Robot Assisted Polishing - RAP

STRECON has developed a machine system for high-quality surface polishing. Our approach is RAP®, which stands for Robot Assisted Polishing.

RAP is based on the skill and profession of hand polishing where the polishing work is transferred to an industrial robot. Our polishing machine system can be compared to the human arm, though with several limitations and consequently addressed accordingly in the system design of the machine. The machine system is “assisted” and by that we mean the aid, which the craftsman or operator gets from the polishing machine in “doing the work”.

The RAP machine needs to be programmed, set correctly, and monitored for obtaining the specified surface quality of the parts, and this responsibility remains with the skilled craftsman. However, once the polishing process has been confirmed and run-in for the individual part, the machine runs relatively automatic with limited assistance from staff members.

Depending on the specific part, the polishing machine can take over all of a significant part of the polishing job leaving the machine settings, quality control, and final polishing to the craftsman or operator.  

The STRECON Robot Assisted Polishing machine for surface polishing for 2D and 3D molds and tools
The STRECON Robot Assisted Polishing machine polishing a specific component

General technology concept

The surface quality of tools and molds has great influence on their performance and service life. Parts and components with high demands to dimensions and surface quality as well as parts with complex shapes and cavities require polishing by highly skilled individuals.

For example, critical surfaces of tools for cold precision forging are often specified in the range of Ra 0,06 – 0,04 µm, and Rz below 1,0 µm. For a mold for plastic injection the surface finish would often be specified in the range of Ra 0,03 – 0,01 µm, and Rz 0,3 – 0,1 µm. Such surfaces have a mirror or mirror-like appearance and put high demands to the individual craftsman’s competence and experience in surface preparation.

This challenging and manual work process can be solved by the RAP machine, which can be programmed to polish complex 2D and 3D components benefiting from a consistent, repetitive, and high-quality surface finishing.

The skilled craftsman is setting and controlling the polishing equipment for the different parts as opposed to doing the polishing work by hand. The process programming is based on read-in capabilities of CAD files, and RAP polishing is programmed specifically for the selected geometrical surfaces.

RAP machine concepts

The RAP machine consists of a spindle and polishing module held by an industrial robot. The spindle provides for rotation of an axisymmetric part or indexing of a stationary part. The polishing module offers two different polishing methods, namely oscillation (pulsation) or rotation (rotating tools or spindles).

The contact between the workpiece and the polishing tool is pneumatically controlled. For the method of pulsation used for polishing of rotation-symmetric part, the polishing module has a speed up to 2000 strokes/min. and a variable stroke length up to 2 mm. The pulsation module with a variable stroke length up to 5 mm has a speed limit of 400 strokes/min. For spindle polishing the speed can be up to 10.000 rpm.

For 2D part polishing the spindle and polishing module are mounted on the robot arm, whereas for 3D polishing the tools could be stationary, and the robot will be carrying the part to be polished. The RAP machine has been developed for automatic tool change and a diamond paste dispenser.

RAP can polish surfaces as fine as Ra 0,02 – 0,04 µm, and Rz below 0,1 µm. The machine can polish all kinds of pre-machined surfaces and all kinds of materials. In other words, the equipment can fulfill the needs for high-quality surface polishing of a broad range of industrial parts.

The STRECON Robot Assisted Polishing (RAP) Machine robot arm changing the polishing tool
Different parts polished by the STRECON Robot Assisted Polishing (RAP) Machine

Industrial Applications

The RAP polishing equipment is intended for high-end companies, which has a need for a fully controlled, traceable, and quality consistent surface polishing process. Our polishing machine has been proved successful for:

• Surface polishing of different tools used for various metal forming applications,
• Molds for plastic injections,
• Machine components such as tubes, cylinders, etc. made of different materials, hardness levels, pre-machined surfaces, and sizes.

The RAP technology significantly reduces the dependency on individual craftsmen and operators but offers the possibility to program and store the optimal polishing process for the individual part. Furthermore, the machine has proved to be very consistent over time including process stability, repeatability, and a long lifetime.

Due to the complexity and different customer needs, a RAP system solution would be subject to customization in each customer project.

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