Page 27 - Plastics News August 2019

FEATURES

articulated-arm robot requires coordination of several
different articulated joints. Some molders feel they need
specially trained personnel to handle the programming
and maintenance of these robots.
All that has changed. For example, Sepro recently
introduced its 6X Line of articulated-arm units adapted to
use the same Visual control systems as its Cartesian robots.
Using simple pick-and-place programming, the user only
needs to identify step-by-step the different points and
positions in the robot cycle (picking, quality inspection,
unloading, stacking, etc.). Then the operator manually
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trajectory (either straight-line or curvilinear) is computed
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axis robots much easier to program and operate than in
the past. They can now evaluate Cartesian and articulated-
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application best.
FLOORSPACE REQUIREMENTS

Another common criticism of six-axis robots is the amount
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machine and operate mostly above and near the side of but beam robots are generally regarded as being
the machine, articulated-arm robots are most commonly faster at moving into and out of the mold space to
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limited overhead clearance, this can be an advantage, but applications employ Cartesian beam robots or
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molding machine—usually the back of the machine where manage a payload (part plus EOAT) of about 200 lb. In
they will not interfere with access to the operator control contrast, its largest six-axis robots, sized for molding
panel.
machines of the same tonnage, can handle 250 lb or
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vertical-clamp insert molding. Positioned beside the Maximum payload generally is lower as reach gets
machine, their movement is not limited by the vertical longer.
clamp and they can easily reach multiple stations on the ‡ &RVW 7KH FRVW RI DUWLFXODWHG DUP URERWV KDV EHHQ
rotary table often found on those machines.
coming down lately, but as a general rule a Cartesian
+RZHYHU VL[ D[LV URERWV GR QRW KDYH WR EH ÁRRU PRXQWHG robot—even with the addition of the servo-driven
7KH\ FDQ EH PRXQWHG DERYH WKH PROG RQ WKH À[HG SODWHQ wrist—will cost about 30% less than a six-axis unit.
on a nearby wall or even the ceiling, when the application Cartesian and articulated-arm robots are sometimes
and the working environment allow. used together. The machine-mounted beam robot
OTHER FACTORS TO CONSIDER picks the part and presents it to the articulated-
arm unit for secondary operations. This may be the
There are other factors that set articulated-arm robots
apart from their Cartesian cousins: ideal setup when molding cycles are relatively short
and downstream functions are especially numerous,
‡ 6SHHG 7KH VSHHG RI DUWLFXODWHG DUP URERWV KDV complicated or time-consuming.
increased in recent years to a point where it is

27 August 2019 Plastics News