Page 46 - MetalForming March 2011
P. 46
44 MetalForming/March 2011
www.metalformingmagazine.com
Tooling Technology
install a secondary heavy-duty wiper to clear away the caustic fluids from the rod.
Preventive Maintenance
Contrary to popular belief, mainte- nance of nitrogen gas springs does not begin when the spring has run its course through the production cycle. Maintenance begins by recognizing the different factors that influence the performance and life of a gas spring. Much of what affects the performance can be controlled prior to experiencing any problems, such as safe design and diligent preventive maintenance.
Sound preventive maintenance pro- cedures require operators to periodi- cally check the pressure and physical condition of springs for signs of wear. If a sampling of springs exhibits unsatis- factory appearance or pressure, the operator should check the remaining springs in the die. Changes in spring pressure and condition can indicate potential problems in die design, build or operation. When checking gas- spring pressure, compare the current reading to the original pressure listed on the die tag outside the die. If the pressure appears low, examine the spring for leaks. Apply fluid around the top of the cartridge assembly, around the piston rod and, in some cases, at the port. If no leaks are found, recharge the spring to the desired pressure and retest for leaks.
To check the physical condition of the spring, begin by visually examining the piston rod and tube assembly— this can be done without dismantling the spring. Worn springs should be evaluated and, if in good condition, rebuilt. Look closely at the rod finish to anticipate any problems with the spring, since the majority of springs manufactured today seal on the piston rod. Upon examination, if the rod is damaged it will need to be replaced.
When handling damaged springs, use extreme caution and do not attempt to repair them, under any cir- cumstances. Badly damaged springs should be safely disposed of, after relieving any remaining pressure.
Rebuild Options
When a spring has failed but gener- ally remains in good condition, a met- alformer has a couple of rebuild options: rebuild inhouse or send the spring back to the manufacturer for repair. Maintaining and repairing nitro- gen gas springs is relatively quick, easy and cost-effective.
Some springs have been designed to be recharged, but not rebuilt. Check with the manufacturer prior to repair to verify reparability and to obtain the appropriate instructions and repair kit. Repair procedure varies between manufacturers and spring models; therefore, maintenance technicians need specific instructions for each model. In some cases, standard bench tools can be used to repair gas springs. However, using the recommended load cells, removal and installation tools, and filling equipment is highly suggested.
The repair technician should have a solid understanding of how to perform maintenance and repair on the springs. Nitrogen gas springs are charged to a high pressure, so the maintenance technician must closely follow all safe- ty precautions as outlined by the spring manufacturer, and maintain a clean working environment to avoid any contamination. Some manufacturers offer training courses on gas spring repair, which is a great way to encour- age your employees to follow the prop- er procedures.
Performing routine maintenance allows the metalformer to evaluate and record the performance of the springs, by recording individual spring serial numbers and the date of manufacture marked on each product. Some manu- facturers offer warranties based on the number of strokes a spring performs or the length of time the spring remains in service. Should a spring fail prema- turely, the metalformer can provide the performance-history data to the manufacturer when making a warran- ty claim. MF
Article provided by Dadco: 734/207- 1100; www.dadco.net.
