Please add more timing gear profiles to FCGear - Most important T5 is missing

[azalanono]

Hello, looooo.

I was very surprised to find timing gears in FCGear workbench after doing an update. (I also upgraded to FC 0.19). I was waiting so long for a way of creating timing belt gears directly in FC.

But having a closer look, I see only "GT" belt profiles. Could you, please, add "T" profiles? They differ a lot and are more suitable for handling higher forces, therefore I use them very often. Especially "T5" is more or less my standard - the T profile with 5mm pitch.

I placed a feature request in "freecadweb.org", too, but I was suggested to do it also here.

Why T profile:
The T-Profile is a very simple one, but it is also very common in Europe. It has a little bit less precision (compared to GT), but it helps nothing to be able to print GT gears and have almost no chance to buy a belt for it. So at least T5 would help me a lot, but there are also smaller pitches (T2, T2.5, ...)

My current way therefore is to use openscad (there a T5 generator exists), create only a ring of teeth with a big hole in center, export that as .obj, import that in FreeCAD, and embed it into my part (create a volume part from .obj). This is extremely complicated and often leads into FreeCAD crashing when I need to modify this part made of thousands of meshes.
This is no real fun.

It would be very helpful if I could create a T5 timing gear directly in FreeCAD.

For your reference, I attach an openscad drawing. This is a timing gear with 110 teeth. As it is configured, it perfectly fits T5 belts. If you need help, I can offer you some testing. I can print timing gears, test them with existing timing belts of T5, and give you feedback. Sadly it exceeds my knowledge on how to write code, so I cannot help you with extending your great FCGear module.

This is an openscad drawing:
Pulley_Generator-110Z-T5.scad.zip

Here I found a technical drawing for T5 profile
The profile of T5 timing belt: (https://lh3.googleusercontent.com/proxy/gZGO9QLk4KyEFlDIvBqJ7xr2yuW6ITHuOMzUUmjTUfOX4y93Rd6hEXQubBStCCYatTi6s1JnX1GtUVqwo8QxBNjME1XIkPUjL-41kh1xrXk-WDYEKOuCSCnuywYZr4sk7g)

I hope I can help you a bit. As mentioned, I can do physical tests for you if you do not have a T5 Timing belt at hands.If you add T5 to your FCGear workbench, I can pull an FreeCAD update, create a timing gear, and test.

Thank you in advance.

[azalanono]

I made a test right now - to show you how crazy it currently is:

1. create the timing gear profile in openscad
2. export as .stl file
3. import the .stl in FreeCAD
4. convert mesh into shape
5. convert shape into volume body

And now you have "something" that looks like a timing gear, but is a nightmare in detail. You can see this by all this lines on surface going in all directions. You are absolutely unable to chamfer teeth, or even drill a hole between teeth (for worm screw), not to mention subtracting more complex parts from this "something", i.e. a reciption for a shaft.
If you try, it is very likely that FreeCAD crashes hereby or does something wrong.

Therefore it is very important to me to get a plain, smooth part directly, all other things are - friendly named - crazy workarounds.

[AKielhorn]

I would like to second that request.

There is a whole family of timing belts: T2,5, T5, T10 and T20.

There is a similar family AT3, AT5, AT10 and AT20 for higher transmission power.

These two families are metric, the corresponding imperial sizes are XL, L, H and XH.

And in order to make it more interesting there are T1/5", T3/8", T1/2" and T7/8" as well.

You can find drawings of the profiles at Brecoflex.

I have a parametric model that I use as a template right now, but having these in the gears workbench would be a great improvement.

[AKielhorn]

I suggest a separate class TimingGearT for trapezoid.

Will look into it over the Easter Break but can't promise nothing.

[herrgerd]

I made a test right now - to show you how crazy it currently is:

1. create the timing gear profile in openscad

2. export as .stl file

3. import the .stl in FreeCAD

4. convert mesh into shape

5. convert shape into volume body

And now you have "something" that looks like a timing gear, but is a nightmare in detail. You can see this by all this lines on surface going in all directions. You are absolutely unable to chamfer teeth, or even drill a hole between teeth (for worm screw), not to mention subtracting more complex parts from this "something", i.e. a reciption for a shaft.
If you try, it is very likely that FreeCAD crashes hereby or does something wrong.

