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Used SCARA Robots: When They Beat a Six Axis Arm

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Used SCARA Robots: When They Beat a Six Axis Arm

A SCARA robot beats a six axis arm when the job is fast, flat and repetitive: picking parts off one surface and setting them on another, pressing in pins, or loading trays. Most SCARAs have four axes and a stiff vertical stroke. If the part has to be tilted or reached around, a six axis arm is the better buy.

What a SCARA Is

SCARA stands for Selective Compliance Assembly Robot Arm. The arm swings in a flat plane like a shoulder and elbow, then a shaft at the end moves straight up and down and spins the tool. The arm gives a little side to side and almost nothing up and down, which is what you want when you push a part into a hole. That is why SCARAs grew up on robotic assembly lines building electronics and small assemblies.

Because it only works from above, a SCARA bolts to a table or a frame and takes very little floor. Our Adept SCARAs are listed with our used Adept and Denso robots, and the FANUC units sit with our used FANUC robots.

Where a SCARA Wins

  • Short pick and place moves. On a short hop from one spot to another, a SCARA is usually quicker than a six axis arm in the same size class. It has fewer joints to coordinate and less arm to move. Our post on parts transfer robots covers the kind of cells where that pays off.
  • Insertion and assembly. The vertical axis pushes straight down without bending away. Press fits, pin insertion and screw driving are classic SCARA work.
  • Dispensing. Laying a bead of glue or sealant across a flat part is a good fit. See our write up on dispensing robot applications.
  • Vision picking. Put a camera over a conveyor or a flat tray and a SCARA will pick loose parts all day. Our post on robotic vision applications explains the basics.
  • Tight cells. A SCARA can sit right next to a fixture or another robot. Our FANUC SR-6iA SCARA robot cell listing shows a SCARA set up as part of a cell.

Where a Six Axis Arm Wins

A SCARA cannot tilt its tool. If the part comes out of a vise at an angle, has to be flipped, or loads into a lathe chuck from the side, you need more axes. That covers most machine tending robots, most welding, and any job where the gripper reaches into a box or around a fixture.

In the same size class, the FANUC LR Mate is a common alternative. The LR Mate 200iD carries 7 kg with 717 mm of reach, and the FANUC LR Mate 200iD/7L stretches that to 911 mm. The Denso units we stock are small articulated arms, not SCARAs, and they fit the same kind of bench top cell.

Vertical travel is the other limit. A SCARA's up and down stroke is short compared to its side to side reach. If parts sit deep in a bin or at different heights, an articulated arm built for material handling is the safer pick.

Delta Robots: The Other Fast Pick Option

If the job is light parts coming down a conveyor at high speed, look at a delta robot too. A delta hangs from a frame over the line, with parallel arms driving one small tool plate. It is built for speed over payload, which is why you see them in packaging and on food grade robot lines.

The deltas we carry are FANUC M-3iA units. FANUC's data sheets list the M-3iA/6A and the M-3iA/6S at 6 kg and 1,350 mm. For smaller, lighter parts there is the M-2iA/3A delta robot at 3 kg and 800 mm.

What to Check on a Used SCARA

  • The controller. A robot runs on its own maker's controller, so make sure the matching one comes with the arm. The FANUC SCARAs we have run on the R-30iB Plus controller.
  • Cables. Ask for the arm to controller cables and check both ends for bent pins. Our post on robot connection cables explains what each one does.
  • The shaft. Look at the vertical shaft for scoring, dents and dried out grease. Feel for play when you push on the end. Spare motors, amplifiers and cables for FANUC units are in our FANUC robot parts inventory.
  • Tooling. Grippers and vacuum cups are usually built for the old job. Plan on new end of arm tooling for yours.
  • Pendant and software. Confirm the teach pendant is included. FANUC's newer tablet teach pendant is worth knowing about if you are setting up a new cell.
  • Freight. SCARAs and deltas are light compared to a big arm, but the controller still ships with them. Everything ships FOB Imlay City, Michigan, and the buyer arranges freight.

SCARA and Fast Pick Robots in Stock

Stock changes often. Check each page for what is on the floor today.

Related Guides

Pulling SCARAs Out of a Line?

We buy used robots, from a single SCARA to a whole assembly plant. Start on our sell your used robots page, or ask about robot and equipment appraisals.

To ask about a specific unit, call 586-752-0090, extension 1 for sales, or send our sales team a message.