Large Scale Central

Fasteners for Resin Prints

Modeling Technical Modeling
#1

So for those of us into resin 3D printing we all now that resin is pretty brittle. It breaks, cracks, chips, and otherwise does not really like to take fasteners. As such I have been a bit reluctant to use it for much more than just detail parts.

But possible solution may have presented itself. And I am wondering if anyone has used threaded metal inserts that can be epoxied into a hole in the resin print. I found these at McMaster Carr and am thinking about using them on the body bolster of car frames. If a hole that is slightly larger than the insert is printed then the insert could be epoxied into the hole. With the knurled sides the epoxy should hold it nice.

Thoughts? Experiences?

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#2

Devon,
With my form labs printer i have a material called Durable, and i use it on things that need some forgiving. one example i have made an outside frame for my Connies front truck. it seems to derail all the time and dosn’t break. some time ago on “Whats Neet this week” i remember there being some discussion of a more forgiving resin for led printers. i do not remember the specifics, and it may have involved mixing resins. Formlabs has some other resins that would be better suited, however the post process requirements make it unaffordable. By the way i have been using the same durable material to make Roto mold masters. the guy making the mold loves it because they masters come out completely clean, where as the other materials as you mentioned are brittle, and while they make a good impression, came out in multiple pieces and often had hidden retirements.

Al P.

#3

All there are some resins out there that I have not played with. Mike Williams who is the guy who has helped me a bunch with my resin printing has a mix that he uses that is far more forgiving than a lot of stuff. A resin I have not played with but want to is Tenacious which is supposed to be very ABS like in nature. But what seems to become the issue is durability means sacrificing detail. Now something like a bolster under a car body, I am to worried about detail. In fact I may very well print this with an FDM printer in ABS for strength. I have pretty much resolved myself to the idea that I need to buy an FDM printer to do larger parts that need strength.

But even then I like the idea of these metal threaded inserts. Would be a much more resilient connection point for something that needs to be taken apart.

#4

Those inserts are designed to expand when the screw is inserted to lock them in place. Might still work with your resin part, but the epoxy may keep it from expanding as it needs to.

I’ve not used these. I do use a similar product called a rivet nut. Installed like a pop-rivet with a special too. I’ve had mixed results but I have a really cheap tool.

#5

Jon,

I was aware that they expanded. And that is why I would say for sure the hole will need to be bigger to allow for the expansion. Who knows maybe I won’t even need the epoxy, maybe it will bind good enough on its own. I have seen the rivet nuts also . Was trying to figure out how I could make that work. This all started with using threaded tubing which is what I use now. And would probably work also. I just liked the idea that these are knurled and expand so it should lock in nice.

#6

I have epoxied rivnuts in place, instead of using the tool, to use as the insert for attaching trucks. Works pretty well.

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#7

Devon,

For what it’s worth, I’ve used these heat-set nuts on acrylic, and they might work with resin.

For acrylic, you use a soldering iron to set them. I’m not saying that works with resin.

My bigger point is that they have a lot of fluting / surface area, to which epoxy could bond (to Bob’s point).

I agree that you’d need to avoid anything expanding, unless you bedded it in something flexible. And resin isn’t very flexible. Even if the resin could tolerate it at the moment, there could be built-in stresses that, when the part ages, wins.

If it were me, I’d print a slightly over-sized hole, and pot in a non-expanding insert with an epoxy.

Cliff

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#8

Devon, why not simply design the hole to accept a plain ol’ hex nut and epoxy or CA it in place and then simply screw the two parts together. I do it all the time. It works great, especially if you can hide the nut where it can’t be seen. You can also use simple square nuts and design a slot in the hole to accept it and again screw the parts together.

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#9

What he said.

I’d recommend stainless nuts though, you wouldn’t want any rust building up in that interface.

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#10

This has actually been a fascinating conversation. There are apparently a lot of ways to skin this cat.

I agree with all, that anything expanding could be problematic with resin. Hence the over sized hole idea. But both the rivet nut and an epoxied regular nut should work equally as well.

What I was trying to avoid was a screw like we see in softer plastic. I have never been find of that. So with wood I started using internal threaded nylon or aluminum bushing/rod. I like that a lot better. This is just expanding in the idea. I simple nut probably would work just fine if I design the part to fit it and a little epoxy or CA should hold it. But the rivet nut also sound like a great idea. Might have to play with both ideas.

Of course I am still very much considering an entirely different route and printing a master and casting white metal trucks. I would like to find a system I like for when I have to do 30 Bettendorf trucks for my future string of log cars. . . Oh wait thats for that other thread about unfinished projects. .

#11

Devon, I use them all the time to hold trucks on the bolsters in my wooden builds.

I’m still waiting for someone to come up with tough resin. I have broken so much of the detail parts
off of my stuff from Mike, that I’m about ready to give up. :confused: :frowning_face:

#12

John,

That’s the problem with 3D resin printing. Mike, rightly so, is trying to find a balance between strength and detail. I too am frustrated with resin printing because it is so fragile. I do want to play with some of the stronger resins but all reports say you will sacrifice detail.

It’s one of the reasons I just pulled the trigger on a FDM printer. I can make strong parts and then dress them up with detail resin parts.

Another option I want to explore is using resin prints to make masters for resin or white metal casting.

#13

I’ve only used Siraya resins, blu and sculpt. The sculpt is excellent with detail but is very fragile. The blu is much more resilient with a minor sacrifice of detail but not enough to really notice unless you specifically compare the two side by side. The nice thing about the Blu is it is somewhat flexible even after curing. Now, its not the cheapest resin on the market, but I think the durability is well worth the additional expense. Dan’s 2¢ and that’s about all its worth.

#14

See and I hate Blu. . . Lol. I threw 1/4 of a bottle away. Can’t get a decent print to save my life. Most things I use Fast. But mike has a combination that he is getting decent results from. I want to play with Tenacious and see if its more durable.

I am hoping with the filament printer I can get durable parts and then use the resin printer for detail

#15

Did you read the fine print on the Blu resin? It clearly warns to not wear a tinfoil hat while using it or results will be questionable :stuck_out_tongue_winking_eye:

I think you’re going to find that the FDM printer compliments the resin printer very well. I prefer FDM prints, but that is what I started with. Much cleaner and easier once you get the printer dialed in. Now, I do love my resin printer and love printing detail parts on it.

We are looking forward to seeing your first prints on the new printer when it arrives. No more excuses then :grin:

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#16

I have been making Detail parts and figures. I have started using the Mix of ABS like resin for strength and Tenacious for flex. I am having good success to the point I’m even experimenting with things I’d normally FDM print so I can get more detail. I’ll post some photo later - have to go work in the storm now.

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#17

What resin are you referring to as ABS like?

#18

Jon and or Bob,

I just ordered a package of aluminum Rivet nuts with 6-32 threads. One thing that I was curious about as I was ordering them, do you actually get them to crush? I am afraid that the amount of force it would take to crush them would break the resin first. Or are you simply epoxying them in place. I am thinking since they have the splines that if it’s a bit of a resistance fit so the splines cut into the resin and this is done before final cure so as to not be as brittle and then putting them in the curing chamber I would have a decent fit without the need to crush them. I could also then make the materiel thicker and ignore the materiel thickness spec that it normally crushes over.

I am assuming this is what you are doing or some version of it and not crushing them.

#19

When I use them in models, I dont crush them, I just epoxy them in place.

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#20

Roger that.

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