AGMA 2000-A88 4

[mfgenggear]

Please Consensus on this matter

Customer Engineering Drawing
Gear Tab Block

Gear Data Specifies
AGMA Q8
# Teeth
Diametral Pitch
Pressure Angle
Measurement Over wires
TTCE
TCE
Lead
TIF
Major Diameter
Minor Diameter
fillet radii

It does not specify
Involute error
Pitch error

IF the diametral pitch & # of teeth in the AGMA 2000-A88 Standard, rquires Involute & Pitch error
and it is not specified in the Engineering drawing
Is it required?
yes or no

Please give your take on this.

 

[israelkk]

If you specify AGMA 2000-A88 with the QXY

X - AGMA accuracy number
Y - tooth thickness tolerance

Then you legally covered and do not need to specify the TTCE, TCE lead error etc. This is defined in the AGMA same way as you define a thread for example UNF-2A or 3A etc.

I usually do add the TTCE, TCE to make it easier for the manufacturer and save him the need to dig into the AGMA spec.

I would recommend to replace the dimension over pins with Minimum and Maximum testing radius, because you can get it when you do the TTCE, TCE test in a rolling test against a master gear and it is more comprehensive, accurate, quicker and less expensive than the dimensions over pins.

You had to specify dimensions over pins yourself because the AGMA spec doesn't give it. The AGMA only deals with the variations on the base gear dimensions but not the base dimensions.

To calculate the maximum dimension over pins you had to use the TTCE, the tooth thickness tolerance (Y) and tooth thinning to achieve minimum backlash. Therefore, it is more natural to define the Minimum and Maximum testing radius because it check the whole gear in one roll test against a master gear.

If you insist on the dimensions over pins then you have to measure all the teeth. Therefore, if the gear has 100 teeth for example, you need to do 50 tests for each gear to get the TTCE and the TCE which is a time consuming process.

 

[mfgenggear]

Israelkk

Please review the AGMA 2000-A88 standard Para 3.3 page 16 & 17, then Para3.6.1 page 23

The manufacture may choose Elemental or Composite Methods.

Element Method :
Radial Runout
Pitch Variation
Profile Variation
Tooth Alignment

Composite Method:
Tooth to Tooth Composite Variation
Total Composite Variation

Generally most Designers will mix the two above methods
The gear data block will contain the following

Tooth Alignment
Tooth to Tooth Composite Variation
Total Composite Variation
Profile Variation.

That is why my OP was asking the question?
According to this standard it should Element Method or Composite Method.

 

[israelkk]

I see what you mean. I mainly use fine pitch gears therefore, I always use the composite method because it takes all the factors of tooth and gear variations in one roll test which make it easier, cheaper, and faster.

Even though the manufacturer can select the measuring method as you mentioned, the gear has to conform to all AGMA requirements. Therefore, even if he used the Element Method you can ask (and probably pay) for the composite method and may even find that the gear will not pass even though with the element method it passed.

To my opinion there is no way to actually touch the tooth at all points using a ball or cylinder, therefore this type of test may miss high or low points and give less accurate results.

Therefore, where a composite method can be used I prefer to use it.

 

[mfgenggear]

Israelkk

I agree that a compsite method is better.

but now a days with the CNC Gear Inspection.
it is more convient for small lots.
however if the drawing specifies TCE, & TTCE
then that is verified,

I try to cover the designer, if the drawing specifies
AGMA class 10, I give them a class 10 gear.
but my view does not all ways prevail.

if the designer omits an attribute then it can be said
it is not required. & this is a constant argument.

I wanted more opinions on this issue.
I am disapointed there not that many responces.
Starr for you Israelkk for taking your valuable time to
respond to my question.

Take care

 

[tbuelna]

mfgenggear,

AGMA 2000-A88, sec. 3.3.1: " No particular method of inspection or documentation is considered mandatory unless specifically agreed upon between manufacturer and purchaser."

Section 3.4 also lists the "recommended" methods of inspection for various features based on quality class, DP, and PD. A class 8 gear generally permits element or composite methods.

However, I do have a relevant question for you. If you or your customer are ISO 9000 or AS 9100, I believe you are required to use the latest version of a particular spec. unless otherwise specified. Does your customer's documentation specify the quality class in accordance with AGMA 2000-A88, or are you just assuming that? The reason I bring this up is that the current AGMA spec for profile and index tolerances is ANSI/AGMA ISO 1328-1 & -2. And the quality classes in the new spec are different (ie. reversed?) from the older spec.

