Threadless ball-screw

[hoff70]

I’m at the point in my Morgan build where I’m rounding up some of the hardware. One of the odd bits is the Z leadscrew. I’m still not sure if I want to go with a drill bit, threaded rod, acme, etc.

My first inclination is to find one of the masonry bits and stick with the original design but it doesn’t seem to be very common in the US.

Anyway, I figured I’d share this: http://www.thingiverse.com/thing:112718

Some folks have tested it with good results and I was wondering if it could be adapted to the Morgan Z bracket. It would simplify the part count because 8mm rods could be used for the slides and lead screw.

I’m not good with CAD but if anyone wanted to design a Z bracket with this “ball-screw” incorporated into it I would be glad to print it and try it out.

I’m not sure if it would be a “fast” enough thread though…

[RobertKuhlmann]

Interesting thing!

I’ll make a z-bracket for this one tomorrow (it’s too late for that today and I had wine already 😉 ). And I’ll try it myself too.

Quentin should love it, because he doesn’t like to use threaded rods. 🙂
Even if it rises the vitamin-count for the morgan though.

And don’t worry about the speed. It’ll be fast enough I guess.

[hoff70]

Great!

Please post a link to the file. I printed your tool holder for the German bowden setup and it turned out pretty well.

Thanks for the work you are doing!

[Quentin Harley]

I like it a lot, and started to experiment. I do not have it on a machine yet, but it should be much faster than threaded rod. You can adjust the angle of attack, which will adjust the speed.

Let me know how your experimentation goes!

Q

[RobertKuhlmann]

Here’s the z-bracket with a plate for the threadless ball screw (for 8mm this time): http://reprap.org/mediawiki/images/1/1e/12-bed_z_mount_bracket_for_threadless_ball_screw_8mm.stl

[hoff70]

Thanks! I’m printing the bracket now. Rostock has been temperamental lately so hopefully it will go well.

[hoff70]

I noticed the part where the “Z arms” mount is a lot thicker:

Morgan sure has some beefy parts compared to most other repraps!

[Quentin Harley]

Hi Robert,

Thanks for making a bracket, but please check the following:
– the teardrops are upside down. This will have the opposite of easy printing as effect…
– the bracket is not supported, making it necessary to use support. This is not a major problem, but I always make sure that all the parts could be printed without support. Think of a way how this could be done.

Cheers,
Q

[Quentin Harley]

PS, i think the sections on the end are also a mishmash of the 12mm and 8mm versions. Making it a lot thicker than it was supposed to be.

Was this done in inventor?

I will try to do a version in SCAD.

[hoff70]

Robert was gracious enough to put this together Q!

I think I would have preferred the bracket to be all the way at the bottom so it could print flat on the bed as you say as well as have the points on the drops at the top. But those are minor niggles and we appreciate your work Robert!

I hope to have the print finished soon and will begin on the “ball screw” I believe I may actually have the bearings and hardware on hand which will be nice.

I’ll post some side by side pics of both parts when this one is out of the oven.

[hoff70]

I think it’s going to work fine but it could probably use some stiffening up:

[RobertKuhlmann]

I’ll make a new version that needs less or no support and with more stability. Give me a minute… 😉

…and of course with correctly oriented teardrops.

@Quentin: Yes, it’s done with Autodesk Inventor. I’ll add the new z-bracket to the extended BOM in RepRapWiki (http://reprap.org/wiki/RepRap_Morgan_extended_BOM), as soon as it is ready.

[Quentin Harley]

Thanks. I will model a SCAD version on yours

[RobertKuhlmann]

You now find a new version under the same link:
http://reprap.org/mediawiki/images/1/1e/12-bed_z_mount_bracket_for_threadless_ball_screw_8mm.stl

I’ve turned the mounting direction of the ball screw 180° so that the tensioning screws are better to handle.
I’ve added some plastic for more stability and corrected the teardrops.

[RobertKuhlmann]

RepRap Morgan extended BOM is updated.

