follow focus gear in FreeCad

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jmaustpc
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Re: follow focus gear in FreeCad

Post by jmaustpc »

Its great that it worked out. :)

This would eb a good thing to post on the "show case forum", if you would like to
viewforum.php?f=24
evgeny_magata wrote: i assume there is minimal shrinking of the plastic when it cools down...
Yes, I think there would be.

Like you said though, not doubt it sticks on well. Perhaps if you wanted to experiment, you might find you could carefully heat the gear to less than its melting point, and then it might slip on more easily and then shrink down tight as it cools. That is the process that was used to fit steel rims/tyres on wooden horse cart wheels and various other applications.

Jim
muntus
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Re: follow focus gear in FreeCad

Post by muntus »

I want to thank everyone for their contribution on this topic! I'm a complete novice and had never even used any sort of CAD program until a couple of days ago, but I'm already printing gears for my lenses and they're just what I needed.

I would like to reduce the 90 degree angle on the sides of the gear. How would I chamfer(or bevel; don't quite know the right term) the edge so that it is less sharp? Thanks!
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bejant
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Re: follow focus gear in FreeCad

Post by bejant »

muntus wrote:I would like to reduce the 90 degree angle on the sides of the gear. How would I chamfer(or bevel; don't quite know the right term) the edge so that it is less sharp? Thanks!
If you want to ease the corners you could use Chamfer or Fillet and if you want tilt the entire side(s) you can use Draft in the Part Design WB.
muntus
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Re: follow focus gear in FreeCad

Post by muntus »

I want to just ease the corners. While in Part Design, I've tried to use Chamfer and Fillet, but they seem to do nothing. A chamfer or fillet is added to the design tree without a dialogue box popping up in the tasks view. When I right click to edit the chamfer, the only option it gives me is the chamfer parameters with a default of 1mm. I've tried changing the parameter with a number of different values and it seems to have no effect.

What do you think I'm doing wrong?
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bejant
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Re: follow focus gear in FreeCad

Post by bejant »

muntus wrote:What do you think I'm doing wrong?
I don't know, can you upload your file to the forum? There might be a modeling error in it...
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Re: follow focus gear in FreeCad

Post by muntus »

Here's an example of the focus rings I'm printing. After I pocket out the center hole, I have been unable to figure out how to ease the corners. I would like to shave the tips of the teeth down to the sides of the gear at an angle just so they are less sharp. I am in the Part Design workspace and I've tried using the Fillet, Chamfer, and Draft tools to no avail.

My file was too large for the forum, so here's a download link for Dropbox: https://www.dropbox.com/s/n8gs87m29euyu ... FCStd?dl=0

Thanks!
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bejant
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Re: follow focus gear in FreeCad

Post by bejant »

I made a tapered blank, then tried to use a boolean intersection between the original gear and my blank, but the boolean operation failed; maybe because of the bezier curves in the gear teeth.
20141103g.png
20141103g.png (10.81 KiB) Viewed 2216 times
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quick61
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Re: follow focus gear in FreeCad

Post by quick61 »

I think what you'll be wanting to use is the Part Design > Grove tool.

First you will want to set the first Pad, the one for the Involute Gear, to Midplane = true.

Make a pad to get a face to map a sketch to and place a sketch in the profile you want the edges of the gear to have like so.
Gear_Teeth1.png
Gear_Teeth1.png (4.9 KiB) Viewed 2207 times
Next apply the Grove tool and with the Axis set to Vertical sketch axis and an angle of 360* click the OK button.
Gear_Teeth2.png
Gear_Teeth2.png (32.07 KiB) Viewed 2207 times
Next select the Grove feature from the tree view and select the Mirror tool. remember that the first pad was set to middle plane? This is why. Mirror on the Horizontal sketch axis.
Gear_Teeth3.png
Gear_Teeth3.png (15.82 KiB) Viewed 2207 times
Now all that needs to be done is to Pocket away the little helper Pad and were done.
Gear_Teeth4.png
Gear_Teeth4.png (34.87 KiB) Viewed 2207 times
The Grove tool really comes in handy for applying these types of features, getting rid of sharp angels and such. This is often what is done with gears that have sharp edges, they are not filleted away, they are just knocked down with a turn on the lathe. Think of the grove tool like that, a lathe tool.

Mark
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bejant
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Re: follow focus gear in FreeCad

Post by bejant »

Nice Mark, thanks for that; I never thought of using the Groove tool...
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quick61
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Re: follow focus gear in FreeCad

Post by quick61 »

bejant wrote:Nice Mark, thanks for that; I never thought of using the Groove tool...
:) Thanks. Handy little thing that is often overlooked, especially by me at times.
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