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Posted · Ultimaker - Black Edition

Guys, on my CAD there are some unfinished drawings of aluminum arms with better embeddind of the bearings.

I've not manufactured nor tested them up to now but if you're interested I would post them...

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Posted · Ultimaker - Black Edition

Great!

here is a first draft I did a while ago.

Idea is to just exchange the side arms and keep the other ply stuff as you can see in the rendering.

Bed Mod

 

The Alu arms have slots as it is difficult to manufacture the pockets for the stage.

I have to generate the dimmensional drawings and will post them soon :-)

 

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Posted · Ultimaker - Black Edition

Do you think that they Z stage should be more ridged? Some thing like:

An Alu plate top and bottom that holds the ends of the shafts possibility with some way to adjust for parallel-ness and then the captive bearings should be rigidly mounted possibly with some adjustment to ensure they can be made parallel?

 

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Posted · Ultimaker - Black Edition

My intention was to get the stage stiffer from bending as simple as possible with no additional parts. So to mount you just have to

- press-fit the two bearings from top

- mount the other parts should fit as they are currently mounted

Anyway - as it might be difficult in my workshop to produce the holes for the bearings accordingly, the second approach is to make additional holes from the side and use a nail e.g. to fix them in the horizontal position.

B.t.w. another possibility: wait for the release of the original UM heated bed and hope that they also included a fix for the table...

 

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Posted · Ultimaker - Black Edition

My intention was to get the stage stiffer from bending as simple as possible with no additional parts.

...

 

I started with that thought, too. But when I assembled my second z-stage for reference purposes, I decided to completely ditch the standard wooden parts and replace all of them. I'll keep the lead screw nut because these are pretty expensive. Mounting this one is a bit tricky, but I found that the parts with flanges use like 5mm mounting holes. Why 5mm?? And M5 screws don't even fit because the holes are too close to the body of the part...

I did also ditch the linear bearings, and for two reasons:

1. The UM original bearings seem to be very low quality. I will check all four I have as soon as I take my first UM apart. But the one I compared to a Misumi bearing was just awful.

2. Mounting gets a lot easier with flanged bearings.

So, I will use flanged bearings which are easy to mount (they also have huge mounting holes, but I'll get them fixed somehow...) because they have a "pilot / guide". And, I will use two bearings per shaft, one on top and one on the bottom. This will add more rigidity because overall, the length where the z-stage is fixed to the shafts is longer. (about 100mm height compared to 70mm original). So yes, I will lose some build height, but I can live with that and it happens anyways with the heated bed.

Here's my WIP:

Z stage assembly WIP

Seems a bit messy, but it's just Sketchup... I only draw every unique part. The arms for example are ambidextrous, so I won't draw the right one...

These parts are 2mm thick, the idea is to have them made of chrome steel or some hard aluminum alloy. Should make for a nice rigid part...

I used the same mounting technique as the original UM parts (but with square nuts, I wonder why they don't supply square nuts with the kits...).

Endstop "plungers" will be screws added at the correct position (easy length adjustment).

As you can see, I took a lot of inspiration from the UM2 but made it much more rigid (the UM2 doesn't have the side arms at all).

/edit:

By the way, I'm using three point levelling with M4 screws and much stronger springs. This should make it possible to level (my first machine can not be levelled perfectly because four point levelling just doesn't work) and remove most of the wobbling / rattling.

/edit2:

Forgot to mention: The current design is made for CNC milling with a 2mm tool (I hope that works for chrome steel, I have no idea...), that's why there are a lot of "unncessary" dents in the parts. If possible, I want to have the parts lasered which will simplify the construction a bit.

If the thing works and I publish it, I will keep both versions and maybe even add versions for different material thicknesses. It shouldn't be too difficult to just make this out of 6mm plywood instead of metal.

/edit:

Just ordered the linear bearings needed for this setup... They should arrive May 16th.

 

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Posted · Ultimaker - Black Edition

Do you think that they Z stage should be more ridged? Some thing like:

An Alu plate top and bottom that holds the ends of the shafts possibility with some way to adjust for parallel-ness and then the captive bearings should be rigidly mounted possibly with some adjustment to ensure they can be made parallel?

