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This paper aims to use cone-beam computed tomography (CBCT) and computer-aided design/3D printing technology to design and fabricate a drill guide template for access cavity preparation of permanent molars, and conduct a preliminary evaluation of its effectiveness.

CBCT scans were performed on two permanent maxillary first molars extracted due to periodontitis. Based on the scans, guide templates of access cavities were designed. The angle of the guiding cylinders was determined based on the direction of the long axis of the tooth. A 3D resin printer with high resolution was used to print the guide templates. The printed guide templates were used by a dentist with specialized clinical experience to perform access cavity preparation in a dental simulator. Then the prepared access cavities were scanned again by CBCT, and scan data were compared to the design data.

The 3D printed drill guide template had a close fit with the extracted tooth fit. The access cavity prepared using the guide template enabled the removal of the pulp chamber roof, and formed a straight-line access. Points were selected for measurement at regularly spaced intervals of 0.5 mm along the side wall of the access cavity. The mean deviation between the actual access cavities of the two permanent maxillary first molars and the designed cavities was less than 0.1 mm, with a maximum deviation of about 0.5 mm, showing a good conformance between the actual cavity and the designed cavity.

A drill guide template was designed and fabricated by 3D printing technology, which easily guided burs to complete the access cavity preparation work forming an ideal cavity shape with satisfying accuracy, and thus may reduce the complications during pulp chamber entry.

THE subject of this article is different from others in our series and offers less chance of the direct comparison of methods, because the size of the machine is great and the quantity built comparatively small. In another important respect it differs in that, hitherto, the approach has been from the point of view of the way in which a firm has laid itself out to produce one type, whereas in this case, it is the general working methods of the firm and its system of construction which is considered. It should be borne in mind throughout that the demand for flying‐boats, even military types, is limited, and jigs have to be large and costly to accommodate the big components, so that, to a certain extent, each boat is individually built. This individuality problem spreads, of course, even to the planning department; for each type of machine represents many thousands of parts, of which, at best, only a few off each will be required.

THE Piaggio Company has long been known for the design of unconventional aeroplanes; unconventional, that is, in the sense that they have broken with the general practice of the day. Their first post‐war type, the P‐136 five‐seater twin‐engined amphibian flying‐boat, is no exception. The prototype was generally considered to be one of the most interesting aeroplanes exhibited at the 1949 Salon de l'Acronautique. A second prototype was completed for demonstration purposes and, although civil sales were limited to a single example bought by King Farouk, the Italian Air Force adopted the P‐136 as a seaplane trainer and a first series of fifteen was recently completed for them at the company's main aircraft works at Finale Ligure. Piaggio &.C., although well‐known as an aircraft and aero‐engine constructor, is primarily an industrial firm making many different products, including railway coaches and the familiar Vespa light motor cycle.

IN this issue there is a Letter to the Editor (page 42). Its author is D. A. Barron, Chief Work Study Engineer of Marconi's Wireless Telegraph Co. Ltd., at Basildon. The letter is important from two aspects. Firstly, because it enables the writer of this column to clear up any misconceptions lingering in people's minds regarding references to Charles Bedaux in past editorials appearing in this journal.

The purpose of this paper is to present a novel force sensing jig for robot-assisted drilling used to drill holes for the fastening of floating nut plates in aircraft assembly.

The paper describes the drill jig, which consists of a parallel gripper, peg-in-hole pins and a back-plate with a recess where a Polydimethylsiloxane cone is placed on top of a force sensor. As the jig approaches the part, the force sensor registers the applied force until it reaches steady state, which indicates full contact between the jig and the part. The peg-in-hole pins then lock into a pre-existing hole, which provides a mechanical reference, and the support plate provides back support during drilling.

Positional accuracy and the repeatability of the system were successfully placed within the specification for accuracy and repeatability (0.1 mm tolerance and 0.2 mm tolerance, respectively).

The drill jig can be integrated into existing robot drilling solutions and modified for specific applications. The integration of the force sensor provides data for engineers to monitor and analyze forces during drilling. The design of the force sensing drill jig is particularly suited to industrial prototype robot drilling end-effectors for small and medium manufacturers.

The key novelties of this drilling jig are in the compact assembly, modular design and inclusion of force sensing and back support features.

INDUSTRIAL consultants are being increasingly employed both here and in the United States. It is natural that much of their work should fall within the field of work study since the usual reason for calling them in is to secure greater productivity. Such incursions are sometimes looked at askance by those assigned to that particular role in a company. This understandable human attitude will not be exorcised by implying that consultants are a race of infallible beings whose job is to impose superior methods on the permanent staff.

IT is a comparatively simple matter to settle down to the quantity production of an aeroplane in a brand new factory where expense is no object when considering the purchase of new machines and the ordering of tools, but it is far different when the factory already exists and has to be adapted to produce a much greater number of machines than had ever been contemplated by its original constructors and when the cost of the original design has to be added to that of tooling and overheads. The production of the Hawker Hurricane 1 affords a striking example of the successful solution of this problem. No one with any knowledge of the Kingston works can do anything but admit that they are not ideal. The buildings are old and at no time has work been slack enough to permit the closing of any one section for its complete rebuilding. Another handicapping feature was the lack of space in the immediate vicinity to allow for expansion. It is these facts that must be understood and appreciated for the true realisation of the work described in the following pages.

THE manufacturing methods and processes being used by Percival Aircraft Ltd., at Luton, in the production of the Prentice are of more than usual interest because this is the first metal aeroplane to be made by a firm well known for its wooden aircraft. Not only has the company built many hundreds of Gulls, Proctors and other wooden aeroplanes of its own design, but during the war the factory was largely occupied making Oxfords and Mosquitos. It is only in the post‐war period that Percival's have turned to metal, with the Prentice for the R.A.F. and the Merganser and Prince for the civil market. It was decided to design and build much of the works equipment. Examples of this are to be found in the two stretching presses, the strip rolls and the strip slitter.

This paper aims to provide an overview of applications of medical rapid prototyping (MRP)-assisted customized surgical guides (CSGs) and shows the potential of this technology in complex surgeries. This review paper also reports two case studies from open literature where MRP-assisted CSGs have been successfully used in complex surgeries.

Key publications from the past two decades have been reviewed.

This study concludes that the use of MRP-assisted CSGs improves the accuracy of surgery. Additionally, MRP-assisted CSGs make the surgery much faster, accurate and cheaper than any other technique. The outcome based on literature review and two case studies strongly suggested that MRP-assisted CSGs might become part of a standard protocol in the medical sector to operate the various complex surgeries, in the near future.

Advanced technologies like radiology, image processing, virtual surgical planning (VSP), computer-aided design (CAD) and MRP made it possible to fabricate the CSGs. MRP-assisted CSGs can easily transfer the VSP into the actual surgery.

This paper is beneficial to study the development and applications of MRP-assisted CSGs in complex surgeries.

THE advent of the digital computer enables engineering designers to replace manual calculation by accurate high speed computation. The combination of the digital computer and a machine tool‐control system offers the possibility of reduced costs, improved accuracy and the reduction of the time interval between the conception of a design and the production of the finished part.