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Load Parameters (Payloads)

Load shown on motorized UniSlide StageA load, as it relates to motion, has a variety of meanings. For the purpose of using Velmex stages the load usually refers to the payload that the stage or slide will carry. Various characteristics, in addition to weight, affect the load a stage can carry, including speed, position on the carriage, position of the stage (horizontal, vertical or inverted), the object's dimensions, the number of axes and length of time the load might be in position.

Because Velmex stages can be used as X, Y, Z axes or any combination thereof, and in a variety of orientations, there are a number of different load parameters reflected in ratings. We will define these as Velmex applies them.

 

  • Definitions:
  • Load Movement
  • Load Positions
  • Multiple-Axes Stages

(Usually when measuring loads, the most common position is one axis only with the stage in the horizontal position and the load is riding on the top of the carriage. Ratings for "inverted" and "vertical" generally indicate what position the stage is in.)

Load Capacity – The maximum recommended payload for a stage or slide to operate efficiently. (Except for "Cantilever". It is measured with load centered on the carriage.) Sometimes also referred to as "Permissible".

For the various ratings on Velmex products and how to calculate them, see "Load Capacities".

Note: Because of the interlocking nature of the BiSlide® and XSlide™ carriage and their respective dovetail ways, the maximum recommended load centered (normal) or load under horizontal thrust would be comparable whether the slide was upright (Normal – LN), Inverted (LI) or set on the Edge (LE).

The maximum vertical, thrust/lift or cantilever load will always be less than a normal, centered, horizontal load on any one stage.

Odd shaped payload on a UniSlideNote: When working with an off-size or odd-shaped payload, the location of the center of gravity and it's relation to the center of the carriage on the stage determines the load parameter to apply.

Movement

The presence (or absence) of any movement and the type of movement can affect the load rating:

Static – The load the stage can handle when not moving. (Measured with load centered on carriage.)

Frequently with a static load, the payload is placed on the carriage after the carriage has been moved into position.
UniSlide with Load Centered - not moving Load Centered on BiSlide from the end XSlide with load centered. Taken from edge.
Dynamic – The load the stage can handle when in motion. (Measured with load centered on carriage.)
Dynamic load on Rotary Table

Dynamic load is best illustrated by a video. Note the club head turning in the center of the Turntable.

You-tube access  

Momentary – The load that is present for an extremely brief period of time. i.e. punch press. (Measured with the center of gravity of the load being applied to the center of the carriage. Usually the carriage is not moving.)

Momentary Load from a punch press

Thrust / Lift – A force that pulls the carriage in the direction of the motor / crank or pushes the carriage in the opposite direction of of the motor / crank. Lift is the maximum thrust force required to lift or lower the payload vertically.

Showing lift on a vertical BiSlide

Lift and Thrust is best illustrated by a video. Note the club head turning in the center of the Turntable. Note the Rotary Table with the club head moving up and down on the XSlide.

You-tube access

 


For the various ratings on Velmex products and how to calculate them, see "Load Capacities".

Position

The position of the Load on the carriage and the position of the stage can affect the load rating:

Normal Load or Normal Centered Load – The recommended rating for day-to-day operation of the stage. The load would be on an X axis, traveling upright (not suspended or inverted) in the horizontal plane. (Measured with load centered on carriage.)
UniSlide with Load Centered - not moving Load Centered on BiSlide from the end XSlide with load centered. Taken from edge.
Cantilever – A load where the center of gravity is offset. There are four possible measurements in this category:
Cantilever load on BiSlide

Side / Horizontal – The load is not centered over the carriage and is instead offset to one side or the other of the stage, when the stage is laying flat. The center of gravity is perpendicular to the direction of travel.

Cantilever load on BiSlide
Inline Cantilever load on UniSlide

Inline / Horizontal – The load is not centered over the carriage and is instead offset over the stage, when the stage is laying flat. The center of gravity is parallel to the direction of travel. The payload can be offset either toward or away from the knob or motor.

