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Article | April 30, 1999
Robotic tray loaders speed cookie loading
A state-of-the-art line at Voortman Cookies in Canada uses 10 vision-guided robots to simultaneously pack cookies into five trays at 1걄 cookies/min. Saves C$450ꯠ/yr in labor costs and provides 10-minute tool-less changeover.
Near Toronto in the city of Burlington Ontario Canada 10 high-speed robots have logged just over a year of tirelessly picking up cookies and placing them into trays at Voortman Cookies Ltd. The 10 vision-guided robots which have been run up to three shifts during peak times are part of a single packaging line installed early last year to replace a manual tray-loading process.
The line which includes conveyors robots machine-vision cameras and a SIG Pack (Raleigh NC) flow wrapper was assembled by SIG and robot manufacturer Demaurex (Lausanne Switzerland). The line was purchased through Charles Downer & Co. Ltd. (Richmond Hill Ontario Canada) though SIG was the actual integrator of the line.
The line's primary benefit is that it has freed up five workers per shift resulting in labor savings of C$450 (about US$300) per year according to Fred Heikamp Voortman's plant and property manager. Line speeds were also increased by 10% to 20% according to the firm. Gone too are complaints of repetitive motion injuries from the workers.
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Now the 10 robots--packing off the output of one oven--load cookies into trays at speeds of 110 cookies/min per robot with two robots dedicated to each tray (for a throughput of 220 cookies/min/tray). Five trays are loaded simultaneously.
Trays hold anywhere from 12 to 30 cookies depending on variety and are overwrapped in flexo-printed oriented polypropylene film at speeds to 90 trays/min (at 12 cookies/tray). While the distributor claims that this is the fastest robotic packaging line in North America that couldn't be verified. Heikamp does tell Packaging World "I've never seen a line this fast."
The second-most important feature of the line is that it can be changed over without tools in about 10 minutes from robots through wrapping. Most of the changeover is automatically accomplished by selecting a new product setup via the touchscreen operator interface on the supervisory PC that controls the robots. The PC in turn communicates specific instructions to the five separate PC controllers out on the line each of which controls a pair of robots. The robots are servo-driven which means that new movement parameters can be instantly downloaded from each PC robotic controller to the servo drives based on operator input at the main operator interface.
The only physical changeover consists of changing the pick-up heads or end-effectors as Voortman calls them to accommodate the shape of the cookie to be picked up.
"Mostly [changeover] is just pushing a button" says Heikamp.
Although 20 different types of cookies are run on the line only two variations of oriented polystyrene trays are used.
"Both trays have the same outer dimensions to speed changeover but we have two different compartment layouts" explains Heikamp. "We have either three cells or five cells. Both contain four to six cookies per cell but smaller cookies use the five-cell."
Delta means speed
The key to the speed of the system according to Heikamp is the delta-style robots. Instead of a traditional three- or four-axis robot that resembles an articulated arm a delta robot moves via an entirely different concept. Resembling an upside-down tripod the robot consists of three pairs of arms each pair pivoting off its own rack-and-pinion mechanism and driven by a servo motor enclosed inside the top of each robot. The motors are precisely synchronized to move the top end of each arm the desired distance moving the bottom end of the arms that are joined together. To watch them the robots swing about wildly almost too fast for the eye to see according to Heikamp.
The line starts out as baked cookies enter the packaging line on a 1.2-m-wide infeed belt. The belt travels at a speed of 15'/min below the 10 robots which span the length of the conveyor belt.
The belt also passes beneath five perpendicular tray conveyors that carry the trays over the cookie conveyor. Two robots are stationed by each of the cross conveyors. Five tray denesters feed the five tray conveyors mechanically separating empty thermoformed trays from stacks in two magazines. Servo-driven tray indexing belts stop the trays during loading and activate when trays are full.
Meanwhile the robots all of which have their own cameras are programmed to look for and pick up cookies in their immediate vicinity. Each robot's camera also inspects each cookie for quality. Broken cookies or those whose outer diameter exceeds the target size by more than 4 mm are rejected preventing the robots from having to jam an oversized cookie into a tray.
Cookies that meet the quality criteria are picked up by the robotic pick-up heads using vacuum. Rejected cookies are simply ignored and conveyed off the end of the belt into a reject bin.
Filled trays progress across the five cross conveyors and merge into a single-file lane that feeds into the SIG HBM servo wrapper. That machine was selected because it's "one of the best wrappers" according to Heikamp and provides extremely fast changeover capability. Since both of Voortman's trays use the same outer dimensions the only change to the wrapper consists of changing film rolls which can be done without tools in a few minutes he says.
Roll replenishment is even faster--it can be done on the fly due to the wrapper's auto-splice feature. That automatically splices the leading edge of an already-loaded replacement film roll onto the trailing edge of the roll that's about to run out.
Wrapped trays pass over a checkweigher prior to case packing which is currently done by hand though Voortman was in the process of adding a case packer as PW went to press.
Currently only four workers are required to run the line: one robot and wrapper operator one worker that visually inspects trays prior to wrapping and two to manually pack trays into cases.
A final benefit of the robotic pick-and-place system is its control system. "There's nothing proprietary in the system" Heikamp says. He refers to the fact that the five robotic controller PCs and one supervisory PC run under MS-DOS using control programs written by Demaurex (pronounced "DEM-a-ray"). Although the control programs were written in Pascal a programming language not typically associated with machine control it is a standard programming language that isn't tied specifically to one vendor. The PCs also use standard plug-in motion control cards and machine vision cards that can be sourced from multiple manufacturers.
"That's part of the reason we bought it" says Heikamp. "It doesn't really have a black box. We can access the whole system."
With a year of successful operation the line has proven itself in the eyes of Heikamp and other Voortman senior management personnel. Thanks to its graphical operator interface with fast touchscreen changeover control "it's very user-friendly" Heikamp concludes.