Definitions – Holding Fixtures
Angle – See Mounting Interface
C.G. (Center of Gravity) – The center of mass with reference to gravity as the external force. The C.G. of an assembly is that point through which a single force must act in order to support the assembly. The C.G. of an assembly to be mounted on a Holding Fixture must be calculated in order to establish the eccentricity of the C.G. of the assembly in relation to the trunnion centerline. Knowing the eccentricity of the load and the total weight of the load, one can look at the data sheet load graph of the specific Holding Fixture under consideration to determine if the load will be within the fixture’s rated capacity.
Capacity – See Load Capacity
Caster – A relatively small wheel assembly mounted under a fixture. All floor FLOTRON Holding Fixtures are mounted on 4 or more swivel casters, which include a wheel brake. The swivel allows for steering the fixture when moving it and the brake allows the wheel to be locked when needed.
Available as an option on many fixtures is the Total Lock brake, which simultaneously locks both the wheel and the swivel. However, if one desires to lock only the swivel then a separate swivel lock and wheel brake must be ordered.
Depending on the specific Holding fixture you are considering, several different wheel types are available. They include the High Tech polyurethane wheel, the shock absorbing Performa wheel and a conductive wheel to aid in electrostatic dissipation.
Clamp – See Mounting Interface
Clean Room Requirements – If the fixture is to be used in a clean room, the “clean room option” may be necessary. The “clean room option” includes the following:
Krytox grease on trunnion and caster bearings
Stainless steel hardware
Leak checked gearboxes with Mobil SHC007 lubricant (or grease lubricated)
Note: For more information on clean rooms, see the Technical Section.
Conductive Wheel – See Caster
Double Beam – See Main Beam
Double Reduction Gearbox – See Gearbox
Dynamic Load Capacity – See Load Capacity
Eccentricity – See Load Eccentricity
Enamel – See Paint
ESD (Electrostatic Dissipation) – Many electronic components are sensitive to electrostatic voltages, especially if the voltage is suddenly discharged through an arc. To avoid this problem, many materials have been developed to either minimize the production of the electrostatic voltage or to slowly allow the voltage that is developed to discharge to ground (which is ESD). FLOTRON can provide optional ground lugs and drag chains on any of the Holding Fixtures, which will maximize the ability to conduct any electrostatic charge to ground. Conductive wheels are also offered. (E option) NOTE: for more information on ESD, see the Technical Section.
Ergonomics – The applied science of coordinating the system (fixture) design with the capacities and requirements of the worker. FLOTRON holding fixtures are designed with the worker in mind and greatly reduce the risk of injury while increasing efficiency and productivity of the worker. See the Technical Section for more information on ergonomics.
Forklift Tubes – On larger fixtures, it may be desirable to occasionally pick up the fixture with a forklift. To facilitate this, rectangular steel tubes, which are large enough to encase each forklift tine, are optionally supplied with the fixture. These tubes prevent the fixture from sliding on the forklift while it is being moved.
Gearbox – Many FLOTRON fixtures are supplied with a gearbox for rotating the load about the trunnion centerline. The gearbox is especially necessary when the C.G. of the load is not on the trunnion centerline. The standard single reduction gearbox ratios (which are offered on the 400 through 700 series holding fixtures) are 40, 50 and 60 to 1. The double reduction ratios (used on 600 through 1200 series fixtures) range from 250 to over 3,000 to 1 depending on the specific gearbox. FLOTRON recommends the use of a gearbox on all larger fixtures because of the safety concerns resulting if someone leans on a part and causes it to swing around unexpectedly.
If large sized loads require a low backlash gearbox, FLOTRON has many standard options. Both the SR (single reduction) and DR (double reduction) options are low backlash and are offered on the 600 series and 700 series fixtures. On the 800 series and larger fixtures, multiple reduction, low backlash gearboxes are standard.
Note that the addition of the SR or DR gearbox to the 600 and 700 series may shorten the vertical adjustment range of the risers. For details, see the individual Data Sheet of the fixture in question.
High Rotational Inertia Load – (Also see: Inertia, rotational) Often, a large part, even if it is relatively light weight, can have a high inertia. This inertia can create higher torques on the trunnion gearbox than might be normally expected. Also, when high inertia loads back drive the gearbox, a phenomenon called “stair-stepping” may occur (see Stair-stepping definition or go to the Technical Section for more information). FLOTRON offers optional gearboxes on the 600 and 700 series fixtures, which are stair-step resistant. All gearboxes on 800 series and larger fixtures are stair-step resistant.
