INTRODUCTION TO MANUFACTURING PROCESSES-MACHINING-PART 2

Audio: Introduction to manufacturing processes-machining-part 2

In the first article of this series, we learned what manufacturing is, why it is important, and the general classification of different manufacturing processes. In the previous article, we looked started to investigate machining processes, and in this article, we will finish with it.

The processes we will look into are chemical, electrochemical, and electrical discharge machining. Furthermore, we will also investigate sawing, laser beam, electron beam, plasma arc, water jet, and abrasive jet machining. This article is part of the introduction to manufacturing processes series split into multiple parts (articles).

Chemical machining process

Overview

Chemical machining is a material removal process in which material from a workpiece is removed by strong chemical reagents or etchants. The process starts with cleaning the workpiece; afterward, a protective chemical-resistant coating is applied (this step is also called masking). Then the workpiece is immersed in an etchant that reacts with the parts of the workpiece that are not masked (this step is called etching). Finally, the process ends with demasking and cleaning.

Variations

Chemical milling,
Chemical engraving,
Chemical deburring,
Chemical blanking,
Photochemical blanking,

Quantities

Production quantities are low to medium.

Tolerances: ± 0,0125 – ± 0,075 mm

Achievable mean roughness value (Ra): 0,1 – 6,3 µm

Materials

The workpiece can be made from aluminum and alloys, steel, copper and alloys, magnesium and alloys, silicon, titanium and alloys, and nickel and nickel alloys.

Application

Used for weight reduction in aerospace components and panels, tin sheet-metal stampings, machining printed circuit boards, microelectronic devices, decorative panels, printing plates, fine screens, flat springs, honeycomb structures, irregular contours, etc.

Electrochemical machining process:

Overview

Electrochemical machining is a material removal process in which material from a workpiece is removed by combining electrical energy with a chemical reaction. The tool is the cathode, and the workpiece is the anode. The tool is usually made of copper, brass, or stainless steel and is designed in approximately the inverse of the desired final shape of the part.

Variations

Electrochemical machining,
Electrochemical deburring,
Electrochemical grinding,
Electrochemical polishing.

Quantities

Economic production quantities are medium to high. High tooling cost.

Tolerances: ± 0,0125 – ± 0,5 mm

Achievable mean roughness value (Ra): 0,2 – 12,5 µm

Materials

The workpiece can be made from any electrically conductive material.

Application

It is mostly used for materials and shapes that are difficult to machine by conventional methods, like jet engine parts, turbine blades, nozzles, cams, forging dies, burner plates, non-circular holes, deep holes, etc.

Electrical discharge machining process

Overview

Electrical discharge machining is a material removal process in which material from a workpiece is removed by a series of controlled electrical sparks to erode the workpiece material. These sparks are generated thousand times per second from an electrode to the workpiece, and the spark energy vaporizes the material. This vaporized material is resolidified into tiny particles due to the dielectric fluid in the gap between the workpiece and electrode.

Variations

Die sinker system,
Wire-cutting system,
EDM grinding.

Quantities

Economic production quantities are low.

Tolerances: ± 0,01 – ± 0,125 mm

Achievable mean roughness value (Ra): 0,4 – 25 µm

Materials

The workpiece can be made from any electrically conductive material.

Application

It is mostly used for materials and shapes that are difficult to machine by conventional methods. Typically it is used for prototype parts, irregular shapes, tools and die blocks, etc.

Machining process: Sawing

Overview

Sawing is a material removal process in which material from a workpiece is removed by a blade with a series of small teeth (saw), each tooth removing a small amount of material with each movement of a saw. It is normally used to separate the workpiece into two pieces or to cut the unwanted portion of the workpiece.

Variations

Hacksaw,
Bandsaw,
Circular sawing,
Abrasive cutoff,
Friction sawing,

Quantities

Economic production quantities are low to medium.

Tolerances: ± 0,13 – ± 0,5 mm

Achievable mean roughness value (Ra): 1,6 – 25 µm

Materials

The workpiece can be made from any material.

Application

It is mostly used for all types of materials that need to be cut to the length.

