The position of the automotive industry is clear. Over the next ten years, practically every car maker will be building electric cars by the million – with clean electric motors and as plug-in hybrids. However, the question remains: are the right tools available for the large-scale production of electric motors? At EMO 2019, CERATIZIT will demonstrate an extremely effective tool programme that provides the perfect technical and commercial solution for every machining task encountered in the production of electric motors. The two newly developed fine boring tools for the high-performance high volume production of electric motor housings are simply outstanding.
The machining demands represented by the housing of a car’s electric motor are no different from those of an internal combustion engine – apart from the stator bore of the thin-walled electric motor housing. Depending on the size and type of the motor, the stator bore will vary between approximately 200 mm and 300 mm in diameter, extend to a depth of more than 300 mm and must satisfy extremely tight accuracy requirements; for example, tolerances conforming to IT6 and roundness criteria as low as 2/100 mm. These are huge challenges for a finishing tool designed to produce the complete bore in a single operation in high volume production. However, they have to be met if electric motors are to be produced in a timely and economic manner in quantities in excess of 100,000.
Solid steel tools are ill-equipped for these tasks, as they are far too heavy for most machine spindles. The solution is to be found in lightweight bodies that reduce the tool weight to somewhere below 20 kg, which today’s standard CNC machining centres are able to accommodate. Available in multi-step designs for complete machining applications, they feature several cutting edges per step and in some cases guide rails as well. Despite their light weight, fine boring tools like these must possess a high degree of rigidity to successfully transmit the power to the cutting edges and hence achieve the required tolerance results.
Additively manufactured high-end solution
With its new fine boring tool, which is additively manufactured throughout, CERATIZIT has developed a special tool for stator bores that satisfies all the stipulated requirements and leaves nothing to be desired in terms of machining speed and precision. The totally new design makes it rigid enough to satisfy IT6 tolerance requirements and the corresponding roundness criteria.
Despite its large diameter (in excess of 200 mm) and considerable length, the developers have managed to keep the weight of the fine boring tool below 17 kg and designed it to accommodate the tilting moment of machining centres. That such a lightweight tool can be manufactured at all is down to the experience in 3D printing gained over the years by CERATIZIT. The delicate, optimally braced structure of the base body can only be produced by an additive manufacturing (AM) process. Experienced AM designers, who are not only aware of the potential offered by generative manufacturing but are also familiar with the requirements of 3D printing, have used FEM calculations to investigate the effective forces and optimise the topology of the structure. The result is a fine boring tool whose design can be scaled almost at will to meet a customer’s needs. With four cutting edges per step and up to five steps per tool, even challenging boring tasks can be completed at high feed rates in a single operation.
Effective plug & play solution
The PCD cutting edges are soldered into cartridges that are also additively manufactured. This eliminates any heat input into the base body and prevents the associated deformation. Once the loaded cartridges have been fitted into the designated fixtures in the base body, CERATIZIT grinds the tool to precisely the required size – with micrometre precision. Customers obtain a plug & play solution that will enable them to achieve process-secure machining results that are always within specification.
By using 3D printing, CERATIZIT was able to take advantage of other strengths of the additive manufacturing process. The coolant holes in both the base body and the cartridges are designed such that every cutting edge receives exactly the amount of coolant it needs while at the same time flushing the chips out of the bore. Scratched surfaces are avoided, which contributes greatly to increased process security and a reduction in waste.
The CERATIZIT branch in Stuttgart-Vaihingen is responsible for the individual design of the fine boring tool with regard to tool size, guide rails and the required number of steps. It is also where the tools are manufactured on an ultra-modern machine.
The advantages at a glance:
• Complete finish machining of the stator bore in a single operation
• Up to five steps, each with four PCD cutting edges, offers high-performance capability
• Extremely precise machining results (tolerance class IT6)
• Topology-optimised, additively manufactured lightweight body
• Additively manufactured tool cartridges with soldered PCD cutting edges
• Optimised coolant hole configuration for cooling each cutting edge and flushing chips out of the bore
• Customer-specific design
Plastic step boring bar for the stator bore
CERATIZIT has developed another fine boring tool for the electric motor housing. Its design is somewhat simpler, but it’s no less innovative. It is more affordable and of a modular design that makes it easier to manufacture.
