Non circular gears

[zafarsalam]

Hi all,

I am visiting this forum after a long time. Need some help and advise. A customer brought these gears to me for cutting on wire edm. We don't have any drawings and just the gears to get the dimensions from. This is the first time I am cutting non circular gears on my wire edm. I need dxf data for the gears' 2D profile. Can gearotic draw these gears, if not then how do you suggest I design it.

Zafar

[BobL]

Zafar;
 
  Not sure if this will work, but here it goes anyway... In GM, select the GTA tab, now select the tooth count required, you may be able to come close of your original gear design by varying the wheel order, eccentricity and modification coeeficient within this tab. Once your satisfied, select tooth wheel and/or tooth pinion to generate the teeth. Resolution should only be increased if any loops exist in the teeth you just generated, beware the higher the res, the longer it takes to generate. If all is good, generate your dxf through output manager. Anyhow hope this helps, if it doesn't not sure how you'd do it... Some information does exist in the pdf document within GM, or you can search the forum.


Cheers
Bob
:)

[zafarsalam]

Zafar;
 
  Not sure if this will work, but here it goes anyway... In GM, select the GTA tab, now select the tooth count required, you may be able to come close of your original gear design by varying the wheel order, eccentricity and modification coeeficient within this tab. Once your satisfied, select tooth wheel and/or tooth pinion to generate the teeth. Resolution should only be increased if any loops exist in the teeth you just generated, beware the higher the res, the longer it takes to generate. If all is good, generate your dxf through output manager. Anyhow hope this helps, if it doesn't not sure how you'd do it... Some information does exist in the pdf document within GM, or you can search the forum.


Cheers
Bob
:)

Bob,

Thanks a lot for the help. I've already tried demo version of gearotic. I can recreate the shape of one of the gears with it. But the problem here is that the mating gears are of different shapes (their number of teeth are same). I can recreate the pitch curves of both the gears by rolling a master gear around them and recording it's displacement. Looking for a software to load the pitch curve and generate the tooth form from it. Any suggestions?

Zafar

[BobL]

[/quote]
I can recreate the shape of one of the gears with it. But the problem here is that the mating gears are of different shapes (their number of teeth are same).
[/quote]


Zafar

  Not sure if software of such nature even exists out there, you may be up for a challenge on this one, Sorry, I can't help.


Cheers
Bob

[BobL]

Zafar;

I know Art is working on something similar in the re-write of GM but it is all in priliminary stages at this point, I'll make sure to mention it though upon his return.

You said  " I can recreate the shape of one of the gears with it. But the problem here is that the mating gears are of different shapes" 

Correct me if I'm wrong, but doesn't the mating gear shape have to be one of a kind in order to roll around the primary gear as long as the shaft centers match?

Bob
:)

[zafarsalam]

Correct me if I'm wrong, but doesn't the mating gear shape have to be one of a kind in order to roll around the primary gear as long as the shaft centers match?

Bob,

It can be observed in the attached pic too. The gear pair on the left is the one I am talking about. When I roll both the gears together, the center distance is 110 mm all around. I am planning to create the pitch curve for the second gear by rolling it around the first one with the center distance. The tooth profile can be drawn in a CAD software by rolling a circular gear of same module on the pitch curve. But that would be a very tedious operation. I would have to draw gear profiles for all the 80 teeth manually. That's why I am looking for some automated software to do it.

Zafar

[BobL]

When I roll both the gears together, the center distance is 110 mm all around. I am planning to create the pitch curve for the second gear by rolling it around the first one with the center distance. The tooth profile can be drawn in a CAD software by rolling a circular gear of same module on the pitch curve. But that would be a very tedious operation. I would have to draw gear profiles for all the 80 teeth manually. That's why I am looking for some automated software to do it.

Zafar

Zafar

I understand, this is why I suggested the GTA module at first, one click would generate the secondary wheel from the primary wheel.. If primary gear is right, it leaves only one possibility for the secondary (pinion)gear to mate.  Anyway, if I come accross something similar, I'll let you know.

Cheers
Bob
:)

[John T]

This set was created from the GTA tab.  The pinion is 100% controlled by the gear and although they look like they are the same they aren't but they do mesh just fine.

John

[ArtF]

Zafar:

  It can be very very hard to do such a gear as your photos show. There is no accepoted method of figuring out the modification proceedure or elliptical formulation used for a non-circular gear. No one measurment will tell you what youd need to know to duplicate someone elses gears. GM cannot yet do rotational analysis ( which is what youd need to figure out what the actual calculus is behind the gears shape.. )

Art