Index Plate – An index plate is a round steel plate mounted to the trunnion shaft and drilled with holes at 15-degree increments. By aligning one of the holes in the plate with the hole in the riser and inserting the index pin, rotation of the trunnion is prevented. An index plate can be used either with a balanced load where no gearbox is used or with an unbalanced load where a gearbox is used but where vibration or other manufacturing loads may cause back driving of the gearbox. If you have special indexing requirements, which are other than the standard 15 degrees, FLOTRON can supply custom index plates for your application. Index stops can also be supplied which will limit the rotation of the trunnion to less than 360 degrees.
Note that the addition of an index plate to the 300 and 400 series may shorten the vertical adjustment range of the risers. For details, see the individual Data Sheet of the fixture in question.
Inertia, Rotational – Rotational Inertia is the property of matter where an object tends to either retain its state of rest or retain its state of rotational velocity unless it is acted upon by an external force. See Stair Stepping in the Technical Section for information on how to calculate rotational inertia.
Leg – The Leg of a fixture is the horizontal part of the fixture frame connecting the riser with the caster.
Leveling Jack – A Leveling Jack is a hand cranked unit which can be mounted near each caster. When the fixture is stationary and is not on level ground, the four Leveling Jacks can be adjusted up or down as required to level the load and/or keep it from rocking.
Less Gearbox (LGB) – Less-Gearbox simply means supply this fixture without a gearbox. This is an option on some Holding Fixtures which normally only are supplied with a gearbox. FLOTRON highly recommends the use of a gearbox on all larger and/or heavier loads.
Lift Eye – Lift Eyes are rings or other devices, which can be added to the fixture as a special option, and will allow lifting slings to be attached to the fixture for the purpose of moving it with an overhead crane.
Load Capacity – All standard FLOTRON Holding Fixtures have a rated load capacity using a safety factor of 2, 3 or 4 based on the yield strength of the materials of construction. Additionally, many of the fixtures will have both a dynamic and a static load rating. The dynamic rating includes a 1.0G downward load and .5G horizontal load. Most standard off-the-shelf FLOTRON Holding Fixtures have been both analyzed and tested to these specifications. All Custom designed FLOTRON Holding Fixtures are normally designed to a safety factor of 3 based on yield strength and 5 based on ultimate strength or may be designed to any other more stringent criteria you may require.
Load Eccentricity – This is the distance measured perpendicular from the trunnion centerline of the fixture to the C.G. (center of gravity) of the load.
Lock Rod – As a custom designed option, FLOTRON can provide lock rods, which are used to prevent rotation of large sized loads. Although a standard Index Plate can be used to prevent rotation, sometimes on large sized loads the backlash is unacceptable. When the load only needs to be held in one or two positions and lock rods can be attached to the load at a large radius, lock rods are the answer.
Low Backlash Gearbox – See Gearbox
Main Beam – The Main Beam is the square tube connecting the two end frames of the standard FLOTRON Holding Fixtures. The 300 through the 500 series fixtures are available in either a single beam or triple beam design. On the 700 series fixtures, either a single beam or a double beam design is available. The 600 and 800 series fixtures are available with a single beam, while double beam versions can be supplied as a special. The standard 900, 1000, 1100 and 1200 series are available with double beams only. The single beam design allows for easier access to small parts and the double/triple beam designs give much more rigidity and strength.
On the 300 through the 500 series fixtures, a telescopic main beam is available as a standard option. It allows for a large adjustment range without so much of the beam extending beyond the end frames of the Holding Fixture.
Maximum Swing Radius – The required swing radius for a particular part is measured perpendicular from the trunnion centerline to the furthest extremity of the part. The maximum swing radius allowed for a particular fixture is limited by the size of the fixture and measured with the riser in its highest position. The allowable swing radius for the fixture must always be greater than the required swing radius of the part.
Note that if the height of the trunnion centerline must be lower than the maximum riser height, then the allowable swing radius will also be less.