Lightweight construction and the AM expertise at CERATIZIT were also to the fore in this new development. The plastic step boring bar consists of a tubular lightweight base body that is made using conventional cutting processes. The diameters of the stator bore are fashioned using additively manufactured steps containing cartridges equipped with PCD or indexable inserts.
Carbon-fibre reinforced special plastic
These steps are the absolute highlight of the tool, as they are created additively using a special plastic developed by CERATIZIT. The high degree of rigidity of the plastic is due to the integrated additional materials. Having been optimised topologically during the development, they are, despite their minimal weight, able to divert the machining forces generated into the base body. The special plastic is also vibration-damped, while the 3D printing method allows the coolant holes to be configured as required. The coolant can therefore be channelled in the best way to flush the chips to the rear and out of the hole.
The cartridges for each step are equipped with PCD cutting edges or indexable inserts. Not a standard tool holder, but a design that prevents the tightening torque of the indexable insert from acting on the plastic. The cartridge also has an electronic component that enables fine adjustments to be carried out digitally on the indexable insert. A display can be docked via a digital interface and cutter adjustments then performed to micrometre-level precision.
Modular design
The modular design featuring base body and steps allows the lightweight counterboring tool to be configured as a multi-step tool entirely to a customer’s requirements to facilitate the complete machining of the stator bore in a single operation. Additional enhancements to hold an additional tool on the front, e.g. for the rotor shaft bearing, are under consideration.
Available quickly
Customers will love the fact that the delivery period is so short – even though everything’s made to measure. CERATIZIT holds the base body as a semi-finished product in stock – with a flexible KOMET ABS or HSK interface. The plastic steps are produced very quickly on a 3D printer. Without having to wait too long, the customer therefore receives a tool that can be used to machine stator holes with previously unattainable levels of efficiency.
The advantages at a glance:
• Flexible machining of stator bore to customer’s specification. For rough machining, finish machining or a combination of both
• Facility for additional tools possible
• Extremely precise machining results (tolerance class IT6)
• Modular tool design
• Topology-optimised, additively manufactured plastic steps
• Digitally adjustable tool cartridges can be fitted
• Optimised coolant channelling for flushing chips out of the bore
• Short delivery times
Tools with intelligence
CERATIZIT has always made the availability of digital support for its users a priority. KOMET KOMlife, the newly developed digital maintenance indicator, is a helpful add-on that further increases process security. KOMET KOMlife can be fitted to the two new fine boring tools as well as any rotating tool with a diameter of 50 mm and above.
With its KOMlife predictive maintenance system, CERATIZIT has set another milestone in the development of innovative maintenance strategies. KOMlife allows operational data to be recorded directly on the tool itself and displayed on an integrated display, which is activated using a magnetic stylus. The maintenance indicator can be adapted to a customer’s specific needs – such as when to change a cutting edge – using the adjustable maintenance interval. If the interval is exceeded, a flashing red LED indicates that maintenance is overdue. To acquire operational data digitally, the recorded data can be retrieved by the KOMlife app using the dynamic and patented QR code.
The advantages at a glance:
• Low-cost, digital maintenance indicator
• Autonomous data acquisition on the tool itself
• Integrated display
• Dynamic QR code – can be read using KOMlife app
• For all rotating tools with diameters of 50 mm and above
Ingenious combination of measuring probes and spindle head
Another new CERATIZIT tool is making waves in motor machining (and elsewhere): the KOMET MicroKom KOMflex spindle head, which is designed for the precise machining of bearing seats and cylinder bores, enables CERATIZIT to fill the gap between manual spindle tools and the flexible U-axis systems.
The KOMflex is extremely compact and uses the radio technology of a measuring probe to intelligently produce bores with self-correction (cutting edge compensation). This combination of measuring probe and spindle head in a single system is unique, offering the customer both technological and financial advantages. The precision spindle system works completely independently. All you need to use this tool is a machine with a built-in radio receiver so that the KOMflex spindle head and measuring probe can be controlled. The spindle head can also be manually controlled and adjusted via the machine control system or a magnetic switch located on the head itself. The KOMflex operates at speeds of up to 8000 rpm and ensures positional accuracy to 0.001 mm.
The advantages at a glance:
• Precise machining of bearing seats and cylinder bores
• Combination of measuring probe and spindle head
• Compact design
• Radio technology for intelligent cutter compensation
• Speeds of up to 8000 rpm
• Adjustable to within 0.001 mm
