Designing first model

Hi,

I'm trying to design and print my very first project. Perhaps this is a bit complex for a first model but the thing I picked has a couple special requirements that are making it harder to design due to my lack of experience and the fact I never held a 3d printed model on my hand. So, I do not know exactly how precise I can be or exactly what is strong enough for my needs.

Assuming the white, strong and flexible material, here are my questions:

If I design a 2-4cm wide pen (just a tube) just how thin should I make the walls to make sure it's strong enough not to break when using it (e.g. writing or letting it fall)? Just for comparison sake, what should be the wall thickness to be (or feel) as strong as a standard BIC pen?

Second part, I need to put electronics inside that tube from one of the ends. Additionally I need to have a couple buttons on the tube body. So, I plan on having a rail that allows me to put the stuff inside some one of the cap ends. Ideally this wouldn't be such a problem if I didn't need the push buttons that are part of the body to match my tactile buttons on the circuit. The button looks like this but without all the spring stuff.

So, my "rail" (I dunno the technical term for this type of fit/mechanism) should look like this and this. And the draft schematics are this and this.

What I don't know is how well the second part will fit and move on the main body and how much clearance should I give in this case. I don't plan to print those 2 parts near each other. In those schematics the head of the T has 5mm, if on the other part I give that face 5mm length will it fit well or should I give some clearance as it's shown on the current sketch? How much clearance?

To be clear, I plan on putting a tactile button and using the rail to make sure it will be aligned with the button. Also the length of the button "pin" and the head of my tactile button must meet precisely enough so that neither the button goes out of the body too much, neither it's pressing all the time. A push button has something like a 0.3mm activator.

Recently I was in the same position, needing to design something for printing in WSF without really knowing the material. What I did:
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[*] Ordered the sample kit Basic Kit. Included is a 25 USD gift card, which I later used for the order of my own design.
[*] Read the design guidelines for WSF. Note that the Basic Kit, mentioned above, contains a card for each material also with design guidelines. They are slightly different. For example minimum clearance according to the card is 0.6 mm while according to the web it's 0.5 mm. I designed according to the data on the web, which I assume to be up to date. Some of my parts are interlocking. The guidelines that I used: min. wall thickness 0.7 mm, min. clearance 0.5 mm, accuracy ± 0.15 mm
[*] Designed and ordered variations of the same parts. Some work quite well, others not so much. Getting the first 3D model designed was a mental challenge. Creating the variations, on the other hand, was rather straight forward.
[*] Made sure that my parts pass the automatic tests when uploading. These tests can be circumvented using the new Print It Anyway feature, but I was not interested in that.
[*] Yesterday, I made some stress tests with a part that I don't need. For example, I put the part in hot water that was nearly boiling. Then I bent the part strongly. In the end, I am quite satisfied with the material. Only it's a pity that it's not available in solid black.
[*] For comparison, I sent some of the same 3D models to fabberhouse, for FDM printing with ABS. I expect to receive my order next week.
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In a nutshell, I suggest: Experiment!

Check the price: If you pack everything to >10% density, then you get the 50% rebate, and printing variations may not be that expensive.

Only for strong and flexible and only if the volume to be printed (i.e. material used) is greater than 20 cm3.

When trying to decide on things like this, I reach for a caliper to get an idea of the very small dimensions. Also keep in mind that if you use 0.5 mm of clearance, then - if printed perfectly - the part would wiggle left and right by 1 mm, quite a lot!

In any case: Be sure that the outside and the inside part are oriented in the same direction. Because: The printer has different tolerances in different directions. I realized that small circles can come out as ovals if oriented vertically. In the x-y-plane, i.e. horizontally, you should get the highest precision.

Thanks,

I was started to believe creating some "cross sections" and ordering some variations would be the best bet anyway.

@ feklee
iirc I saw somewhere that orientation doesn't really help in these cases because they will print several models in the same session. Thus orientation "alignment" might not end up as the real orientation in their session. I guess it's not something we should rely on. Check it out

I am aware of the fact that Shapeways may print your model in any orientation. In fact that's where my recommendation stems from: Put all parts in one 3D file. Inside of that file, orient in the same direction those parts that need to fit.

I see, they will printing my entire file aligned as in the file! However, this still poses a problem if I need to print with different materials (e.g. different colors) yet, still nice to know.

Maybe there should be a wiki for people to add these details and/or explain things better. Sometimes their documentation leaves some details out