Problem In Gear Box

The nameplate for the gearbox should give the gear ratio, and either or both of output torque and max input hp (or kw). This information would be useful, along with the hp/kw of the attached motor.

Some possible issues include mismatch between motor and gearbox ratings, lack of oil or wrong type of oil, too small of a gearbox/motor selection for the actual load being driven, and blockage or binding in the driven load.

Did you change bioth the worm and the gear?

Usually I have seen the persons check visually and find the worm OK and replace only the gear (or in some rare cases vice versa)

It must be noted that

- Worm and gear profiles vary between manufacturer to manufacturer - Especially Flender haas its own profile (cavex). Even other-wise these are not considered to be miscible. (Even certain manufacturers supply these as matched set).

- After sufficient length of operation, the Shaft threads too lose their profile. Though that can not be visibly ascertainable. Thereby an used (Say Flender) worm can not be used with a new Flender gear.

- One of the ways are (in case the both are same make), reverse the worm (so that a new unused flank of the worm comes in contact with the new gear flank). But this is applicable in case of single direction of rotation (ie not if the gearbox rotates both clockwise and anticlockwise)

Usually the problems of materials etc are not likely especially since you are dealing wih Flender (or should you call it Siemens Transmission now )

Once you confirm whether you have replaced both, we may try to think over other reasons.

Dear Mr. nvn1988,

Many Forum members have given there views and all of them are valid and vital.

I wish to supplemnt the following:

1. The Selection of gear box for shock load, service factor, to be properly accounted.

2. The Root Stresimes it should be limited to 1300 N/MM^2.

3. The Z_NT factor should be 10E+10, some times designers choose 5x10E+7.

4. Application Factor should be 1.75 and NOT LESS.

5. THERMAL ASPECT for Forced Lubrication or Oil cooling is to be taken in to account.

6. How frequent is the shock/jerk load.?

7. Teeth damage - is it for full length

FULL DETAILS OF gear box, service condition, selection basis to be furnished, and CR4 members can give their view.

DHAYANANDHAN.S

Change the worm and wheel both from the same OEM. Unless you register all the important specifications and find out a new one but not recommended.

First: How long did the original worm/wheel run before the damage occured in the first instance (before the 1st repair):

- If the gear box was installed and run for a very long time (relative to the 2 month: like 12 or 18 month or more), then you must look at the whole gearbox and driven apparatus: Check all the bearings and any play on the shafts of both the worm and wheel. Check the output from the gearbox to the load and see if nothing happened to the load in term of wear etc. Most of the time, something happened to accelerate the wear or to damage the wheel. Therefore, any new wheel you put will experience the same strain and will get damaged quickly.

- If this is a recent installation which did not last more than 3 to 4 month before the damage, then you should worry about the sizing of the gearbox to the load it is carrying, or suitability of the material used in it.

If the gear box is sized correctly, there may be a problem with the material used for the worm gear. You mention that the wheel is of brass, but not the material of the worm. In most cases if the wheel is of brass, the worm should be of a hardened material resulting in much less wear on the brass wheel. A cast iron worm should not be used with a brass wheel.

Flender may have created modified tooth profiles on both the worm and the wheel to obtain the load and application needs. Unless Flender provided you with detailed information on tooth data it is nearly impossible to manufacture the exact tooth profile of the original wheel or worm. The material hardness specification they required would also need to be known. Have you contacted Flender about your problem? When did your warranty run out? Are you running this gear box at or near the max capacity? If so for what percentage of its duty cycle? Do all of these fall within the Flender specifications? If this unit has been in service for very long, is it past the time for rebuilding and servicing? This would include the replacement of all bearings and seals. It is possible that the real problem is not the gears but bearings that are failing or an alignment that changed do to some event.

Mr. nvn1988,

You are conspicuously absent from discussion not responding to the queries fro experts. Why don't you contact Flender for your problem?

Hi friends,

Frequent damaging the gear teeth is may be error in the variation in Setting Helix angles, O.D and Root diametres of worm & worm gear.And also concentricity of the ID and OD of worm and worm wheel are also important.

If hardness is the case,teeth of worm or gear wear uniformly.

THANKS

What did <...flender...> say when the problem was discussed over the phone?

I'm not familiar with the Flender brand, so this may not apply, but all the gearboxes I've ordered in recent years were shipped without oil. If they are put in use without adding the appropriate amount of the correct oil, they will wear rapidly.

It sounds like you replaced only the gear. Again, after re-assembling the unit, adding the appropriate amount of the correct oil before use is absolutely necessary.

Also, after reassembly, check for oil leaks. New seals and/or gaskets may be necessary.