[hoff70]

Here’s the beta version:

They are balloons instead of teardrops 😛

I printed the 38.5 deg version because I figured it needed a pretty fast thread. The orientation of the bolts seem OK to me Robert. I like the way it tucks into the bracket instead of sticking out. Probably be best to remove the 3 bolts holding the assy. to the bracket and removing it for maintenance…

And good job Robert! I was thinking about just adding a pad to the bottom of the original bracket but that would have made access to the mounting screws difficult. Your solution makes for easy access 🙂

I gotta say it’s pretty darn “grippy”. As long as the bolts stay tight I reckon it’s a pretty good solution.

[RobertKuhlmann]

I think it would be good to use the same steel for the rod, the bearings are made of to reduce abrasion.

[hoff70]

Yes, I’ve noticed some galling already with the rods I’m testing with. They are supposed to be drill rod but are really soft. I could just have the bearings adjusted too tightly but some pretty hard rod would be a good idea.

[RobertKuhlmann]

I think the bearings will wear of the rod or vice versa, if they have different degrees of hardness.
Anyway, I like this solution a lot. It’s got the same charm, like the Morgan. 🙂

[hoff70]

I like it as well! I also think it’s neat because it’s possible to print roller bearings. Not that we could print very usable bearings now, but maybe in the future…

I also like the fact that they are pretty common and inexpensive items.

My only worry is that it adds 7 more bolts that can come loose. I have a rostock so I’m an expert at loose nuts \o/

[RobertKuhlmann]

It’s quite frustrating to see my new parts printed while I have to order and wait for them – I’ve got no own printer yet. 🙁

😉

But it’s very amazing to see my work realized so fast and that it seems to be useful.

I have to explain, that I can design and draw at my office, because I have a lot of idle time at work. But, of course, I can’t work on my real Morgan here. So it’s virtual brother always is a few hours ahead.

One word one loosening bolts:
How about fixing them with special lacquer?

[RobertKuhlmann]

One thought about printable bearings:

Did anybody ever thought about using air pressure instead of metal bearings?
It’s an idea I’m running around for years in my head. Never talked to anybody about that until today.

[jade39339]

Hi Robert,

I believe air bearings would be impractical. They are specifically designed to have almost no friction once up to pressure and since no contact is made but the air, there would be no way to prevent slip on the rod.

[RobertKuhlmann]

…since no contact is made but the air, there would be no way to prevent slip on the rod

But that’s an advantage. not a drawback, isn’t it?

Found this one just a second ago:

[Quentin Harley]

I think the only disadvantage is that you need to run a compressor to make them work properly. Not ideal for protability. It would be advantagious in a lab where compressed air is available all the time.

[RobertKuhlmann]

Of course the needed compressor is a part I’d like to print too. Shouldn’t be too complicated. 😉
I’ve started a thread in the RepRap-Forums for that: http://forums.reprap.org/read.php?1,237867

[hoff70]

I say go for the air bearings! Sounds like it would over complicate things a bit but what the hey! You may be on to something. Plus experimentation is always fun 🙂

I believe the Morgan would be a good candidate for simple printed linear bearings. My guess is that since Z is the only axis on linears the relatively small motions (compared to X and Y slides on other variants) may allow them to hold up for a good long while. The length of the Morgan slides should also help spread the load and reduce wear. It would also knock 4 “store bought” components off the BOM!

More mock-up:

Another view:

Someone should run with this printed nut and make more of it printable :O It may not be possible with roller bearings but printed rollers on screws may work… The galling that the bearings are making on the soft rod puts me in the mind of a fixture for making a lead screw out of smooth rod. Once “threaded” the rollers could be replaced with plastic rollers.

[hoff70]

A vid showing the speed:

[Quentin Harley]

Works even better than I expected. Yes, we may have to use hardened rod to prevent it from deterioration over time, but this will still be a lot more affordable than using leadscrew.