 

For now, I didn't include any notable tolerances where you could adjust anything. Instead, I hope that a rigid, precision lasered or CNC'd construction will actually be parallel and make any adjustments obsolete.

I don't know if that works in practice, I'm not a mechanical engineer...

/edit:

It may be wise to save as much weight as possible on the parts which are far away from the shafts, but add as much weight as possible near the shafts. Stupid thing is, the build platform will be exactly the opposite of that... :(

 

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Posted · Ultimaker - Black Edition

Hi Jonny, your pic of the platform is private. Can you make it public? I'd like a closer look.

I don't know about the parallel-ness in practice. I guessing that was a problem with the plywood and that is why one side of the platform is rigid and the other side floats in the XY direction.

I'd be interested to know how you go about getting parts laser cut. I've wondered if you could take the laser patterns for the plywood and just send them to a place to have the same parts cut from alu or some other material.

 

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Posted · Ultimaker - Black Edition

I'd be interested to know how you go about getting parts laser cut. I've wondered if you could take the laser patterns for the plywood and just send them to a place to have the same parts cut from alu or some other material.

 

That depends on how the original files are made. The laser beam has a given thickness, usually around 0.1 mm, so common practice is to offset certain parts inward/outward to get a tight or loose fit. When working with wood or plywood this is not so critical since it can easily be compressed with a little force if you missed something. You don't have that freedom with acrylic or aluminium so you have to be careful and plan ahead.

 

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Posted · Ultimaker - Black Edition

LOL, it's the first time (since 14 images) that someone tells me that this doesn't work -.-

Should be ok now, I set the gallery to public. I thought that wouldn't apply to directly linked pics...

Lasercutting steel is a whole different story than plywood or acrylic. It takes a laser that packs a bit more of a punch :)

As for the steel designs, I will do these so that a professional manufacturer can produce them. Means I will just draw the exact dimensions that I desire, and the manufacturer will do the adjustments.

If you want to make the same platform out of plywood, then there's a lot of changes that will be necessary. 2mm thickness will only work for something similarly strong as steel.

Also, a heated bed is pretty much a standard for upgraded printers, so I won't waste any time making drawings for materials which aren't heat resistant. Acrylic is not suitable imho, because it doesn't really like continuous heat while being under pressure.

The UM original files are made just for that purpose - lasercut plywood. That's why they don't bother much about tolerances - no avail with plywood anyways. Instead there's a lot of space between parts to allow for adjustment. Don't think that with plywood it can be done much better than the UM original files. The only way to improve the z-stage is to make it out of a more rigid material.

 

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Posted · Ultimaker - Black Edition

Looking at your various z stages, i cannot help but wonder: any arm that is more or less L-shaped seems in my opinion a lot less stiff than atriangular shaped arm. I assume the reasons for this are clear and i assume all of you are aware of that.

So: why do you design L-shaped arms if i may ask?

 

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Posted · Ultimaker - Black Edition

Just because you'd sacrifice a lot of build height if you do it any differently..

I hope making it out of 2mm thick steel will get rid of the problem.

Use brute force when elegance is not easy to achieve ;)

/edit

If it's not strong enough, I'll just use two 2mm steel sheets per arm...

(Use more brute force when brute force is not enough)

 

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Posted · Ultimaker - Black Edition

:-)

Brute force... yes, that´s right... sometimes needed...

Reg. the triangular shape mentioned by Burki, I thought also some time ago about a simple but (using "brute force") effective steel wire with a tensioning screw to be placed from one of the top screws of the arm diagonal down to one of the screws on the L bringing some tention into it.... and then I realized that there is a moving head/fan shroud which would give a nice crash... :-(

@ Jonny, the steel plate idea is good, but I would add a bit "stiffness" in the middle of the table part...

 

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Posted · Ultimaker - Black Edition

...

@ Jonny, the steel plate idea is good, but I would add a bit "stiffness" in the middle of the table part...

