specified stainless steel cable? It's a pig to work with in soldering, braising and welding in my experience. Why not just just some cheap non-stainless cable instead?

Edited 1 time(s). Last edit at 08/10/2007 10:19AM by Forrest Higgs.

The cable is no problem, it's a bit I had left over from a garage door opener but it solders very easily. It's the drive screw that is SS. I bought the parts a while ago when the design did not include soldering. I could only get stainless from Farnell at the time. I was worried it would be too hard to machine but that went ok.

When the design changed I thought no problem I have some cable, I did not stop to think that stainless would be hard to solder, obviously it is, the clue is in the name.

What happens with either electrical flux or plumbers flux is that the surface goes black and the solder just forms a bead.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> What happens with either electrical flux or
> plumbers flux is that the surface goes black and
> the solder just forms a bead.

That's what it does all righty.

You have probably seen this page. It mentions using phosphoric acid based flux as well as cleaning and roughening the surface.

[www.azom.com]

or maybe just use some thermite .

Yes that was the page I saw. I have not been able to find a source for the flux. I think I will try JB weld next as Eric M has had some success with it. If that fails I think I will make a new shaft from zinc steel. I don't know why I didn't do that in the first place as it is available cheaply from the local DIY shop B&Q.

Edited 1 time(s). Last edit at 08/10/2007 07:25PM by nophead.

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[www.hydraraptor.blogspot.com]

I have tried to combine all the advice in this thread and some from the JB Weld thread.

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.

So far, touch wood (or should I say plastic) it seems to be holding up. It has certainly outlasted the solder attempts by a long way.

I think my advice to others would be to avoid stainless steel but if you have already made it, like me then ,this seems to be a solution.

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[www.hydraraptor.blogspot.com]

I've been wondering why you don't drill and tap the shaft, and put a screw through the cable.

That might work but it would be have to something like M1 or M1.5 if that exists as my cable is only 2.5mm diameter, the recommended one is 3mm.

It would also have to be headless, i.e. a grub screw otherwise it will catch the incoming filament.

Edited 1 time(s). Last edit at 08/12/2007 07:02AM by nophead.

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[www.hydraraptor.blogspot.com]

I've been thinking that using high-temperature silver solder (from your welding supply store) or a brazing rod might give the best hold.
Also drilling out the hole a bit deeper, so as to hold a longer length of the cable might give you better durability for the long-haul.
Then again, perhaps building a tiny Universal joint and running a rigid drive-shaft might be the answer, or just extend the drive shaft long enough that it doesn't interfere with the feedstock entering the toolhead.
But this is just me thinking out loud, and I'm new, so don't go putting too much faith in my ideas just yet.
~Rick

Well so far the cut a cross, rough up the hole with a grinder, JB Weld and bake in the oven method has held up for me. It's actually easier than soldering and JB Weld is required for the heater anyway so you are cutting down on tools and materials required. The only downside is that it takes 24 hours but if you do it as the same time as the heater then you have lost nothing.

I will post on this thread if it ever breaks.

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[www.hydraraptor.blogspot.com]

Good to know Nophead, and glad to hear that it is still operational.

I finally have my (Zach's CNC run) extruder completed.
I had a heck of a time soldering the flex drive line. Nothing was flowing, no flux seemd to work... After reading all the above posts. I took the pieces apart (drive screw, SS cable, and drive nut assy.) cut a new piece of cable, cleaned everything else every way I could think of and finally ground out the last of the crud from the nut and the drive screw with a 1/8" ball ended dremel tool. I dipped both ends of the SS cable in ordinary rosin soldering flux and put every thing back together. I dialed the heat all the way up on my solder iron applied heat to the screw and watched for the rosin to bubble then touched the rim of the screw and the SS cable with ordinary rosin core solder. To my amazement the solder flowed just like it should and in 30 seconds I had a good clean joint. The nut went on just as easily. I think the key steps were grinding the surfaces so they were oxidation free and having the now clean surfaces covered in flux before the saw any heat.

Best,
Dan

thanks for that write-up dan. i'll try and get it into the wiki asap.

I attempted the plumber's solder approach first and finally resorted to brazing the joint. I don't know if the cable was S/S or galvanised but brazing worked as usual.. only that once I brazed the cable it lost some of its temper.

There has to be a mechanical connector (maybe electrical terminal block with grub screws) that avoids this fandangle.

tobyborland Wrote:
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>
> There has to be a mechanical connector (maybe
> electrical terminal block with grub screws) that
> avoids this fandangle.
>
Of course, if you do that you defeat the whole purpose of putting in the flexible shaft in the first place.

My JBWeld is still holding up, see the post above.

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[www.hydraraptor.blogspot.com]