What is the processing part that matches the small batch product?
Workpieces are a very important factor for designers of machinery and production equipment. Not only is it about functionality and performance overall, but it also has a lot to do with cost.
When you design parts for low-volume products such as FA equipment, do you consider the manufacturing process when designing?
For mass-produced products, although the cost of a single product is reduced, the initial costs such as mold costs are huge. On the other hand, FA equipment is produced in small batches, so it is necessary to choose a production method with low initial cost.
Manufacturing methods suitable for small-lot production include, for example, machining represented by machining, sheet metal processing such as laser cutting, welding, and the like.
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In particular, the following processing methods are often used for device parts on FA equipment.
Machining
Secondary processing of mechanical parts, parts with strength, rigidity and precision requirements, and canning processed products
Sheet metal processing
Thin plate parts such as covers and housings, parts that require little strength, rigidity, and precision
welding process
Canning processing parts (frames, skeletons, etc.) composed of angle materials and pipe materials, etc.
First, focus on major machining.
A powerful partner in the production of mechanical parts! Machining
Although it is simply called machining, there are various methods. Machining is basically the process of removing unwanted parts from a base material to achieve the desired shape. This processing is also called removal processing. The main machining methods are as follows.
Milling (machining)
It is a process of removing unnecessary parts by fixing the material and cutting it with a rotating tool. Also called machining, it can be said to be one of the protagonists of machining.
The tool is called an end mill, and different shapes and sizes are selected and used according to the application. It is a highly versatile machining method such as drilling, cutting surfaces and machining grooves.
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Main mechanical equipment: general milling machine, CNC milling machine, machining center, five-sided machining center
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CNC milling machine
Machining Center
※The photos of the processing machine were taken by the author and related personnel
Lathes (turning)
It is a process in which a material (mainly a round material) is rotated and a tool is pushed against it to remove unnecessary parts. Also called turning, it can be said to be another protagonist of machining.
Unlike machining, where the material is fixed and a rotating tool is in contact with it, turning is where the material is rotated and a tool called a cutting tool is brought into contact with it. Therefore, the shape that can be turned must be a coaxial cylinder or cylindrical shape.
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Compared with machining, it is characterized by the ability to process coaxial shapes quickly and neatly. Commonly used for machining high-precision cylindrical and cylindrical shapes, such as shafts, rods, etc.
In addition, it is also a common processing technology that the impeller and the like are switched to the machining center after turning and then machined.
Main mechanical equipment: general lathes, CNC lathes, compound lathes, turning centers, automatic lathes
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General Lathe
CNC lathe
Discharge class
This is the process of bringing an energized electrode (made of copper or graphite) or wire close to the material to create an arc discharge that melts and removes the material. It has the advantage that no matter how hard the material is, as long as it is conductive, it can be processed. For example, it can also process corners and bottoms that cannot be achieved with a milling machine.
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Wire-cut electric discharge machining that removes contours with a wire electrode, electric discharge forming machining that can realize various shapes by contacting symmetrically shaped electrodes, etc. EDM is mostly used in mold making and so on.
Main mechanical equipment: EDM wire cutting machine, EDM machine
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Wire EDM
EDM machine
Grinding
It is the process of performing precision finishing on the surface of the material by contacting the rotating grindstone. For parts that require precision finishing, such as joint surfaces between parts, etc.
In addition to machining precision flat surfaces, there is also grinding for finishing the outside of cylindrical shapes and the inner diameter of holes.
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Main mechanical equipment: surface grinder, cylindrical grinder, coordinate grinder, honing machine
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Surface Grinder
First, let's explain the milling cutting process, which is also the protagonist in machining.
This processing method is suitable for processing plate and block parts such as bottom plates and shells. It can be said to be the main processing method for processing parts such as FA equipment.
Let's build an impression of the machining site!
