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Iris Box v3

by emmett, published

Iris Box v3 by emmett May 10, 2011

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Summary

I decided to revive the venerable iris box by redesigning it in OpenSCAD and making it printable with fewer parts and less assembly. It's also somewhat larger (though now the dimensions are easily adjustable with OpenSCAD), the tracks are redesigned to give more rigidity when closed, and it now opens and closes according to righty-tighty, lefty-loosey. The ring is also aesthetically redesigned and the base interior tapers down the wall thickness to give a little more internal volume.

Instructions

Print the three parts (base, ring and leaves). Note that unlike v2, the base is printed right-side up and the ring is upside down. You can also test the mechanism with testbase, which takes much less time to print than the full base. You can test the tolerance by clipping a leaf onto a ring peg to make sure it turns easily but doesn't wiggle. Remove before beginning assembly.

While holding the ring upside down, place each leaf onto it as shown in the picture and hold them there with your fingers (don't clip them on yet). Put this assembly onto the base, putting the ring pegs into the larger openings in the base. Press down and apply a little left torque to the ring (some wiggling may be necessary) until the base pegs fall into the leaf tracks. Now it should be possible to twist the ring back and forth a little, so twist it all the way right. Next, line up the leaf keyed holes with the ring pegs and pop each keyhole onto each peg. You can usually only get them on half way at first, then the second time around they'll go on all the way.

These STLs made a very smooth mechanism on my TOM, but if your calibration gives you different results, then adjust the parameters in the scad file (peg clearance diameter is probably the most important).

UPDATE: I found the mechanism to be a little sticky when the box was half-way open, which turned out to be because I miscalculated the clearance for the geometry. I've fixed the error (this version is much smoother), so the scad file and IrisLeaves.stl are new.

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Like many, i found the weakness of this design to be the ring pegs. to fix this, after printing the ring, carefully break off the pegs. you will see there is a small hole through the centre of the peg and on the ring where the pegs broke off. cut some small pieces of paperclip, you will have to work out the length. the idea is to CA glue the paperclip pieces into the peg through the hole with a small bit poking out from the peg, about 1-2mm. then put a drop of CA on the stump where the peg broke off, line up the paperclip sticking out of the peg to the small hole in the stump and push it in. this will CA glue the peg back onto the ring with the added support of the piece of paperclip through the centre of the peg and into the ring. this works well.

I'm having problems with my printer, it keeps putting a flaw in the pins of the lid. I'd like to subtract the pins from the lid so there are solid wall holes for me to insert screws with countersunk heads.

But I'm a rank beginner when it comes to OpenSCAD, and I'm having problems using Difference() to do this. Any suggestions? The OpenSCAD tutorial says everything after the first item under Difference() is subtracted from the first item. I tried moving the code for just the pins to just below the code for the box that is subtracted to make the bottom of the lid ring flat, but the pins just show up as normal.

Thanks,
Steve

You'll want to remove the lines that create the pins from the code entirely. To figure out what a line does, put a # in front of it and compile with F5. Then it'll highlight that object in red. Try commenting lines out and seeing what happens. Eventually you'll get the hang of it. If F5 is looking spastic, put a render() command in front of the top-level object. Takes a little longer, but looks much better.

Thank you, Emmet, for including the SCAD file.

I'm going to print some of these as gifts. I'm trying to print a shortened version. Now that I've shortened it in OpenSCAD, how do I export just the base? I know next to nothing about how to use OpenSCAD.

At the top of the file, comment out assembly(); and uncomment base(); (// is the comment symbol). Then click Design -> Compile and Render (CGAL). Once the object shows up, click Design -> Export as STL...

Thanks! That took a lot less time to print.

I made the box out of ABS, and the Leaves out of PLA. My parts did not come out remotely close to fitting, and I immediately broke off one of the pegs fiddling with it. I could have followed all the "Test print and Tweak the SCAD" instructions, but I was printing something else, and the drill was right there.... #6 wood screws replaced the pegs, I drilled out the holes in the leaves, and I jiggered it all together. it's still all loosey-goosey. To top it off, I couldn't even get the picture to load properly. I'm one more setback away from a garage fire. It is kind of unexpected that the nubs on the ring are a bit sharper than they look.

Very cool model though. Thanks, Emmett.

