3 Types of Pitch Variable Gripper Mechanisms Applied in Packaging Automation Processes
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Among our past projects and our experience obtained during the years dedicated to packaging automation, it is not something rare that the automated process is expected to provide a solution to transfer articles or products from a certain equipment or device to another and meanwhile to equally divide the space and distance between each other.
Such a process involving variable pitch-changing solutions can be either handled by robotics and grippers or by designing corresponding mechanisms to offer robust solutions and a more affordable budget than the former, providing a more flexible packaging automation approach. Such kind of mechanism is so-called the pitch changing mechanism, sometimes referred to as a pitch shifter or pitch changer.
Courtesy of ELITER
We will be introducing the different types of pitch mechanisms commonly used in packaging automation and packaging end-of-line, explain their composition, structure, kinematics, etc., from the perspective of a packaging automation engineer, based on the knowledge shared by people at the Engineering Department of ELITER Packaging Machinery.
What are pick-and-place mechanisms?
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What are Variable Pitch Changing Mechanisms?
Pitch-changing mechanisms are usually combined with pick-and-place mechanisms and get converted into a variable-pitch pick-and-place device. Such kinds of designs are widely used not only in packaging automation processes but also in situations like assembly lines of modern electronic devices such as integrated circuits and semiconductor chips.
We have as follows 2 examples for you to understand the purpose of a variable-pitch changing mechanism：
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In the CPG packaging end-of-line
Imagine that you are a snacks processing and manufacturing company of chocolate bars and that there is already a set of high-speed PFM Flow Wrapping Machine that works for the primary flexible packaging of these snacks.
Rows of White Packaged Snack Bars into Cartons
Credit: ELITER Packaging
The chocolate bars are firstly discharged from the flow wrapper, heading toward a conveyor, and then collected by a racetrack collator. Meanwhile, flat carton blanks are erected by a top-load carton set-up machine and loaded onto a conveyor paralleled to the collator where chocolate bars are collected.
To transfer the chocolate snack bars from the racetrack collator towards the set-up cartons with open tops, we will need a mechanism with the following functions or devices:
- With a series of vacuum grippers, arranged in a row and that can pick the chocolate bars in an aligned manner
- Moving the picked bars over the plane of the open top of those set-up cartons
- Spacing the bars and making the distance between each group correspond to the distance between each carton
- Place the bars into the cartons
- Track back to the home position and repeat the above processes
Such a mechanism is typically featured for the functions of picking and placing and spacing the articles simultaneously.
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On filling machines
A volumetric filling machine usually has multiple filling heads to fill various containers at a time. The challenge happens when the machine is supposed to handle different containers for each shift, switching between things like bottles, glass, or tin cans that have different overall diameters and heights – that is to say, when they are organized in a row, the pitch between each bottleneck will vary accordingly.
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In semiconductor packaging process
In the semiconductor industry, placement accuracy is of utmost concern [1]. Apart from the high value born by these articles that even tiny damage can lead to considerable losses, modern devices are getting smaller and more compact, and accurate placement is needed to fit everything into the allotted space without compromising functionality.
Variable-Pitch Mechanism
Credit: MiSUMi®, reproduced by ELITER
Till this point, the idea about pitch-changing mechanisms is quite clear. It is a combination of components integrated together to realize the function of both gripping articles, convert the distance between each of them to a desired space, for the convenience of feeding them to another device.
3 Types of d Variable-Pitch Mechanisms
The key factor in defining the type of variable-pitch mechanisms is the kinematics by which the function of equal spacing is realized. In common sense, such a section is usually lined to a plurality of drippers arranged in a uniform row but of variable pitch and spacing between each single gripping device.
Variable Pitch Mechanisms by Pantograph Linkage
Spacing and pitching can be preserved by a linkage desirably arranged in the form of a Scissors mechanism or pantograph comprised of rigid beams linked together to form a series of parallelograms.
Pantograph Linkage
Credit: ELITER Packaging
The pantograph linkage here should be calculated deliberately and requires a certain level of professionalism in terms of mechanical engineering. Yet compared with other forms of design we are going to introduce in the following part like cams, pantograph linkage is more affordable in cost and yields improved positioning precision as well as flexibility. [2]
ELITER Cartoning Machine‘s Variable Pitch Pick and Place Mechanisms based on Pantograph Linkages for Blister Packs
Credit: ELITER Packaging Machinery
Variable Pitch Mechanisms by Form Closed Wedge Cams
Cams are mechanisms used to convert motions between different patterns like rotational and linear.
The form closed wedge cam is also called the cam groove plate, on the surface of which is a series of cutouts or contoured surfaces designed to fit closely with the cam follower (which translates the motion). The profile and shape of the cutouts determine the output motion of the follower.
Form Closed Wedge Cam
Credit: ELITER Packaging
In the case of a variable pitch mechanism designed based on a cam groove plate, the latter has cutouts with a plurality of cam guide groove to which the grippers or suction mechanisms are mounted and works as the cam follower and slidably arranged there.
The grooves are organized symmetrically to the plate’s central line, and from top to bottom, the grooves approach gradually to the latter in the width direction. Thus in this way, when the motion of grippers along the grooves is realized with the participation of other devices such as guides and servo motors, the pitch between each gripper mounted will follow the same pattern by which the grooves are designed to close to each other.
Variable pitch mechanisms with grippers mounted on closed wedge cam
Credit: ELITER Packaging
Variable Pitch Mechanisms by Cylindrical Cam
A cylindrical cam is a cylinder-shaped cam that rotates on its own axis and on the surface of which there are groves where followers are mounted to follow the cam profile ether reciprocating or oscillating.
Cylindrical Cam
Credit: ELITER Packaging Machinery
The variable pitch mechanism mounted on the cylindrical cam will have the cam as an active device, driven through pulleys, timing belts, and servo motors, These cam guide grooves on the active cylindrical camshaft that connect the camshaft, which are those grippers mounted in this case, to the slide blocks by way of a follower.
The pitch between each gripper will follow the cam profile to increase or decrease as the axis rotates on itself so as to fit the specific applications to transfer articles by different pitch distance.
Pitch Variable Mechanism Mounted on Cylindrical Cam
Credit: ELITER Packaging Machinery
Bibliography
- [1] The truth about placement accuracy, Semiconductor Digest, https://sst.semiconductor-digest.com/2000/04/the-truth-about-placement-accuracy/
- [2] Variable-pitch pick and place device, Micron Technology Inc, US20020153735A1, https://patents.google.com/patent/US20020153735A1/
