3d printable spool (for Helmoltz coils...)

[JiPe38]

Hi everybody.

This is my first freecad real part, so be indulgent please. Each of the two identical bodies (gray-blue) is one half of a spool. It's intended to support copper wires to create a magnetic field (Helmoltz coils) but the design could be used for other dimensions, other materials...

spool.jpg (87.11 KiB) Viewed 2536 times

spoolHalf.jpg (96.26 KiB) Viewed 2530 times

In order to be able to print on 3d printer, and cope with the hanging hot plastic problem, the spool has been cut in two identical parts . They are linked by interleaved teeth. On the internal side, the teeth have a hole. On the external side, the teeth have a clip which comes into this hole and make the assembly.

All the parameters are in a spreadsheet, named "parametres". Yes, it's french, but knowing the problems caused if I rename a spreadsheet once the model is built, I gave up and let it in french.

In a first design, I made a geometrical construction in "Sketch015" to shape the clip whatever were the dimensions of the teeth : too difficult. So I made a light construction, not exact on the geometric point of view, which allows to see if the chosen angle for the clip base is correct, not letting the edge of the clip come inside the internal overall diameter of the spool. I think it's better to leave this manual.

Thanks for comments and corrections if any.

spool.FCStd

(270.74 KiB) Downloaded 52 times

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4 (GitTag)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)

[Kunda1]

OP, please add screenshots and also add FC About info to your OP.

[galou_breizh]

Nice work!

I liked your design so opened it to see how you modeled it. I saw two things that think could be improved
- No alias for parameters
- Flat clips

So I improved this for fun. See the attached file. Can you please check that I didn't break anything?

spool.fcstd

(225.39 KiB) Downloaded 56 times

Gaël

OS: Ubuntu 18.04.3 LTS (i3/i3)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Python version: 3.6.9
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

[JiPe38]

Thanks for your mods : I learn a lot. Two remarks.

- I tried to change the width of copper zone to 30 mm and it failed. Looking why, I found that the sketches of the upper part of the tools were placed in position z = 9 mm still. Tried to change this to place them at height <<Parameters>>.flange_thickness + <<Parameters>>.width_of_copper_zone. It failed, I found this z placement impossible to modify. I don't know if it's something that can be adjusted just at sketch creation or if I miss a condition to be able to modify this.

- The clip positionning is a headhache. Very interesting exercice indeed. I prefered working by defining an angle, because when changing the tooth base widh, it changes the absolute angle of the tangents to this clip relative to axis z. This is functionnal, because when you clip the two spools together, you need that the effort be limited to a reasonable value, and also if you want to be able to disassemble the two half spool you need also a reasonnable effort. This effort condition is related to the ratio beetween the height in z of, say, the center of this clip, and the width of the teeth. Ideally, I should have fixed in the spreadsheet the angle of the clip tangent at the insertion point, relative to axis z, and same for extraction point. If anyone has an Idea to create a sketch of the clip which fulfills these conditions, I buy it

[Kunda1]

Please test using 0.19pre (since that is what the file was created in) and then report back.
You can easily do this via the AppImage

Also since this is a User Showcase thread, lets keep the discussion here related to showcasing. To discuss improvements and other logistics, please lets continue the thread in Open Discussions. If there is anything that comes of that, you can post the results back to this showcase thread. Make sense?

[galou_breizh]

- I tried to change the width of copper zone to 30 mm and it failed. Looking why, I found that the sketches of the upper part of the tools were placed in position z = 9 mm still. Tried to change this to place them at height <<Parameters>>.flange_thickness + <<Parameters>>.width_of_copper_zone. It failed, I found this z placement impossible to modify. I don't know if it's something that can be adjusted just at sketch creation or if I miss a condition to be able to modify this.

It's indeed working on my setup (package Version: 0.19~pre2~202001151537~ubuntu18.04.1). By the way, the version from "About FreeCAD" is broken it seems.

- The clip positionning is a headhache. Very interesting exercice indeed. I prefered working by defining an angle, because when changing the tooth base widh, it changes the absolute angle of the tangents to this clip relative to axis z. This is functionnal, because when you clip the two spools together, you need that the effort be limited to a reasonable value, and also if you want to be able to disassemble the two half spool you need also a reasonnable effort. This effort condition is related to the ratio beetween the height in z of, say, the center of this clip, and the width of the teeth. Ideally, I should have fixed in the spreadsheet the angle of the clip tangent at the insertion point, relative to axis z, and same for extraction point. If anyone has an Idea to create a sketch of the clip which fulfills these conditions, I buy it

Could you make a scheme so that it's easier for other to help fixing this?

Thanks,
Gaël

[JiPe38]

Please test using 0.19pre (since that is what the file was created in) and then report back.
You can easily do this via the AppImage

Also since this is a User Showcase thread, lets keep the discussion here related to showcasing. To discuss improvements and other logistics, please lets continue the thread in Open Discussions. If there is anything that comes of that, you can post the results back to this showcase thread. Make sense?

OK it makes sense. I will try this with 0.19.

[JiPe38]

I understand that to use 0.19 (appImage) I need Linux. I am with Windows 10... too many apps on windows, a single computer, no time to go to a dual boot solution, not enough neurons to shift from Windows to Linux environment : I need them for other tasks. I will wait for a 0.19 on WIndows.

[openBrain]

I understand that to use 0.19 (appImage) I need Linux. I am with Windows 10... too many apps on windows, a single computer, no time to go to a dual boot solution, not enough neurons to shift from Windows to Linux environment : I need them for other tasks. I will wait for a 0.19 on WIndows.

https://github.com/FreeCAD/FreeCAD/rele ... g/0.19_pre

[Kunda1]

0.19pre can run in parallel with 0.18.4
Just make sure to backup the files you created in 0.18.4 before opening them in 0.19 for obvious reasons.