// Showcase

Vacuum Chuck for a 2.5 Square Meter Reference Surface

The chuck is the reference plane for the whole machine - every bit of unevenness lands straight on the part, in Z and, through the kinematics, in X and Y too.

Sensors & Metrology

Vacuum Chuck for a 2.5 Square Meter Reference Surface

Sensors & Metrology

01Starting point

The chuck is the reference plane for the whole machine - every bit of unevenness lands straight on the part, in Z and, through the kinematics, in X and Y too. We had to hold substrates equally well from 0.5 mm foil to 5 mm plate - a factor of ten in stiffness - across 1800 × 1400 mm² for substrates up to 1740 × 1300 mm². And all of that at micrometer flatness and roughness. Since vacuum hold was required, the surface had to be porous or perforated - a ground granite plate alone wasn't enough.

02Approach

Before the machine even existed, we ran a feasibility study to find out what a porous vacuum surface this size could really do. A microscope became a profilometer - we recorded Z profiles along X and Y, deliberately including the transitions between porous material and adhesive. That's exactly where a bonded surface fails first. Result: flatness under 5 µm, roughness Ra under 4 µm - and a systematic step of 4–6 µm at every joint. We compared four approaches: granite or ceramic with bores - dimples under thin foil. Electrostatic - needs a conductive substrate, which we didn't have. Pure edge clamping - too soft at 1.7 m substrate length. Porous plate - distributed suction, no individual bores. That was our path.

03Result

Twelve independently switchable segments on the production plate - a partially loaded surface doesn't lose its hold, and thin foil can be pressed down segment by segment instead of all at once. The work surface is swappable via a clamping system - different porosity, different surface, different color. Three colors to choose from, because the chuck is visible through transparent substrates in the camera image and affects contrast. And vacuum generation is on board right from the start - no dependency on central building supply.

What's inside

A production plate with twelve independent vacuum circuits, a swappable surface, and its own vacuum generation. We didn't just write off scratches on the existing work surface as a defect - we machined and inspected real parts over them. No measurable effect on part quality. A suspicion became a documented tolerance. At acceptance: both mandatory values met, the two ambitious target values honestly logged as not reached.

And what happened next

The study plate had to be built unusually thin to fit into the existing test machine - an unfavorable thickness-to-aspect ratio. That very constraint turned into an insight: thicker means stiffer, less deformation under vacuum load, and a flatter grind. That lesson went straight into the production plate - and stays our benchmark for the next chuck generation of this size.

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