Definition of Angles
Angles are defined with 0 at the top. Gravity is assumed to act at 180° and is shown with a black arrow. For the other 2 effects the angle is defined in terms of the physical location of the force.
So if the web is specified at 90° and 270° they are (as shown by the arrow heads) pointing downwards, providing a net force in the 180° direction. No attempt is made to sort out strange wraps - if things look wrong, they are wrong and you need to fix them.
If the Nip is specified at 0° then it is pushing down from the top with a net force in the 180° direction.
These forces might act with or against each other so the overall deflection and the angle in which it is deflected is the vector sum of the three components. The angle of this vector is given and is shown in red. If the overall deflection is straight down then the angle is 180° and so forth.
Summary of Inputs and Outputs
| Inputs | |
| Web Load | Load (Tension) of the web (kg or lb). This is doubled because of the incoming/outgoing webs |
| Nip Load | Load applied by the Nip (kg or lb) |
| Web | Direction in which the web is pulling the roller |
| Nip Angle | Angle from which the nip is pushing the roller |
| Roller OD | Outer diameter of the roller shell (mm or in) |
| Roller ID | Inner diameter of the roller shell (mm or in). If accidentally entered as larger than OD, a shell of 1mm thickness is used in the calculation. |
| Face | Face width of the roller (mm or in). The Loads are divided by this value - i.e. the web is assumed to cover the full Face width of the roller |
| Brg-Brg | Total width of the roller including bearings (for Live rollers). If this is less than Face then the Dead Shaft calculation is used |
| Steel, Al, Low, Med, Hi Composite | Choice of material for roller shell. The moduli used are respectively: 200GPa, 69GPa, 100GPa, 165GPa, 270GPa. Although the composites are comparable to steel in modulus, they are ~5x less dense so bend far less under their own weight. Al is much less strong but 3x less dense than steel so the trade-off is more marginal. |
| Dead | A Dead Shaft roller so the deflection applies only to the Face Width |
| Live | A Live Shaft roller so the deflection applies to the Brg-Brg width |
| Inset | The inset from the edge of the roller of a support which reduces the central deflection |
| Outputs | |
| Delta | Deflection of the roller (µm or mil) |
| D/F Class | Deflection/Face width x 1E6 plus the Class |
| Angle | Direction in which net force is acting |
| React. | Reaction on bearings, i.e. Resultant/2 of the combination of loads |
| Weight | The weight of the basic shell (no bearings/shafts) |
| Crit. | Critical speed (in RPM and velocity) for vibration onset |
| MI | Mass Moment of Inertia |
| Vectors | |
| Forces | Directions colour coded to match text |
Cantilivers
If the
Cantilever option is selected then two extra variables appear and Roll load can take on a new meaning:
| Shaft Length | Length of the (steel) shaft supporting the cantilever roll |
| Shaft OD | OD of the (solid steel) shaft supporting the cantilever |
| Roll | When selected the Nip load is the weight of a real roll, Angle is set to 0 |
| Dead/Live | These are disabled, only the Face length is used in the calculation |
D/F Class
According to Dr Roisum in The Mechanics of Rollers, the ratio of Deflection over Face Length (D/F) can be used to define a Class of rollers. For ease of viewing, D/F is multiplied by 1E6 and the Class is defined as:
| D/F | Class | Meaning |
| <80 | A | Precision or nipped applications |
| <150 | B | General purpose rollers |
| <300 | C | Tissues, nonwovens and thick materials |
| <600 | D | Conveyer belts, spreaders, cores... |
| Higher | X | May be unsuitable for web applications |