Inline Cantilever load on Vertical BiSlide

Inline / Vertical – The load may or may not be centered over the carriage, however the stage is positioned vertically, the load is traveling vertically and the center of gravity of the load is suspended outward from the carriage.

The payload in this image is on an XZ assembly. Additional parameters are involved with multiple axis assemblies. Please see the next section of Load Definitions when considering more than one axis.

Cantilever load with the XSlide positioned on its edge.

Edge – The load may or may not be centered over the carriage, however the stage is positioned horizontally on its side. The load is traveling horizontally and the center of gravity of the load is suspended outward from the carriage.

This position has more affect on the load allowed on UniSlide Stages than BiSlide or XSlide Stages because of the interlocking nature of the latter assemblies.

Inverted – The stage is inverted, so that the load is suspended from the carriage. The stage is operating in the horizontal plane. (Measured with load centered on the carriage. Load can also be cantilevered and that makes the maximum allowable calculation more complex.)

Inverted UniSlide with load

Note - In certain applications it may be advantageous to place the load on the inverted stage rather than the carriage. (Seen in some XY applications where the carriage is actually affixed to another stage.) Although the stage is inverted the load technically isn't inverted because the payload is not suspended.

This position has more affect on the load allowed on UniSlide Stages, than BiSlide or XSlide Stages because of the interlocking nature of the latter assemblies.

Vertical – The stage is positioned on the Z axis (in the vertical plane). The load is lifted and/or lowered (traveling vertically). The load capacity is going to be smaller than the normal centered load.

Vertical BiSlide with load Elevating Table with load This position has more affect on the load allowed on UniSlide Stages, than BiSlide or XSlide Stages because of the interlocking nature of the latter assemblies.

For the various ratings on Velmex products and how to calculate them, see "Load Capacities".

Multiple-axis Stages

Another factor to consider is the number of axes the system has. When looking at multiple axes, this includes the weight of any additional stages and adapter plates the base stage may be carrying, as well as the payload.

When you add additional axes whether horizontal or vertical, the load rating is generally measured at the base or bottom stage ("lowest common denominator").

Figure 1 Top stage with payload

When there is a vertical axis involved, the key load is the load on the vertical axis. Any additional components beyond the payload attached to that axis such as adapter plates, additional stages, etc. cannot exceed the maximum load for the vertical axis. And all the components together including the vertical stage and the payload cannot exceed the maximum load and/or the cantilever load for the base stage.

Lastly, you need also need to consider whether any of the axes or the payload creates a cantilever to the base stage.

Figure 2 Y axis stage

While the maximum load a stage can handle may remain the same; the size of the payload that can be placed on the top stage would diminish because you need to allow for the weights of other devices that are part of the system.

Figure 3 Z axis stage

Figure 1 - Shows the top stage - a Velmex Turntable - with the payload and a Velmex Turntable. Weight to consider here is the payload, the turntable and the plate that affixes the turntable to the next stage in the system depicted by Figure 2.

Figure 2 - Shows the second stage in the multi-axis system. This is the Y axis. Weight to consider includes the weight from Figure 1 plus the linear stage and the adapter plate that affixes the Y axis to the Z axis depicted by Figure 3.

Figure 4 X axis stage - base of the system

Figure 3 - Shows the third stage in the multi-axis system. This is the Z axis. Weight to consider includes the weight from Figure 1 and 2 plus the linear stage and the adapter plate that affixes the Z axis to the X axis depicted by Figure 4.

Figure 4 - Shows the base stage in the multi-axis system. This is the X axis. Weight to consider includes the weight from Figure 1, 2 and 3 plus the linear stage. In this specific example an additional element to consider is the fact that the X axis is set on its edge making all the axes above it cantilevered.

  Load on a Multi-axis System

Velmex Application Engineers can help calculate maximum permissible loads on specialized systems as well as determine whether a Velmex system could support your specific payload parameters.