Robots done right: Inspection Efficiency

All photos courtesy of AVR Vision & Robotics

A ceiling-mounted robot using a long-shank rotary bur to remove burrs from holes.

Can robots improve your deburring operation?

Robotic deburring has been discussed since the mid-1970s, but does the process work? Shops need to answer that and other basic questions before considering replacing manual deburring with a “staff” of robots.

First, it is important to distinguish exactly what the user is looking for. Many finishing robots are not truly deburring robots. Some remove casting flash rather than burrs and that difference is important. Robots employed to move parts within deburring cells have abilities far below that required for sophisticated deburring. Robots that polish surfaces (rather than finishing edges) are good applications also, but the term “deburring” is not reflective of what they are doing.

Before considering true robotic deburring, part manufacturers must define their part requirements. That includes drawings and specifications, production rate and quantity expectations, and other essential details that are sometimes not clearly defined.

Part Requirements are Key

Table 1 on page 38 shows the part requirements that determine if robotic deburring is a viable production option. Beyond this information, however, manufacturers must also define the degree of difficulty presented by part geometry. Success in robotic deburring will be determined, in part, by edge and size tolerances, proximity to other edges and surfaces, part complexity, machinability, burr properties and feature accessibility.

For example, a paper by Serefettin Engin, high performance machining specialist for Pratt & Whitney, and other authors, to be presented at the North American Manufacturing Research Conference in May, provides a convenient numerical means of identifying the impact of all these factors, but no formal public system exists to identify the limits of robotic deburring capabilities. Several robot builders use proprietary matrices of issues to understand the limits of their systems to process parts.

While cost reduction is the primary reason to consider robotic deburring, other benefits include safety (removing operators from hazardous work), improved quality, higher production rates and simplified QC.

Like any machine, robots have associated costs, including procurement, shipping, installation, maintenance, supplies, training and labor. Program and process development costs for new parts are often not accounted for in projecting payback periods for robotic deburring.

Payback is predicated on the ability to impart acceptable edge quality. If the robot falls short, payback is extended, so potential users must define expectations in writing and images and inspect all deburred and affected features before accepting robots. This can be challenging because most companies do not define what a burr is or how it inspects for burrs or other edge conditions. For example, so-called “secondary burrs,” such as burrs formed by countersinks as they remove a large burr, may be acceptable to some but not others. Also, most potential customers want a robot to remove all burrs, but the most common approach is to follow robotic deburring with some amount of manual finishing.

A robot point-finishes the edge of a cutout with an abrasive-filled, cotton-mounted tool.

A final consideration is the probability the company will continue to produce the part in question. The author worked on a team developing a highly precise robotic deburring operation, but when the system was ready, the part was canceled—as was the need for the robot we spent 3 years developing.

Variation is Critical

While part manufacturers try to account for all production factors when considering robotic deburring, some factors are frequently omitted. Variation is one of those overlooked factors, according to Francois Arrien, vice president for robotic material removal, AVR Vision & Robotics Inc., Montreal. “[Manufacturers] forget about part-to-part variation and variation in burr formation during production,” he said. “They provide nominal part and burr information, but not the variation. The burr on the first part is different than the burr on the 1,000th part because of tool wear and other factors. The part geometry may also vary.”

Table 1: Robotic potential for deburring applications.

Production requirements

Large variety of 3-D part configurations produced each month

Small variety of part configurations

Long runs of same shapes

20 to 50 parts/month

More than 100/month

More than 500/month

Robot potentialTypically not feasiblePossibleReasonableGood potentialPart sizeMiniatureFinger sizeHand sizeHand size and largerEdge quality requirementsLevel 1Level 2Level 3Level 4Level 5Level 6

Burrs

100 percent removal

100 percent removal

100 percent removal

100 percent removal

Microburrs OK

Remove loose material

Inspection (acceptable quality level)

100 percent of edges

100 percent of edges

100 percent of edges

100 percent of edges

Sample

Sample

Inspection magnification

30×

10×

10×

4×

Unaided eye

Unaided eye

Surface finish (Ra)

8μin. (0.2μm)

16μin. (0.4μm)

32μin. (0.8μm)

64μin. (1.6μm)

64μin. (1.6μm)

More than 64μin. (1.6μm)