The development of the CNC machine

What are CNC machines?

Computer Numerical Control (CNC) machines are automated milling devices that are designed to make industrial components without the need for direct human assistance. Using coded instructions that are sent to an internal computer, these machines enable factories to manufacture parts accurately and quickly.

The history of CNC machining

Computerised Numerical Control or CNC as it is now known, first came about after World War II as a result of the US Air Force’s desire to produce more accurate and complex parts.  The modern machine’s advent can be traced back to the invention of the numerical controlled machine made by John T. Parsons.

First concept developed for the manufacture of helicopter blades

Alongside Frank L. Stulen, John T. Parsons first utilised computer methods to overcome machining setbacks, especially the accurate interpolation of the curves found in helicopter blades. In the process of developing smoother rotors, Parsons and Stuler generated an early version of a Numerical Control (NC) machine.

Developed with assistance of MIT

To further develop this machine, in 1949, Parsons turned to Gordon S. Brown’s Servomechanism Laboratory at the Massachusetts Institute of Technology (MIT). At MIT, a feedback system designed to gauge how far the controls had turned was developed.  

While the US Air Force halted its funding in 1953 due to expense, the project was resumed by Giddings and Lewis Machine Tool Co. who reduced expense but improved quality and efficiency.

Reduced production time from 8 hours down to 15 minutes

The first CNC machine was developed when John Runyon managed to produce punch tapes under computer control. By doing this, he managed to reduce the normal production time of 8 hours down to 15 minutes. By 1956, the US Air Force had accepted the proposal to produce a generalised programming language for NC.

The invention of CNC machines paved the way for automated tools that enabled efficient production for manufacturers. Today’s CNC machines bear little difference with the original machines in terms of concept. Both produce outputs in three dimensional directions: X and Y axes and depth.

The types of CNC machine

The types of CNC machine that exist today include the following:

CNC turning lathes –  CNC turning lathes produce parts by turning rod materials and feeding a cutting tool into the turning material.

CNC milling machines – Using a rotating cylindrical cutting tool, CNC Milling utilises a machining process similar to both drilling and cutting. The cutter in a milling machine has the ability to move along multiple axes and can create a variety of shapes, slots and holes   

CNC routers - CNC routers are similar to handheld routers but the tool paths are instead controlled via computer numerical control. CNC routers can be used for cutting various hard materials including wood, composites, aluminium, steel, plastics and foams.

Stone Mastic Asphalt Details

There are three major types of asphalt surfacing, characterized by a mixture of bitumen and stone aggregate. These are: Dense Graded asphalt (DGA); Stone Mastic Asphalt (SMA) and Open Graded Asphalt (OGA). Asphalt surfacing differs by the proportion of different size aggregate, the amount of bitumen added and the presence of other additives and material. 

Stone Mastic Asphalt

Stone mastic asphalt (SMA), also called stone-matrix asphalt, was developed in Germany in the 1960s. It provides a deformation resistant, durable surfacing material, suitable for heavily trafficked roads. SMA has found use in Europe, Australia, the United States, and Canada as a durable asphalt surfacing option for residential streets and highways. SMA has a high coarse aggregate content that interlocks to form a stone skeleton that resists permanent deformation. The stone skeleton is filled with mastic of bitumen and filler to which fibers are added to provide adequate stability of bitumen and to prevent drainage of binder during transport and placement. Typical SMA composition consists of 70−80% coarse aggregate, 8−12% filler, 6.0−7.0% binder, and 0.3 per cent fiber.

Difference Between SMA & Conventional Mixes:

 

Stone Mastic Asphalt Composition

SMA is successfully used by many countries in the world as highly rut resistant bituminous course, both for binder (intermediate) and wearing course. The major difference between conventional mixes and SMA is in its structural skeleton .The SMA has high percent about 70-80 percent of coarse aggregate in the mix. This increases the interlocking of the aggregates and provides better stone to stone contact, which serves as load carrying mechanism in SMA and hence provides better rut resistance and durability. On the other hand, conventional mixes contain about 40-60 percent coarse aggregate. They does have stone to stone contact, but it often means the larger grains essentially float in a matrix composed of smaller particles, filler and asphalt content .The stability of the mix is primarily controlled by the cohesion and internal friction of the matrix which supports the coarse aggregates.

The second difference lies in the binder content, which lies between 5-6 percent for conventional mixes. Below this the mix becomes highly unstable. Above this percent will lead to abrupt drop of stability because the binder fills all the available voids and the extra binder makes the aggregates to float in binder matrix. The SMA uses very high percent of binder > 6.5 percent which is attributed to filling of more amount of voids present in it, due to high coarse aggregate skeleton. The high bitumen content contributes to the longevity of the pavements.

