Bishop-Wisecarver’s HepcoMotion HDRT (Heavy Duty Ring and Track) Systems are specifically developed for high-performance applications. HDRT guidance systems are characterized by their ability to carry high loads — moving reliably and accurately with very little wear. At Eurocylinder Systems AG the HDRT guidance system has proven itself in a demanding production environment with large amounts of contamination and residues.
Eurocylinder Systems AG is a medium-sized company in the metal processing industry and a high-pressure steel cylinders manufacturer. These cylinders are used to store and transport compressed, liquified, and dissolved pressure gas used in technical, fire protection, diving, beverage, and medical applications. Each cylinder is made from a steel tube, cut into casings between eight and twelve meters. The wall thickness varies from three to nine millimeters, with six different diameters — 140, 172, 178, 204, 229, and 267mm. At the plant, around 1000 casings are cut per day. Every year, Eurocylinder Systems produces approximately 500,000 high-pressure steel cylinders. The plant is predominantly operated in rolling shifts or in three-shift operation and is in operation for over 300 working days per year.
Historically, the cutting of the casings was done using two bandsaws. For this, the supplied tubes were cut into casings of the required lengths with vertical cuts (perpendicular to the tube axis). This was a lengthy process taking up to five minutes per cut. Eurocylinder Systems wanted to optimize this complex process. In 2009, the bandsaws were replaced by a plasma cutting machine. The cutting head of the plasma system has two plasma torches. They are placed opposite each other and rotate during the cutting process on a circular path 180° around the steel tube. One cutting head is responsible for the upper half of the pipe, the other for the lower half of the pipe. Eurocylinder Systems needed to ensure reliable, low-maintenance guided motion of these critical cutting head elements.
Requirements: no wear and low maintenance
To guide the plasma cutting heads along a prescribed circular path, a ring-shaped high-performance guide system was required that can meet the required operating times free of faults. The main requirement was to install a guide system that can be wear-free and low-maintenance in operation. Additionally, the rings need a high load-bearing capacity to support the entire cutting head (approximately 330 lbs. or 150 kg in total) and operate at the required rates. The plant is in a hall subject to ambient temperatures. Therefore, the guide must, be resistant to contamination arising from the production process and withstand the external influences — in particular, the temperature variations. This means that the plant and the guides must be operable with minimal downtime during any weather, in any season, with temperatures between 77 and 104 °F.
Challenges: deposits and impurities
Due to the plasma cutting process conditions, large amounts of combustion residues and contamination are produced during this production step. During the cutting process, the burnt material is carried into the interior of the pipe casing by the plasma jet, which causes problems later on in the processing. Therefore,the casings must be cleaned following the plasma cutting. Guide systems also become polluted with slag splashes and fine dust deposits from the plasma fumes.
To withstand the demanding environment, the solution consisted of two HDRT (Heavy Duty Ring and Track) ring systems to hold the cutting heads and guide the circular paths. These rings feature vee guide technology that delivers a self-cleaning action, which means that any contamination is wiped away by the vee bearings as they run along the track. Eurocylinder Systems installed a special housing with a felt ring seal for the HDRT rings that protect the HDRT rings from external influences such as dirt and dust to further combat the slag splashes and material deposits. In this application, each ring has a 786 mm diameter and is made from hardened, high-quality tool steel with precision-ground running surfaces.
The two parallel rings each use four 95 mm diameter eccentric vee bearings for the high loads. Lubrication is provided by four lubrication blocks (two per HDRT ring). The blocks are made of impact-resistant plastic including, a spring-tensioned, lubricant-soaked felt wiper for low-friction lubrication and high load capacity and lifetime. The lubrication blocks have now been in service for more than seven years without being refilled.
The main aim of Eurocylinder Systems was the optimization of their plasma cutting process while at the same time accelerating and automating the cutting process. Using the bandsaw, up to four pipes were cut simultaneously, depending on the diameter. The bandsaw required five minutes, just for the cutting. With an overall cycle time of about six minutes, that means 90 seconds per casing. The plasma cutting system only needs five to ten seconds for one cut, depending on the tube diameter and thickness. The total cycle time amounts to about 30 seconds per casing. The time saving using the HDRT and plasma cutter system is about 60 to 70%, if the tube length, diameter, and wall thickness are the same.
Self-cleaning HDRT vee rings provide low-maintenance guided motion
The system of plasma cutting heads and HDRT guidance has been in use since 2009. Since then, the system has required no maintenance and has resulted in no errors or faults. The angled geometry of the HDRT system expels soot and slag debris as the vee guide wheel runs along the matching vee ring surface. Both the plant and the HDRT system are exposed to these harsh environmental conditions, but the system has proven reliable, running without any maintenance or failure for over a decade.