By Wolfgang Sedlak, Technical Manager of Tool Design Engineering, Gerhard Schubert GmbH
The automation of packaging lines has greatly increased production speeds. Products used to be placed into trays or boxes manually, but, for decades, agile robots have been performing this task (and many others). As a result, pick & place processes have become not only more versatile but also more challenging. Not every tool is suitable for every product. Product structure, the line environment itself and process speed all play a part in determining which tool should be selected.
Imagine you’re grabbing a biscuit quickly and somewhat absent-mindedly from its packet. Perhaps it slips out of your hand because of the sudden movement. Or you grip it a little too tightly because you’re in a hurry – and the biscuit crumbles. This does not happen with pick & place robots. They do work quickly, however. This makes it all the more important to have the right tools on the robot arm – along with the motion path and speed – to gently pick up and place different baked goods.
As we all know, there is a great variety of baked goods on the market: light, airy pastries such as croissants, biscuits with and without fillings, as well as products with special shapes, such as doughnuts, are all part of the daily packaging routine for many manufacturers. Rarely do they produce just one product. This increases the demand for flexible, interchangeable and product-specific pick & place tools. The tools used to pick up products from conveyor belts, transport chains or robot-based transport modules at high speeds and place them into packaging need to be closely matched to the specific products.
Most importantly, they have to operate as gently as possible, so as not to damage products through excessive pressure or the use of an unsuitable tool design. This can quickly lead to rejects, which companies strive to avoid given the high cost of raw materials as well as production and sustainability targets. Tools featuring different technologies and designs are used, depending on the specific application.
Wolfgang Sedlak, Technical Manager of Tool Design Engineering, Gerhard Schubert GmbH | all pictures © Gerhard Schubert GmbH
Gentle picking via vacuum
Delicate products call for an exceptionally gentle approach: robots usually pick up brittle or soft baked goods, such as biscuits, from above using suction tools. These create a controlled vacuum at high flow rates, ensuring that light products with any surface texture adhere reliably to the tools. Instead of a lateral, two-sided grip – which can quickly put strain on brittle or porous baked goods – the vacuum pick-up is carried out from above, making it especially gentle. Once picked up, the products can be placed into their packaging.
To this end, a valve disconnects the suction nozzle from the vacuum source, allowing ambient air to flow into the nozzle. The products are deposited either by their own weight or, aided by the spring-like action of the suction nozzle, are placed onto the discharge surface. Cyclone separators are used in the line for products that contain fat or those with toppings such as jam or nut fragments: they remove dust, crumbs and similar particles from the air stream before the air reaches the vacuum generator. In some cases, separators can be installed on the tool. Alternatively, additional air is deliberately introduced into the system to minimize contamination by increasing the air flow rate.
However, not all vacuums are created equal: the exact design of the suction tool also depends on the porosity and air permeability of the baked goods, as these factors influence the achievable vacuum force. When in doubt, testing can provide guidance on the most suitable design.
Fingers and clamps for a firm grip
A firmer grip is possible in the case of more robust products. Gripping tools hold objects precisely in position and are less dependent on surface texture than suction cups. Mechanical fingers or clamps hold the products securely on their way to the packaging without damaging them. Grippers always exert only as much force as necessary. Pneumatic variants achieve this through precise pressure control, while electric systems regulate current or torque.
Vacuum-operated grippers are also used, where the negative pressure generates the gripping motion. This allows the force to be adjusted with exceptional precision. Well-adapted gripper fingers enable a form-fit and are therefore suitable even for delicate products made from puff pastry or for chocolate-coated baked goods.
Another factor contributing to a secure yet gentle grip is distributed force: with grippers, the force is spread across the product thanks to wide clamps or tools shaped to match the product’s contours, thereby reducing surface pressure. And because grippers are fitted with soft materials such as silicone or other elastomers, they adapt to the product’s geometry. This makes grippers suitable even in cases where a suction cup might initially appear to be the obvious choice. Small, round biscuits, for example, do not necessarily require a gripper to be transferred safely from the conveyor belt into the box. Unless, however, their surface poses a problem for the suction cup: products with cream fillings can be picked up by suction but are difficult to release again. Quite simply because the cream filling – and with it the biscuit – can stick to the tool.
“Because grippers are fitted with soft materials such as silicone or other elastomers, they adapt to the product’s geometry, making them suitable even in cases where a suction cup might initially appear to be the obvious choice. ”
Wolfgang Sedlak, Technical Manager of Tool Design Engineering,
Gerhard Schubert GmbH
For highly specific requirements like these, specialized designs are often necessary, such as those recently produced by Gerhard Schubert: a multi-gripper tool combined with a centrally mounted suction cup, which, without applying a vacuum, serves a stabilizing function. The gripper enables lateral handling, which is essential due to the filling. A suction cup is used because it holds the lighter, not especially robust biscuits in position during the picking process and gently pushes them out of the gripper into the discharge position. A solution such as this one calls for more than just technical expertise: a wide range of tools and direct dialogue with users support the development process – and demonstrate that rigid categories in toolmaking are often not entirely applicable.
A puncture for a firm grip
This is demonstrated by another option which neither uses suction nor gripping, yet still guides the product securely. Here, the airy structure of some baked goods plays into the hands of technological innovation. Slightly porous, predominantly solid structures – such as those of muffins and cakes – can be pierced with a fine pin, picked up and placed into the packaging without developing any visible indentations.
Handling from above is more practical if products come into contact with each other – for example, on baking trays or feed conveyors. The minimally invasive pick prevents aesthetic defects: the puncture is barely visible; the products remain intact and display no pressure marks. In the unlikely event that a pin breaks, the tools are equipped with safety mechanisms and sensors that detect any change if necessary. Additional metal detectors within the line detect foreign objects.
Baked goods and production processes greatly influence the type of tool selected – and this, in turn, impacts the overall line performance: the heavier a tool, the greater the mass that needs to be accelerated and decelerated. This results in longer acceleration and braking times, lower speeds – and, put simply, fewer products being picked. Instead of one-size-fits-all solutions, it always makes sense to take a close look at the product range and your own lines in order to customise the right pick & place tool – one that meets very specific requirements without compromising line performance.