The third difference is the use of stabilizing additives in SMA, which is attributed to the filling up of large number of voids in SMA so as to reduce the drain down due to presence of high bitumen content. On the contrary, there is no stabilizing agent in conventional mixes since the bitumen content is moderate, which only serves the purpose of filling the moderate amount of voids and binding the aggregates

Composition of SMA:

1. Asphalt (Binder)

2. Aggregate

3. Fibers

4. Mineral filler

Advantages:

• High stability against permanent deformation (rutting) and high wear resistance.
• Slow aging and durability to premature cracking of the asphalt
• Longer service-life
• SMA has a higher macro-texture than dense-graded pavements for better friction
• Reduced spray, reduced hydroplaning and reduced noise.
• Good low temperature performance
• Even though SMA has a higher cost than conventional dense mixes, approximately 20 to 25 percent, the advantages of longer life (decreased rutting and increased durability).

Disadvantages:

• Increased cost associated with higher binder and filler contents, and fiber Additive,
• High filler content in SMA may result in reduced productivity. This may Be overcome by suitable plant modifications,
• Possible delays in opening to traffic as SMA mix should be cooled to 40 ^oC to prevent flushing of the binder surface, and
• Initial skid resistance may be low until the thick binder film is worn off the top of the surface by traffic.

Sources:

Stone Mastic Asphalt

Wiki Stone Mastic Asphalt

From Rounders Bats to Royal Navy Warships

When we think of Royal Navy Warships, we think of their damaging capacity and rich history more than their technology. However, technology has a monumental part to play in ensuring the Navy Warships are safe and effective. Customised 2m stainless steel tubes are used for Royal Navy type 45 Destroyer Warships. These tubes and their customisation reduce the rotation that is caused by the seas movement. This is integral for the ships to operate at maximum efficiency and safety. The process used to ensure this? A process called tube end forming.

At the other end of the scale, believe it or not, tube end forming is used to produce children's sports equipment. Ever wondered how metal rounders bats are made? Look no further. Tube end forming is used in the production of rounders bats, creating a firmer, more durable bat. This means that the sport is being actively influenced by Tube end forming and its benefits.

What is Tube end forming?

Tube end forming is a process in which a tube of any material is altered at its end to achieve a specific functional or aesthetic effect. The tube can be flared outwards, pinched inwards, expanded outwards; tapered...the list goes on. These varied individual tube end forming all serve a purpose, but specifically seem to be important within the engineering and technological world.

The companies that create tube end forming contribute largely to our development of engineering and technology, and indeed to everyday life. The amount of different products generated by tube end forming is astonishing, uses from engineering and machinery parts to the putting together of marquees and tents!

What is the significance of varied Tube end forming?

Tube Endings come in various different forms from expanded tube endings, which are used to fit on different parts in machines to tube end reduction, which is used for tube layering. This allows tubes of different materials to be reduced into each other causing a 'sandwich' effect.

Micro tube end forming can be immensely useful, used to alter tubes less than 2 mm in diameter.

This can be used to create effective needles for IV fluid in the medical world and also can be used to make throttle components for jet engines.

All of these different types of tube end forming enable engineers and designers alike, to produce and create innovative technology and indeed develop current patents making them easier to produce. For example, if 2 or 3 components of a machine can be replaced with something as simple as a modified tube end then this will save money on production, increase efficiency of the machine or product and even increase profit with money being saved in the production process.

What materials are used by tube end forming?

The answer is just about anything. The materials can all be customised to different tube ends, to name a few; aluminium, brass, carbon steel, copper, kovar, nickel and ni alloys, rodar, stainless steel and titanium. With this range of materials available, we can see how the uses of tube end forming and the variation of things they can be used in is vast.

Tube end forming is found all over the UK and indeed the world.

Tube end forming can be found in a number of different industries, mainly technology and engineering based, but a few that would certainly surprise you. The eclectic nature of the business is shown in this list of different industries it is used in:

• Aerospace and Aircraft
• Air Compressor
• Air Conditioner
• Automotive
• Beverage
• Electronics
• Engine
• Gas and Appliance
• Heat Exchanger
• OEM
• Utilities (Power/Sewer/Water)

This is just a list of the more practical uses for tube end forming. There are other uses for this process which can be used even artistically. Last year in the 2012 Olympics, tube end forming was used to make the absolutely iconic Olympic torch. Made of 204 flared and customised tube ends or 'petals', the torch represented a beacon that toasted not only the Olympic Games coming to the UK but the celebration of the possibilities of engineering, customisation and design.

Contributed by:

Dean Ronnie

www.techniswage.co.uk