Designing handling systems for heavy applications

Chris Rees offers advice on the design of heavy-duty systems for pick-and-place operations.

When designing systems for heavy handling and pick and place applications, choosing the right linear motion solution can be overwhelming.

With such an extensive selection available, the decision often comes down to wheel versus recirculating ball bearing technologies.

Considerations in addition to satisfying the application requirements will, of course include price and delivery but often to a lesser extent assembly time and long term maintenance are relegated down the list of requirements as cost issues can take over.

The hidden costs can then sometimes be ignored especially if some of the components can be made in house by the customer or contractor.

In considering the total cost we should include labour time associated with installation and long term maintenance.

How much work is the customer willing to undertake with respect to fitting the guidance system to machined steel beams?.

How easy will access be when the system is installed, what about spares, what is likely to fail first and how easy is it to change the failed part?.

A properly sized system can last the lifetime of the machine but only using quality parts can this be guaranteed When analysing specific application requirements, the Hepco HDS range provides a versatile solution.

With its unprecedented range of components, HDS can meet design needs from the simplest to the most sophisticated system.

At the heart of HDS is the concept of rigid aluminium beam to accommodate the attachment of the system's single edge precision and commercial plain or rack cut slides.

There are, in fact three sizes of beam the standard version for medium to heavy duty gantry x-axes 130mm wide x 220mm high, the compact beam for z-axis requirements and now the much larger 200mm wide x 300mm high beam for heavy duty gantries Key features include: The versatile construction beam in two standard sizes, plus a compact version; The slide in single lengths up to 4m - longer length systems can be achieved by joining; single edge slides for best load spacing, integral rack drive or plain; two types of bearing elements - range of double row ball bearings up to 128mm diameter for high load, high speed, no maintenance or blocks containing four needle roller bearings for high load where space is an issue; a range of pinions to suit complete with locking bush; loads to 40kN; very high speeds - 5 m/s is not unusual; low friction vee bearing/slide arrangement; high stiffness beams that can be used over long lengths unsupported; a continuous lubrication option available through cap wipers; debris tolerance; quiet operation; and the ability to works in any plane.

: The rigid beam and drive capability make the HDS ideal for gantry robot design or driven carriage assembly.

Whilst rack driven systems are often preferred in gantries belt driven linear elements are easily accomplished from a standard product.

The HDLS product uses single edge vee slides attached to the beam.

The hollow beam, in turn allows for return of the belt, while the end box design enables easy attachment of the motor and pulleys.

This solution is available as a complete product.

HDS is also ideal for many cutting, lifting, handling applications in automotive and general demanding Industries where customers need to integrate the components into their complete machine.

Aluminium alloy construction beams are a lower overall installed cost alternative to steel sections.

While they do not have the inherent strength of steel sections, when assembled and supported, they will provide more than adequate rigidity and accuracy for even the heaviest pick and place application.

There is also no need to machine steel beams and fit slides as the beam design will accommodate the slides fitted directly to the corners.

When Hepco Heavy Duty steel slides are fitted to the standard Heavy Duty aluminium beam they are especially useful in long length applications, where typically the time and precision required to set recirculating ball bearing type systems can be hours due to the high accuracy required to achieve satisfactory operation.

In contrast, the compliance of the wheel technology utilised by HDS allows a slight reduction in the overall accuracy setting required.

HDS systems can be shipped as assembled units, complete with drive transmission capability, and ready for installation, which reduces overall assembly and installation costs.

So there is no need to set the rails yourself.

What importance does the customer place on required maintenance?.

The answer seems somewhat obvious, but the do-it-yourself approach often taken by customers can, in the long run, be costly in terms of reliability and long term maintenance.

The environment must also be considered - not all environments are conducive to achieving long life.

Certain cutting applications produce debris that can break down many recirculating systems and cause them to fail, particularly without proper maintenance and re-lubrication.

HD wheels are normally fitted with cap wipers, which help prevent debris from contacting the guide wheel, and also provide a lubrication.

An x-z gantry system using the high strength aluminium beam with 220 x 130 and 95mm diameter bearings The larger beam 200 x 300 which could be used for the same application where higher capacity is needed normally uses 128mm diameter bearings, and provides 6 tonnes capacity.

The smaller of the two beams also makes an ideal y-axis, and for the lighter load application, as already mentioned the Compact beam is an ideal choice.

Newly developed for z-axis applications is a high capacity telescopic system axis useful where ceiling or head height is restricted.

The application also benefits from an integral rack drive incorporated into the slide, which saves on the cost and time of installing a separate rack and aligning it accurately.

Continuous lubrication is provided for both vee bearings and rack/pinion.

The Hepco HDS range is suitable for most high load applications where cost and performance are both essential.

Due to its ease of installation, low maintenance and capability to achieve long lengths, it is an ideal choice for heavy duty automation and pick and place gantry systems.

A wide range of accessories and options make HDS extremely versatile, and HDS can be purchased assembled for quick installation, or as individual components for custom designs.

Furthermore constant additions are being made to the range to provide even more choice the addition of a ballscrew driven version utilising the compact beam is one such example.

As expected this is available as a standard product HDCS and has been incorporated into the latest HDS catalogue.

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