Challenging grinding and weld finishing operations can substantially benefit from custom, automated solutions. It could be research and testing of new abrasives to improve quality or throughput, or it could be trying an entirely new process, which could potentially disrupt current manufacturing. With the increase in demand to deliver products faster at the highest quality, all while facing skilled labor shortages, as manufacturers turn toward automation, many challenges and opportunities are possible.
To help customers develop innovative materials, processes and automation, Norton | Saint-Gobain Abrasives established its Abrasive Process Solutions (APS) program. The APS team has access to a host of resources to solve practically any material removal or surface generation problem. Abrasive process expertise along with access to the best equipment allows the APS team to offer an extremely broad array of grinding process development solutions, which can be useful to customers in many fields – from metal fabrication and welding to automotive, aerospace, medical and more.
The Norton APS team is devoted to providing abrasive process development, optimization, automation and in-house testing for optimizing customer grinding applications, whether off-hand or automated. The APS program uses the expertise and vast knowledge of its team along with access to 30 different machines and a robotic automation cell that is at the core of its new solutions lab located at the Norton Higgins Grinding Technology Research Center in Northborough, Mass. The APS robotic lab is capable of solving abrasive-to-part and part-to-abrasive applications, wet/dry processing and has access to a full range of abrasives, such as coated, non-woven, thin wheel, bonded and superabrasives.
Two stages of automated weld grinding
No. 1 Weld preparation typically involves removing paint or rust from the surface and adding a bevel to the workpiece to provide a gap for the weld filler. Because paint and rust are more common in job shops, the cleaning phase is not a common application for automation.
Using automation to grind a bevel, however, ensures there is a clean, straight gap that will allow for a more constant, reliable weld. Flap discs or depressed center wheels are the best-suited abrasives for weld preparation.
No. 2 Weld finishing is the process of removing excess stock from the weld and polishing the welded area to match the surface finish of the surrounding area of the part. Usually, this is performed in two steps, including grinding and blending.
For the grinding step, coarse-grit abrasives are chosen for high stock removal rates. Abrasive belts, flap discs and depressed center wheels are the optimal tools for weld grinding.
Because the purpose of the blending step is to provide the best possible finish, less aggressive fine grit abrasive products are optimal. Flap wheels, nonwoven discs, wheels or belts, and paper discs on an orbital sander are the best products for weld blending.
Customer-centric program
If a customer does not have the time nor the ability to test a new part or process, the APS robotic lab can be utilized to do the testing for them. The testing is conducted concurrently with the business’ normal day-to-day tasks, therefore not disrupting the output of the company. The combination of access to the best equipment and expertise in many processes also guarantees that the customer’s needs will be taken care of.
Similarly, if a customer has a particular part on hand – maybe a new part for a new project – that they need to have processed and are unable to do it themselves, in some instances the APS team can offer these processing services. Such a part may require a specific machine or process, and the significant investment in equipment like this may not be economically viable for a lot of companies.
Outsourcing work has significantly increased, especially in the post-Covid-19 era. Companies that may be trying to scale back their technical support staff due to financial hardships or other issues linked to the pandemic may not have the staff on hand to develop processes for new parts or upgrade processes for existing parts. This is where the APS team can be of assistance. The experienced APS application engineers utilizing the APS robotic lab can assist customers that may be shorthanded.
APS Project Example A
Who: Manufacturer of stainless steel bowls and other cooking utensils
Challenge: Improve productivity and eliminate discoloring that was occurring during the manufacturer’s original process when fabricating and finishing the bowls. The manufacturer was using a sisal buff with an excessive use of compound and then another cut and color buff to finish the outside.
Solution: The Norton APS team recognized the buff was generating too much heat and recommended and tested an automated flap wheel process for metal removal. For the finishing process, a new Norton Fixed Abrasive Buff was proposed, which uses 75 percent less compound and often runs 10 percent to 20 percent shorter cycle times. Because reaching out to an automation system integrator for testing was not a realistic option due to the expense and potentially long timeframe, the APS team was able to give the manufacturer the parameters for a viable and proven solution for implementation with the system integrator, saving time and costs and improving product quality.
Robotic cell 101
The APS lab features a Fanuc R2000iC robot with a 210-kg load capacity that allows the testing team to perform processes using nearly any size part or tool. The force sensor-capable robot performs in a multi-capacity role, meaning it is fitted with an end-of-arm gripper to allow for part-to-media processing as well as tool changers that use traditional hand tools to perform abrasive-to-part processing.
The integrated robotic-centered process development system includes a programmable pivot table, 6-in.-deep coolant pans, abrasive tools, toolholders and radial compliant devices. Also integrated are spindle motors and compliance slides as well as two heavy-duty grinding heads that have a 15-hp and 40-hp motor, respectively.
Furthermore, a programmable pivot head with dual belt and wheel is offered. Belts, cut-off wheels and grinding wheels, for example, can all be accommodated on the stacked head for part-to-media applications that require heavy pressure, such as casting cut-off and gate grinding. A side-by-side spindle head can use two belts and up to four radial wheels that can produce high surface finishes by buffing or using filament brushes.
APS Project Example B
Who: Automotive component manufacturer making extruded aluminum truck parts
Challenge: Transition from off-hand finishing to an automated process to improve output and safety while maintaining a fine finish. The manufacturer was also seeking a way to improve productivity by reducing the number of finishing steps.
Solution: The Norton APS team was able to assist the manufacturer as well as its system integrator to move to an automated solution. Also, various abrasive product types and grit sequences were tested, ultimately determining the best products for the application.
Importance of compliance
Grinding automation “compliance,” defined as the adjustment of pressing force via motion modification, is a key feature to have in any automated grinding cell, especially critical when it comes to weld grinding. Basically, a compliance device uses pneumatic pressure to allow an abrasive to maintain a constant force at any point within a specific mechanical stroke.
Compliance makes programming a robot simpler as it reduces the accuracy requirement for points in the toolpath. It also helps accommodate for variations in the part, allowing the robot to still move its intended point rather than crashing in the event there is extra material on the weld. Using compliance to ensure the grinding force is constant, provides a more consistent finish while reducing cycle time and increasing the abrasive life. Maintaining ideal force allows for an optimal material removal to abrasive wear ratio. Because of these reasons, it is recommended to use premium abrasives which will provide the longest life in an automated cell, reducing abrasive changeover time and maximizing the uptime.
The compliance in the grinding cell can either be on the grinding head or the end of the robot arm. In an abrasive-to-part system, the force control comes from a compliance device placed between the spindle or abrasive tool and the robot arm. In a part-to-abrasive system, the compliance generally comes from a pneumatic cylinder on the grinding head, allowing the grinding force to remain constant regardless of the contact point between the part and the abrasive.
The Norton APS team helps welders and fabricators identify and optimize the best abrasive process solution and, in some cases, demonstrate how a robotic setup can dramatically increase productivity. For example, robotic arms can be used in instances where it is not safe or realistic for manual grinding operations. Robots can also be more cost-effective and help alleviate the stresses of workforce shortages.
Equipped with a verified turnkey solution, fabricators can then contact an automation system integrator to implement the solution. This avoids costly trial and error at the integrator level.
