In the past, cutting tool repair was something any machine shop could do. Today, this is no longer the case. As indexable insert tools become more complex and require more precision, the machinery required to repair these tools is often the same as that required to manufacture new tools. As a result, it has become more difficult for many shops to repair their own tools with old-fashioned manual equipment.
A hand-restored tool may look good, but it will be difficult to achieve the required cutting performance. Many businesses continue to cut back on their in-house machine shops, and the lack of skilled machining personnel makes it difficult to repair tools in-house. As a result, they need to turn to specialized agencies that can repair tools according to strictly controlled, proven procedures.
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Repairing a tool in the wrong way can lead to longer tool indexing times and more frequent tool changes, which in turn increases machining costs—the opposite of what a shop is looking for. (Refer to the method of milling threads with multiple tools on CNC machining center) Although many tool repair services have invested in advanced CNC machines and automation in order to restore complex indexable tools to “new look” condition, they still need to work with the belief that all tool repair work can only be done by I struggled with the notion that it was done by hand—sometimes the restoration wasn’t ideal.Repairing the failure of an indexable tool on a CNC machine tool requires careful inspection, diagnosis, and maintenance. Here are the general steps you can follow to repair the failure:
- Safety First: Before you begin any repairs, ensure the CNC machine is turned off, and follow all safety procedures. Wear appropriate protective gear, such as safety glasses and gloves.
- Identify the Problem: Inspect the indexable tool carefully to determine the nature of the failure. Common issues include chipping, wear, breakage, or improper seating in the tool holder.
- Remove the Tool: If necessary, remove the indexable tool from the tool holder. Follow the machine’s specific procedures for safely changing tools.
- Examine the Tool Holder: Check the tool holder for any signs of damage, such as deformation or wear. Clean and inspect the tool holder’s clamping mechanism and seating surfaces. If any parts are damaged, replace them.
- Inspect the Indexable Insert: Examine the indexable insert for wear, damage, or chipping. Measure its dimensions to ensure it’s still within tolerance. Replace the insert if it’s worn beyond acceptable limits.
- Clean and Lubricate: Clean the tool holder and indexable insert thoroughly. Use appropriate cleaning solutions and brushes to remove debris and coolant residues. Apply lubrication if required to prevent friction and wear.
- Proper Reassembly: Reinstall the indexable insert into the tool holder, ensuring it’s properly seated and secured. Follow the manufacturer’s recommended torque settings for clamping screws.
- Adjust Tool Offsets: If you’ve replaced the indexable insert or made any adjustments to the tool holder, update the tool offset values in the CNC control. This ensures the tool is positioned correctly during machining.
- Test Run: Conduct a test run with the repaired tool to ensure it’s functioning correctly. Observe the machining operation for any unusual vibrations, noises, or performance issues.
- Fine-Tuning: If necessary, make further adjustments to the tool offsets or cutting parameters to optimize tool performance. Consult your CNC machine’s manual for guidance on fine-tuning.
- Regular Maintenance: Implement a regular maintenance schedule for your indexable tools and tool holders. Proper maintenance can extend their lifespan and prevent unexpected failures.
- Training: Ensure that your CNC machine operators are trained in proper tool handling and maintenance procedures to minimize the risk of tool failures.
If you encounter more complex issues or if the failure is related to the CNC machine itself (e.g., spindle or tool changer problems), it may be necessary to consult the machine’s service manual or contact a professional technician for assistance. Always prioritize safety and follow manufacturer guidelines when performing repairs on CNC machines.
The key issue in tool repair is the cost of quality. The acquisition of CNC machining tools and precision inspection equipment requires significant capital investment, but companies that use them say they are necessary in order to restore more complex indexable tools to “like new” condition.
If a shop has tried hand-repairing a tool, and the results are unsatisfactory, it may opt to buy a new tool. Many shops have given up on repairing damaged tooling due to substandard repair quality, and as a result, they have lost the potential to save millions of dollars in tooling costs. However, tool repair work using sophisticated testing and inspection equipment as quality assurance can extend the life of indexable tools. For some specialized tools designed and manufactured for a specific process, repairing a damaged tool can save up to 90% of the cost of buying a new tool. Also, it often saves a lot of time, since repairing an old tool can take less time than producing and delivering a new tool.
Only a small number of tools with insert seats are damaged and difficult to repair, and most other indexable tools can be repaired after damage. Users often assume that a tool cannot be repaired, only to be surprised to find that this is not the case. Unrepairable tools are generally those with severe cracks throughout the tool, bent shanks, or severe deformation. Most indexable tools can be repaired and returned to their original state multiple times (2-5 times or more, depending on tool type and usage conditions). Some shops have made 3 cycles of repair tools as their standard.
The machining equipment used by tool manufacturers has improved significantly over the past decade. High-precision indexable tools using modern shank technology place higher demands on their repair work, and precise machining control and more importantly, precise tool inspection are essential. In order to fully restore a knife without destroying or sacrificing the original integrity of the steel selected by the knife manufacturer, proper controls must also be implemented. Altering the integrity of the original tool steel will jeopardize the cutting performance of the tool, regardless of its accuracy. The precision of the tool and the integrity of the steel must be considered and controlled throughout the tool repair process.
