• Screw Elements
• Threaded Elements
• Kneading Elements
• Eccentric Kneading Elements
• Pushing Flight Elements
• Threaded Mixing Elements (Conveying and Reconveying)
• V-Mixing Elements
• Tooth Mixing Elements
• Blister Elements
• Distance Elements
• Transition Elements
• Transition Conveying Elements

The following screw elements are implemented in SIGMA: - Threaded elements - Pushing flight elements - Threaded mixing elements (conveying/ reconveying) - V-Mixing elements - Kneading blocks - Shouldered kneading blocks - Eccentrical kneading blocks - Distance elements - Blister elements - Tooth mixing elements

To define a new screw element, choose the New element button in the Machine configuration and select the kind of element you would like to define. Then the dialog box for entering the values will open up.

As with barrel elements, already created screw elements can be modified by opening the corresponding dialog through double-clicking the element to be edited, by selecting the icon Edit properties of the selected element, or by making the desired changes directly in the Element Properties list.

For seven of the ten available elements, the dialogs provide the option to define the geometry precisely through additional inputs. As an alternative to specifying the volume correction factor, the actual screw diameter and either the pitch angle or the root angle of the screw profile are entered, with the other angle being calculated automatically.

The input screen for defining and modifying threaded elements (both forward and return elements) contains all the values required to clearly describe tightly meshing profiles.

The specific meaning of the variables to be defined can be seen in the drawing of a pair of elements in the figure.

Please note the following when entering data:

• The centre distance cannot be changed in this screen, as it is predetermined by the general machine data already entered.
• The length of the screw element and the pitch can be entered either in absolute values ([mm]) or in multiples of the grid dimension.
• The volume correction factor is a measure of the deviation of the theoretically close-fitting geometry used in SIGMA from the actual geometry.
• (As an alternative to the volume correction factor, additional inputs can be specified to define the geometry exactly. In this case, the actual screw diameter and either the cutting angle or the base angle of the screw profile must be entered. The other angle is calculated.

The geometry of push edge elements differs from the geometry of conveyor elements only in that it has an additional free surface. In SIGMA, this surface is characterised by two parameters, the angle of inclination $$\phi_s$$ and the radius of curvature r. Otherwise, the same specifications as for conveyor and return elements apply.

Unlike conveyor elements, screw mixing elements have grooves cut into their flanks. In addition to the pitch and number of grooves, the geometry of the groove in the normal section must also be defined. To ensure maximum flexibility, the geometry of the groove has been simplified by using a rectangular cross-section (characterised by groove width b and groove depth h).