This component generator is intended for parallel spline calculations and designs. It designs spline shafts and provides a strength check. Using the calculation of spline joints the economic hub length for specified transferred torque is determined.

Circumferential force is transferred by the pressure of sides of shaft keys to hub grooves or vice versa. The necessary hub length is determined from the condition that the allowable pressure in the groove bearing area must not be exceeded.

Parallel splines are suitable for transfer of great, cyclical, and shock torsional moments. These couplings represent in practice the most common type of splines (approximately 80%). This type is used both for fixed and sliding couplings of cylindrical shafts with hubs.

Advantages of the coupling:

Lower pressures than in couplings with keys, higher loading capacity of the coupling
Smaller wear with sliding couplings
Suitable for cyclical torsional moments
Simple assembly and disassembly of the coupling

Disadvantages of the coupling:

Higher production costs than in the case of couplings with keys
Higher notch coefficient than in the case of couplings with keys

The method of centering is chosen according to technological and operational requirements and demands for accuracy. Centering is possible on the inner diameter (used rarely) or on sides of teeth. Centering on diameters is used in case of a need for higher accuracy of the bearing. Couplings centered on the sides show higher loading capacity and are suitable for loading with variable moments and shocks.

TipSee the Engineer's Handbook for used calculation formulas in metric and English units and other instructions for designing parallel splines.

Procedures

How to design parallel splines

Insert parallel spline connection

On the ribbon, click Design tab Power Transmission panel Parallel Splines.
On the Design tab:
- Click the arrow next to the Splines Type edit field to select the spline.
- Enter the spline dimensions.
- Specify the position of a shaft groove. You can either create new shaft groove or select existing groove. According to your selection, the placement options in the Shaft Groove area are enabled.
- Specify the position of a hub groove.
- On the Select Objects to Generate section, select the objects you want to insert. By default, both two options are enabled. Disable the options by clicking the icons.
Select OK.

NoteYou can switch to the Calculation tab to perform a calculation and strength check. The calculation is performed when you click Calculate.

Edit parallel spline connection

Open the Autodesk Inventor assembly with the Design Accelerator parallel spline connection already inserted.
Select the parallel spline connection, right-click to display the context menu and click the Edit Using Design Accelerator command.
You can add components to the connection or change dimensions. Inserted components cannot be deleted from Parallel Splines Generator. You can delete them in the Autodesk Inventor assembly only.

Insert individual connection component - shaft groove

On the ribbon, click Design tab Power Transmission panel Parallel Splines.
On the Design tab:
- Click the arrow next to the Splines Type edit field to select the spline.
- Enter the spline dimensions.
- Specify the position of a shaft groove. You can either create new shaft groove or select existing groove. According to your selection the placement options in the Shaft Groove area are enabled.
- Specify the position of a hub groove.
- Click the second icon in the Select Objects to Generate area to disable hub groove insertion so that only the shaft groove is inserted.
Select OK.

Additional insertion of connection components

Open the Autodesk Inventor assembly with the Design Accelerator parallel splines connection already inserted.
Select the parallel spline connection, right-click to display the context menu and click Edit Using Design Accelerator.
On the Select Objects to Generate section, click the icon of the appropriate inserted object (shaft groove, hub groove).
Specify the geometry.
Select OK.

Calculate parallel spline

On the ribbon, click Design tab Power Transmission panel Parallel Splines.
On the Design tab, click the arrow next to the Splines Type edit field to select the spline and enter the spline dimensions.
Switch to the Calculation tab.
Select the type of strength calculation.
Enter the calculation values. You can change the values and units directly in the edit fields.
Click Calculate to perform the calculation.
Calculation results are displayed in the Results area. The inputs that fail the calculation are displayed in red (their value does not correspond with other inserted values or calculation criteria). Reports of the calculation are displayed in the Summary of Messages area which is displayed after clicking the chevron in the right lower part of the Calculation and Design tabs.
If the calculation indicates design compliance, click OK.

References

Parallel Splines Generator - Design tab

Sets parameters for a parallel spline calculation.

Access:

Ribbon: Design tab

Power Transmission panel

Parallel Splines

Dimensions

Specifies the spline type and the basic spline properties.
Splines Types	To open the dialog box for a basic spline type selection, click the arrow next to Splines Type. Select the standard and the appropriate spline type.
Spline	Spline dimensions are updated based on the selected spline.
Length	Enters the spline length. You can insert spline length using the following options: select from predefined list, measure, insert user length, or use graphical preview.

