The Core Position and Significance of Drawings in CNC Machining+ View more
The Core Position and Significance of Drawings in CNC Machining
+ View more
Date：2024-11-09 10:24
Introduction CNC (computerized numerical control), is one of the most modern power tools for machine shops.
They offer all sorts of precision, speed, and control over any kind of basic metal or wooden parts needed in a limited or unlimited run. When you compare them with older sorts of power tools, such as lathes and mills, they are as the car is to horse and buggy. CNC is far better and more efficient, but, still, it takes a well-made drafting of your part to get the section where they are completely superior—and that is high-precision work—because they can do it and can do it at high speed.
CNC (computer numerical control) machining makes it possible to fabricate parts with precise geometries by controlling the movement of machine tools via computer programs. The process typically includes several stages. First is the design stage. Here, engineers create three-dimensional models of parts using professional CAD (computer-aided design) software. A model formed in such a way contains crucial information that fully defines the piece in question. Next is the programming stage, where the model must be converted—by hand or by computer—to a form usable by the CNC machine tool. This conversion amounts to a translation from the language of design into the language of manufacture. With the model and the program, we can move on. Still, several more stages must be passed through before fabrication begins. In the processing preparation stage, we select appropriate raw materials, which we prepare with suitable fixtures and tools. Then, with the workpiece installed on the machine tool, we must "set the tool" before starting the fabrication process. Finally, in the processing stage, we hit "go," and watch as the apparatus carries out the orders given in the program.
Drawings' Functions and Roles in CNC Machining
Conveying design intention
The CNC machined product starts with one expression: a drawing. A drawing is the visual language of engineering. To an engineer, it is common knowledge that for every design concept, there should exist a drawing. Since the dawn of engineering civilization, basic geometric principles have been used to express design. From these rudimentary beginnings, engineers have developed into meticulous artists who can perform magic with a drawing board or, more commonly nowadays, CAD software, and transform their half-formed design dreams into the beautiful reality of coherent graphical representation and engineering notations that in a pinch can be understood by a Cretaceous dinosaur.
This "magic" is no small feat, especially in the era of concurrent engineering. The artist/engineer must work with a team of other artist/engineers and face the watchful gaze of their "big boss." Whether using a T-square, set of compasses, or plotting software, the drafter must remain resolutely within the confines of two-dimensional space while creating in the mind's eye a rendition of the three-dimensional reality of the part for which the drawing serves as expression and instruction.
CNC (computer numerical control) machining makes it possible to fabricate parts with precise geometries by controlling the movement of machine tools via computer programs. The process typically includes several stages. First is the design stage. Here, engineers create three-dimensional models of parts using professional CAD (computer-aided design) software. A model formed in such a way contains crucial information that fully defines the piece in question. Next is the programming stage, where the model must be converted—by hand or by computer—to a form usable by the CNC machine tool. This conversion amounts to a translation from the language of design into the language of manufacture. With the model and the program, we can move on. Still, several more stages must be passed through before fabrication begins. In the processing preparation stage, we select appropriate raw materials, which we prepare with suitable fixtures and tools. Then, with the workpiece installed on the machine tool, we must "set the tool" before starting the fabrication process. Finally, in the processing stage, we hit "go," and watch as the apparatus carries out the orders given in the program.
Drawings' Functions and Roles in CNC Machining
Conveying design intention
The CNC machined product starts with one expression: a drawing. A drawing is the visual language of engineering. To an engineer, it is common knowledge that for every design concept, there should exist a drawing. Since the dawn of engineering civilization, basic geometric principles have been used to express design. From these rudimentary beginnings, engineers have developed into meticulous artists who can perform magic with a drawing board or, more commonly nowadays, CAD software, and transform their half-formed design dreams into the beautiful reality of coherent graphical representation and engineering notations that in a pinch can be understood by a Cretaceous dinosaur.
This "magic" is no small feat, especially in the era of concurrent engineering. The artist/engineer must work with a team of other artist/engineers and face the watchful gaze of their "big boss." Whether using a T-square, set of compasses, or plotting software, the drafter must remain resolutely within the confines of two-dimensional space while creating in the mind's eye a rendition of the three-dimensional reality of the part for which the drawing serves as expression and instruction.
Tolerance and fit stipulations: Tolerance is the allowable variation range of part size and geometric shape and is crucial for ensuring part interchangeability and assembly accuracy. The drawing details the size tolerance, shape tolerance (such as straightness, flatness, roundness, etc.) and position tolerance (such as parallelism, perpendicularity, coaxiality, etc.). In CNC machining, operators need to adjust the machining accuracy of the machine tool according to tolerance requirements and select appropriate processing techniques and cutting tools to ensure that the part is within the tolerance range. For example, in the processing of automobile engine cylinders, the size tolerance requirements of the cylinder bore diameter are very strict. During processing, it must be strictly controlled, otherwise it will affect the fit accuracy of the piston and cylinder bore, and then affect the performance of the engine. Fit requirements specify the assembly relationship between different parts, such as clearance fit, transition fit, or interference fit. Processing personnel understand these requirements through drawings so that the processed parts can meet the assembly requirements.
Information about the materials and needed thermal treatments both before and after machining are absolutely essential to ensure high-quality machined parts. It's not just that the drawings specify which materials to use; they contain crucial information about the mechanical properties those materials possess both before and after any machining is done. That is especially true for materials that undergo heat treatment of any kind. Heat treatment doesn’t just make a material harder; it makes it tougher as well. The toughness difference can be enormous. But if I were ridiculously overgeneralizing for the sake of an argument, I could squeeze things down to saying that if you heat-anodize aluminum, it will be tougher than if you just machine it without heat treatment. And depending on which part you're looking at, the drawings may very well dictate that you do heat treatment to some stages and not to others.
