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Under the Hood

Sakurai Maestro SD

In today’s industry, it is all about the extra step that one can take to impress customers. Brian Sims goes under the hood of the Sakurai Maestro SD to find out how it can offer an extra layer

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Maestro SD series of presses have been honed over many years

Tactile print with the Maestro SD

When we think of a screen-printer, I would suggest most of us we have an image in our mind of a small wooden screen, a squeegee and a rather messy process. Typically if asked what products you would think are screen-printed you would think of T-shirts and other less technologically advanced items.

These images in our head are not uncommon but do a great disservice to the one of the smaller sectors of the printing industry. If it was not for screen-printing, equipment such as mobile phones, touch panels, biometric sensors, fuel cells and RFID equipment would not be possible. As it happens, screen-printing allows us to have some of the most high tech gadgets we now take for granted.

The equipment needed to produce these components or products needs to print parallel lines or patterns with great precision and to miniature levels, as small as ten to 30 microns in width with a tolerance of plus or minus two to three microns.

Obviously, the image of the equipment we possibly have embedded in our minds, the aforementioned wooden screen and squeegee is clearly not used for this type of work. It needs precision devices capable of the very precise application of ink or whatever material is needed.
One of the companies at the forefront of this technology is Sakurai with its flagship press, the Maestro SD. This printer comes as either the MS-80SD or MS102SD versions depending on what sheet size you need, 800 x 550 mm or 1,100 x 750mm.

As part of a fully operational screen-printing line

Sakurai has been investing millions over the years in honing this technology and has a number of patents which keep it at the top of the industry. They have developed what is known as a cylinder press which, by design, has the material stretched over a rotating cylinder and the screen-printing frame passes over the substrate at a matched speed to the cylinder itself.

Screen-printing is generally known as ‘out-of-contact printing’ which means there is a gap, albeit very small, to allow for the inks or fluids to pass through the screen stencil onto the substrate. One of the main issues with the process is that during the application, the holes in the mesh of the screen stencil stretch or deform. The problem is when you need lines or patterns to be as small as ten microns across, any change to the mesh will cause the output to be over or under the tolerance required.

To overcome this problem, you can predict the amount of squeeze and distortion and alter the screen to compensate, for example, build in distortion to compensate. Sakurai claims to be the first company to see that this did not give the required sustainable precision required and they needed to find another way to overcome this issue.

What they did was to reduce the gap, and subsequent distortion, they reduced the gap to virtually zero. This ‘Zero Clearance’ technology is one of the key patents which makes the Maestro SD a market leader.

The key to the ‘Zero Clearance’ technology is in itself, quite straight forward as most good solutions are. What Sakurai did was to choose to drive the cylinder independently to the screen stencil. They designed the concept model that uses servo motors to drive the cylinder and another to drive the screen stencil and squeegee.

The system allows you to alter the position of the screen during the rotation of the cylinder, up to five times in any given pass. This effectively alters the print length and allows you to accurately position the printed pattern onto the substrate to the levels of accuracy needed.

This sounds simple, but clearly there is a significant amount of technology and design that takes the concept to delivery. It does however solve the problem and allow the ‘Zero Clearance’ sought after by Sakurai. The contact quality is now at levels previously thought impossible, leading to the techie gadgets, devices we take for granted being cheaper and more available.

So much for the concept, what does the machine actually look like and what does it consist of?

At the heart of the machine is the cylinder and screen frame, which contains the flood coater and squeegee. Sakurai has understood there needs to be a minimum of movement during each screen pass and as such designed a very solid frame and bed structure from cast iron developed from the offset printing products they also produce.
Screen and cylinder are all supported on precision bed ways and bearings and move with the smallest of force which maintains the precision positioning needed for the printing of the circuits and products.

Sakurai technology can create print with a tactile finish

There is standard feeder equipment that will allow a sheet to be lifted, separated and then fed down a traditional feeder table to be registered at the front lay system with a push/pull device.

Post-application there is an equivalent delivery system consisting of a large pair of ventilated belts which can be hinged down to gain access to the screen mesh to allow the squeegee and flood coater to be cleaned or fixed.

The screen frame can be removed at the delivery end of the press due to the use of the hinged delivery table so the feed positon of the substrate can be checked, adjusted or repositioned. When the frame is replaced, due to the design of the machine it fits exactly back where it was so no readjustment is needed.

The squeegee itself is driven and adjusted by motors and pneumatics but is easily accomplished by the use of numerical controls via the touch screen operation panel. The use of numerical control means you are able to produce sharp and vivid products with great repeatability.

The running speed of squeegee and flood coater is set and driven independently so optimising the printing condition.

As you would expect, there is a long list of standard equipment that is now taken for granted on highly automated presses and there is also an expansive list of optional extras such as a hickey picker, static eliminator and ultra-sonic double sheet detector for translucent substrates.

The Maestro SD press from Sakurai allows for the mass production of a number of key products we now rely on

It may not be on everyone’s shopping list, but the Maestro SD press from Sakurai allows for the mass production of a number of key products we now rely on and who knows what in the future.

Brian Sims principal consultant, Metis Print Consultancy, www.metis-uk.eu

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