Installation and maintenance Ball Screw Jacks

INSTALLATION
When arranging the ball screw jack and coupling it to machines, pay attention to the axis alignment. Failing an exact alignment, the bearings would be subjected to a greater overloading and anomalous overheating as well as to a greater wear, with a consequent reduction of their operating life.It is important to check that the spindle and the casing mounting plane be orthogonal and that the load and the spindle be on the same axis. Employing multiple screw jacks to handle the same load (see the mounting schemes section) requires further verifications: it is critical that the load support points, (the end fittings for KT models and the lead nuts for KR models), be perfectly aligned in order that the load can be uniformly distributed; otherwise the misaligned screw jacks would act as brake or counter-load. Whenever several jacks have to be connected by means of transmission shafts, it is recommended that they be perfectly aligned in order to avoid overloading the worm screws. It is advisable to use joints capable of absorbing alignment errors without loosing the torsion strength necessary to keep the synchronization of the transmission. It is necessary to mount the transmission in a way to avoid any displacement or vibrations, keeping attention to the fixing by means of bolts or tie rods. Before assembling the connection parts it is necessary to properly clean the contact surfaces in order to avoid any seizing and oxidizing problems. Assembly or disassembly shall occur by means of tie rods or extractors, using the threaded hole on the shaft end. In case of forced couplings, a shrink-fitting is recommended with a temperature up to 80-100°C. Installations environments with dust, water, vapors, etc. require precautions to protect the ball spindle, such as elastic protections (bellows) and rigid protections. The above protections are also used in order to avoid any accidental human contact with the moving devices. For civil applications it is always advisable to use the safety components.

PREPARING FOR SERVICE
All UNIMEC’s screw jacks are supplied filled with long lasting lubricant which ensures a perfect lubrication of the worm gear/ worm wheel group and all the inner parts. All K series screw jacks are equipped with a lubricant filling cap, a drain cap and an oil level indicator in order to allow the filling-up of the lubricant as necessary. As clearly explained on the relative paragraph, lubrication of the ball spindle is a user’s responsibility and it must be carried out periodically depending on the service conditions and the operating environment. Special sealing systems allow to hold the screw jacks in any position without creating leakage problems. The application of some accessories can limit these assembly possibilities: the various solutions to be adopted will be explained in the relevant paragraphs. Some screw jacks are equipped with an “add oil” label. The installer shall carry out the necessary oil filling when gears are not working. Fillings should not be excessive in order to avoid any overheating, noise, inner pressure increase and power loss problems.

START-UP
All screw jacks undergo a careful quality examination before being delivered to the client, and are dynamically tested load-free. When starting-up a machine where screw jacks are installed, it is critical to check for the lubrication of the ball spindles and for the absence of foreign material. During the calibration of the electrical end-of-stroke systems, the inertia of the moving masses should be taken into account, which for vertical loads will be lower in ascent and greater in descent. Some hours of operation at full load are necessary before the screw jack reaches its maximum running efficiency. The screw jacks can be placed under a full load immediately if necessary. If some circumstances, it is nonetheless advisable to operate the screw jack under increasing loads, reaching maximum load after 20-30 hours of operation. It is likewise recommended to take due precautions to avoid overloads in the initial stages of operation.There may be a higher temperature during these initial stages but this will be reduced once the screw jacks is completely run in.

ROUTINE MAINTENANCE
Screw jacks must be periodically inspected, depending on the level of use and work conditions. It is advisable to check for losses of lubricant from the casing, and if this occurs, it is necessary to find and eliminate the cause and fill the lubricant up the correct level. The lubrication conditions of the ball spindle must be periodically inspected (and restored if necessary) as well as the presence of any foreign material. All safety devices should be verified according to the normative in force.

STORAGE
The screw jacks must be protected from deposits of dust and foreign matter during storage. Particular attention must be paid to saline or corrosive atmospheres. We also recommend to:

  • periodically rotate the worm screw to ensure proper lubrication of inner parts and avoid that the seals dry up, therefore causing lubricant losses.
  • lubricate and protect the threaded spindle, the worm screw and the non varnished components
  • support the ball spindle in case of horizontal storage.

WARRANTY
The warranty is valid only if the instructions contained in our manual are carefully followed.

Unimec
UNIMEC S.p.A.
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Via del Lavoro, 20
20865 Usmate Velate (MB) | ITALY
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