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This article is a brief guide to improving the turnaround of both the mechanical design and sourcing of prototypes parts during the early stage of a product or technology development program. The process is mapped and priorities explained to reduce risk and improve overall project timelines.

Regardless of the complexity of a product development there will be something new which carries risk. Project timelines are often stretched and discoveries, by their nature, are not planned. Delays in the infancy of any project can cast a big shadow in more ways than one on a project.
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Process Advantages
Engineered blow molding offers a highly versatile process for fabricating parts. Effective designs for its blow molding take advantage of the inherent advantages of the process:

• “Hollow” aspect of design
• Strength-to-weight structural integrity
• Suitability for large shapes

Process Limitations
• Extent to which material can be stretched
• Degree to which complexity/detail can be reproduced
• Part length limitation by material melt strength

The design must also make economic sense compared to other processes and materials.

The design/processing relationship
Engineered blow molding forms parts by blowing a hollow parison outward to conform to the shape of the mold (Fig.1). Inherent to this process is stretching of the thermoplastic resin material. That stretching thins the walls. Forcing the material to stretch too much may make it impossible control wallsection thickness or even cause the parison to rupture/fracture.
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The Mechanical Design Forum is now 3 years old. It really doesn't feel like that long since it was started.

Below are a few screenshots of how the site has developed over the last three years.

The current incarnation of MDF (let's call it MDF 2.0) uses the excellent vBulletin software. The previous versions that are pictured below (let's call them MDF 1.0 to 1.3) used phpBB. The latter is open-source so it's freely available. As great as phpBB was, it could be quite buggy and unweildy to work with, hence the decision to move to the more sleek and professional platform of vBulletin in October 2011.
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Generally, when we use a cast component in an assembly, we are using the machined version of the component. Though the design of a machined component is sufficient for simple castings, the design for a cast component becomes necessary for some parts. In such cases, while designing in Pro/Engineer a designer would not only like to maintain the associativity between the cast and the machined versions, but would also like to design the CAST part in the context of MACHINED part.

The scope of this article is to highlight the use and benefits of Inheritance feature. The procedure below describes ONE of the methods using basic elements. However, the Inheritance method is the preferred one for such application.
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Here are some notes on car wheels that we put together a few years ago as part of a university project. These notes give some insight into the history, manufacturing processes, materials and design considerations relating to car wheels.

1. History
The first light-alloy sheet wheels were used in Daimler-Benz and Auto-Union racing cars in the 1930s. In the 1960s, Porsche began the batch production of sheet wheels, which consisted of a wheel rim and nave. The first high-volume production of sheet wheels in Europe started in 1979 for Daimler-Benz cars destined for the USA.

Through further development of the production process for wheel rims and naves, the manufacturing costs were reduced markedly so that an aluminium sheet wheel has been produced in large numbers for the BMW 5 Series since 1995

Using aluminium wheels on passenger cars began with the upper class or flagships models in order to give them a distinctive personal touch.
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This article helps mechanical engineers understand the selection of ball bearings depending upon the application and load conditions. Primarily the article helps you calculate the minimum and maximum load bearing capacity of bearing and most importantly... life of the bearing as an individual. Here the designation number of the ball bearing helps you know the design, working nature and the physical property of the bearings.

In this new edition, I have come up with accuracy, operating temperatures, re-lubrication features along with applications, utility and system of operations recommended by American Society of Mechanical Engineers (ASME). You can also observe reflections of rules abiding ANSI/API standards putting a significant relevance with bearing operations from maintenance point of view.

Introduction
For Pumps used in Petroleum Industries and Gas Industries, we have some standard statements meant to be followed:-

Each Shaft shall be supported by two radial bearings and one double acting Thrust Bearing which may or may not be combined with one of the radial bearings. This means, The thrust bearing may or may not be in the same axis as the rest of the two radial bearings. In other words, it can also said as, the thrust bearing can be arranged in such an order that, it may or may not be a part of the system bearing calculation although supporting the shaft.

Here, there can be only three possible system of arrangements,

1. Rolling Element radial and Thrust.
2. Hydrodynamic radial and rolling element thrust.
3. Hydrodynamic radial and thrust.

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Here’s the job I was working on a long time ago – a massive granite beam held in place with M20 tie-rods in an anchor plate. The clearance holes in the beam were Ø30mm, so lots of room.


So I did the drawing using classical tolerancing, which should have been fine. A ±0.01mm tolerance should be more than needed to clear in case the holes weren’t perfectly straight.

This is how the tie-rods looked in the manufactured plate – not straight and there’s no way this will fit in the granite beam. The shop apologized and remade the plates with straighter tapped holes and it worked. They only had to remake 2 plates. Of couse the schedule took a hit.
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