HYDRAULIC CYLINDER TUBES

The production capacity installed corresponds to more than 12.000 tons per year of skived and roller burnished / honed tubes.

All the equipment have been designed and built by Stelmi, taking a great advantage of a 25 years long production experience.

Stelmi equipment machines the tube horizontally; the tube turns and the tool translates, carried at one end of the boring bar. Rotation and translation may be varied continuously. Machining the tube horizontally means an easier control of the tube itself from both sides and an easier positioning for long tubes. The machining operation is fully automated.

PROCESS EVALUATION

Compared with honing, skiving and roller burnishing process offers not only a better accuracy but also a better surface quality.
A comparison between standard production samples is shown hereafter; skived and roller burnished material has a lower Ra and Rz and a better bearing factor. The picture displays a 60% Tpi achieved, by honing, at a depth of 1,39 ?m The same Tpi value can be found at a depth of only 0,17 ?m thanks to the skiving and roller burnishing process. The shown differences are very important for the gaskets life; for honed tubes, after 100 working hours the gaskets are already 50% worn out. This is due to the fact that the gaskets operate like a "tool",
working to smooth the small, sharp peaks resulting from the honing operation. This phenomenon is unknown for skived and roller burnished tubes.The superior surface quality offered by the skived and roller burnished tubes is essential when a cylinder operates at high speed. The skived and roller burnished surface is superior also for
very slow displacements, avoiding the "stick-slip" phenomena. Honed surfaces on the opposite require frequent gaskets maintenanaces.

Product Characteristics:

• Dimensional accuracy
• Excellent surface finish
• Multiple grades
• Special shapes

Specifications:

• ASTM A519
• DIN 2391

Grades:

• 1010, 1020, 1026, ST 52, 4130, 4140, 8620

Size Range (indicated in blue):