Computer Numerical Control

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CNC Machining - An Overview

CNC stands for computer numerical control. It refers to a computer "controller" that reads instructions code which dictates how a machine operates. And is typically associated with the removal of material such as metal for the creation of a complex part. The design and cutting is controlled by software programs like, CAM and others.

The earlier version of CNC was a system referred to as NC or Numerically Controlled machines, which were basically physically wired and their operating parameters where difficult at best to change, if at all.

Punched tape was used and continued to be used as a medium for transferring codes into the controller for many decades after 1950's. It is now replaced with computer networks and software program that aid greatly to efficiencies and the ability to adapt mid project.

CNC machines have changed the tool and die industry and manufacturing in general since their introduction. The programs have lead to eliminating most of the human involvement. For example, curves are now as easy to cut as straight lines, complex 3-D structures are much easier to produce, and the number of steps to produce a part has been dramatically reduced.

Beside the efficiencies of manufacturing created by CNC, a further benefit has been a major improvement in quality control. With less human involvement more consistency in production, quality has been the result. Bottom line, CNC eliminates many mistakes and errors that human involvement can lead too.

In a company that focuses on CNC machining, they often set up a series of CNC machines sometime referred to as a Cell. The interesting thing here is that a series of CNC machines can be set up together allowing the part to go from one machine to the next, all without human involvement. For example, some companies have automated the process to the point that they will leave their machines running over night and over weekends with no operator involvement. Laser devices check for quality control and alert the controllers if any defects are found.

Mike Webster, Webster Engineering is a prototype and low-volume machine shop specializing in complex and precision metal work since 1962. Located in Roseville, Michigan, Webster Engineering is privately owned and certified to the ISO 9001:2000 International Standard. Webster Engineering has a reputation for providing solutions that exceed expectations for speed, accuracy, delivery, quality and cost - achieving real customer satisfaction. Contact Webster Engineering at 586-777-0116 or CNC Machining or complex prototype design

Article Source: http://EzineArticles.com/?expert=Mike_Webster

Industries That Constantly Define CNC Precision

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Since the dawn of the CNC (Computer Numerical Control) machines introduction in the machining sector, they have been praised for being accurate, fast, consistent and flexible. Although CNC machines are not totally independent, a lot of major industries depend on these wonder machines. Common CNC-dependent industries include the metal industry and the woodworking industry. However, these industries, when small-time, can be operated by hands.

In this article, you will learn about the industries which are CNC dependent not because they have grown big in time but because they have to. It can be also that they are CNC dependent because their industries demand a low level of tolerance and a high level of sophistication. There are no “small-time” members of this industry. Let’s start discussing.

THE AEROSPACE INDUSTRY

First off, this is already a very sophisticated industry. An engineering degree (solely) will not get you anywhere in the Aerospace industry. Not even within striking range. This industry demands so high from their members so machine shops that belong to this industry trust only the best of the best of CNC machining. In fact, sources say that the term “Precision Machining” has been coined from this industry.

In the materials they use, the aerospace industry already demands a lot. CNC machines which are used here are mostly capable of handling Inconel, Titanium, Magnesium, Stainless Steel and so much more. From parts of the landing gear, to shuttle seats, to housings, and even oxygen generation, CNC machines play a big part in their manufacturing.

It’s not just that. Every CNC machine used in this industry also has to be approved AND RATED by the Federal Aviation Administration (FAA) to be safe and to be surely capable of “Precision Machining”. A NASA experience is highly praised too.

THE MEDICAL INDUSTRY

If the Aerospace Industry demanded precision above all, the Medical Industry demands sterility as much as precision. That’s something that you may have known since you got your first vaccine. Most CNC machines which work for this industry are multi-spindle and contain multi-turret lathes.

These special features allow the company to turn out components for hospital equipment, pulse meters, blood purification systems and mother medical devices. They are also useful in the mass production of disposable items and non-embeddable components.

High-torque milling and turning spindles are heavily demanded in this industry to enable users to process all substrates currently used in the medical device and orthopedic implant markets. Moreover, CNC machines recommended in the medical industry are those which can properly handle Titanium, Cobalt Chromium, Nitinol and others.

THE MILITARY INDUSTRY

This industry’s main concern aside from precision is security. In fact, if you try to search online the CNC-manufactured materials or CNC machines used in this industry, no matter how famous their reputation is, the manufacturer cannot display (pictures of) the materials that they have produced for their clients. They can only display products which they are used in.

This industry deals heavily with Inconel, Titanium, Kevlar, Monel and Hastealloy; so most CNC machines recommended in the Military industry must be able to handle those.

Famous CNC standards evaluators in this industry include the Department of Defense (DOD), the Mil Spec (Military Specifications) and other selected military sectors.

The top managers of these industries also demand their CNC machines to be purchased from CNC machine suppliers which adhere to the International Standards Organization (ISO). And because these industries are CNC-dependent, their shops can occupy a vast amount of space. Basically, that makes no room for old school methods and errors.

CNC Machine Setup and Operation

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Computer Numerical Control Machines are sophisticated instruments that only trained CNC operators should operate them. There are certain rules and guidelines to consider if you are planning to use a CNC machine by yourself.

CNC checklist before startup

Before starting up the Computer Numerical Control Machine, there are safety rules that must be considered first. First important aspect before starting up the CNC machine is to ensure your own safety, therefore wearing protective gear, such as eye glasses and short sleeved shirts is an important dress code during CNC operation. You should also be careful whenever you are handling tools and sharp edged work pieces to avoid any accidents. You must also ensure that the cutting tools are fastened in the machine spindle to avoid any movement during the cutting operation.

Actual Startup, Operation and Machine Setup of the CNC

The Computer Numerical Machine startup procedure varies depending with the type of machine being used but usually there is a main power switch or a circuit breaker to turn it on. Some machines also require hydraulics or air pressure before it starts up.

When the Computer Numerical Machine starts up, the machine usually starts at its Machine Home Position. The Machine Home Position allows the control and the machine to have a preset starting position for all its axes. After startup, the CNC machine must be sent to this position before the work begins. This position will later be changed to an appropriate location whenever you are machining a particular part of a product.

The Tool Length Offset Value or TLO is the distance from the tip of the tool from the spindle in the Home Position. The TLO must be set for each tool in the current job. The TLO can be set using a height gage, fixture location, as well as the reference tool. When these values are determined, they are stored in the Controller to be used during the program operation.

After setting the Tool Length Offset Value it is time to setup a part origin of a CNC machine. Setting up the part origin on a CNC machine is the same as setting up a conventional machine. It usually involves positioning the axes to a point where the plan designates as its origin. There are many ways to locate the position on the reference point, it is by using edge finders, wigglers or magnifying glasses.

After setting up the whole system for the Computer Numerical Control, it is time to Load the program to the machine. Program loading is different for each machine. Some machines have tape readers to input the program into the Computer Numerical Control Machine’s memory. Newer machines have internal or external floppy devices to input the program to the machine. After the program is loaded to the machine, the CNC machine is now ready to use.

There are certain instances when you have to change the tools in the Computer Numerical Control manually during machine operations. When a certain machining operation is complete, the program will move the aces to the tool change position and display the next tool needed. It is now the job of the Machine operator to remove and replace it with the next tool.

Extra Care must be taken whenever you are starting operations with the CNC machine, any mistake taken during the part of the operation may lead to serious injuries from the machine operator.