Types of Assembly robots: Articulated, SCARA, Cartesian, and Parallel

If you're in the market for an Assembly robot, your first port of call is choosing a robot. The type you choose heavily depends on what you need to assemble and how quickly you need to get it done.

• Articulated robots are flexible and dexterous, with rotary joints that move like human arms. They are great for complex assemblies with multiple steps and can manipulate parts in multiple orientations. However, they typically move slower and operate in a fixed location. Brands like FANUC, Standard Bots, and ABB are all popular for articulated bots.
• SCARA robots are fast, precise, and rigid, with joints that only move horizontally. They’re perfect for high-speed pick-and-place tasks with fixed motions from a fixed position. Epson, Yamaha, and Mitsubishi are major SCARA robot makers.
• Cartesian or Gantry robots move along a grid of three linear axes, giving a wide range of motion with high repeatability. They're ideal for basic transporting, stacking, and palletizing but lack flexibility. Unlike the robots mentioned previously, they can move around a factory ceiling, assuming tracks are in place. Brands such as Bosch Rexroth, Danaher, and Festo offer Cartesian robots.
• Parallel robots have multiple arms connecting the base to the end-effector, which allow for very high speeds. However, their motion range is limited. They’re perfectly suited for high-volume, conveyor-based production lines. Some options for parallel robots include products from FANUC, Epson, and Yamaha.

When choosing your Assembly robot, consider the types of parts you need to manipulate, the precision and speed required for effective throughput, and the available cell space to operate one or more robots. Factors like whether or not you will have conveyor belts in place will help you decide whether a fixed robot is satisfactory, or a more mobile solution like a gantry bot is necessary.

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Assembly tasks robots can perform

If you’re not entirely sure which robot type is right for your application, understanding the various assembly tasks they can complete may help narrow down your selection. Here are some of the most common uses.

Pick and place

The most common task for an Assembly robot is pick and place, where the robot picks up components and places them onto a product assembly line. Nearly all assembly robots are capable of this in their own way and use end-effectors such as grippers to grasp parts. SCARA and Cartesian robots are fast-moving choices for this type of assembly. 

Welding and gluing

Many Assembling robots can also weld or glue parts together. They require specialized end-effectors like welders, glue dispensers, or even UV light cure systems. Welding robots can handle Spot Welding and Arc Welding, while Gluing robots can apply adhesive sealants and epoxies. Articulated robots paired with a conveyor are often the best choice for this application.

Screwing and bolting

Some Assembly robots are also able to drive screws and bolts to fasten components. They use end-effectors like nut runners, screwdrivers, and bolt tighteners. This requires the parts to be precisely aligned and positioned first, either with a separate accessory or a laser-guided Articulated robot.

Press fitting

Certain robots can press parts together, pushing one component into another to lock them together. They use end-effectors like pressers to apply adequate force. Similar to screwing, this also requires very accurate part positioning. Often the simpler nature of these parts means that a Parallel or Cartesian robot is the best solution.

A complete solution will require multiple robots working together in unison. Articulated Robots are great all-rounders for ever-changing, high-mix assembly lines, and are equipped with welding torches for binding parts together. A high-volume and static production line could pair well with Cartesian robots for loading items to a conveyor. And to finish the job, a SCARA robot can be used for polishing off the completed welds at the end of assembly.

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End-effectors for Assembly robots

Regardless of your choice of a robot, the ability to complete a task is granted by having the correct end-of-arm-tooling, also known as an end-effector. Most human tools have a version adapted for a robot. Here are some of the end-effectors we commonly see used in assembly.

Grippers

Grippers are the most common end-effectors. They grasp and move parts from one location to another. There are all sorts of grippers, such as Vacuum grippers which use suction to pick up flat, solid parts like glass, and Magnetic grippers which are optimized for handling metal parts. For basic lifting, Mechanical grippers have two or more fingers to physically grasp parts, just like a human hand would. They come in different sizes and clamping forces for delicate or heavy-duty work.

Screwdrivers

For more advanced operations, screw-driving end-effectors automatically drive screws and bolts. They handle a variety of screw sizes and types, such as the Phillips head or hex socket and can be equipped with laser guides to help the robot precisely fasten. If the end-effector is equipped with force sensing, your robot can apply different torque levels for specific fastening needs. 

