Mersen USA, part of the French Mersen Group, has installed a 37' (11-m) high cold isostatic press (CIP), believed to be the largest one of its kind in the world. The new press improves Mersen’s position in the isostatic graphite market, increasing the company’s ability to produce large cross-section graphite blocks. Typical applications include silicon production and refining, foundry and ceramic processes, EDM, and other high-temperature applications. Large graphite blocks 1.5-m diam and 2-m long are currently available from the company, a capacity the new press is expected to increase.
Iso-molded graphite products exhibit characteristics like high density and thermal conductivity, low thermal expansion, and high thermal shock resistance that make them well-suited for a wide range of refractory applications. Ellor graphite grades are available for EDM applications from roughing to ultrafine precision machining, or as custom machined electrodes. Other Mersen high-temperature materials include Aerolor CFC-carbon/carbon composites.
The CIP features a working cavity of +500 ft³ (14 m³), capable of producing graphite materials weighing more than 14,000 lb (6350 kg). The press has a 31.3 × 23.6' (9.54 × 7.2-m) footprint and weighs in at a total of 1.1 million lb (499 t). Powered by two 300 hp (224-kW) pumps, the CIP operates at pressures in excess of 20,000 psi (138 MPa) over cycle times averaging 1 hr.
With more than 7000 employees in 60 production facilities in 40 countries, Mersen Group is a leading producer of graphite anticorrosion equipment, power semiconductor fuses, and brushes for electric rotating machines, as well as isostatic graphite production. The CIP was installed over 18 months at its Saint Mary’s, PA, manufacturing facility (formerly Carbone and Stackpole).
For more information about Mersen USA, go to www.Mersen.com/en, or telephone 814-781-8423.
Thermal Volumetric Compensation
No one doubts that compensation for volumetric positioning errors can greatly improve the accuracy of machine tools, especially the largest machines. Machine tool builders have encouraged evaluating their machines for their volumetric accuracy, and, along with major CNC controls manufacturers, have introduced error compensation to their controls. What hasn’t been too clear until now is the impact of temperature field variation on positioning accuracy of the machine tool, and the potential benefits of error compensation considering thermal effects.
A study, entitled "Measurement and Compensation for Volumetric Positioning Errors of CNC Machine Tools Considering Thermal Effect," recounts experimental results obtained by a team of researchers: Zhang Hongtao, Yang Jianguo, Zhang Yi, and Shen Jinhua from the School of Mechanical Engineering, Shanghai Jiao Tong University (Shanghai, PRC) and Charles Wang of Optodyne Inc. (Compton, CA).
All measurements were performed using an Optodyne laser system on a VMC with a working volume of 500 × 400 × 320 mm, X, Y, Z axes, equipped with linear-motor drives. To measure the thermal variation of each axis of the machine, 12 thermocouple temperature sensors were placed at different locations on the machine frame. A sequential step diagonal measurement technique was used to calibrate nine volumetric positioning errors. Measurements under various thermal conditions were performed to understand the relationship between the volumetric positioning errors and the temperature field variation. A radial basis function (RBF) neural network was used to predict the volumetric positioning errors with the axis positions and temperature points located on the machine. Measurement results show that with the increase of the machine temperature field, the change of volumetric positioning error is from 1 to 8.6 µm. The experimental results show that compensation of the four diagonal errors was reduced to a variation of 7 µm, a significant improvement in volumetric accuracy after error compensation.
For more information from Optodyne, go to www.optodyne.com, or telephone 310-635-7481.
Fluid Formulations Matter
When the US Department of Health and Human Services’ National Toxicology Program (NTP) recently classified formaldehyde as a known human carcinogen, it shone the spotlight directly on the formulation of metalworking fluids. NTP specifically identified triazine, widely used in conventional metalworking fluids for microbial control, as a formaldehyde-releasing compound. The importance of metalworking fluids without formaldehyde-releasing biocides, triazine, or DCHA was brought sharply into focus.
Chemetall (Frankfurt/Main, Germany; New Providence, NJ) had formulated a complete line of semisynthetic Tech Cool metalworking fluids with no formaldehyde-releasing biocides, triazine, other formaldehyde-releasing biocides, or DCHA some time ago. The Tech Cool line exhibits high lubricity, enhanced corrosion control, and increased tramp oil rejection even in high-pressure applications. Tech Cool is compatible with ferrous and aluminum alloys and can be used in stand-alone machine sumps and central coolant systems. The semisynthetics are stable in hard water, low foaming, residue-free, and can be recycled.
To inhibit bacterial growth, Chemetall employs high-grade raw materials, proven sanitary maintenance practices and fluid control, and advanced microemulsion technologies in production of the fluids. Chemetall, an ISO 9001 company, offers products ranging from metalworking fluids and drawing and stamping compounds to cleaners, rust preventatives, and surface-treatment chemistries.
For more information on Chemetall, telephone 800-526-4473, or e-mail: firstname.lastname@example.org
Nano Testing Thin Materials
The Nano Test from Micro Materials Ltd. (Wrexham, UK) is designed for use with a wide range of materials. It applies forces between 30 nN and 500 mN depending on the operating mode and measures penetration depths of between 0.1 nm and 50 µm. Measurements involve applying a small force to a sample using a sharp probe and measuring the resultant penetration depth, much like the classical hardness test, but carried out on a much smaller scale. The measured value is used to calculate the contact area and hence the particular property of the sample material. Both the method of force application and the geometry of the indentation tip can be adjusted to suit the particular application.
Because nanoindentation can measure in the subnanometer range, it can be used to determine the hardness of thin layers as well as material properties such as elasticity, stiffness, plasticity, and tensile strength, or fracture toughness of small objects and microsystems in fields such as biotechnology. Measurement is carried out by a high-resolution capacitive sensor, the PISeca sensor, which measures the penetration depth of the tip as a function of time. In static operation, the coil current and, thus, the load is measured at the same time, enabling a load displacement diagram to be compiled. In dynamic operation, the load is derived from the effective acceleration of the loading head.
The system can be used to increase the load slowly over a defined period of time (quasi-static indentation), or to perform a dynamic test where the tip is accelerated toward the surface, depositing a large amount of energy on contact (nano-impact). The wear of materials can be assessed by moving the sample slowly to produce a scratch while applying either a constant or ramped load as the sample moves along. The frictional properties of the surface are measured simultaneously. The system applies the force using electromagnetic actuation.
The indentation method used by the NanoTest can be combined with an imaging technique to investigate the sample surface pre and post-indentation. This combination of indenter and scanning probe microscope provides a quick method for assessing the sample surface. It is also possible to perform measurements at different locations without a lot of effort.
For more information on the Nano Test system, go to www.micromaterials.co.uk; or www.nanopositioning.net
This article was first published in the September 2011 edition of Manufacturing Engineering magazine. Click here for PDF.