Once I got my machine tweaked in, was able to print and assemble from provided stls .. only required a tiny reduction on ends of 'flathead' pins on ring with a file ...

After many tries I gave up on the printed pins and just used some little screws instead.

Hi, need to make some iris contraption, willing to pay for the design if interested email me at [email protected]

This is one of the first few things I printed, I'm new to 3d printing and just got my Up printer a few days ago.

This Iris tub worked a treat, I broke the pins off the ring a couple of times intill I cleaned the tracks up on the leafs and cut a small guide to help the pins flex into the hole then it went together real easy. It has a great action but my print dosent close the leafs all the way.

Its a neat little box, I think I'll store screws and stuff in it. Thumbs up!!

I used this to test that my profile was dialed in. It fit together perfectly. The action is nice and smooth. Great work!

Thanks, glad to hear it! Nice looking print.

I printed this out, but had to really tweek the tolerances a lot to make it assemble-able, but after assembly it was pretty-much frozen in place. I thought about it for a bit, then decided to drop some Tri-Flow lubricant (the kind I use for my bicycle chain) into all the channels after prying it open with a screwdriver. That worked some kind of miracle and after working it open/close for about an hour, it loosened up enough to be easily-opened.

One question I have is: using replicatorg 25 and sf 35 and print-o-matic, how do you calibrate things so that a 3mm peg winds up 3mm and a 3.1mm hole ends up 3.1mm? My prints are currently pretty awesome quality is great, but the dimensions don't seem to be on, and I have to do a lot of tweaking/c
utting/sanding on anything that requires assembly.

Yeah, this is a tricky one. Even if your SF profile is perfect, a 3mm peg and a 3mm hole won't be the same size because of how ABS shrinks. This model should be a bit better because the holes are really slots, and so don't shrink the same way. The worst part is that the leaf thickness will always be an integer number of layer thicknesses, so every different profile will have a different tightness. I found reducing the leaf thickness by 0.5mm helped a lot the last time I changed calibration.

I haven't used print-o-matic yet, but I heard a good way to tweak your settings is by changing the drive radius, which effectively changes how much plastic the bot tries to cram into a volume. If things are too tight, it might be putting more volume in than it expects.

Good design, except that all of those tiny little pegs broke off the first time I printed it in ABS. I think I will put this print aside for a while.

Hmm, at what point did they break off? Calibration can affect the strength quite a bit. Perhaps the clips on the leaves need to be widened to make them fit onto the pegs easier.

Mine broke on the first print too. I used a piece of 3mm filament, drilled holes for the pegs, melt and inserted the pieces of filament then heated them up and formed them into the right shape. Worked like a charm, so good I cant get it apart now.

I am going to revisit this one again as I have my settings very dialed and a range of colors too! (my next one is going to be black with nuclear green leaves)

Very nice design!

emmet - would it be easier to assemble if there were a little side slot off the curved actuator slot which would allow the boxes pins to seat then slide side ways for the screw type heads to set in then turn. I think it would sort of be self locking since the little assembly side slot would be in an awkward position for the iris to just slide to and pop out. .... Am I confusing?

suggestion for assembly pin groove.

It's a possibility, but it's not necessary if the tolerances are set right. That's really the key; you've got to print out some test bases and tweak the value of dc (clearance diameter) until everything fits nicely. Then it assembles pretty easily. I wish skeinforge could be more accurate about reproducing dimensions, but right now it just isn't made for that.

What SF tweaks? I'm just getting my feet wet with the bot.

All you operators/designers running to OpenSCAD are killing me. My machine doesn't run the software. I can't upgrade to the needed newer OpenGL which is required for the app. :(
I've ProgeCAD, student versions of AutoCAD and Inventor, Sketchup, and Blender (don't know how to figure out this one..
.) and now everyone is doing OpenSCAD - Agh!

Could/Would you make the walls of the bottom thinner and then have it thicken near the top to make the fittings and pins possible? There is a lot of plastic in this box's walls. Yeah - I know - overhang. But, then, my lid printed nice and we have to lear
n to use our machines - Right?

Also, to those who print a lot - what settings is it to make thin walls solid rather than two thinner walls close to each other (a shell within a shell.)?

