I ran out of film.
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So, we have some options and I have some questions.
Currently I think I am going to release a flat cuttable option or a 3D printable option for the largest part.
For mounting the rails to that part (think the wood side on the current LR2), obviously wood screws into wood, plastic, or threaded holes for aluminumâŚbut for the 3D printed version M3 nuts are too small to work well on a printed part, so I can build in room for extrusion style Tnuts (these or thesehttps://amzn.to/3BF1Uxp?) or I can make a slightly tapered M3 hole and thread them in directly.
I was thinking like a 1 degree tapered hole, there are minimum 6 screws per rail, 4 rails in total. I would test it, but I am confident they would hold. 6.5mm of threads would be in the printed part on each of the 24 screws.
Or do you have any other idea for attaching a linear rail to a printed part?
I think I have nearly all the parts ready to test. I have three minor parts left to make but I will be printing and assembling as much as possible tomorrow while I make them.
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Exciting stuff! Looking forward to seeing the result of your hard works so far!
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Well, I put M3 screws into printed parts fairly often, and it generally doesnât cause a problem for lower stress applications. Iâve also used heat-set nuts, and of course just captured M3 nuts, depending of course on the amount of stress that the screw will be under.
Capturing the M3 nuts works well for parts where the screw will be under tension after itâs fastened, but not while itâs being threaded in or tightened (much). Of course it becomes possible to turn the nut in the printed part, sometimes even just from the resistance of a nylock nut.
The heat set ones are also pretty good. No nylock there, but theyâll take a bit more torque for a tightening pass.
The extrusion style nuts (And their relative expense) is something that Iâd rather avoid, though I guess for a limited numberâŚ
I donât think it would be reasonable to expect much pulling tension from a linear rail, and probably the tapered holes will be fine.
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I have mounted MGN12 rails to plastic using inset M3 trapped nuts. It worked without issue. I just made sure I modeled it to use all the screws. That way if there is an issue with one then I know the others will hold.
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Heat set, kinda take a âspecial toolâ Not excited about using them for that reason. I guess I can try some M3 locknutsâŚor just include loctite in the kit and use regular M3 nuts that way they shouldnât spin out.
I guess I will print some sort of test part, I just know some people have hole compensation and threading directly will probably be a trouble spot for people printing their own.
I think itâs inevitable that some number of people are going to turn them too hard. Like with the old corners, even though directions are clear, people bring their own intuition which is wrong in the specific case.
Perhaps a captive nut and the screw threads also engage the hole in the printed part. With the M3 nut, stripping threads is not an issue, and the printed part replaces the nylock.
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That could be a great solution!
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The tnuts are an interesting idea. There are also threaded inserts (for wood). They seem like they would be happy to shred a nice printed part.
Have you considered M3 nuts and washers?
The taper makes me worried that you will have even less tolerance and printers that make holes too small will be creating a strong wedge. Having a threaded hole and a nut seems like trouble because if the nut isnât lined up, then it wonât be fully seated until you strip the thread holes.
Iâm also not confident that many screws will add up linearly. If the part flexes, or something gets wedged in a weird way, then I can imagine it putting all the force on one screw until that gives, then all the force on the next highest screw, etc. It makes me want you to test with only the top and bottom screw installed.
This all looks pretty negative. Sorry. I am sure it will work.
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It only looks negative if youâre not trying to make things better, dude.
Anticipating a problem that doesnât need to be solved is better than solving a problem you didnât anticipate.
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All great ideas here.
Jeff has a very valid point.
I personally like your idea off the 2nd t-nut example. Where you could make as slot or even a recessed space to insert the t-nut.
Also Jamieâs captive nut, can be the solution but Iâm afraid that the little teeth could end up splitting the printed part when tighten them
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I like the idea of using threaded inserts. They would allow for a larger hole size in the printed part. Threaded inserts also tend to have larger coarser threads for biting into the plastic better. Plus you could use the same tolerance in the flat part for inserts there too. Users can still use threadlock on the bolts to hold them in.
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The extrusion nuts seem like a good compromise to me.
Is this one of those parts that will most likely be immediately upgraded to wood/metal anyway after the machine is running? âŚI guess that would be a point against purchasing any specialized hardware.
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Well, this all kinda seems like I should just design it for a flat part and include wood screws.
Taper and angle calculation a 1.5degree taper over 6.5mm drops the hole 0.1mm in diameter. I will start with some tests with that taper and see how it goes. I only considered the taper to help with wonky printers. A simple, tiny test part would let people validate the fit before printing.
I am going to be honest, I really wanted this to be printable because as a flat part it is kinda ugly right now. When I consider one side will probably be near a wall and the other side will be covered up with a control boardâŚI am probably over reacting.
Something else I will throw out there, wood screws in plastic are pretty tolerant of print errors. I canât say Iâve compared directly side by side with M3, but one would think with deeper, coarse threads it should be more tolerant.
For my own projects I use #6 pan head for literally everything 3D printed. I donât have to track different size screws, and I havenât found a case where I couldnât make it work.
Technically I think they are sheet metal screws, but I canât tell the difference in the thread form. Wood screws typically have flat heads and happily split the plastic, with or without a countersink feature.
No, youâre not. I donât buy the âarchitects can hide their mistakes with treesâ argument (sorry Frank Lloyd Wright).
As a designer you will know that there is nothing so satisfying as getting it right. Putting a control box over it to hide it is not getting it right. Ignoring the control box is not getting it right either.
Push on - you can do this, donât stop just short of the finish line!
BTW - I think the side plates on the LR2 are a kind of âiconicâ element on that machine - but to hand out a stick of healthy criticism, because there was no provision for a control box in the design there are a lot of machines that look like a dogâs breakfast with that bit covered in all manner of ill thought about contrivances. I think that devalues the work you quite clearly put into all those other perfectly fitting perfectly printable easily assembled bits.
Now I know a dogâs gotta eat and I mean no ill to those who like the utilitarian approach, but you have an opportunity to do this beautifully, donât devalue all the work you put into all those other cleverly contrived parts by thinking because itâs against a wall, it doesnât matter!
I do hope that wasnât too much of a rant.
Keep up the good work.
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I think this is the winner. It works for everything but metal sides, and if you are capable of making metal sides and tap your own threads, getting a couple screws will be no big deal.
Dude, you are rad, I love that solution.
Agreed!
No that was exactly what I needed. Why stop when I am sooooooo close. Make it right. We can test and beta test while I polish some things if needed.
I am printing some parts right now, It will not be fully functional but I need to put it together in real life to get my hands on some of these parts that have been virtual for long enough. I will see one side fully assembled in a couple hours. It is close enough I am trying to finish the Repeat that is on my bench so I can print some contrasting parts at the same time. I popped one of my hot end heaters so I am trying to get another one running.
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I want to seeeeeeeeee with my eyes, after this weekend, I want to start doing furniture!
That flatpack stuff is crazy. PLEASE!!!
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So I built a side, mostly, and I am not sure. We might need two bearing blocks per rail. Hard to say, I printed everything at 10-15% infill so everything had a bit of a flex to it. Reprinting the critical parts tonight with 70% infill to be certain, I will have another look in the morning.
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If it turns out you need more than 2 bearings. Then you can always design it to use four(two per rail). But then you could test it with three and see if it works well enough.
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