 

Thought about that, too. But 2mm chrome nickel steel is REALLY strong :)

I'm not yet done however. I'll probably take out some material from the bottom plate in order to save some weight. Then I'd need to compensate for the loss in stiffness by adding a center "wall" into the bottom plate. Kinda like copying the front wall into the center of the piece. Maybe even make one from the front to the rear, or instead of orthogonal, make them diagonal.

I'll see where it goes.. I usually don't plan my constructions much in advance but develop them as I go. Maybe not the best technique because I end up deleting stuff over and over, but I don't have the experience to be able to think up a good solution right from scratch...

/edit:

By the way, I'm surprised no one's screaming "WOOOT" yet when I say "chrome nickel steel". This z-stage will probably cost somewhere around 300 Euros, including build platform and heated bet assembly...

 

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Posted · Ultimaker - Black Edition

WOOOT :)

Also Jonny have you considered Carbon Fibre. One seller on eBay selling sheets of it offers a quote for laser cutting as well if you send your drawings.

 

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Posted · Ultimaker - Black Edition

Carbon fibre is very flexible, so the sheets would need to be fixed very well on all sides. Steel is much stronger...

I also ruled out carbon fibre plates for me because they have something like 85°C maximum operating temperatures. "Could" still be used, but it's not so beautiful... Also, 85°C max. operating temperature does not imply that the sheets can't become a little softer already, which would probably lead to deformation.

And then, there's the fact that carbon fibre plates are ridiculously expensive (depends where you buy them...). Maybe that evens out when you pay a lot for lasercutting cheap steel, compared to paying less for lasercutting expensive carbon.

I'd have to ask in the FabLab (got membership this week @ FabLab Zurich :D) if they can lasercut carbon fibre. That would make it worth considering. Thanks for the hint!

 

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Posted · Ultimaker - Black Edition

I' d like to come back to the L- or triangular arms.

From what i learned when i studied, practically every single millimeter you add at the bottom would help greatly. so, provided you keep the short end of the L upwards which does not offer much more than guidance, and you added say 10 millimeter at the bottom, then this would indeed sacrifive those 10 mm, but it shoult be a massive gain in stiffness of the arms.

Since you are designing your own printer, Jonny, and are still in the painting process ;-) you might redesign the 4 large vertical body parts to give back that height?

Thus you coult keep the lenght of the vertical arm of the L, but move it down by, say, 20 mm. use these 20 mm for a triangle. then, redesign your printer frame so your guiding rods sit 20 mm lower. thus you would have the same build volume.

Unless i am missing something important here?

And talking about stiffness, weight and cost: some space frame setup, 3d printed in aluminium or titanium should, in theory, be the thing to want, don' t you think?

I visited a company doing metal prints about a year ago. from what i learned that is far less expensive than one might think.

plus, printed metal cannot be beat in terms of coolness :-)

 

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Posted · Ultimaker - Black Edition

...

Thus you coult keep the lenght of the vertical arm of the L, but move it down by, say, 20 mm. use these 20 mm for a triangle.

...

 

You mean like this?

raised Z Arm

Sure, not pretty, but I mean the principle. Of course I'd make it more triangular than the "T" it is on the picture, but I was just scratching that up...

I think I understand why that would make the arm stiffer. You move the attack point of the lever?

The problem is, that for now I won't redesign the frame. I'd need to cut out that space in the bottom plate, make the 12mm z-shafts as well as the leadscrew longer, and add a construction which is sturdy enough to reattach these parts again a bit lower. The only reasonable thing would be to actually just lengthen all the side parts and make the shafts / leadscrew longer.

So, in the short run, my only option is to just sacrifice more build height if I want to go triangular. Maybe some time I will redesign the frame, but right now I need a working printer as fast as possible.

 

...

And talking about stiffness, weight and cost: some space frame setup, 3d printed in aluminium or titanium should, in theory, be the thing to want, don' t you think?

