Linear Positioning Systems for Manufacturers of Additive Manufacturing and 3D Printing Systems - Part 2

Published by Schneeberger USA

 

Part 2 of 2: Rigidity, Speed, Precision — and The Future

Besides new additive manufacturing and 3D printing technologies and their myriad of current and future applications, designers must also stay abreast of new developments and essential functionalities in critical core components. These include the linear positioning systems that enable their printer components to function according to design.

Rigidity

The performance of an additive manufacturing or 3D printing system’s linear positioning solution rests, literally and figuratively, on its base. 

Wherever high performance is required, sufficient rigidity or stiffness demands close attention to factors such as thickness, frame construction, and materials. All must be consistent with the final performance specifications you want to achieve. 

Rigidity affects factors such as flatness and straightness. For example, a manufacturer may attempt to attach a linear positioning rail made of stainless steel, of the required thickness and suitably rigid design, to an aluminum plate thinner than the rail. The inevitable result: deflection. (Linear positioning components are typically designed to resist forces along the X, Y, and Z axes to prevent this.) Here, the deflection would mean that the rail could curve, however slightly, in the direction dictated by any force applied. This affects smooth travel and repeatability, degrading the printed product’s uniformity. 

But even the most advanced linear positioning products can’t deliver superior speed or precision if they rest on a base that allows extraneous movement. Traditionally, most 3D printers have been mounted on structures such as sheet metal cabinets or aluminum tables. Unfortunately, these bases won’t deliver the acceptable rigidity demanded by modern additive manufacturing and 3D printing equipment. So instead, the recommendation is for strongly built steel or iron structures or granite bases. 

An innovative choice is a substructure composed of minerals and epoxy resins.

These mineral cast bases furnish printer beds with excellent vibration dampening, strong chemical resistance, and excellent thermal stability. In addition, they can be formed to accommodate any contours and dimensions a given printer requires, including custom-shaped openings, spaces, and wiring channels. They also offer clear technological, economic, and ecological advantages over steel, gray iron, or cast iron. 

Discuss expected loads and printer configuration with the linear positioning supplier early so that the resulting system is designed from the start to withstand all the forces and conditions and meet all the accuracy and precision requirements of its intended application.

Speed

The travel speed of a linear positioning system essentially defines the printer’s production speed. 

Relatively slow speeds are required for some additive manufacturing and 3D printing systems tasks to prevent such issues as deformation. On others, excessive travel acceleration can create problems from ringing to ghosting to lack of layer adhesion to filament blobbing. In most cases, manufacturers ask linear positioning suppliers to deliver maximum speed wherever possible.

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When the highest productivity or output is required, the linear positioning element must be able to accelerate as rapidly as possible. But settle time is often another key metric: how long it takes the rail or other component attached to the moving part (print or beam head, material bed, etc.) to come to rest without appreciable vibration after each acceleration step. However, such factors greatly depend upon the printer design, the material, shape, thickness, resolution, and other characteristics of the specific item the printer produces; and which linear positioning components are employed.

Generally speaking, in an optimum configuration, some of today’s high-performance linear positioning systems can attain constant velocities with step-and-settle intervals — even at exact positions — of as low as 50 milliseconds.

That would allow extremely rapid travel to support the fastest industrial printers available today, which operate up to 1000 millimeters a second. A discussion between the manufacturer and supplier is required to determine what can be achieved in any specific application.

Precision

The choice of linear positioning equipment directly impacts the degree of positional accuracy and repeatability — the precision — that an operating additive manufacturing and 3D printing systems demand. Therefore, the linear positioning technology will impact the end application’s critical performance requirements, including accuracy, repeatability, and resolution.

If the end user in an additive manufacturing or 3D printing process employs after-print finishing steps to attain given tolerances or flatness/smoothness specifications, extreme precision in primary printing may not be necessary.

However, a good linear positioning system for this range of printers might deliver positional precision down to plus or minus 50 or 100 microns. 

However, internal features of the finished item may not be easily accessible after completion. Additionally, leading additive manufacturing and 3D printing system designers and manufacturers are evolving their approaches to minimize extra finishing. Thus, an extremely accurate linear positioning may be required to achieve precise dimensions and shapes at every point. 

Many additive manufacturing and 3D printing applications are now exceeding the level of linear positioning equipment precision traditionally required by high-performance machine tools. And as technologies continue to evolve, expect many applications to demand even higher degrees of precision — such as leading linear positioning suppliers’ design into ultra-precise nanoscale equipment for semiconductor manufacturing. For additive manufacturing and 3D printing system requirements that fall into these latter groups, a linear positioning technology supplier must be willing and able to consult on specific requirements. The supplier must compare the exact capabilities of possible linear positioning solutions that will enable the manufacturer to achieve new levels of precision. 

Much depends on the specific printer design and on the item that must be bio-printed. Beyond, a linear tech supplier must address issues from the linear positioning system’s stiffness, flatness, load/preload, and construction materials to its operating temperatures and vibration/resonance potential, as well as considering factors such as constant velocity and stroke length. But under the right conditions, a superior linear positioning system today can enable particular additive manufacturing and 3D printing systems (for example, bioprinting) to attain repeatable accuracy from 0.5 down to 0.1 microns.

Moving into the Future of Bioprinter Manufacturing

Today’s advanced linear motion systems can, and are, delivering the precision that bioprinting applications can demand. 

As bioprinter manufacturing continues its explosive development, speeds will increase, efficiencies will grow, and the use of biomaterials will proliferate. 

There is ample room for bioprinters’ linear motion capabilities to grow. For instance, precisely controlling the movement of dispersing elements on smaller and smaller scales can empower bioprinters to manufacture ever-finer somatic structures. Vein tissue was first successfully printed in 2016. Fully functional 3D-printed human organs are predicted in the not-so-distant future.

The Bottom Line

An increasing number of leading additive manufacturing and 3D printing system manufacturers are exploring the benefits of advanced linear positioning solutions for their challenging, cutting-edge, and in many cases, unique products.

The right linear positioning systems supplier can overcome concerns and obstacles to help deliver advantages such as expert design, acceptable lead times, reduced cost of ownership, reliable quality, and rewarding partnership.

In addition, the right linear technology can provide critical characteristics such as rigidity, speed, accuracy, precision, miniaturization, customization, material compatibility, and biosafety that enable truly high-performance additive manufacturing and 3D printing.