Advanced Finishing Solutions for the Modern Foundry
By Scott Shaver, Executive Vice President, EMI Inc.
- Robotic cells offer advantages for the modern foundry
- Improved quality, speed, and eliminated injury offer outstanding ROI
- New robot advances in “off-line” programming
- Comparisons in robotic and CNC systems
The modern foundry is an amazing manufacturing operation. While the principles of metal casting are among the oldest manufacturing process, dating back thousands of years; today’s modern foundry must combine sophisticated metallurgical, chemical, EHS, mechanical engineering disciplines into a well-choreographed operation. The most successful modern foundries work to maximize productivity in each unique process and department.
There have been hundreds of papers and technical best-practices written over the decades that focus on optimizing the main components of our foundries, melt, sand, molds, cores, handling, etc. Most every foundries are constantly working to optimize these areas of their business. More recently, one of the last steps in the foundry process that is beginning to gain the attention of foundry managers is the cleaning and finishing department.
Modern foundries all over the world seem to have one common goal in mind, a holistic automation approach. Today, many steps in the foundry process are automated.
- Sand is constantly monitored and adjusted
- Molds & cores are made in highly automated machines and use automatic handling systems
- Melt & pouring is accomplished with little human involvement
- Shakeout & separation is accomplished with little human involvement
- Cleaning and finishing – the last department in the process and usually the one department with the highest manpower requirements.
This article will focus on the benefits of automated cleaning or finishing cells and de-bunk some of the negative myths.
Traditionally cleaning and finishing a casting has benefited from the human operator in that a well-trained operator has the knowledge, visibility, feel, and dexterity to accurately and efficiently clean most castings. These are among the only process steps that seem to warrant the human touch. But the cleaning and finishing department is also the least productive in a foundry, requiring the highest number of man-hours with (unfortunately) the highest number of recordable accidents. Most often, the finishing department is the bottleneck in the foundry.
Automated finishing cells are offered in two types: computer numerical control (CNC) or robotic. Recent technology advances and thoughtful engineering approaches are quickly pointing interested foundry’s towards robotic cells instead of CNC machines. With a focus on robotic finishing, it’s important to mention the importance of working with a company experienced in the foundry industry. There are hundreds of robotic automation experts in the country, but only a few have the knowledge and experience needed for the specialties of the foundry industry.
The right robotic finishing cell starts with (…not the robot…not the tool…) the right company. An in-depth analysis of the casting(s) must start by understanding the casting model, the finishing needed, and desired production. Most finishing cells will be engineered for a number of different products today and flexibility to add new products in the future. The best cells will offer features that allow the foundry to add new castings with their own staff and with minimal fixturing.
Once a clear understanding of the various castings planned to be processed in the cell is understood, the next step is to analyze cycle times. Cycle time calculation is both art and science. Cutting and grinding tools all have stated feed and force rates but having an understanding of what is practical is important when engineering the process path. A skilled finishing engineer has a number of options when planning the process path. These process path options become more complex as different tools are called on. The goals are to deliver a quality finished casting in the least amount of time and maximizing tool life.
Figure 1: provides an example of a finishing model that identifies the areas on the casting. Each area may need a different tool or finishing process. Each will have varying feed rates, tool changes, casting manipulation, etc. all must be calculated with expert precision.
Figure 2: provides an example of cycle time calculation. We apply feed rates for various process, we calculate the length of cut or grind based on the details learned in figure 1 and we include transfer, approach, manipulation, times to determine the cycle times.
A well-designed robotic finishing cell will include flexibility to use either robot manipulated tools or robot manipulated castings. Normally larger castings are fixed in place and the tool is brought to the casting by the robot. Depending on the complexity of the finishing needed, the robot may change tools several times during the cycle and may even manipulate and move the casting to different fixtures.
Other design features must include flexibility for different types of tools and consideration for scrap handling/removal. Tool examples may include circular or band saws, grinding wheel, spindle, or belt, milling, boring, drilling. Ferrous and non-ferrous alloys change the tool types and characteristics. The power and torque of the spindles as well as their rotation speed are important factors in the application engineering. There are a wide range of the tools to consider, it is critical to select the right tool type. i.e.: for diamond coated rotating tools for cutting, milling and grinding equipment it is important to consider the surface granularity of the tool to maximize tool life and final finish.
The use of different spindles is highly recommended as it allows to perfectly match the features of each tool type and desired results (grinding, milling, cutting). The correct adjustment of these factors leads to cycle time optimization and the protection of the spindles during the processing. Cycle time of the finishing process plays the dominant role, the question of the feeding speed during processing is one of the key points. All the application engineering, tool selection, and operational mechanics are critical to the success of the finishing process.
After all the finishing engineering is completed and the process plan is understood, the next step is to program the robot’s paths. Advances in robot technology allow this to be a relatively simple process for a trained technician. For instance, Fanuc and ABB robots are supplied with off-line programming software that allows approximately 90% of the movements to be programmed via the software. The final “fine-tuning” will be done in the cell with the casting. These movements are taught to the robot via joystick or pendants.
Robot programming has historically scared many potential users away from robotic cells in favor of CNC. With the off-line programming suites available just about any maintenance or engineering technician can effectively program new castings for finishing in the cell. The right robotic finishing cell vendor will offer the foundry off-line programming as part of their continued service. Vendors provided off-line programming in concert with local foundry technical fine-tuning is a cost-effective process that introduces new castings to the finishing cell without having to contract on-site services.
Other features of a well-designed robot finishing cell should consider:
- Sound-proof safety enclosure
- Rotating table accepting any casting fixture and utilizing automatic clamping devices (for tool handled robots)
- Quick change EOAT capability
- Scrap handling and removal system
- Thoughtful layout to accommodate cleaning
- Flexible exhaust and debris collection hooding
- Safety interlocked access door(s)
- Remote teaching pendant or joystick
Foundry’s considering automated cleaning or finishing cells we’ve prepared this brief comparison of robotic finishing cells vs traditional CNC cells. robotic cells offer:
- Increased accuracy and processing speed
- Faster ROI
- Several different castings can be loaded and processed per cycle
- Greater flexibility for casting or tool handled processing
- Almost unlimited casting capability and easy to add different tools
- Increased tool life
- Operator friendly loading onto fixtures
- Off-line programming speeds set uptime and can be achieved without vendor technician’s
- Flexible scrape handling and removal
- Easier maintenance
Modernizing any foundry must consider all processes and departments. Hopefully, this article helps to point out the advantages of robotic finishing cells as an appropriate tool in any modernization effort while providing guidance for vendor identification and selection.