I visited a company doing metal prints about a year ago. from what i learned that is far less expensive than one might think.

plus, printed metal cannot be beat in terms of coolness :smile:

 

I'm already very pleased with lasercut metal parts :D

ETH Zurich has some steel sintering technology (I don't recall how it was called exactly). The chief mechanical engineer at "my" last company showed me a part which was made there. 90% the strenght of regular steel, but with almost microscopically small structures (it was a nozzle for an epoxy dispenser, making lots of little dots and including a particle filter).

Maybe.... What if I made the parts so that you can just choose whether if you want an L or T shape? I can make all the other parts in a way that they would fit both variants of side arms. This way I could make both versions and compare. I don't yet know how I'm going to get my chrome nickel steel lasercut, but if I get a somewhat reasonable price....

Or I could start with plywood dummies. I can do these at the FabLab almost for free. OR, maybe I can CNC-cut my beloved chrome nickel steel there... I doubt it, but I haven't asked yet (will visit the lab on friday evening).

/edit:

LOL

Actually I don't have to change anything at all in order to make a T out of the L:

Im using these bearings. (LHIFS12, choose 12mm and quadratic flange).

I'm planning on mounting them the same way as the UM2 does it: sitting on top of the bottom plate (the shorter end goes through the hole in the bottom plate which takes care of precise alignment issues).

Instead of that, I can just mount them to the bottom and / or turn them upside down, so that the longer side sticks out below. There you have the triangular shape :)

I could even make the whole thing lower again, and give the option to turn around the top bearing for more stiffness, or keep it as it is for more build height. Jeez such freedom :D

The arms themselves should well be stiff enough so that it doesn't matter if they stay "L" shaped..

By the way, I noticed that these bearings will stick out 4mm on the bottom even when mounted upwards. That's actually a mistake I made, but doesn't hurt much. However it does mean that I can add some more meat to the arms on the low edge.

/edit:

There are also longer versions of these bearings, so you have like 20 different height-, L-, T-, or whatever configurations :D

 

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Posted · Ultimaker - Black Edition

If you really want stiffness and are ok with going a slightly different route, duplicate the bearings, shafts and stepper in the front too. If you could figure out a way to capture the tops of the shafts in the corners under the XY axes, you could get them out of the way neatly tucked in the corners. With the second stepper, it would be really stiff.

 

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Posted · Ultimaker - Black Edition

I want to avoid that because there might be problems with this. See:

http://umforum.ultimaker.com/index.php?/topic/4177-improved-z-stage/

And I don't want to add a whole other leadscrew and motor in the front, because when I'm done, the front will be the only accessible side left to reach into the printer (crossflow fan).

It doesn't take that much more stiffness. The UM1 does work after all. Most important thing is to eliminate drooping by eliminating the wooden parts. And add as much stiffness as possible. But I don't think it's necessary to reinvent the wheel here..

/edit:

Just to pick up some thoughts from that other thread:

- I don't think that swinging in X direction (left - right) will be an issue with my current steel setup. The Misumi bearings are very tight, and the 12mm shafts definetly don't bend. They're rock solid.

- It could be possible to add one shaft in the front which doesn't go all the way up to the top, but reaches only just under ther x-y-gantry. But I don't really see the benefit of this so I'll leave this out for now.

- Adding more weight to the z-stage and the whole machine could make a big improvement. I will definetly experiment with that. There is some space in between the shafts and the leadscrew to add weights (Dim3nsioneer showed http://umforum.ultimaker.com/index.php?/topic/5541-let-your-um-original-gain-some-weight/ last week)

This, plus moving the lever attack point a bit upwards, should improve things more than enough. I hope :)

 

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Posted · Ultimaker - Black Edition

just one note: there is a large difference between an L-Shape and a triangular shape.

Consider the way forces are led through the material. you have a vertical force being led horizontally to the shafts. if it was truly horizontal, the force would be infinite. so, the greater the angle (if horizontal is zero), the smaller the resulting force. so, it's the height of the horizontal arm that matters, and most of all it's height at the bend.

that means if you have an L-Shape with the short arm pointing down, and draw a triangle on that, the diagonal shows you where the force goes (give or take some). meaning: if instead you used the complete available space to make a triangle (connecting the ends of the arms of the L), you can take a lot more force than without the diagonal.

