Shrink wrap applications made more efficientShrink wrap applications made more efficient
January 29, 2014
The popularity of shrink-wrap packaging has
Shrink wrapping is used in a wide variety of applications, because it provides a rapid and dependable method for protecting delicate products. Less expensive than many other packaging methods, shrink packaging helps protect products—from pizza to pickles—against harmful environmental conditions, thus improving a product's marketability.
Shrink wrapping's benefits, however, have led end users to expect speed, speed and more speed from packaging machines. In addition, packagers' demand for corrosion-resistant components and minimized maintenance also has grown.
Shrink-wrapping can offer low-cost packaging for a diverse range of products from pickles to pizza.
Faced with this need for speed and corrosion resistance in shrink-wrap applications, packaging equipment manufacturer Stork-Texwrap turned to Rexroth's eLINE linear motion components to reduce machine weight and costs and expand speed and productivity. Working with Bosch Rexroth, Stork-Texwrap not only increased throughput to more than 200 packages/min in some applications, but also speeded up changeovers and added quick-disconnect capabilities for conveyors that needed to be washed down.
Packaging end users that need to watch their overall investments very carefully usually expect to have these advantages on a budget. With expectations for high speed, low maintenance and washdown performance, it can all add up to a tall order for packaging machine builders. But it's become the norm.
Thanks in large part to Rexroth's eLINE linear ball rail and eLINE cam roller guides, however, Stork-Texwrap, is now able to offer a side-seal/orbital cross-seal wrapper that meets all these demands and more.
This machine, Texwrap's 205CR, is a corrosion-resistant packager that is ideal for bakery and similar high-output applications. Features for the 205CR include a wide product size capacity and a removable washdown infeed conveyor. And Rexroth's eLINE linear motion products are responsible for some of the 205CR's more critical features, such as high speed operation. It wraps up to 250 packages/min and provides heavy-duty performance, while minimizing weight with lightweight components. The use of these cost-effective, off-the-shelf linear-motion products from the Linear Motion and Assembly Technologies division of Bosch Rexroth played a large role in cutting costs and optimizing the 205CR's performance.
Bosch Rexroth's contributions to the speed and performance of the 205CR began in spring 2005 when Bosch Rexroth's Mike Buesking introduced Rexroth eLINE ball rail linear motion products to Stork-Texwrap, which was looking to upgrade the performance of its existing shrink-wrap machines while keeping control of cost, size, and weight. The eLINE ball rails, a maintenance-free and economic solution for materials handling, proved to be a good fit within several different linear motion configurations. The products offer impressive performance with low weight and high cost-effectiveness, with their straightforward but rugged construction.
High-quality components used to build equipment , such as the high-speed, side seal/orbital cross seal machine pictured above, can offer heavy duty performance and still be lightweight.
The components proved to be a good choice for adapting into existing machines. Projects adapting various machines that include other continuous motion side sealers, like the 1809SS ServoMax with “Generation 3” Design, 2203 Horizontal Side Sealer and 2814 Servo Side Seal, with eLINE ball rail products were big successes.
In 2006, Stork-Texwrap learned about another new Rexroth linear motion development from Scot Rohlfing of Hitech Automation, a full-service Rexroth distributor that has long been a source of components for Texwrap's packaging line. That year, Bosch Rexroth introduced the fast, quiet eLINE cam roller runner block, allowing smooth movements of light loads (up to 60 kg) over extended lengths.
With an aluminum runner block body with stainless steel, corrosion-resistant cam rollers, the eLINE cam roller block (and associated eLINE rail) with its precise manufacturing eliminates the need for preload adjustment.
The feature that really got Stork-Texwrap's attention was the combination of high travel speeds (up to 12 m/sec), and lightweight stainless steel components. “The eLINE products can combine high speeds with the corrosion-resistance that you need for tolerating frequent washdowns,” explains John Butler, vp of sales at Hitech Automation. “This makes them ideally suited for applications like bakery shrink wrapping.”
Again, the specific shrink wrapping application Stork-Texwrap had in mind was its 205CR.. Texwrap designed the eLINE ball rail and cam roller guides into this new product. Thus extending the range of applications for which the machine would be suited. The speed and reliability of the new Rexroth linear motion components could meet the key challenges of virtually any of the machine's potential applications.
Those challenges were not limited to line speed and corrosion-resistance. “We were definitely interested in getting high-speed performance without extra weight and cost,” says Brian Stork, engineering manager at Stork-Texwrap. The eLINE cam roller runner blocks provided this with an aluminum runner block body housing corrosion-resistant cam rollers, giving Texwrap a compact, cost-effective version of heavier-duty linear-motion products used in higher-load applications.
Lubricant consumption requirements can be dramatically reduced by manufacturing
The eLINE components' design features that further reduce total cost of ownership for the 205CR include hardened steel inserts and the use of anodized aluminum. These ball-rail and cam-rail eLINE products also enable easy interaction with additional axes (the standard 205CR has five axes) and external attachments. This is an important feature because flexibility in adding extra equipment is one of the 205CR's selling points.
The low friction levels of these eLINE components also dramatically minimize lubricant consumption, resulting in smooth moves for shrink wrapping applications. The eLINE ball and cam-roller blocks run smoothly and quietly, even when running at their maximum speed of 12 m/sec.
The eLINE products also offer higher moment and load capacities than single-rail solutions, helping machine designers do more with less. And by placing both cam roller and ball-runner blocks on the same rail, Rexroth components help machine builders reduce space requirements. Rugged, reliable and almost maintenance-free, eLINE components provide a good return on investment throughout the life of the machines in which they are incorporates.
In 2007, after a testing period, the initial 205CR model was installed in the plant of a bakery products packager. The machine has been a great success, with its strongest popularity among bakeries looking for a high-speed shrink-wrap system with low maintenance and washdown-safe capabilities. Another favorable feature of the 205CR has been rapid and smooth machine setup, utilizing Rexroth eLINE components for slow moving manual adjustment slide rails. Some machine adjustment slides, to accommodate different product sizes, also are facilitated by eLINE. Maximum film speed is 200 ft/min, a lively pace that makes a 250 packages/min output a reality.
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