Search results

This study aims to develop and evaluate an inexpensive and durable metal cutting wheel using thermal spraying and polymer binding to enhance the wheel’s cutting capability by bonding hard particles (abrasives) onto the wheel.

Thermal spraying was used to deposit the coating powder (chromium and silicon carbide) onto high carbon substrate. Wear loss and depth of cut as function of load, time and speed were evaluated on uncoated and coated wheel.

The coated cutting wheel performed better than the uncoated cutting wheel in terms of wear performance. However, the coated cutting wheel experienced coating peel off at higher load and cutting speed, leading to a decrease in wear resistance of the cutting wheel. Thus, optimally cutting should be performed either at low cutting speed and high load or at high cutting speed and low load to prolong the wheel’s lifetime.

The outcome of the study will be beneficial for academicians and industrial working on cutting wheel process.

IN modern machining practice, precision grinding (the operation known in France as “rectification” is carried out on a limited number of parts and the use of the term immediately suggests the type of component usually subjected to this method of working—the gear wheel.

It is common practice in the engineering industry to deburr newly cut gears by the lengthy process of hand filing. Recently the Elgro Machine Tool Co., a subsidiary of Gem Brushes (Luson) Ltd., London, N.W.10, has produced a machine which greatly reduces the time taken to deburr a gear.

The computer‐aided design (CAD) and manufacture of custom‐fitting surgical guides have been shown to provide an accurate means of transferring computer‐aided planning to surgery. To date guides have been produced using fragile materials via rapid prototyping techniques such as stereolithography (SLA), which typically require metal reinforcement to prevent damage from drill bits. The purpose of this paper is to report case studies which explore the application of selective laser melting (SLM) to the direct manufacture of stainless steel surgical guides. The aim is to ascertain whether the potential benefits of enhanced rigidity, increased wear resistance (negating reinforcement) and easier sterilisation by autoclave can be realised in practice.

A series of clinical case studies are undertaken utilising medical scan data, CAD and SLM. The material used is 316L stainless steel, an alloy typically used in medical and devices and surgical instruments. All treatments are planned in parallel with existing techniques and all guides are test fitted and assessed on SLA models of the patients' anatomy prior to surgery.

This paper describes the successful application of SLM to the production of stainless steel surgical guides in four different maxillofacial surgery case studies. The cases reported address two types of procedure, the placement of osseointegrated implants for prosthetic retention and Le Fort 1 osteotomies using internal distraction osteogenesis. The cases reported here have demonstrated that SLM is a viable process for the manufacture of custom‐fitting surgical guides.

The cases have identified that the effective design of osteotomy guides requires further development and refinement.

This paper represents the first reported applications of SLM technology to the direct manufacture of stainless steel custom‐fitting surgical guides. Four successful exemplar cases are described including guides for osteotomy as well as drilling. Practical considerations are presented along with suggestions for further development.

The purpose of this paper is to evaluate surface integrity of quenched steel 1045 ground drily by the brazed cubic boron nitride (CBN) grinding wheel and the black SiC wheel, respectively. Surface integrity, including surface roughness, sub-surface hardness, residual stresses and surface morphology, was investigated in detail, and the surface quality of samples ground by two grinding wheels was compared.

In the present work, surface integrity of quenched steel 1045 machined by the CBN grinding wheel and the SiC wheel was investigated systematically. All the specimens were machined with a single pass in the down-cutting mode of dry condition. Surface morphology of the ground specimen was observed by using OLYMPUS BX51M optical microscopy. Surface roughness of seven points was measured by using a surface roughness tester at a cut-off length of 1.8 mm and the measurement traces were perpendicular to the grinding direction. Sub-surface micro-hardness was measured by using HVS-1000 digital micro-hardness tester after the cross-section surface was polished. The residual stress was tested by using X-350A X-ray stress analyzer.

When the cut depth is increased from 0.01 to 0.07 mm, the steel surface machined by the CBN wheel remains clear grinding mark, lower roughness, higher micro-hardness and higher magnitude of compressive stress and fine microstructure, while the surface machined by the SiC grinding wheel becomes worse with increasing of cut depth. The value of micro-hardness decreases, and the surface roughness increases, and the surface compressive stress turns into tensile stress. Some micro-cracks and voids occur when the sample is processed by the SiC grinding wheel with cut depth 0.07 mm.

In this paper, the specimens of quenched steel 1045 were machined by the CBN grinding wheel and the SiC wheel with various cutting depths. The processing quality resulted from the CBN grinding wheel is better than that resulted from the SiC grinding wheel.

The aim of this study was to explore the application of rapid manufacturing (RM) to the production of patient specific, custom‐fitting removable partial denture (RPD) alloy frameworks. RPDs are metal frameworks designed to retain artificial replacement teeth in the oral cavity.

The study was undertaken by applied case study. An RPD was designed using computer‐aided design software according to well‐established dental technology design principles, based on a digitally scanned cast produced from an impression of the patient's mouth. The RPD design was then exported as an STL file in preparation for direct manufacture using selective laser melting. Dimensionally accurate frameworks were manufactured in 316L stainless steel and chromium‐cobalt alloy. These were assessed for accuracy of fit and function on the patient cast and on the patient in clinic.

This successful case study demonstrates that an RM approach can produce fully functional, precisely fitting RPD frameworks for specific individual patients.

The study was based on a single design produced using two materials. Further studies are in progress to show that the results can be achieved on a regular and predictable basis.

This study provides some practical guidance for the application described and suggests that similar success may be achieved in related custom‐fitting applications.

The paper demonstrates the successful application of a novel approach to the design and manufacture of custom‐fitting dental devices.

IN the current issue of the journal of the Institute of Practitioners in Work Study, Organisation, and Methods one of its Members, a Mr. E. Cule Davies, plausibly argues that ‘professional standards’ are interdependent with what he terms ‘practical results’. Mr. Davies cites a notional case of a company inviting a ‘specialist’ (the quote marks are his) to improve productivity in a given section and who gave their own professional work study practitioner the same objective to attain.

THE Treaty of Rome is one of the least publicised, yet potentially most important, international documents of our time. Under that treaty the six signatory powers began on the first day of this year that process of tariff reductions which will, over the next twelve or fourteen years, reduce and ultimately abolish all tariffs and trade barriers between them. For all practical purposes six national economies will be welded into a single supranational authority, with a common trade and commercial policy. That is to re‐draw the economic map of Europe.

Curves have been drawn to show the compressive (flexural instability) strength of tubes made from four materials in common use. Although these curves are subject to all the limitations of usual strut analyses, their use eliminates much arithmetical work.

Production Engineers have been continually seeking to find new and improved ways of converting an unmachined component into its finished design. Much of their time is spent investigating the contribution that new cutting tool materials and coolants could give them in the production of their components. In the field of production grinding more and more attention is being focused on the use of Superabrasives and in particular on ‘Cubic Boron Nitride’ for the grinding of ferrous materials. The purpose of this paper is to discuss the use of ‘Cubic Boron Nitride’ (C.B.N.) in the production grinding field and how the Engineer should approach the application of this highly versatile abrasive.