Not sure if what i write here is anyhow understandable? :-)

 

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Posted · Ultimaker - Black Edition

I think I understand what you mean, and I will definetly try to improve the arm geometry based on your instructions. Thanks!

If I understand this correctly, then there are actually two different problems:

1. The arm itself must not bend

2. The z-stage as a whole must not be allowed to bend down, for example because of play in how parts are joined together, or play on the linear bearings.

Now, if I change the arm's geometry from a "hard T" with 90° corners into more of a triangle, then I will make the arm much stronger and prevent it from bending.

But, let's say the chrome steel arm is by far strong enough, even with a T shape, then I don't actually gain anything from this. Right?

I don't know if it is "by far strong enough". I suppose it is, because after all it's just going to be a few kg which shouldn't be a problem for massive steel parts. But nonetheless - I will of course optimize geometry as far as possible.

But this will not solve problem #2.

So, I think on one hand it is necessary to have high quality bearings and shafts with little to no play.

There are different tolerance classes, and the bearing must match the shaft in order for this to work. I don't know the specifications of the UM parts.

To be honest, I couldn't make out any differences in play between the UM shafts / bearings and their Misumi counterparts. The only thing I noticed was, that the Misumi bearings slide much smoother on the Misumi shafts than the original UM stuff. Maybe, just maybe (it's almost impossible to feel this by hand), the Misumi combo has a tiny little bit more play. That's probably because the shafts are g6 tolerance which is always slightly smaller than nominal. The UM standard shafts might be h6 which can also be slightly above nominal.

By the way, the UM bearings are still worse than the Misumi if both are tested on the Misumi shaft. So there definetly is a difference in quality.

I also have to note that I bought the "Eco" Misumi bearings which are cheaper, and not made in Japan. Maybe, the really good stuff from Misumi is even better (should be...).

And then, there's the matter of my construction. The different parts must be fit absolutely tight so that there is NO movement between the arms and the bearings. That's difficult, because the bearings are mounted to a part (possible play) which is mounted to the arms (more possible play).

This is where things get difficult for me, because I lack the experience and education of a mechanical engineer.

How do I reduce play between two steel parts mounted together?

-> clamping them together with two screws makes it stronger than if I just use one screw, right? So there's a weak spot on the top plate (see picture below) which has two "hooks" that go into the arm, but are only mounted with one screw.

-> The hooks will hardly fit 100% snug into their counter holes. But I have to make it as tight as possible. If I mill these parts, then I may have a big problem because I can't get the short sides of the "rectangular" holes straigt. They will instead have a 1mm radius.

So, lasercutting these parts should give me a better result than CNC milling them. I hope the costs won't be too high on this...

Ok, let's say I settle with lasercutting steel. If I specify the hooks to be 6x2 mm, how much tolerance should I give on the counter hole?

-> I expect that my drawings will be adjusted so that the lasercutter draws the "exact" dimensions I specify.

My approach would be to make the counter holes eaxctly 6x2mm, too, and fit the parts together with a hammer. Could that work? Maybe cooling the hook down with ice spray helps?

/edit: re-added the picture from before so you don't have to go look for it:

Z stage assembly WIP

 

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Posted · Ultimaker - Black Edition

I think your problem nr.2 is not that much of a problem.

Supposed you actually had play in the bearings. Your build plate has a weight > 0. so, there is always a force acting downward, thich can be idealized as originating from the center of the build plate.

the countering force is of equal amount in the opposite direction, but it is (idealized) in the center of your lead screw.

As you can see the two forces are opposed and parallel. So we have a momentum. That in turn forches the whole setup to rotate, if there is any play. resulting in the lower part of your bearing to be pushed towards the back, and the top towards the fromt of the machine.

As long as your bearings and rods are straight, this rotation (angle) will alwas be the same. An effect you already counter by levelling your bed.

