Grinding ball mill girth gear root clearance

I can't answer your question directly however I found a couple places that may help you get to an answer. See if the following will help you any: http://www.artec-machine.com/documents%20free/cement_drives_for_grinding/Central_or_Girth_Gear_Drive_for_ball_mills.pdf

Kumera has manuals on line as well. Example:http://www.kumera.com/documents/Girth_gear_manual.pdf

search through their extensive list, they surly may have the answer.

A

It is not so much the root clearance you are after but the side clearance between teeth.

What is the diametrical pitch or Module of the gearing? From that you can calculate the theoretical centre distance between pinion and gear. However, it may be just as good to allow about 0.1 - 0.2 mm side clearance. The DP might be 4, or 3 or so?

Are you manufacturer or user ?

As manufacturer only you should be interested on the tip clearance.

The tip clearance should be

a) Able to take care of the thermal expansions during the operations. The gear ratio shows it to be a large gear. Our gears with ratio 222/27 ahs a diameter of more than 5m

b) Take care of the profile machiining - the root radius etc should not be damaged during hobbing the involute.

I saw in an article the tip clearance should be between 0.1 to 0.3 of the module- for our module of 27 it is between 2.7 to 8.1mm.

However I must clarify that we do not manufacture the gear, we buy it for our equipment (obviously tube mill to be of this size)

If you are the user then pl forget about the tip clearance - it is taken care of by the manufacturer (if you are designer then you must specify it)

Pl concentrate on the

a) Blue contact - pattern

b) back lash

The blue contact should be evenly spread (to avoid the skew) and centered around the pitch lines (to maintain center distance) and the back lash should be maintained (again it ensures the skew and cd)

By the way - why helical ? our equipment is spur.

- root & pressures to be taken prior to replacing brgs / removing a pinion

- biggest challenge is fitting a new pinion on an old girth and still getting acceptable vibration, still with acceptable root depth

- the general tendance is to increase the root to solve high vibr is damaging the girth to a point of nonreturn / replacement

- grinding the pinion easiest / quickest, or reconstruct girth tooth profile

- lead wire pressure measurements are only accurate to a sertain degree; final shimming adjustment procedure setting pressures based on delta temps

Nico de Villiers

PCM - specialist in vibr, laser, gear alignment, condition based maintenance on mills

nico@pcmlaser.com

Grinding / honing of gears could be a long process; sparying / barring / grinding; rotary cutters...

Tip contact could generate high vertical vibration and pitchline contact high horizontal vibr. Vertical vibr easily decreased, but horizontal vibr challenging.

nico@pcmlaser.com

grinding the pinion easiest / quickest, or reconstruct girth tooth profile

In the gears after sufficient running, the profiles get disturbed. And doing manual grinding to get the involute is next to impossible especially maintaining the thread tolerances even in large gears (Girth gears)

This is from a practical experience, approx 8-10 years back a vendor has supplied a girth gear/pinion There was a high vibration from the day it was commissioned and we visited (as a part of the OEM) within few minutes the problem was obvious, the involute generation and try whatever (by the vendor service person, supposed to be an expert) the profile could not be generated and the gear was scrapped.

As you try to correct the profiles, the errors could not be maintained and the un-equal gaps between consecutive teeth resulted in the faulty three teeth contact, ptch line rolling and so on.

It degenerated into the famous story of the two cats and monkey and finding no significant improvements we had to take the harsh but seemingly unavoidable step.

The class of the teeth that are generated on machines are a bit too difficult to achieve by hand matching- not impossible- but difficult.

Attached is a link to a rotary engine. The interest here is purely the gearing used which seems to consists of shallow straight grooves machined with a helix angle. Obviously the flanks can not be straight and must have an involute shape to engage, I think. The contact would then not be a line but a point strictly speaking that wanders across the gear width as the gears rotate.

To my assessment such 'gearing' would not be able to carry as much load as standard spur gearing and the axial laods need also be taken up. What is the general consensus on that? Would such 'gearing' be useful and practical?

Regards

Floram (on another machine).

http://www.youtube.com/watch?v=XY-ABZjVoeU&feature=player_detailpage