The repair of indexable tools must meet strict precision requirements. Given the tighter workpiece tolerances, it is critical that the overall quality and dimensional accuracy of the reconditioned tool is the same as or better than the workpiece being machined.
With regard to workpiece tolerances, tool accuracy is critical for machine tool retrofit, refurbishment and remanufacturing companies, because as machine tools become more sophisticated, the dimensional and shape tolerances of the workpieces also become tighter.
Today, in many job shops, it is common practice to require machining with tolerances of a few tenths of a millimeter, a level of precision that was only possible with grinding operations in the past. The success of tool repair usually depends on two key variables: the quality requirements of the workpiece and the number of workpieces the repaired tool must machine. If one of these two variables is demanding, a shop should probably choose a professional facility with advanced equipment to repair its indexable tools.
Change Tool Structure
Changing the tool structure makes tool repairs potentially more cost-effective. A growing trend in machining is the use of multi-functional composite tools that reduce machining time and tool changes, such as multi-diameter plunge milling cutters. Because compound tools tend to be specialty tools, and the purchase price of new tools is more expensive than single-function standard tools, shops are more motivated to repair such tools. The skills of knife restorers are just as important as the equipment they use. Tools must be repaired by a technically qualified machinist with proper use of appropriate machining and inspection equipment. However, the decisive factor in whether a tool needs to be repaired on a CNC machine is the complexity of the tool and the number of tools that need to be repaired.
The batch size, the complexity of the tool, the skills and experience of the machinist all combine to determine whether the tool should be repaired by hand or on a CNC machine. Many mass-produced parts are machined on automated equipment. In this process system, if there is a problem with the tool, it will cause a large number of workpieces to be scrapped at a rapid rate. The more automated a machining process is, the more reliable each component of the process must be. Of course, knives are also one of those components. Indexable tools that do not meet specifications will wear faster. In high-productivity machining, sub-quality indexable tools will fail faster due to irregular or inconsistent chip loads from one insert to the next. If the tool is not functioning properly because it is not repaired properly, some inserts will cut a larger diameter than others, removing more material per revolution than others. “All of these issues will shorten insert life,” Leigh noted. “In any machining, especially high-speed, automated machining, this will quickly consume a large number of carbide inserts, not to mention the increased downtime required to troubleshoot and replace inserts. .”
The best results can only be achieved if the tool restoration work is carefully organized and made part of the workshop regime. This plan includes tool collection, distribution and operator training. For example, a major aircraft manufacturing company implemented a reconditioning program for indexable tools (drills, milling cutters, and toolholders). Part manufacturers should develop a comprehensive program to ensure that all tools that can be repaired are repaired to maximize tool cost savings.
Although the most important reason to repair a knife is to save money, the most important goal to pursue when repairing a knife is quality. Typically, a reconditioned indexable tool costs 50%-85% less than buying a new tool, but if the cutting performance of the reconditioned tool does not match the performance of the new tool, the cost savings will be meaningless . In fact, if a repaired tool fails prematurely, or is not repaired to the correct size and accuracy, it may end up costing more than buying a new tool.
Global competition and lean production are two drivers of tool reconditioning. A few years ago, it was more common for a shop to scrap a worn tool, and repairing a tool could save about 50% of the cost compared to buying a new tool. Take the tool repair company’s advice – recycle the tool 3 times after repair.
To carry out tool repair work, we must first formulate a tool recycling system covering the entire factory. Tool repair companies can offer a variety of services that make the repair process easier to perform. For example, we can provide offsite inventory management of tool return bins, shipping containers and returned tools. Shops considering a tool restoration program should also carefully examine the restoration equipment they intend to use. Depending on the tool type and complexity, it may be necessary to mark the repaired tool, and the tool repair company should also provide a quality inspection certificate for the repaired tool. This requires proper inspection equipment and fixtures, as well as a machinist with extensive knowledge of the various indexable tools on the market.
A tool repair shop should also be ISO certified and be able to implement precise quality control, including managing the relevant technical documentation and inspection procedures. A quality tool repair shop requires sophisticated equipment, proper fixtures and well-trained operators. Understanding the precision requirements of the tool and maintaining the integrity of the tool material is critical to the repair process.
Inspection is especially important for the repair of certain tools. For example, an American automaker uses a special indexable toolholder to machine certain parts. This imported collet is expensive, requires high precision, and has a long lead time for ordering a new collet. Carbide Tool Services has developed a repair program for these toolholders, which now saves users more than $200,000 per year in tooling costs.
All tool restoration services are not set in stone, and even if your shop has had an unpleasant experience with tool restoration in the past, thinking again about how to do a tool restoration job—including a site visit to a potential tool restoration service provider—may still be Significant. Expensive indexable tools can make or break a machining process, so they can’t be entrusted to anyone.
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