Threaded component needed

Hi guys,
I'm looking for a part to be designed & printed. I was hoping someone here would be up to the challenge.

What I need is one of these "Self reversing screws":

[www.abssac.co.uk]

This is to be a component in a pet project of mine, making a mechanism for a hose reel that layers the hose neatly as it winds in.

The bar should be approx 25mm diameter, thread depth of 4 mm, width 4mm, with one turn every 12mm. The screw should be 400mm long (two smaller sections that fit together may be easier to print) with the centre 300mm threaded & 50mm on each end left blank. The rod should have a 10mm hole in the centre for a threaded bar for fixing & strengthening purposes. Take special note of how the thread ends & reverses on the link above!

Budget is "as little as possible",.. but obviously I don't expect anything for free.

I understand the thread may be a little rough from the printing process, but would hope that it could be cleaned up with a file (Print the walls thick please!)

This is the most complex part of my reel, so I'm willing to adjust the rest of the design to make the production of this part a possibility, or at least easier.

Let me know what you can do.

Where are you located?

I'm in Fermoy, Cork, South of Ireland. Will gladly pay postage costs from anywhere in the world though.

There's a drawing of a similar component here if its any help:

[www.engineersedge.com]

Sounds like a good use of syvwlch's openscad screw library on thingiverse:
[www.thingiverse.com].

I don't think the screw library will help much. The trick with these is the end tangency. The little animation they show is a simplified version of the device. The ends need a smooth reduction in lead angle until they are tangent, otherwise the follower will jam.

I'm 90% sure I can whip up one of those in Solidworks and print it in 5 parts. I'll take a crack at the cad tonight to see if it is within my abilities.

Do you have dimensions for a follower to test the screw with?

Hi Andrew, I don't have dimensions for a follower,.. I was planning on getting out a dremel & doing a very technical "bodge it till it works" production method. once i've a shape that works I'd use the measurements to produce a solidworks model.

Ditto with the end tangencey,.. my plan was tweak it till it works

But if you reckon you can get the design right without bodging,.. its a much better way to go!!

Printing out a short segment to see if it works. Looks about right, though.

Nice work. How did you end up doing the reversal section? Is it smooth or just the two threads intersecting?

Also, how do you plan to print this? With support? In 2 halves laying down? could the thread be chamferd enough to print standing up? I notice you have designed a square thread cross section.

That looks awesome Andrew!!

How did the short segment print Andrew?

Reversal is 99.9% smooth. Solidworks lets me do a variable pitch thread, so the end pitch was set to .01 and returning to 12mm at 1/2 revolution.

I printed one vertically and one horizontally. Both were done with 60% support and .3mm layer thickness, 100% fill. Horizontal is the way to go, as it uses 70% less support material, and the pitch of the threads is much smoother.

I'm going to run it through my smoothing station tonight and see what that does (not that I think it really needs it.)
I'll take pictures, too.

Any ideas how to cheaply ship to you? Fedex said close to 100$ from Pa, USA.

Fedex are expensive to Ireland. Most bits I get from America are sent USPS & it works out a fraction of the cost. What's the size & weight & I'll search for a good quote?

What do I owe you for your work Andrew?

All figured out it would cost $55+ whatever USPS charges to ship it.

I wish I could do it for less but it's a lot of material, and I feel it will need to be printed mostly solid and at .22ish layer height to turn out really well. The part in real life looks a bit better than the super close ups.

Up to you if that's within your budget.

Attached is an image of the full assembly and some 'as printed' and 'post smoothing' pics to help you decide. (this was only printed at .3mm layer)

Either way, I'll upload the .stl's to thingiverse in a few days.

I love your smoothing station results. Is this what you described in "Surface Finish Improvement" thread? i.e. dangle in a container of with heated acetone in the bottom for 30 seconds?. Is this ABS? Do you know if that works for PLA?

Thats perfect, thank you Andrew. Let me know what e-mail to paypal the funds to!

How's progress Andrew?

I should start printing tonight. PM me your Paypal and I'll send you a bill after I figure out what usps costs.

PM sent.

All printed. Just need to clean them up.

So cool. Any chance we might see the files on thingiverse, if both of you are amenable? Also, what about the carrier that actually changes direction? I can imagine a smaller version of this, geared to a reel holder, to allow neat transfer of filament onto reels.

I have no problem donating the source if Njones doesn't mind.

The carrier should be easy enough to make with normal tools; it is pretty much just a semicircle. Following the initial links should make it fairly obvious what it looks like.

I think this would be really tough to make this small enough to be useful for winding filament.

That looks fantastic Andrew! I've no problem at all with the source files being shared.

You manage to find out postage costs yet Andrew?