ROBOTS: the inside story
O ver the last decade, a growing number of Canadian plastic manufacturers have seen the inherent benefits of investing in robots and automation. For many processors, the robot's ability to pick and pl...
Over the last decade, a growing number of Canadian plastic manufacturers have seen the inherent benefits of investing in robots and automation. For many processors, the robot’s ability to pick and place finished parts has led to significant capital cost savings.
“Folks are normally just concerned with getting [the parts] out of the mold and getting them on an index conveyor, as an example,” explained AEC’s automation sales manager Doc Breger.
However, many manufacturers are now also looking beyond post-mold operations, and investing in robots for in-mold solutions that provide their companies with a competitive advantage.
AUTOMATING THE MOLDING MACHINE
Even if your company is investing in a robot for rudimentary post-mold ops, AEC’s Breger notes that they should give some thought to automating the molding machine for future applications.
“One of the things that happens a lot is people focus a lot on the job at hand, they don’t focus on automating the molding machine,” he said. “If you have done this effectively, you can do anything between the clamps and work with it down the road.”
Companies can make their initial investment go further by investing in full servo robots instead of hybrid or pneumatic models from the get go. Although servo robots require a slightly larger budget, experts like Breger note that they offer greater versatility when adapted for in-mold operations.
“When you automate with a full servo robot, you gain a full range of motion in the clamps,” noted Breger. “Hybrid robots are capable, but if you really want to be able to jump on a lot of work, you need to look at automating the molding machine.”
As well, Wittmann Canada notes that pneumatic models are better suited to applications where precision isn’t of the utmost importance.
“It has to do with flexibility, pneumatic robots are basically using end positions to get your stroke limits, and you only have two positions,” said Christian Weiss, technical sales, robots and automation, Wittmann Canada. “With a servo, you can control speed and the variance of position…[for example] if the part is too large for the tie bars, you can angle it slightly to get the clearance. This saves you a huge amount of time waiting for the axis to make its full rotation.”
Weiss also recommends that processors give thought to the design of the tooling and the mold. If the mold is being designed from scratch, he notes that it is best to position and angle the cavity with the knowledge that a robot will be removing the part. Additionally, processors should make provisions inside the tooling — such as docking pins for greater precision — if they opt for pneumatic robots.
Most suppliers agree that insert molding applications where the robot places a metal insert or fastener in the mold have become increasingly popular. “Insert molding is getting very common, especially where you have fasteners going into the part…it reduces the total part count for the company,” said Dale Arndt, engineering manager for FAnuc Robotics canada.
Arndt noted that insert molding applications run the gamut from complex automotive parts to simple consumer products such as screwdrivers.
“If it’s a consumer product, the robot can extract multiple finished parts inone gripper, then rotate the gripper and load multiple inserts before backing out. This reduces the mold-open time, which increases the production throughput,” he continued. Long molding cycles may also allow insert molders to share one robot between two machines, making a better use of capital equipment.
Fanuc also notes that it has seen significant growth when inspecting the part to ensure that the inserts made it in. “Our robots have a built-in vision system, so when the part is extracted we can send in a camera to make sure the fasteners made it in,” said Arndt.
In addition, sensors can help a processor make sure that inserts are placed correctly and the part reject rate is reduced. Wittmann canada points to the example of Toronto-based centennial Plastic: the insert molding robot solution supplied by Wittmann allowed the company to insert small metal rings into the mold using magnets. The magnets grab the insert and the stripper plate pushes the rings onto pins in the mold.
centennial uses inductive sensors on the robot’s custom-designed end-of-arm- tooling to sense the inserts. “If [the robot] misses the insert, you can program it to try again,” explained Weiss. “When the robot picks up the inserts it makes sure they are all there, [and if not] it rejects them and picks them up again…there are multiple steps in verification that sensors can perform.”
In-mold labeling technology has been well-entrenched in the European markets for many years, but the operation has been steadily gaining momentum in the Canadian plastics industry.
“Canadians are much more open to seeing and understanding what Europeans are doing in their markets,” said Wittmann’s Weiss. “In the last year now the increase in requests for IML information has gone up considerably.”
Processors utilize static charge or vacuum ports to hold the label in place in the mold, allowing the manufacturer to produce a part with the label permanently adhered to the plastic.
“The ultimate result is a visually stimulating part,” noted En-Plas Inc. sales manager Brad Lemieux. “And the label cannot be removed from the product, providing permanent advertising.”
The IML process also eliminates the need for post-mold operations such as gluing to affix the label to the container. En-Plas demonstrated its IML capabilities using a Yushin RA800SL servo robot with a Nissei molding machine at last year’s Plast-Ex show. With several years of implementing IML solutions, En-Plas noted that there is often some “black magic” associated with IML.
For one, the processor has to ensure that the process takes place in a clean molding environment, in order to avoid dust and contaminants. Also, En-Plas said that there is the chance of servo motor arching due to the static charge process, especially if the processor opts for a less experienced supplier.
Also, although many Canadian manufacturers are exploring IML for the very first time, established IML solution providers such as Wittmann can use their experience to provide full turnkey solutions. For example, Wittmann acquired France-based thin wall toolmaker Regad, allowing the company to supply tools and integrated systems for its customers. The company utilizes standard robot models and components to supply IML solutions, recommending standard side-entry robots for short cycles and top entry robots like the W 711 where the cycle time exceeds eight seconds.
Although insert molding and in-mold labeling are the most common robotics applications inside the mold, there are very few limitations on what processors can accomplish with the right robot.
Manufacturers can use two-shot molding or overmolding to reduce the number of components, where a produced part is placed in another mold or machine for additional manufacturing. For example, ENgEL helped its customer Boucherville, Que.-based Vision2 automate two cells for the production of water goggles.
One cell produces the lenses, with a robot that moves the molded lenses through several applications such as a deionizer station and a defogger station before the inserts are placed on a conveyor. Finished lens inserts are then moved to a second cell, outfitted with an ERC 44 E-series robot, for overmolding.
Manufacturers can also utilize robots to download some of the work traditionally done by a machine operator. For instance, Wittmann points to one customer who used their robot to apply a mold release on the mold between cycles.
“This particular tool was very difficult to get parts out, so they put a mold release [using a spray] every cycle or every other cycle,” said Wittmann Canada’s Weis
s. “It would apply it on its own without adding any physical labour, and with little effect on cycletime.”
Processors utilize static charge or vacuum ports to hold the label in place in the mold
AEC Inc. (Schaumburg, Ill.); www.aecinternet.com; 800-233-4819
AEC-Equiplas (Toronto); 416-407-5456
Lutek Plastic Equipment Inc. (Dorval, Que.); www.lutek.ca; 888-505-8835
En-Plas Inc. (Toronto); www.en-plasinc.com; 416-286-3030
Engel Canada Inc. (Guelph, Ont.); www.engelglobal.com/na; 519-836-0220
FAnuC Robotics Canada, Ltd. (Mississauga, Ont.); www.fanucrobotics.ca; 800-477-6268
Wittmann Canada Inc. (Richmond Hill, Ont.); www.wittmann-canada.com; 888-466-8266