Hmm, are you sure about OpenGL? I have an old macbook that also can't get the new OpenGL, and OpenSCAD bitches about it, but it actually still works. Basically openCSG is disabled, so "Compile" (F5) doesn't work, but "Compile and Render" (F6) does. It takes a little longer, but it's actually more robust and you have to do it anyway to export an STL.

It's tough to make thin walls solid rather than having a gap. I often tweak my scad file until the walls are exactly 2 threads wide. I did thin the walls of the base down to 2mm at the bottom, but it's still a huge amount of plastic if the walls are filled solid. You don't need nearly that much
plastic to give them strength.

Yes - OpenGL - My video card will not update to v.2.0. So, OpenVSC? won't run. I have opened the application SCAD and I can see/view a file. I play to find out where I am limited. Thanks for the prompt to try the thing - again.

I love the iris boxes! I'm thinking about some design modifications for easier printing, assembly, use and more durability.

Instead of the sharp ridges on the ring, how about a pair of rounded knobs coming off the sides?
Make the top of the ring flatter so there is less overhang
Replace the pegs in the ring with M3 bolts
Replace the pegs in the box top with either M3's, M2's or just some holes for 3mm filament.

The scad file is there for your adjustment; I think a different ring would be great. Your other suggestions are actually more like J Hodgie's Iris Box v2, so you might want to check that out. I wanted this one to be 100% printed without all the extra assembly.

@bscott - My first layer went down perfectly, but on the second layer the overhang, probably combined with some shrinkage, caused the string to pull into the middle of the circle in a few places and the next several layers followed suit.

@emmett Thanks! I was looking at the scad file. Now to make time to work on it.

@carmiac - I'm trying to assemble. The slot holes are too small for the pegs. The holes in the iris for the lid are too small too. I quickly broke the screw type peg which is just printed on the surface. I'm now cheating. I'm using M3 screws for the lid. The printed pegs on the box are ok. You guys that can print and place. I'm amazed and impressed. So - I'm sorry about hitting you about screws. But, if the design prints on bots its pretty cool idea to print assemble and play.

Wow, carmiac - all the bolts you want get you back to version one or maybe two. This design is good. emmett has made two great looking boxes. Or - one box with two sets of petals?

I agree about the nubs on the top being sharp. Maybe just make them a little larger and fillet them more.

You mention get rid of the overhang. I don't understand? My top was nearly flawless. If I hadn't had an uneven BP which kinda made my first three layers weird and an odd stepper skip up a l
ittle higher I'd be very content. The posts on my top look great. The holes in my petals are very uniform but may be a little small. I can't tell till I go to assemble.

I've still got to print the four (4) hour bottom. My bot mysteriously stopped ejecting filament about an hour into my first botto
m print or I'd have a complete picture posted. :'(

But, I've got a very nice parts tray now. lol.

@bstott: Yeah, I was surprised how sharp the nubs were too. As for the ring, one of mine came out perfect and another dropped some loops. I think the problem is the combination of overhang and shrinking on the inside. Probably more w/t would help.

If you tweak SF, you can print the base in more like 2.5 hours; see the comment on your build pic. The testbase is a lot faster and good for checking tolerance.

Printed in your ridiculous color scheme. Unfortunately, it came out so tight that I cut myself trying to open it

Awesome, the points are yours. A trick with this design is that because of the angles on the pegs, the thickness of the leaves affects the tightness of the joints. That means for a different layer thickness in SF, you'll get a slightly different leaf thickness, so you'll have to adjust the clearance accordingly. I'd recommend increasing dc in the scad file by maybe 0.2mm or so and rebuilding the base (this is why testbase can be nice).

alright! I gotta go put the bot back together and print tonight. I've been staring at the iris box for now the third version and this IS it! Hopefully picture by tomorrow....

Wow that looks nice. I like how you made it so there is no glue or screws required. How much clearance did you leave for the pegs?

Thanks. The pegs are 3.5mm diameter, while the clearance is 3.6mm. I was surprised that so little worked, but I think it's partly because the pegs shrink more as complete circles than the holes do as incomplete ones.

That's good to know. I'm working on a project with snap together joints so I've been trying to get an idea of what works. I'm trying to get Thingiverse to create a library type wiki where people can post stuff like fit clearances, gear info, CAD tips etc.

The OpenSCAD file is also set up for animation. Extra points for anyone who prints it in my ridiculous color scheme.

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