Automated Polishing Stainless Steel with an Industrial Robot

Why Force Control and Servo Motors are Needed to Automate

One of the primary goals of polishing metal is to achieve a smooth finish. Taking a rough metal and giving it a fine, polished finish is one of the most important steps in creating a final product. Implementing an industrial robot and End of Arm Tool (EOAT) in your manufacturing process helps achieve not only consistency in results but efficiency in the polishing, sanding, and grinding processes.

The Limitations of Manual Polishing

Manual polishing is a very labor-intensive process. In addition, regardless of how experienced your staff may be, there is always the potential for slight inconsistencies in manual finishing. If polishing a tube by hand, for example, a person visually has to inspect the curved surface and try and apply the abrasive media to the part’s substrate in a consistent manner. Since a person is not rigid and their arm is effectively a spring, it is not possible to apply an equal amount of pressure, especially in tight areas or as they rotate around curvature. This results in inconsistent use of the abrasive materials, leading to an inconsistent or uneven surface. In addition, using different staff members to perform finishing processes can limit the consistent finish of products and negatively influence the overall production process with irregular results.

Some irregularities produced by hand finishing are extremely subtle and may not impact the look of your finished product. However, the look of the product may not be the only factor influenced by inconsistent polishing processes. Minor inconsistencies in force, angle, and application can also cause uneven wear to your abrasives. Moreover, the abrasive mineral is designed to fracture with a specific amount of pressure. Too much force and the mineral will glaze over and result in a slower material removal rate. Conversely, with too little force, the abrasive will not re-fracture to present a fresh abrasive. In either case, the abrasive is not being utilized to its full potential. With a robotic process, you are able to apply more force, and in a more consistent manner; therefore, the abrasive life is dramatically improved.

The combination of inconsistent wear and inconsistent results can impact your company’s end product while wasting time and money in the process. Automated polishing can help eliminate these issues and allow you and your team to focus on other aspects of your manufacturing goals.

Pre- and Post-Finish Sanding

Robotic sanding is ideal for pre-finish and post-finish sanding. Automation can consistently remove material faster with less chance of error. Pre-finish processing of components typically requires multiple sanding steps to bring the product to a fine, smooth finish. For maximum consistency, constant feed rate, spindle speed, and force are necessary.

Post-finish sanding is sometimes required to achieve the desired finish or to correct a prior error in the finishing process. One of the main post-finishing processes is paint repair for automotive applications.  For example, dust and debris can fall on a car before paint is applied. This results in a blemish to the car’s exterior finish, which is undesirable to most manufacturers. In order to eliminate this, it requires post-finishing to sand the surface and remove the particulate. Then, it is necessary to follow up with a polishing process to blend this area with the rest of the finished surface. Robotic sanding and polishing help bring consistency to difficult post-finishing processes like paint repair.


The Benefits of Automated Polishing

Automated finishing also offers the advantage of being incredibly efficient when processing a large order of products. A consistent finish can be achieved due to:

  • Consistent force being applied to the object you are polishing regardless of orientation or complex geometry
  • Constant rotational speed from the DC Servo Motor
  • The robot’s ability to travel at a constant feed rate
  • High-quality abrasives used for these processes


Automated polishing has proven utility, as demonstrated with the AFD1240 Active Compliance Device and STC1515 Spindle’s ability to perfectly polish bent metal tubing.

Decrease Risk in Your Projects

Demonstrations, such as the one shown in this PushCorp video on polishing metal tubes, illustrate for our customers how to process each type of feature on their part and also provide parameters such as force, spindle speed, feed rate, and abrasives. As Isaiah Flora states in the video, “This recipe will give the customer a baseline for the finish they can expect, which will ultimately de-risk the project.”

The part was fastened to a table and an AFD1240 and STC1515-BT30 was mounted onto our 300kg Kawasaki robot. The AFD1240 is PushCorp’s largest active compliance device providing up to 215lbs of force in any orientation in which it is positioned. The constant force provided is vital to achieving a consistent polish over the entire metal tube. The STC1515-BT30 spindle mounted to the AFD1240 provided 15 HP and a max rpm of 15,000. Spinning the buffing wheel at a constant RPM provided consistent results. However, by monitoring the current draw from the amplifier during the process, our staff was able to determine that an STC0612-BT40 would be a better fit for the customer and make the appropriate adjustments, as the STC0612-BT40’s torque curve is better suited at the lower RPMs used. It would also allow the customer to size up the buffing wheel to reduce cycle time.

Certain practices should always be maintained too. For example, when polishing, a buffing compound should be repeatedly applied. For best results, the polishing wheel should be oriented perpendicular to the object being polished (metal tube shown). The Norton Fixed Abrasive Buff or FAB wheel features abrasive grains within the wheel. The wheels are waterproof and tear-resistant, giving up to 35% longer life than a traditional cotton buff. This makes them a great pairing for robotic applications. The FAB wheels were held with a PushCorp toolholder with custom flanges.

Where To Start with Robotic Refinishing

Knowing where to start can be the most challenging part of integrating automation into your finishing process. Understanding which equipment is right is necessary to achieve your desired results. Our equipment benefits our customers by addressing:

  • Safety concerns with manual finishing – abrasives breaking, repetitive motion injuries, and breathing in harmful dust
  • High cost of shop air required for manual air tools
  • Labor shortages
  • High staff turnover
  • Inconsistent results of a manual process due to inconsistent force, speed, and travel
  • Throughput – our product systems do not take breaks, do not have days off, can run multiple shifts, and can apply more speed and force to process faster
  • Helps account for some inconsistencies in the part or fixture

Our products serve a wide range of purposes and are well-suited to help customers achieve important manufacturing goals. PushCorp force compliance devices have a linear stroke between 20-40mm, reducing programming time. You will simplify the purchasing and programming process. Every system comes with an array of standard components that set customers up with everything they need to get started.

With tools designed for various functions, our products are meant to give you countless flawless finishes. Automated robotic polishing is a superior option to hand polishing for many reasons, including the ability to efficiently and consistently polish products with a variety of sizes and shapes to a fine, smooth finish. For more information, call us today at 972-840-0208 or fill out the quick contact form on our website.