Mounting Interface – This is what holds your part in the fixture. FLOTRON manufactures several standard mounting interfaces. They include a mounting angle, an angle clamp, a scissors clamp and a mounting plate. Not all interfaces are standard on all fixtures. Once the size and type of fixture is determined, look at the appropriate data sheet to determine what mounting interfaces are available as standard.
Mounting Angle – See Mounting Interface
Mounting Clamp – See Mounting Interface
Mounting Plate – See Mounting Interface
Nickel Plate – Selected steel parts of the Holding Fixture may be electroless nickel plated as a standard option. This would most likely be only for special clean room requirements or in applications where the standard zinc plating poses compatibility problems with the load.
The (N) option replaces parts that are normally zinc-plated with electroless nickel-plated parts or stainless steel parts.
The (C) option is identical to the (N) option but with the addition of electroless nickel-plating on the interior of the end frame slide tubes and vertical support tubes. On the smaller models, the exterior of the end frames are also electroless nickel-plated. On the larger models, the exterior of the end frames as well as the exterior of the gearbox are painted with high gloss urethane or epoxy paint.
Off-Center Load – This refers to the C.G. of the load being located some distance from the trunnion centerline. Also see Load Eccentricity.
Paint – Selected parts of FLOTRON Holding Fixtures are coated with high quality blue enamel paint. At the manufacturer’s discretion, powder coat finishes and colors may be substituted. On the “clean room option” (C) white gloss urethane or epoxy paint is used on the gearbox case and in some cases on the End Frames.
Performa Wheel – See Caster
Plating – Selected parts of FLOTRON Holding Fixtures are zinc plated. On the “nickel plate option” (N) and the “clean room option” (C), electroless nickel plating is used. Other types of plating are by special order only.
Polyurethane Wheel – See Caster
Powder Coat Paint – See Paint
Rated Load Capacity – See Load Capacity
Riser – The Riser is a vertical telescoping tube to which the trunnion bearing is attached at the top. It is typically adjusted vertically by moving it with the load removed, then inserting a pin in the desired hole to hold the desired height. The 500 and 700 fixtures have hydraulically raised risers as on option (HYD) that allow the height to be adjusted with load on the fixture. A Holding Fixture normally will have 2 risers.
Safety Factor – There is always the risk that the working stress to which a member is subjected will exceed the strength of the material. The purpose of a safety factor is to minimize that risk. Safety factor can be defined as follows:
(working stress) (safety factor) < (strength of material)
FLOTRON uses safety factors of 2, 3 or 4 based on the yield strength of the material. Also see Load Capacity
Scissors Clamp – See Mounting Interface
Single Beam – See Main Beam
Static Load Capacity – See Load Capacity
Stair-Stepping – Stair-stepping is a jerky motion, which can occur when self-locking gears are used in the back driving mode. When this is a concern, FLOTRON offers stair-step resistant gearboxes as an option for the 600 and 700 series fixtures. On the 800 series and larger fixtures, stair-step resistant gearboxes are standard. See the Technical Section for more information about stair-stepping.
Swing Radius – The Swing Radius is measured perpendicular from the trunnion centerline to the nearest point of interference. It will vary widely depending on the model and the height to which the riser is adjusted.
Swivel Caster – See Caster
Swivel Lock – See Caster
Telescopic Main Beam – See Main Beam
Temperature – The standard operating temperature for all Flotron Fixtures is +32 to +140°F (0 to 40°C). Contact the factory for special applications with extended operating temperatures. Most fixture operating temperature ranges can be extended with optional wheels, seals, lubricants, etc.
Torque – A rotational force
Total Lock Brake – See Caster
Triple Beam – See Main Beam
Trunnion – The bearing system on the Holding Fixture, which allows the part or load to rotate about a horizontal axis.
Trunnion Brake -On the 200 through the 500 series Holding fixtures, there is a knob which when tightened, forces a pad against the trunnion shaft. The friction from the pad tends to prevent rotation of the load. Note that this is a brake and should not take the place of a gearbox or index plate to prevent unexpected rotation.
Trunnion Centerline – The imaginary line at the center of the trunnion bearings. It is a horizontal axis about which the load can rotate in the fixture.
Trunnion Interface – See Mounting Interface
Zinc Plate – Selected parts of the FLOTRON Holding Fixtures are zinc plated to prevent corrosion.