Why not integrate the whole mechanism into the bracket? Something to investigate. The great thing is that the bearing module itself is already SCAD. Should be the minimum of work to pull it into the Morgan source.

Nice job!

[hoff70]

I too was surprised at how well it seems to work. I chose the 38.5 deg because it seemed to closely approximate the fast thread of your brilliant lead screw. The pitch is approx. 5 TPI but I’ll have to put an indicator on it for exact numbers.

Incorporating the module into the bracket is a superb idea and would knock 6 parts off the BOM. You’d have to take care to allow access to the bolts because they go through at such sharp angles.

Any input on the thread pitch Q?

[hoff70]

Oh and Robert. Hopefully you will have a printer soon and thank you for the work you are doing! I’m still amazed at how fast a rapid prototyping machine can spread ideas so… well… rapidly :O

I assume you are in Germany and it’s amazing the way you can design a part half a world away and send it to my desktop in the US where it materializes within minutes or hours \o/

Exciting times!

[Quentin Harley]

The pitch looks good. There is not a specific pitch required, as long as its stable and resonably fast because the homing takes the bed through the whole movement range.

Stability is the most important requirement, and I would gladly sacrifice a couple of seconds of my life waiting for homing in order to gain better printing quality.

[RobertKuhlmann]

Good morning to you all.

@hoff70: You’re right, I’m living in Germany. I’m amazed too, how easy such a project can jump forward by working together around the world the way we (and many others) do.

For me it’s a political issue and a personal objective.

But that’s OT over here. 😉

Your prints look very good. I just can’t wait to begin printing and make my own filament.

BTT:
Did I mention, that using an air bearing should not only save metal bearings but metal rods?

Today I may get another step forward with my Morgan I hope. What I’m planning to do will show up first on my progress-page at the RepRapWiki (http://reprap.org/wiki/User:RobertKuhlmann/RepRap_Morgan#Progress_of_my_own_Morgan).

@Quentin:
Your goal to use no support, if possible, is okay. I didn’t pay too much attention to that, because of my goal to use self made filament and use recycled materials. Therefore the size and weight of the printed parts don’t have to be minimized for me, because they will, or at least should, be the inexpensive parts.

Stability: I think a shorter angle for the ball screw should work as well, while more stable at the same time.

[hoff70]

Thanks for the kind words about my prints Robert! I started the Morgan with black PLA which was printing great. This silver PLA is proving a little troublesome so the prints aren’t as good as I would have liked but are serviceable. Different colors and different batches can behave very differently with the same settings…

Concerning the support material, it’s not just the wasted material it’s the fact that slic3r just doesn’t handle it well and sometimes buggers up prints. I’ve used Cura as well and it’s not much better 🙁 You’ll generally have nicer prints if you can prevent using it.

The 1st Z bracket you designed is great! I like the symmetry of having the bracket in the center. I’d suggest adding it to your reprap page as an alternative to the other brackets.

And thank you as well Q! I think I’m going to run with this ball screw version. I’ll use hardened rod for the final build and see how it goes.

[RobertKuhlmann]

Okay. I’ll publish it in the extended BOM after finishing my work on the building platform. The rear platform holders, e.g., had to be changed a bit to better match with the front holders and I’m drawing a new base for the building platform (except Quentin tells me why it is better to use the OpenHW-XPlate).

[Quentin Harley]

There is no specific reason why the OH one is better except that is is available easily (and something simpler would cost the same to cut at our current laser cutting service…)

If you have something simpler that works better, I will gladly add it to the repository.

[RobertKuhlmann]

Third z-bracket is published in the extended BOM (with some modifcations).

Building platform is under construction.

[evamvid]

Does this work with the STLs and bearing sizes at http://www.thingiverse.com/thing:112718 ?

[hoff70]

I’m using the tiny_ballscrew_8mm_38_5 Works fine with Roberts bracket.

My machine isn’t running yet so it’s all pretty experimental. I’ve drawn up a stiffer bracket that should be easy to print just haven’t printed it yet.

[Quentin Harley]

I believe so

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