“When making a decision between various finishes for your product, seeing the actual finish on the metal is a valuable aid to your decision making and seeing a process in action is even better!”

In recent years, “drag finishing” has become a popular alternative for surface finishing of high value and somewhat delicate metal components.

“Drag finishing” is pulling the components through the media mass thus, honing and polishing in the process.

In a drag finishing system, the parts or components are mounted, fixed and equipped with multiple workstations.  Each component is then “dragged” through a circular work bowl filled with grinding or polishing media.

Pressure and Speed

Drag finishing stands out above other finishing methods because:

• The high speed at which the parts are dragged through the media and the high pressure generated
• It works 40 times faster compared with vibratory systems
• It is approximately 4 to 5 times faster than high energy centrifugal systems, because of its high speed and high pressure
• This is especially true for parts made from hard-to-machine, “tough” metals such as high-alloy steel (stainless, titanium, Inconel, and so on), tool steel or component parts with a high surface hardness.

No Part-on-Part Contact

The outstanding characteristic of drag finishing is that the parts are individually mounted onto the workstations of the carousel. Depending on the machine size, the carousel is usually equipped with four to 12 workstations. Each workstation may be loaded with one or multiple component parts.

In drag finishing systems, the component parts are individually attached to the workstations and can never touch each other during the finishing process. This prevents any part-on-part contact and therefore nicking or marring of the finish.

Drag Finishing Processes Can Accommodate Aggressive Deburring to High-Gloss Polishing

The applications for drag finishing range from aggressive deburring and edge breaking all the way to high gloss polishing of a range of parts.

Here are a few examples of successful drag finishing applications:

Grinding and polishing of stainless steel boat propellers: These are either cast or fabricated and undergo a two-step drag grinding process followed by a polishing process in the same machine.

 

Paint preparation of outboard marine drive  components: These are die castings that require the removal of scale after heat treatment and core knockout, breaking of sharp edges and a homogeneous surface finish prior to painting.

 

Surface smoothing and polishing of turbine blades after machining and shot peening: This application reduces the surface roughness from Ra = 70 to Ra < 2 (1.8 micrometers to < 0.05 micrometers).

 

Grinding and polishing of medical implants such as artificial knees, hip stems, ankles, and so on: After casting, these parts are machined and then undergo a multi-stage drag finishing process for aggressive surface grinding, surface smoothing and high-gloss polishing.

 

There are many other successful drag finishing applications that you can discuss with our Rösler team.

Tell me more about drag finishing.

Consistent, Repeatable, Economical Surface Finishes

Drag finishing is not the least expensive surface finishing technology, but the technical and economic rewards far outweigh the cost.

These systems frequently replace manual deburring/grinding operations.  Manual deburring/grinding is highly labour intensive, and it is difficult to find operators willing to perform this physically demanding and extremely noisy and dirty work. Above all the quality of manual grinding depends entirely on the people doing the work and their physical and mental condition. For this reason, manual deburring/grinding usually produces a significant amount of rework or even scrap.

Once a drag finishing process is programmed in and engaged it consistently produces the same high finishing quality day in and day out. By automating the finishing process the human factor can be totally omitted. With many drag finishing installations the scrap/rework rate is reduced to practically zero from sometimes double digit percentages.

In the medical implant industry drag finishing systems have displaced robotic grinding and buffing systems. As versatile as robotic finishing systems may be, they are limited when it comes to reaching certain surface areas of parts with a complex geometry.

Recent media developments with regard to their composition and abrasive contents have contributed to the success of drag finishing. For example, there is now media available that produces a pre-polish finish on parts from their “as cast” condition.

Tailor-Made To The Customers’ Requirements

Drag Finishing systems are ideal for finishing high value and sensitive parts which cannot touch each other during the finishing process. Drag finishing systems are usually designed around the customers’ requirements.

There is a range of different types and sizes of drag finishing equipment available.

Whenever a manufacturer produces high value parts with a complex geometry and these parts require a first-class surface finish (be it strictly functional or decorative), drag finishing is certainly a surface finishing technology worth considering.

 

For further information please visit www.rosler.com

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Post written by

Eugen Holzknecht
Consultant
Rösler Metal Finishing USA