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Gears, speed ratios, rack and pinions at cnc, someone manufacturing it?

ricardo_gt

Aluminum
Joined
Aug 5, 2012
Location
Portugal
I have a work proposal, well paied, at a huge company. The job is to fabricate gear boxes with cnc lathes, for a big automotive brand. I have only once done something related so, i do not know the secretes of the trade... my question is, what is it to know? Specific tools, technical info, time curve to learn what it takes? Should i refuse it or try the risk without knowing all there is to know?
Thanks.
 
More information would be great. :)

Will the gearbox be for a drivetrain? To run a windshield wiper? Something else? How large, how small, how complex, what power handling capability?

What "lathe"? Mill/turn? Live tooling? Y-axis? Twin-spindle?

etc.


thx
PM
 
It will be drive train gears, for one of the biggest automobilist brand in the world.
I will be a machinist at one of the automotive manufacture fabric, so i guess they will have all the methods provided, however, as a machinist i do not know for sure what is needed to know about it.
Someone with experience on the trade can tell.
 
ricardo_gt,

You mentioned “gearboxes” and lathe in your first post.

If you are investigating gear manufacturing specifically (not the entire transmission or “gearbox”), then about the only thing a lathe will get used for is making blanks.

Gear cutting methods are very mature, at least when it comes to involute based gear design (which probably covers 99% of the gears in existence). This would include spur, helical, bevel, spiral bevel and hypoid gears.

Hobbing and shaping would be the primary methods of spur and helical gear cutting (external gears) — and shaping (blind holes) and broaching (through holes) for internal gears. These “methods” (admittedly with machines modernized since the advent of CNC controls) remain fundamentally and geometrically unchanged for almost 100 years. Cutting tools and cutting oils have improved, so manufacturing cycles times have come down, however the general methods remain unchanged.

There are newer and possibly faster methods of gear cutting which can work well (under “certain” circumstances), namely: gear skiving and gear skudding.

And of course, external splines can often be “formed” via rolling… which is very fast, though does not lend itself well to full depth gears with pressure angles below 45°.

Large, specialty gears can be cut in a 5-axis CNC milling machine, though this is not a process which would be used in mass production (far too slow).

For highly accurate gears, grinding is a common “follow-up” in the complete manufacturing process — where a gear is typically cut slightly oversize in a “pre-grind” form, then heat treated, then ground. Once again, this is also a very developed process, (though once again has improved with the advent of CNC controls).

PM
 
It will be drive train gears, for one of the biggest automobilist brand in the world.
I will be a machinist at one of the automotive manufacture fabric, so i guess they will have all the methods provided, however, as a machinist i do not know for sure what is needed to know about it.
Someone with experience on the trade can tell.

If working in a big auto or tier1 facility they will have all the equipment and processes documented with rules and written instructions on how the work is to be carried out.
There is no room for "do it your way" or improvisation here.
Everything down to how to remove chips from the machine will have a "SWI" (pronounced "swee", standardized work instruction) and all measuring will have rules to be followed.
Gear making is high precision work but all the steps will be laid out and there will be a paperwork, traceability, and audit system to make sure you are following the process to the letter.

Such a place will have to be IATF certified which is ISO:9000 on steroids.
Mostly in such places the only true machinists are skilled trades toolmakers and such which are support staff and they do not actually make auto parts.
It is a very different world now compared to the old days.
Bob
 
ricardo_gt,

You mentioned “gearboxes” and lathe in your first post.

If you are investigating gear manufacturing specifically (not the entire transmission or “gearbox”), then about the only thing a lathe will get used for is making blanks.

Gear cutting methods are very mature, at least when it comes to involute based gear design (which probably covers 99% of the gears in existence). This would include spur, helical, bevel, spiral bevel and hypoid gears.

Hobbing and shaping would be the primary methods of spur and helical gear cutting (external gears) — and shaping (blind holes) and broaching (through holes) for internal gears. These “methods” (admittedly with machines modernized since the advent of CNC controls) remain fundamentally and geometrically unchanged for almost 100 years. Cutting tools and cutting oils have improved, so manufacturing cycles times have come down, however the general methods remain unchanged.

There are newer and possibly faster methods of gear cutting which can work well (under “certain” circumstances), namely: gear skiving and gear skudding.

And of course, external splines can often be “formed” via rolling… which is very fast, though does not lend itself well to full depth gears with pressure angles below 45°.

Large, specialty gears can be cut in a 5-axis CNC milling machine, though this is not a process which would be used in mass production (far too slow).

For highly accurate gears, grinding is a common “follow-up” in the complete manufacturing process — where a gear is typically cut slightly oversize in a “pre-grind” form, then heat treated, then ground. Once again, this is also a very developed process, (though once again has improved with the advent of CNC controls).

PM

Thank you sir, that was the answer i needed to read ;)
 
If working in a big auto or tier1 facility they will have all the equipment and processes documented with rules and written instructions on how the work is to be carried out.
There is no room for "do it your way" or improvisation here.
Everything down to how to remove chips from the machine will have a "SWI" (pronounced "swee", standardized work instruction) and all measuring will have rules to be followed.
Gear making is high precision work but all the steps will be laid out and there will be a paperwork, traceability, and audit system to make sure you are following the process to the letter.

Such a place will have to be IATF certified which is ISO:9000 on steroids.
Mostly in such places the only true machinists are skilled trades toolmakers and such which are support staff and they do not actually make auto parts.
It is a very different world now compared to the old days.
Bob

That clarifies my thought too, thank you.
 








 
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