Shaft Groove

Specifies the shaft groove and its placement.
You can insert the spline based on the existing shaft groove or create a groove. According to your selection, buttons for placement are enabled in the Shaft Groove box. Create new - creates a shaft groove. Select Existing - specifies a selected shaft groove feature from Autodesk Inventor and based on the dimensions finds the appropriate spline. NoteIf you use this option, the existing shaft groove is not modified.
Reference 1	Selects a cylindrical face.
Reference 2	Selects a start face or work plane with the flip option.
	NoteFlip option is available only if a work plane is selected.
Orientation	Orientation plane - places the groove on the cylindrical face (program automatically selects the orientation plane. If there is a problem with definition of orientation plane, select it).
Radius	Enter the radius.

Hub Groove

Defines the hub groove you create and its placement.
Reference 1	Select a start/end planar face or a work plane. (Autodesk Inventor automatically selects the end face. If there is a problem with definition of the end face, select it.)
Reference 2	Select a start point (can be cylindrical edge or work point) with the flip option.
	NoteFlip option is available only if the work plane is selected.
Orientation	Orientation plane - places the groove on the cylindrical face. (Autodesk Inventor automatically selects the orientation plane.)
We recommend that you have a hub groove without an inside hole. The designed hub groove creates the hole according to the inserted values. If the hub groove diameter is bigger than the selected diameter, the design fails and the hub groove is not created.

Select Objects to Generate

Two options define what is inserted:
	Shaft Groove Generates a shaft groove on the selected geometry.
	Hub Groove Generates a hub groove on the selected geometry.
By default, both options are enabled. Disable the options by clicking icons.
NoteIf an object (shaft or hub groove) is inserted, it is not possible to change it during edit.
NoteIf shaft and hub grooves are inserted, their mutual position is automatically fixed by a constraint so their positions cannot be changed individually.

Results

To display the Results area on the right side of the Calculation and Design tabs, double-click the double line on the right or click the chevron.

The area displays the calculated values and the spline strength check. Values are calculated when you click Calculate.

The units of the results values can be changed. Double-click the specified value you want to change.

Summary of Messages

Displays the reports about calculation. To open the Summary of Messages area at the bottom of the Calculation and Design tabs, double-click the double line at the bottom of tabs or click the chevron at the bottom of the tabs.

Graphical Preview

A graphic preview of the selected geometry is displayed in Autodesk Inventor. You can use grips to specify spline length, for example.

Calculation Tab

Menu Commands

Parallel Splines Generator - Calculation tab

This tab extends the Design tab. Calculates generator data based on selections on the Design tab.

Access:

Ribbon: Design tab

Power Transmission panel

Parallel Splines

and click the Calculation tab.

Strength Calculation

Check Calculation	Performs a strength check for the specified load, dimensions, and joint properties.
Length Design	Designs optimum active spline length for the specified load, spline diameter, and joint properties.
Diameter Design	Designs optimum spline dimensions for the specified load, spline, length, and properties of the joint from the selected spline range.

Loads

Loading is entered through power, speed, or torque according to the selected method in the selection list.
Power, Torque Speed	Calculates the speed according to the power and torque.
Torque, Speed Power	Calculates the power according to the torque and speed.
Power, Speed Torque	Calculates the torque according to the power and speed.

Dimensions

Hollow Shaft Inner Diameter	If you use a hollow shaft in the coupling, enter the inner diameter of the shaft. This parameter effects the size of loading of the shaft in torsion and the termination of the minimum permitted diameter of the shaft.
Spline Length	Specifies a length of spline within the standard specified range so that it is larger than the minimum length.