Glue dispensers

For bonding parts, glue dispensing end-effectors precisely apply adhesive. They control the amount, pattern, and location of glue deposited onto parts. Robots with glue dispensers are useful for the high-volume assembly of products where gluing provides a fast, permanent bond between components. These end-effectors work best when equipped with Parallel or Articulated robots.

Other end-effectors

There are also end-effectors for even more specific purposes:

• Welding arms that handle welding torches for spot welding or arc welding parts together
• Palletizing grippers that lift and stack heavy parts, pallets, or boxes
• Deburring tools to smooth sharp edges or remove excess material from parts
• Presses for pushing parts together or stamping shapes from sheets of material

Factors to consider when selecting an Assembly robot

With a robot type selected and end-effectors considered, here are a few more factors you’ll want to consider: 

Payload and reach

Payload refers to the maximum weight a robot can lift and move, including the weight of the end-effector. Its reach indicates the maximum distance a robot can extend its arm. For pick and place applications in your assembly line, select a robot with a payload and reach suitable for your largest and heaviest parts. Too little capacity will slow down your line, while too much is an unnecessary expense.

Powering the end-effector 

When choosing an end-effector, ensure you understand the payload and actuation requirements, and any additional cabling or supply needed. End-effectors are almost always powered separately from the robot itself. 

Environment

Consider the environment your robot will operate from. If space is limited, a smaller robot with a compact footprint is ideal. For food-grade or sterile environments, look for robots with washdown-ready or stainless steel construction. If your robot will be working in close proximity to humans, you’ll want to consider a “Collaborative robot”. Meaning one with built-in collision detection and avoidance.

Cost

Unsurprisingly, robotic assembly solutions come at a price. Prices vary greatly based on robot type, size, speed and necessary accessories. While robotics can provide a good return on investment over the long run through increased productivity and efficiency, the initial capital outlay can be substantial. Compare options from different suppliers to find a robot that fits your budget.

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Top Assembly robot manufacturers

When choosing an Assembly robot, the manufacturer is an important consideration. The top players in the field all offer high-quality, reliable options, but there are some differences in their product lines and specialities.

ABB

ABB, based in Switzerland, is one of the largest robotics companies in the world. They are best known for their Articulated robots, like the IRB series, which are very flexible and can handle complex assembly tasks. ABB also makes SCARA and Delta robots. Their robots are a bit pricier, but are high precision, fast, and have great payload capacity.

KUKA

Germany-based KUKA specializes in Articulated robots and linear units for assembly. Their LBR “iiwa” series is a popular, lightweight model good for small parts assembly. KUKA's products are also on the higher end of the price spectrum, but are high quality, safe, and integrate well with other automated systems.

FANUC

Japan-based FANUC manufactures a wide range of Assembly robots, including articulated arms, SCARA’s, and parallel styles. Their robots are very reliable, fast, and accurate. Models like the FANUC LR Mate and M-10iA are well-suited for assembly and material handling. FANUC's robots are moderately priced and the company provides good technical support.

Standard Bots

US-based Standard Bots manufacture their flagship RO1 articulated arm out of Glen Cove, New York. The RO1 has a high payload capacity of 18 kg and moves faster and more precisely than any other robot in its competing class. Despite this, Standard Bots are known for their affordability, with the RO1 starting from $5/hour.

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Next steps

Whether you need a robot for complex assemblies or a simple pick-and-place system, make sure you think about the size and weight of your parts, the precision and speed required, and how much space you have on your factory floor. Do some research on the major brands, check out their offerings and specs, and find the right balance of affordability and quality for your budget.

Implementing automation in your assembly line is a big step, but with some diligent planning, you can find an Assembly robot that will streamline your production and exponentially increase your factory’s productivity.

Interested in bringing robotic assembly to your own business? RO1 by Standard Bots is a great choice for factories large and small:

1. Affordable: RO1 is the most affordable robotic arm in its class, starting at almost half the price of incumbent competitors. 
2. Powerful: RO1 is faster and more precise than competitors, despite having the highest payload capacity in its class at 18 kg.
3. Collaborative: RO1 comes equipped with safety sensors and built-in collision detection, for safe operation anywhere on your shop floor.

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Speak to our solutions team today to organize a free, 30-day onsite trial and get expert advice on everything you need to deploy your first robot.