The Four Types of Robotics That Are Commonly Used in Injection Molding
The very first experience I had with robotics was back in the mid-1980s when I purchased a used Sadamel vertical press from Switzerland. It was a high-precision press designed for watchmakers. Its pneumatic picker removed parts and runners from a vertical clamp at high speed. It made vertical presses relevant again for high-speed molding. Molded-in inserts wouldn’t fall out when the clamp closed.
As with most choices in life, there are reasons you take one path when there are many to consider–and the same applies to the integration of robotics into a plastic molding company. Robotics have many applications in the industry, and the type that you choose depends upon what you want to do, how much you can spend, and how much flexibility you want. The four main types that are applicable to injection molding are described in this article, with pricing based on the use of 250-ton presses.
Sprue Pickers
Sprue pickers are the least expensive, ranging from $5,000 to $10,000, and the simplest of the four types. They are most cost-effective for basic needs, such as taking a runner and putting it into a grinder, or putting edge gated parts in a tall drum to be gated the next day. You can take this motion and remove runners from a three-plate mold or knock the runner on that mold out from between the plates. Beyond these activities, the sprue picker is limited by its three-axis capability and isn’t as flexible as other types of robotics.
Sprue pickers are excellent for molders just getting into robotics, as well as molders running two-plate, sub-gated tools. The machines travel down into the mold, grab the sprue/part, pull away from the parting line, retract to the start point, rotate away from the molding area, extend to drop the runner/part into a grinder or receptacle, return to the home position, then rotate to the start position. A flex option on the grippers adds a fourth axis to help get a large runner into a grinder.
This type is mounted to the stationary platen on the molding machine. Sprue pickers are typically pneumatic devices, but more expensive servo versions can be purchased for greater flexibility.
Traversing Robots
Traversing robots are mounted to the stationary platen and have a traversing motion instead of a rotation. Typically, these are servo-driven, although there have been versions with pneumatic operation on the extract axis. Because they are often servo-motor driven, there are some limited secondary operations that they can perform, such as delegating, stacking, and filling boxes. When you add fixturing, traversing robots can load inserts and labels as well. Safety cages are necessary for traversing robots, but are much smaller than those required for six-axis robots since most of the work occurs high in the air.
Traversing robots can be used to remove large parts from a press and put them on a chute or conveyor belt. They also can perform special handling of parts that require secondary operations such as drilling, or assembly onto another hot part, where you can shrink-fit onto a cold part like a ball bearing. If the hot plastic part were to be put into the inner race of the ball bearing, it would shrink away and become loose.
The cost of an average traversing robot is $30,000-$45,000.
Side Entry Robotics
These high-speed robots are typically used for installing labels into a cavity or on a core, removing the part from the press, and stacking or loading parts outside of the media in bags or boxes. With total cycle times of 2-3 seconds, they are amazing to watch with parts staking up quickly–but they are the least flexible type of robot and tend to be the most expensive. They require space around the press and are the most challenging to program and operate in order to achieve the greatest output.
Six-Axis Robots
Six-axis robots are the most widely seen on TV and the internet, welding or moving automotive body parts. Though more expensive than other types, six-axis robots are the most flexible and precise option, and they can be rebuilt after hundreds of hours of operation and start life anew without compromise, even if the robots are decades old.
A new Fanuc six-axis robot typically costs $40,000 to $50,000, but a rebuilt unit costs just $25,000 to $35,000. They tend to take up more room than traversing robots, because six-axis robots are typically mounted on a pedestal outside of the molding area, while smaller versions can go on the stationary platen and take up far less space.
Because they have so much flexibility, programming is a more critical factor for six-axis robots. From removing runners to loading metal inserts, delegating parts, loading parts onto a conveyor, and putting parts into cartons, providing a step in an automation process where the orientation of the molded part can become very costly in a separate cell, the flexibility is dramatic–but programming and robotics experience is vital.
The benefits of integrating robotics into an injection molding shop
The use of robotics has many advantages in the injection molding industry. Their use results in fewer rejects and better efficiency. Grinders are less likely to get clogged and the robotics equipment can perform its tasks reliably and consistently. With skilled and experienced employees, robotics are excellent for large parts or long-runs of production, starting with production runs as small as 1,000 parts.
About Recto Molded Products
Recto Molded Products has well over a century of experience in injection molding, and is well known for its extensive use of robotics and automation throughout our plastic molding company. Check out our website to learn more about us and to request a quote.