Machining is a process in which the material is fixed on the table of the equipment, and then a high-speed rotating tool (end mill) is pressed against the material to cut off unnecessary parts. It is mainly capable of cutting surfaces, cutting contours, opening holes, slotting, and cutting out curved surfaces.
And because it is a very versatile processing method, it can be processed by changing the tool suitable for each processing method.
A general-purpose milling machine is a general-purpose milling machine that manually changes tools and is operated by a processor, and a numerical control milling machine that can perform numerical control (Numerical Control: Numerical Control) on the part being operated. Numerical control refers to the function of automatically rotating and moving the spindle and moving the worktable according to the program.
In addition, those equipped with ATC (Automatic Tool Changer: Automatic Tool Changer) are called machining centers. Since multiple tools are automatically replaced during processing, various processing can be performed on the material at one time as long as the material is assembled and the program is activated.
The figure below shows the composition of the current mainstream general-purpose machining centers.
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Configuration of machining center (Mori Seiki: NV4000)
Put the material (mainly block material) on the workbench, fix it, install the tool, set the material origin, and then input the processing program. After that, the spindle and table are machined according to the program to achieve the desired product shape.
Programs for machining are called NC programs. The old method seems to have been to output on paper tape and have the tape read by a machine. There are two main ways to create programs now.
① Input the program directly on the controller
② Use a PC application called CAM to create data and transfer it to the controller.
For simple shapes, you can enter the program in the way of ①, and for complex shapes, you can use the method of ②.
Items that can be machined
So what shape will the objects that can be made by machining be? Here, we first introduce typical parts examples so that you can have an impression.
1~2 axis processed products
The easiest parts to make are shapes that can be made by punching or cutting from one direction. Surface machining such as machining in one axial direction, machining contours at the same height, and grooving are relatively simple machining.
As shown in the example below, base plates with only screw holes or drilled holes on the plane, or blocks with partial cuts or chamfers, etc. are typical processing. In addition to holes and cutouts, contours and grooves can also be machined.
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Multi-faceted processed products
This is a processed product obtained by processing the part shown in the above figure not only from one direction but from multiple directions. As shown in Fig. 3, in addition to contour machining, hole machining, grooving, and notch machining from one direction, hole machining is also performed from the lateral direction.
Figure 4 shows an example of grooving from the lateral direction and hole machining from the other direction. In this machining, the material is turned over, changing its orientation, and the shape is machined in all directions.
After machining from one direction, the material is turned over and fixed again, also known as "workpiece changeover".
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3-axis machining
3-axis machining is a method that can cut smooth curved surfaces (free-form surfaces, etc.) even when machining from one direction. Finish machining is done by moving along the curved surface of a ball nose end mill with a round tip. Not only parts with free-form surfaces as shown in Figure 5 can be processed, but also curved surfaces obtained by scanning people and animals as shown in Figure 6 can be processed.
Since it is necessary to simultaneously move the spindle in 3 dimensions along the curved surface, create an NC program using a dedicated application for CAM (Computer Aided manufacturing) that supports 3D machining. This processing method is often used in the machining of injection molded parts.
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Multi-axis machining products
Parts that are not blocky but have complex overall shapes can also be machined. By resetting the material in all directions and using a 5-axis machine, complex shapes with multiple faces can be manufactured. This processing method is often used in aviation parts and so on.
Figures 7 and 8 are typical aerospace part shapes (schematics). It is characterized in that there are many complex thin-walled structures such as combinations of free-form surfaces and hole processing, protrusions, and overall thinning shapes.
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Multi-axis simultaneous machining
In the latest 5-axis and compound machines, some shapes can only be machined while rotating the material in sync with the tool movement. Typical shapes are what is called a rotor blade as shown in Figure 9 (4-axis synchronization) and a shape like an impeller shown in Figure 10 (5-axis synchronization).
For complex shapes like this that cannot be machined from only a fixed material orientation, machining has advantages.
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Machining can realize the processing of almost all parts from simple shapes to complex shapes.
