Bevel gear - module/script/tutorial

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looo
Posts: 2394
Joined: Mon Nov 11, 2013 5:29 pm

Re: Bevel gear - module/script/tutorial

Postby looo » Thu Oct 22, 2015 9:47 pm

I tried to make a 60° 3:1 bevel gear transmission. I used part-design to make the base geometry and at the end I used an intersection of the geometry with the bevel gear from the gear-wb to cut the teeth. This procedure works quite good, but there might be some better solutions. The boolean intersection for the bigger gear needs quite some time.
Also I have found a error with the clearance. This should work with the latest code from git. But still it is very difficult to set the right amount of clearance. There should be a better way to set this.
bevel_gear.png
bevel_gear.png (167.03 KiB) Viewed 3314 times
Attachments
depgraph.png
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looo
Posts: 2394
Joined: Mon Nov 11, 2013 5:29 pm

Re: Bevel gear - module/script/tutorial

Postby looo » Thu Oct 22, 2015 9:58 pm

do you know I can retrieve the pitch angle value?
The pitch angle for a 90° transmission is easy. it's something like arctan(z1 / z2) where z1 is the number of teeth of the first gear and z2 is the number of teeth of the second gear. For any other "transmission angle" you can use the sketcher to find out.
I have attached a file which shows how to get the data for the gear I have posted in the last post. (3:1, 60°)
pitchAngle.png
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mafer78
Posts: 56
Joined: Sat Sep 26, 2015 2:12 pm

Re: Bevel gear - module/script/tutorial

Postby mafer78 » Fri Oct 23, 2015 10:28 pm

Hi looo ,
thanks for the great info.

In attachment the first attempt to do bevel gear following your wb and method , in the image we can see also a mesh download from traceparts portal
( http://www.tracepartsonline.net/%28S%28 ... RsltType=4 )

what I see is the different form of the teeth, How can adjust/change it?
the other think is the tilt, how can adjust/modify/change the tilt on top and down of the teeth?

is the teeth that your gear wb design Gleason type?

backlash: not working properly for bevel gears as it is difficult to define the mean profile of the shape. it's a factor which makes the teeth thinner
Could be possible to have different profile of the teeth (Gleason and other, I don't know if others exist)?

alpha: 90° - pressure angle (this is a little bug I have never corrected) , my pressure angle is 20° when I try to change this value an error appear, could you help me with a fix of this parameter?

I'm waiting your feedback.

//mafer
Attachments
bevel_campare.JPG
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looo
Posts: 2394
Joined: Mon Nov 11, 2013 5:29 pm

Re: Bevel gear - module/script/tutorial

Postby looo » Sat Oct 24, 2015 7:04 pm

what I see is the different form of the teeth, How can adjust/change it?
set alpha to (90 - pressure angle). In your case this would be 90 - 20 = 70. I have corrected this and renamed "alpha" to "pressure angle". If you download or pull from github [1] this will be updated.
the other think is the tilt, how can adjust/modify/change the tilt on top and down of the teeth?
What is exactly meant with the tilt?
Could be possible to have different profile of the teeth (Gleason and other, I don't know if others exist)?
There are several different tooth-profiles for bevel-gears. My bevel-gear is made from spherical involute profiles. Cutted gears often have octoid tooth shape. I think some cad-tools also use an equivalent cylindric involute.
The spherical involute is made by unwrapping a cone. [2] The math for the spherical involute I used is from this paper (german) [3]. I have also added a link to an interesting document which deals with this topic. [4]
I have no idea which profile Gleason uses.

[1] https://github.com/looooo/FCGear
[2] viewtopic.php?t=4829&start=30
[3] http://geb.uni-giessen.de/geb/volltexte ... _01_16.pdf
[4] http://ijiepr.iust.ac.ir/files/site1/us ... 53108c.pdf
mafer78
Posts: 56
Joined: Sat Sep 26, 2015 2:12 pm

Re: Bevel gear - module/script/tutorial

Postby mafer78 » Sat Oct 24, 2015 9:29 pm

I've download the last version and is great, now is clear for me , many thanks

regarding the tilt , see the attachment image

sorry the the gleason is a system that regard high perform catch gear and not really the tooth profile instead coming in deep on the tooth profile in attachment an image for a product that I concern in my project, could be possible have also this type of tooth profile?

