Topping hob allowance

[esko001]

can anyone tell me what is minimu and maximum topping hob allownace for worm wheel manufacturng. I am using 0.5-0.6mm, but I wander if I can use 0.2-2mm. What would be the result of doing that? Cycle time only? feaibility of the hob to do so?

 

[gearcutter]

You'd have to perform a contact analysis to ensure that there is no 'non-involute' contact, as you are increasing the risk of the gear's teeth tips interfering with the throat of the worm.

I don't understand what you mean with these questions;
"Cycle time only?"
"feaibility of the hob to do so?"

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[dinjin]

It would be dependent on the module. I think a percentage
would make more sense.

 

[esko001]

Thanks for these answers. Maybe I did not formulate quwstion properly. Basically we produce worm wheel with the follwing steps:

-machine blank first. It has the same OD as finished worm wheel, but throat diamtere is increased for "topping hob allowance" 0.5-0.6mm, which is neded in order to achieve throat diameter concetricity.
- Topping hob will cut throat diametter to size as finished gear specification and cut teeth flanks.

I want to unify some blanks for diferent gear sets ratios. To achieve that I need to increase or decrese this "topping hob" allowance. So the question is how much I could increase or decrease from 0.5-0.6. Is the consequence cutting cycle time only (longer or shorter cutting operation), or topping hob has some limitations.

Thanks in advance.

 

[mfgenggear]

esko

due to the lack of answers it seems to me your question is still confusing.
what are to trying to do. I normally finish the OD prior to hobbing & tolerate a little runout.
I generally do not use a topping hob. but most of the parts I produce are short runs.

I would take a shot in the dark to say .5 mm is to much. more like .25 mm.is more resonable.
I would suggest not relying on our suggestions & do an actual experiment or test. run a partial group of parts.
& do a test run.

Do you have a Blue Print?



Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.