FEATURE LINEAR MOTION Two pairs of oval PRT2 track systems
were therefore installed in a V-shape. The first track system delivers containers to the printing machine and is fed by a conveyor, while the second removes products and delivers them to an outgoing conveyor for further processing. For stability, the in-feed and out-feed systems use two track systems mounted in parallel (one above the other), at a distance of around 150mm. The products are delivered and removed from the printing system on the curve of each track system, at a tangent to the printing machine. Conducting this operation at the curve makes for a smooth transition between operations. At maximum speed, the carriages run
A guidance system with a lot of bottle
HepcoMotion explains why its PRT2 track system has been specified for a new digital machine for the beverage industry, which has been designed to print directly onto containers
C
apable of printing directly onto 3D containers without the need for a
label, the fully automated SmartPrint digital print machine is the latest development from Germany based Till, a manufacturer of printing machines for the drinks industry. However, as the printing process can be tailored to customer demands, there were specific technical requirements faced during the development process. The DecoType Performance printing
machine uses up to 48 printing stations mounted on a rotary frame – each can print up to eight colours and eight shades of grey with a resolution of up to 720dpi. The machine is suitable for containers ranging from 47 to 98mm in diameter and 100 to 350mm high, and can process up to 36,000 containers per hour depending on bottle size, artwork height and bottle material. The speed of distribution is between 2m/s and 4m/s, reducing around curves to minimise the impact of acceleration forces on the carriage. For the machine, a guidance system was needed that could cope with the high cycle rate as well as the variation in size of the containers, which would be delivered to the printing machine by conveyor belt. The system needed to be capable of picking containers and populating specific
12 MAY 2018 | DESIGN SOLUTIONS
printing presses, avoiding those which have been taken offline for automatic cleaning and maintenance. It would also need to operate over a three-shift system for up to 350 days a year.
SYSTEM REQUIREMENTS For this application, the containers are mounted to 48 individual carriages on HepcoMotion’s PRT2 track system, with each carriage individually driven by Beckhoff XTS linear motors. The system needed to provide high
frequency operation, moving heavy loads at high speeds, accelerations and decelerations. Furthermore, each carriage needed to be individually driven to allow separation of carriages during the in-feed and out-feed processes, meaning a high degree of precision in the movement on the guidance system was needed. An additional requirement was to minimise the need to stop the machine for maintenance during production hours. Following this, printed containers need to be removed from the SmartPrint system. So, a secondary track system was needed. Due to the high number of products being processed – up to 36,000 containers per hour in a variety of batch sizes and patterns – the load on the carriages had to be kept as low as possible.
at 4m/s with a load of 1.5kg, creating centrifugal forces of up to 1g per carriage on the curves. Connecting two track systems gives greater stability and allows the carriages to accommodate higher loads, the company explains. For this purpose, a HepcoMotion PRT2 track system with size 44 slides, straight length 1255mm with two 180˚ 612mm diameter segments, and 216 x 25mm V-bearings was chosen. The V-bearings are mounted to carriages designed specifically for the task by Till. To minimise
weight, each carriage uses three V-bearings per slide, rather than the typical four bearings per slide set-up. An integrated bleed lubrication system ensures smooth running whilst improving life. A food-compatible lubricant is dispensed from a cartridge through bores in the slide and carried around the system by the bearings, ensuring an even and constant film of lubricant on the running surface. Proper lubrication of the system will help to minimise potential downtime.
“The machine can
process up to 36,000 containers per hour
depending on bottle size, artwork height and bottle material. The speed of
distribution is between 2m/s and 4m/s”
HepcoMotion
www.HepcoMotion.com
For the machine, a guidance system was needed that could cope with the high cycle rate as well as the variation in size of the containers
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