The reason i try to talk you into a better shape (even though i do agree, your steel arms will most likely be more than enough) is that i think using cheaper and easier-to-handle material could also work, if you change the shape a bit.

after all, it's not the weight of the whole setup that requires the strength of the material, it's the buckling length, which you can either handle by very stiff material or by a smarter geometry, i.e. a space frame where you don' t get too extreme triangles.

Of course, none of these would be necessary if you supported your print bed by 3 lead screws instead :-)

 

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Posted · Ultimaker - Black Edition

About the play of two steel parts mounted together:

the way you are planning to clamp them, which is the same as it's done with the ultimaker parts, is not the problem. One screw or two mostly means you can apply more pressure. but if your fittings would fit each other nicely, you would not need the pressure to avoid play.

that would mean that your tongues going into the holes should fit exactly.

a fairly easy way to achieve that is long holes, crosswise: a vertical hole and tongue countering horizontal movement, and a horizontal pair countering vertical movement, while the horizontal pair can move horizontally, i.e. the hole is longer than the tongue, but both have equal height.

Given the fact that the holes are rounded and the tongues will be rectangular: you could design the tongues oversized and file them to a perfect fit (manually)

Or you could fill the gaps, for example with epoxy. that can be separated by heating to 250°+, if i remember correctly.

Just don't use cyanoacrylate if you want the parts to be separable. But i guess you knew that :-)

 

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Posted · Ultimaker - Black Edition

...As long as your bearings and rods are straight, this rotation (angle) will alwas be the same. An effect you already counter by levelling your bed...

 

Ok, suppose you're right..

 

...or by a smarter geometry, i.e. a space frame where you don' t get too extreme triangles...

 

Hmm.. Does it make a difference whether if I make a simple filled geometry, or an actual space frame (with the same contour)?

Of course the space frame would be lighter, but it would also be weaker than filled geometry, right?

I was thinking of using rounded shapes (similar to the state you've seen before), but maybe a bit smarter instead of just quarter circle segments... That was just the easiest thing to draw in Sketchup :p

 

...The reason i try to talk you into a better shape (even though i do agree, your steel arms will most likely be more than enough) is that i think using cheaper and easier-to-handle material could also work, if you change the shape a bit...

 

Fair enough ;)

It might even be strong enough with simple plywood, maybe just use two pieces per arm...

I will try to construct the parts with Creo Parametric, so that I can easily make variants for different material thicknesses. I still hate Creo because it's impossible to handle, but Sketchup is just not suitable for precision constructions..

 

About the play of two steel parts mounted together:

the way you are planning to clamp them, which is the same as it's done with the ultimaker parts, is not the problem. One screw or two mostly means you can apply more pressure. but if your fittings would fit each other nicely, you would not need the pressure to avoid play.

that would mean that your tongues going into the holes should fit exactly.

a fairly easy way to achieve that is long holes, crosswise: a vertical hole and tongue countering horizontal movement, and a horizontal pair countering vertical movement, while the horizontal pair can move horizontally, i.e. the hole is longer than the tongue, but both have equal height.

Given the fact that the holes are rounded and the tongues will be rectangular: you could design the tongues oversized and file them to a perfect fit (manually)

Or you could fill the gaps, for example with epoxy. that can be separated by heating to 250°+, if i remember correctly.

Just don't use cyanoacrylate if you want the parts to be separable. But i guess you knew that :smile:

 

I'd very much prefer a design that you can just put together, tighten the screws, and it's fine. I hope that's not too much to ask from a total noob designer, but I guess I'll find that out soon :)

Separating horizontal and vertical tongues seems to be the way to go if the parts are milled by CNC. The problem is, I have very little space on the top parts. And if I use only one vertical and one horizontal tongue, then the parts can be twisted.

I think I'll try to get it done with square, lasercut holes. Maybe I'll have to slightly file away the corners on the tongues, but the laser's radius should be very small so that it only takes a little bit. Maybe the radii can be eliminated in the lasering process by drawing the lines a little bit too long, but I should leave that to the laser-guy.

 

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