I'm vary happy and to be grateful

//Mafer
Attachments
bevel_campare1.JPG
bevel_campare1.JPG (41.44 KiB) Viewed 3225 times
tooth-profile.JPG
tooth-profile.JPG (65.89 KiB) Viewed 3225 times
looo
Posts: 2394
Joined: Mon Nov 11, 2013 5:29 pm

Re: Bevel gear - module/script/tutorial

Postby looo » Sun Oct 25, 2015 12:54 pm

regarding the tilt , see the attachment image
Use the "Part Design" workbench to make the base geometry. Take a look at the example quick61 showed some posts before. There are also many tutorials on youtube how to use the "Part Design" features. So you simple create the a revolved sketch without the teeth. For the sketch use the z-x or y-z Plane because the gear created from the bevelgear button will allways be aligned in z-direction. The "center point" of the gear is allways the origin.

After you are done with the base-geometry you create a bevel gear from the gear wb. choose the parameters you need. Make the gear overlapping. If needed boolean union a cylinder to the gear so that it is totally overlapping the previous created geometry.

The last step is to boolean intersect these two objects. I have added an example to github where you see how it is done. https://github.com/looooo/FCGear/blob/m ... d?raw=true

sorry the the gleason is a system that regard high perform catch gear and not really the tooth profile instead coming in deep on the tooth profile in attachment an image for a product that I concern in my project, could be possible have also this type of tooth profile?
As far as I know spherical involute is quite good for bevel gears. There exists other forms because the cutting machines often can't produce the spherical involute exactly. But I think it doesn't make much sense to introduce other profiles for bevel-gears. What's the reason for the need of this special tooth profile?
mafer78
Posts: 56
Joined: Sat Sep 26, 2015 2:12 pm

Re: Bevel gear - module/script/tutorial

Postby mafer78 » Sun Oct 25, 2015 1:18 pm

Really many thanks for all of you

great example file, the last question is if with your example file I can create a bevel gear like as we can see in the image attached.
I based my project on this type....inside the image there are some italian word sorry you not consider.

Is it possible to use your example file with the explanation coming from you and quick61?
I can obtain a same bevel gear type as depicted in the image?

BR
Mafer
Attachments
bevel_gear_selected.JPG
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looo
Posts: 2394
Joined: Mon Nov 11, 2013 5:29 pm

Re: Bevel gear - module/script/tutorial

Postby looo » Mon Oct 26, 2015 11:53 am

great example file, the last question is if with your example file I can create a bevel gear like as we can see in the image attached.
I based my project on this type....inside the image there are some italian word sorry you not consider.
The example I have made isn't fully parametric. So you can't only change the parameters to get the gears you are looking for. You have to correct every step... So it's better to create it from scratch.

I have tried to make the gears from the table you have posted. For the geometry I get slightly cutted tooth-heads for the bigger gear. Maybe the profile is shifted for these gears to reinforce the smaller gear. But there isn't any information on this in the table. You can have a look. I have uploaded the files here:

https://www.dropbox.com/s/nxmgd56nbm5sv ... fcstd?dl=0
https://www.dropbox.com/s/1hus655fwxs2a ... fcstd?dl=0
https://www.dropbox.com/s/gqtsqkqnsd45j ... fcstd?dl=0
mafer78
Posts: 56
Joined: Sat Sep 26, 2015 2:12 pm

Re: Bevel gear - module/script/tutorial

Postby mafer78 » Mon Oct 26, 2015 8:09 pm

simple great....many thank.

I try to found info regarding what you said for cutting tooth from the catalog and I found only what is depicted in the image attached, could you update the files according to the new table e parameters.

I use your files and/or bevel gears for design also a box gear.Could you think that I can use it?

br
//mafer
mafer78
Posts: 56
Joined: Sat Sep 26, 2015 2:12 pm

Re: Bevel gear - module/script/tutorial

Postby mafer78 » Mon Oct 26, 2015 8:24 pm

sorry i put here the attachment
Attachments
bevel_gear_new.JPG
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