Laser beam machining process

Overview

Laser beam machining is a material removal process in which material from a workpiece is removed by vaporization with the use of light energy from the laser. Usually, in laser beam machining, carbon dioxide gas and solid-state lasers are typically used.

Variations

Laser beam machines can be used for cutting, drilling, blanking, honing, engraving, slotting, slitting, scribing, and trimming.

Quantities

Economic production quantities are low to medium.

Tolerances: ± 0,015 – ± 0,125mm

Achievable mean roughness value (Ra): 0,4 – 6,3 µm

Materials

The workpiece can be made from any material.

Application

Laser beam machining is used widely for drilling, trepanning, and cutting metals, nonmetallic materials, ceramics, and composite materials.

Electron beam machining process

Overview

Electron beam machining is a material removal process in which material from a workpiece is removed by vaporization and melting with the use of an electron stream focused on the workpiece surface. An electron beam consists of a continuous stream of electrons accelerated to approximately 75% of the speed of light. The beam is focused through an electromagnetic lens. The electron beam machining must be carried out in a vacuum chamber.

Variations

Laser beam machines can be used for cutting, drilling, and slotting.

Quantities

Economic production quantities are low to medium.

Tolerances: ± 0,013 – ± 0,125mm

Achievable mean roughness value (Ra): 0,4 – 6,3 µm

Materials

The workpiece can be made from any material.

Application

Electron beam machining is used widely for very accurate cutting.

Plasma arc machining process

Overview

Plasma arc machining is a material removal process in which material from a workpiece is removed by melting with use of a plasma stream. Plasma is defined as a superheated, electrically ionized gas.

Variations

Hand-held torch,
Numerical control.

Quantities

Economic production quantities are low to medium.

Tolerances: ± 0,25 – ± 2,5 mm

Achievable mean roughness value (Ra): 0,8 – 6,3 µm

Materials

The workpiece can be made from any electrically conductive material.

Application

Most applications involve cutting flat metal sheets and plates (hole piercing and cutting along the path).

Water jet machining process

Overview

Water jet machining is a material removal process in which material from a workpiece is removed by cutting with use of high pressure, high-velocity stream of water directed to the work surface. When used on metallic workpieces, the abrasive particles must be added. This process is then called abrasive water jet machining.

Variations

Water jet machining,
Abrasive water jet machining.

Quantities

Economic production quantities are low to medium.

Tolerances: ± 0,25mm

Achievable mean roughness value (Ra): 1,6 – 6,3 µm

Materials

The workpiece can be made from any material.

Application

Water jet cutting can be used effectively to cut narrow slits in flat stock such as plastic, textiles, composites, floor tile, carpet, leather, and cardboard.

Abrasive jet machining process

Overview

Abrasive jet machining is a material removal process in which material from a workpiece is removed by cutting with use of high-velocity stream of gas containing small abrasive particles.

Variations

Abrasive jet machines can be used for cutting, drilling, slotting, trimming, etching, cleaning, deburring, carving, and stripping.

Quantities

Economic production quantities are low.

Tolerances: ± 0,001 – ± 0,0125mm

Achievable mean roughness value (Ra): 0,1 – 1,6µm

Materials

Suitable for brittle and/or fragile materials.

Application

It is normally used as a finishing process rather than a production-cutting process. Applications include deburring, trimming and deflashing, cleaning, and polishing. Cutting is accomplished successfully on hard, brittle materials.

Closing words

Together with part 1, you have an overview of the most common material removal manufacturing processes. Even though you might not use all of them in your design process, it is always good to be familiarized with different manufacturing processes. You could change some of your company’s currently used manufacturing processes, and there is a great opportunity for additional cost savings and quality improvements.

Now you have an overview of machining processes you could use as a mechanical design engineer. However, I suggest you go through the text once more and identify areas you think need more understanding and clarity. Then, once you have identified those areas, start building up your knowledge in those areas.

To make it easier for you to find related posts, check the “Further reading” chapter below. Do you have any questions or need something to be clarified better? Leave a comment below, and I will give my best to adjust the post accordingly.

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