Quality control in CNC machining is fundamentally linked to the use of accurate drawings and models. These documents specify all the key details necessary for the production of a given part. When a part is completed, quality control inspectors take a number of measurements using various tools, ranging from simple calipers and micrometers to more sophisticated apparatus like CMMs (coordinate measuring machines). These measurements are then compared back to the original document to see if the part is "in spec." If it is not, then the part is deemed defective. The stakes for this kind of inspection can be extraordinarily high. For example, if a part is made for a medical device and is then implanted in the human body, it must be held to an extremely high standard of accuracy. Thus, the responsibility of writing guileless, defect-free documents is something that engineers take very seriously.
IV. The effect of missing or faulty drawings on CNC machining: Error in processing and a coffee shop full of defective products: Without accurate drawings, workers cannot possibly understand the precise details of a workpiece that must be understood if it is to be machined in the first place—its shape, size, and the very nature of making it a "workpiece," as opposed to some other sort of fixture or tool. Should these workers understand the deal, they'll be led to make parts with too many or too few good-to-bad figure errors—errors in tool paths that lead to parts far from "on-spec"; big parts that don't fit, and little parts that can't hold anything. High-value workpieces, like those necessary for aerospace parts, are worth making accurately for a whole host of good reasons, not least economic ones.
Inefficient processing: When accurate drawings aren't available, programmers can have many conversations with designers to make sure they understand the design and the requirements before they can write the control programs. This is obviously a time-consuming process. The same thing happens if control programs are written for parts that aren't drawn correctly. And if poor quality parts are sent to the operators, they may have to stop the machines and make various adjustments or change the tool paths to get the parts into a state where the parts can finish their processing. And if the quality problems are very serious, operators may have to reprocess the parts, with all the resource-wasting and time-wasting that reprocessing implies.
Quality assurance and after-sales service problems: Poor drawings lead to poor quality parts. Parts of "bad quality" always have defects; the more serious the defect, the poorer the quality. Poor quality with poor reliability means no after-sales service is effective. Poor quality with poor reliability usually means parts that have too many defects to work in any application for very long. These past quality problems invariably damage the reputation of the enterprise in question. And poor reliability with poor parts can also mean additional maintenance and replacement costs and even lawsuits.
Information about the materials and needed thermal treatments both before and after machining are absolutely essential to ensure high-quality machined parts. It's not just that the drawings specify which materials to use; they contain crucial information about the mechanical properties those materials possess both before and after any machining is done. That is especially true for materials that undergo heat treatment of any kind. Heat treatment doesn’t just make a material harder; it makes it tougher as well. The toughness difference can be enormous. But if I were ridiculously overgeneralizing for the sake of an argument, I could squeeze things down to saying that if you heat-anodize aluminum, it will be tougher than if you just machine it without heat treatment. And depending on which part you're looking at, the drawings may very well dictate that you do heat treatment to some stages and not to others.
Quality control in CNC machining is fundamentally linked to the use of accurate drawings and models. These documents specify all the key details necessary for the production of a given part. When a part is completed, quality control inspectors take a number of measurements using various tools, ranging from simple calipers and micrometers to more sophisticated apparatus like CMMs (coordinate measuring machines). These measurements are then compared back to the original document to see if the part is "in spec." If it is not, then the part is deemed defective. The stakes for this kind of inspection can be extraordinarily high. For example, if a part is made for a medical device and is then implanted in the human body, it must be held to an extremely high standard of accuracy. Thus, the responsibility of writing guileless, defect-free documents is something that engineers take very seriously.
IV. The effect of missing or faulty drawings on CNC machining: Error in processing and a coffee shop full of defective products: Without accurate drawings, workers cannot possibly understand the precise details of a workpiece that must be understood if it is to be machined in the first place—its shape, size, and the very nature of making it a "workpiece," as opposed to some other sort of fixture or tool. Should these workers understand the deal, they'll be led to make parts with too many or too few good-to-bad figure errors—errors in tool paths that lead to parts far from "on-spec"; big parts that don't fit, and little parts that can't hold anything. High-value workpieces, like those necessary for aerospace parts, are worth making accurately for a whole host of good reasons, not least economic ones.
Inefficient processing: When accurate drawings aren't available, programmers can have many conversations with designers to make sure they understand the design and the requirements before they can write the control programs. This is obviously a time-consuming process. The same thing happens if control programs are written for parts that aren't drawn correctly. And if poor quality parts are sent to the operators, they may have to stop the machines and make various adjustments or change the tool paths to get the parts into a state where the parts can finish their processing. And if the quality problems are very serious, operators may have to reprocess the parts, with all the resource-wasting and time-wasting that reprocessing implies.
Quality assurance and after-sales service problems: Poor drawings lead to poor quality parts. Parts of "bad quality" always have defects; the more serious the defect, the poorer the quality. Poor quality with poor reliability means no after-sales service is effective. Poor quality with poor reliability usually means parts that have too many defects to work in any application for very long. These past quality problems invariably damage the reputation of the enterprise in question. And poor reliability with poor parts can also mean additional maintenance and replacement costs and even lawsuits.
Share to：
Recommend wonderful blog posts