Hope that helps.
Terry

 

[israelkk]

Terry,

The current AGMA is not ANSI/AGMA ISO 1328-1 & -2. It is mainly based on it but with some differences. The current AGMA specs are:

ANSI/AGMA 2015-1-A01 Accuracy Classification System - Tangential Measurements for Cylindrical Gears

ANSI/AGMA 2015-2-A06 Accuracy Classification System - Radial Measurements for Cylindrical Gears

Personally I find them too cumbersome and complicated compared to the good "old" 2000-A88 and when it is possible I prefer to use the 2000-A88 in agreement with the customer.

 

[mfgenggear]

Israelkk & TBuelna

It is possible to pass the Composite Method & fail the element. don't forget the lead must be taken across the full length of a gear.the Involute is normally at the center.
The pitch error is taken normally at the center of the tooth

In order for the TCE & TTCE to pass there must be certain element method quality.

Our customers have Index specifications that specifies if the specification has been superseded or not.
If the AGMA 2000-A88 is specified it is applicable.

what I often see is this case where a partial of methods are combined.& attributes are left out.

I don't like the new AGMA standard either but if it is specified then that is & must be used.

 

[Spurs]

All

The Old AGMA 2000-A88 is a withdrawn standard by AGMA. It has been replaced by AGMA 2015-1 for elemental inspection and AGMA 2015-2 for composite inspection.

Just because AGMA has withdrawn 2000-A88 does not mean that it cannot be used or cited. In fact, AGMA will still sell the standard to those requesting it.

However, to be clear, AGMA 2015-1 or -2 is not a "latest revision" to 2000-A88. It is completely new and self standing and is to be used only if specified either by specification number or by quality class "A" or "C" class as opposed to the "Q" classes of AGMA 2000-A88. Note - stating simply AGMA Class "10" for example is ambiguous becasue it does not identify the applicable standard to be used.

As was stated in an earlier post, use of AGMA 2000-A88 allows for EITHER elemental OR composite inspection but does not require both.

By the same token, AGMA 2015-1 has some mandatory elemental inspection tolerances and also some optional ones. If any optional ones are desired, they must be clear understanding between the supplier and purchaser of this.

AGMA 2015-2 only requires total composite and tooth to tooth composite to be measured.

What most people also do not realize but is clearly spelled out in all of these standards is that there is no "magic" co-relation between the specified tolerances of a given quality class.

For example, in AGMA 2000-A88 just because a part is specified Q10, it does not mean that a particular manufacturing process should be able to deliver a Q10 quality level for every parameter with the same level of effort or dificulty. i.e. some tolerances may be easier to achieve for Q10 than others. Further to this, it may be easier to meet Q10 on tooth to tooth error than composite, or on Lead then on Profile.

This dis-connect is even more apparent in the 2015 standards. For example in 2015-2, it may be easy for a particular gear to pass a C9 level for total composite error, but more likely that a tooth to tooth composite error can only meet C11 requirments.

In 2015-1, the same thing can be said for the profile and helix callouts where once may meet a A9 quality class while the other is better at an A7.

On top of this, there is also absolutely no co-relation between for example a A7 quality class in AGMA 2015-1 and a C7 quality class of AGMA 2015-2.

Sound confusing... It is! The standards were developed to allow for use of nice linear equations as opposed to comply with a particular manufacturing process or part application.

That is why AGMA in all of these standards also clearly spells out that you need not specify a single quality class for each paramater. You can specify C9 for Total Composite Error and C11 for Tooth to tooth composite error and A7 for profile slope error.

In my opinion, the best method is to explicity state on your drawings what you want measured and state the explicit tolerance. Avoid others from having to look it up and avoid painting every characteristic with a single brush stroke.

This begs the question..why have a standard at all if the standard has no co-relation between the tolerances. This is a very very very very good question that you all should put to AGMA. There is some sort of feeling that people want standards about this, but quite frankly there is absolutly no guidance given by AGMA on how to use them because they really dont want to tell people what to put on thier drawings.

My suggestion is that you make your frustrations known to AGMA by sending them an email outlining your frustrations. You should tell them your concerns and experiences with the new 2015-1 and -2 standards. If enough people complain - you will be heard.

 

[mfgenggear]

Spurs

nicely stated

Mfgenggear

 

[dinjin]

I think if you do not have a master pinion to check out
TCE then you would have to default to the element method
of checking the gear. If you have many parts and you can afford a master pinion, you are probably better off using the tce check method. I would prefer the tce method as it probably gives you a better feel as to how it would mate
with its pinion in the application. For certain if you need to control a special element of the standard, it should be specified.