Therefore it is very important to me to get a plain, smooth part directly, all other things are - friendly named - crazy workarounds.

You can generate the openSCAD model directly in FreeCAD so you don't have to go the "import .stl" route. See here.

I made a short screencast for you:

[azalanono]

Hello, herrgerd.
Thank you for this suggestion.

There is only one problem:
I have tried to do that more than one time. It never worked.
This may work on Windows with fully installed programs, but I am running Linux (openSUSE Leap 15.2 x64) and have only appimages. Each appimage for itself works (openscad and freecad), but I never managed to import an openscad file into freecad.

Even when this would work (I would be happy with that), it is still a workaround in my eyes. Sadly it does not work at all, therefore my request.

[herrgerd]

Hello, herrgerd.
Thank you for this suggestion.

There is only one problem:
I have tried to do that more than one time. It never worked.
This may work on Windows with fully installed programs, but I am running Linux (openSUSE Leap 15.2 x64) and have only appimages. Each appimage for itself works (openscad and freecad), but I never managed to import an openscad file into freecad.

Even when this would work (I would be happy with that), it is still a workaround in my eyes. Sadly it does not work at all, therefore my request.

There was a period last time I checked where there was a missing dependency called ply: https://wiki.freecadweb.org/OpenSCAD_Module

Seems fixed in windows, maybe installing this package does work for you on Linux too?

[azalanono]

Hello, looooo.

I noticed right now that I posted this two years ago. Yesterday I had to re-install the FCGear workbench because I upgraded to FreeCAD 0.21.1, so I also checked if (and what) has changed in FCGear. It appears to me that absolutely nothing has changed, I still cannot find any profiles for trapezoid timing belts.

Would be great if trapezoid profiles will find into your AddOn, because all other things it offers are really useful, only this different profiles are missing.

[azalanono]

With normal gears, I want to suggest adding a feature for chamfering teeths from the side.
If you buy gears, they all have a little chamfer on teeth. For 3D printing, this chamfer is very important to prevent "elephant feet", occuring mostly on resin printers, but sometimes also on filament printers
I tried marking the side areas in FreeCAD in the chamfer tool, but - as many things in FreeCAD - there are massive problems with bigger objects, having a high number of edges. So it would be better to do that during generation of the gear.

[looooo]

So it would be better to do that during generation of the gear.

I am not sure how to do this. And I think there is not much improvement if this is done via scripting. Best is to create a cylinder with same size as the gear an chamfer the edges. Then make a boolean intersection to get the chamfered gear.

you can access the properties via:
InvoluteGear.da / 2 for the radius of the cylinder
InvoluteGear.height for the height of the cylinder

I tried this with a gear with 200 teeth and it was computed in 20

sec.

[looooo]

@azalanono do you have a drawing of t5 gear or belt? What properties are needed? For the other timing gears we have only height and number of teeth. Is that enough?

[azalanono]

Happy New Year to everybody!

Looooo, What you show in your screenshot is my current approach. Sadly this bears the problem that teeth can still be overextruded in the lower region, where they touch the build plate. The same happens much more drastically when printing the gear on resin printers (-> elephant leg on first layers because of over-exposure).
This burr prevents correct matching of two gears. As solution I have to manually file away this burr which is no fun at 100-200 of small teeth.
What you describe/suggest I currently do on entire tooth therefore, but this means that the tooth is printed without support, because support is not possible. to not loose too much width, I have to use very little angle, this results in poor appearance.

Therefore my idea is to chamfer the entire tooth along its complete shape only a very little bit (i.e. 0.4 - 0.5 mm). So the core of tooth is starting on build plate, but because if its recess it is printed without a burr. See below picture. this is how I imagine the final tooth.

Of course, this chamfer has to be on both sides of teeth.

Trying that wit gears of >100 teeth and undercut etc. almost always makes FreeCAD crash when I try that by chamfering an area (so all edges are marked automatically). So it is for sure smarter to do this chamfering during generationg the teeth.

Advantage of this way: ll teethstart flat on building plate, but the chamfer (over-)compensates otherwise occuring overextrusion/elephant leg completely, I do not have to use a fine file to clean all teeth by hands after printing.

Hope I could explain what I mean.

[looooo]

I am sorry but this is not possible with how the gear is created. The creation of the gears should be fast, and such an operation is time-intensive with both python-scripting or freecad-gui.