11.1 GEARCALC


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Figure 11.1: GEARCALC settings - page GEARCALC


11.1.1 Permissible deviation of ratio

There are often several designs which will achieve the required criteria but be outside the exact ratio. A permissible deviation as a percentage of the nominal ratio can be entered to allow the assessment of such designs.

11.1.2 Tip shortening

The sum of profile shift factors not equal to zero will decrease the tip clearance for external gear sets. To avoid this decrease of tip clearance a tip shortening is often made. For internal gear sets the sum of profile shift factors not equal zero will result in an increase of tip clearance. Therefore no automatic tip shortening is made for internal gear sets.

There is a choice of three tip treatment methods from drop down list:

Full length teeth The addenda of the gear and pinion are calculated without tip shortening:

h    =   1-+-x1-
  a1       Pnd
         1 + x2
ha2  =   -------
           Pnd
CAUTION : Option may leave insufficient tip-to-root clearance if the operating center distance is much larger than the standard center distance.

Standard working depth

h    =   1 +-x1 --ks∕2-
 a1           Pnd
         1 + x -  k ∕2
ha2  =   -----2----s---
              Pnd
CAUTION : Option may leave insufficient tip-to-root clearance if the operating center distance is much larger than the standard center distance.

Standard tip-to-root-clearance This represents the safest calculation option but the contact ratio is reduced:

ha1  =   1-+-x1 --ks
             Pnd
         1-+-x2 --ks
ha2  =       P
              nd

11.1.3 Manufacturing tolerance

The tolerance method can be defined for the calculation. A choice of AGMA 2000-A88 or AGMA 2015-1-A01 is available from the drop down menu. The scale runs from 15(best) to 3(worst) according to AGMA 2000 or from 2 (best) to 11(worst) according AGMA 2015. In ISO 1328 also the low numbers are for better quality like in AGMA 2015.

11.1.4 Calculate ratio face width to pitch diameter

There are two alternatives for establishing the ratio face width to pitch diameter ma which ar toggled using the radio buttons;

The upper option activates the three cells directly under the radio button. Then factors C1 and C2 can be entered to define the ratio as follows;

ma =  (mG ∕(mG  + C2)) ⋅ C1

where:

C1 = 1.0 for spur/helical gears
C1 = 2.0 for double helical
0 C2 1.0depending on user preference
C2 = 1.0 suggested for general purposes

The lower button allows the direct input of the ratio of face width, F{b}, to pitch diameter, d:;

ma  = F {b}∕d

This option activates the cell directly under the radio button. The cells for factors C1 and C2 will be de-activated, and the cell for the definition of width to pitch diameter can be accessed to enter a fixed value.

11.1.5 Tool addendum

The user can specify an addendum haP0* of the tool for three given machining processes (finish cutting, shiving, and grinding) for a specified range of pressure angle designs. The tool addendum is measured from the datum line with sn = π∕2∕Pnd. An associated radius, ρaP0* can also be specified at this point. The tool addendum form is defined as follows:


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Figure 11.2: This figure shows a normal plane view of a rack-type generating tool (hob, rack cutter or generating grinding wheel).


11.1.6 Use full radius (calculated at run time)

This option implies that a radius is to be determined during the calculation (at run time) which will be the largest possible fitting to the defined tooth form tip.