Joint Properties

Desired Safety	With regards to accuracy and credibility of input information, importance of the coupling, quality of production and accuracy of the calculation, it is chosen in a range from 1.5 to 3.
	Orientation values for choice of safety:
	1.3 to 1.5 - Very accurate input information, perfect knowledge of material characteristics, high quality of production technology, insignificant couplings, damage to which does not cause any serious consequences. 1.5 to 1.8 - Less accurate calculation without any experimental verification, lower accuracy in production technology, couplings of lower importance. 1.8 to 2.5 - Decreased accuracy of calculations, approximate determination of material characteristics, inaccurate knowledge of actual effects of external loading; large diameters of shafts, important couplings, damage to which could jeopardize human life or bring about high material losses. NoteEven higher levels of safety are used if of couplings are working in a corrosive environment or at high temperatures.
Loading Conditions

Shaft Material

Specifies material values you enter or material you select from the Material Database. If a material is selected from the Material Database, its value is inserted automatically, and the edit field is locked. To unlock the field, clear the check box.
Allowable Pressure	Enters the allowable pressure of the spline material with the least quality in the Joint Properties group. The spline is checked for pressure during the strength check.
Allowable Shear Stress	Enters the allowable pressure of the spline material with the least quality in the Joint Properties group. This value is used in designing the minimum shaft diameter.

Hub Material

Specifies material values you enter or material you select from the Material Database. If a material is selected from the Material Database, its value is inserted automatically, and the edit field is locked. To unlock the field, clear the check box.
Allowable Pressure	Enters the allowable pressure of the spline material with the least quality in the Joint Properties group. The spline is checked for pressure during the strength check.

Results

To display the Results area on the right side of the Calculation and Design tabs, double-click the double line on the right or click the chevron.

The area displays the calculated values and the key strength check. Values are calculated when you click Calculate.

The units of the results values can be changed. Double-click the specified value you want to change.

Summary of Messages

Displays the reports about calculation. To open the Summary of Messages area at the bottom of the Calculation and Design tabs, double-click the double line at the bottom of tabs or click the chevron.

Design tab

Menu Commands

Loading Conditions

Specifies the influence of production and operating parameters on the connection acceptability.

Access:

On the Design tab, Power Transmission panel, click Key, Involute Splines, or Parallel Splines, and on the Calculation tab click Loading Conditions.

Joint Type
Fixed	Splines are firmly joined by pressing or fixed by rings, avoiding axial movement.
Flexible	Splines are flexibly joined to allow axial movement.
Crowned	Uses external splines with crowned teeth for misalignment up to 5 degrees.
	Note This option is available for Involute Splines only and if the ANSI Standard is selected.

Ka - Application factor

This coefficient reflects the effect of the character and the type of loading on decrease of the loading capacity or the coupling. It is determined according to empirical values given in the following table:

Drive	Type of loading
Drive	Continuous	Light shocks	Cyclical shocks	Heavy shocks
Uniform	1.0	1.2	1.5	1.8
Light shocks	1.2	1.3	1.8	2.1
Medium shocks	2.0	2.2	2.4	2.8

Fatigue-life factor

This coefficient reflects effects of the operational character and appropriate service life of the coupling (measured in number of torque cycles) on increase of the loading capacity of the coupling. It is determined according to empirical values given in the following table:

No. of Torque Cycles	Fatigue-life factor, Kf
No. of Torque Cycles	Unidirectional	Fully bi-directional
10000	1.0	1.0
100000	0.5	0.4
1000000	0.4	0.3
10000000	0.3	0.2

Wear-life factor

This coefficient reflects effects of wear of contact surfaces during the appropriate service life of the coupling (measured in number of revolutions) on increase of the loading capacity the coupling. It is determined according to empirical values given in the following table:

Total number of revolutions [millions]	K_w
0.01	4.0
0.1	2.8
1	2.0
10	1.4
100	1.0
1000	0.7
10000	0.5

Noteonly for flexible joints.

Load Distribution factor

In couplings with two keys, the loading is not distributed exactly uniformly onto the two keys due to production and assembly inaccuracies. The actual load bearing surface of the coupling is lower than the load bearing surface determined theoretically. The ratio between the theoretical and actual load bearing surface of the coupling is defined by the coefficient of distribution of the loading. With regards to the accuracy of bearing, the size of the coefficient is given in a range from 0.6 to 0.8.

Tip: For common accuracy of production and installation, a coefficient of 0.75 is taken into account .

NoteIn cases of couplings with 1 key, the coefficient is equal to 1.

Factor of Tooth Side Contact

Note This factor is available for Involute Splines only.

The factor indicates the load is not spread evenly on all the spline teeth because of production and assembly inaccuracy. At a common and higher mounting accuracy, it is assumed that half of the teeth carry the load (K_s = 0.5). For splines with higher production inaccuracy, the load is only carried by one third of the teeth (K_s = 0.3).

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Parallel Splines Component Generator

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