Insights and Experiences in CNC Machining of Plastic Parts+ View more
Insights and Experiences in CNC Machining of Plastic Parts
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Date：2024-09-06 11:00
In the contemporary manufacturing sector, the production method of choice for machined plastic parts is CNC. This isn't a result of happenstance but is, rather, a principal production method for good reason. The insight I'm about to share with you is drawn from my work in the CNC machining of plastic parts and the mistakes I've made along the way. If you decide to work with plastic parts, a critical decision you must make is tool selection. The issue of tool selection is not trivial. Different plastics have different properties and, importantly, different natures when being cut. For machining geometry and/or tolerance critical parts made from softer plastic materials, using HSS (high-speed steel) tools is still an acceptable option. But when it comes to producing parts with hard thermoplastics and, especially, thermosetting plastics, carbide tools are a must. And by the way, don't assume one tool (or set) fits all. The right tool and thus the right configuration depends on a number of factors, not the least of which is what plastic you're machining.
In parallel, adopting suitable programming strategies, such as layer slicing and contour crafting, can curtail tool wear and processing deformation. It is essential to grasp the fundamentals of heat management because the machining of plastic generates heat. If the heat is allowed to build up without control, it can cause part deformation and a drop in accuracy. Consequently, a primary heat management strategy in Machining 101 is to select an appropriate cooling medium and method. The types of cooling methods and mediums that are most appropriate for plastic are air, water, or spray mist. Also, because plastics and the tools that work them tend to have "sticky" characteristics when both are heated, it is essential to apply lubricants to the tools to encourage their long life. A superior lubricant is one that, in an experimental setting, produced the most consistent results. Finally, different plastics behave differently in terms of their shrinkage characteristics, moisture absorption, and other significant factors. Consequently, setting the parameters for Plastics 101 Part I and II requires a clear understanding of the significant characteristics of the undergoing material.
Selecting the proper tool and setting the correct cutting parameters are essential to avoid excessive tool wear, which can significantly impair the quality of manufactured parts and escalate production costs. Regularly monitoring the wear condition of cutting tools is fully as important for ensuring high quality as is the much more commonly practiced regular adjustment of machine tool settings.
In the case of producing parts from plastics, it is also necessary to set the cutting parameters sensibly at first, because if the cutting force is too great, the part being worked can easily twist or bend, particularly if it is extremely thin or large. Processing errors associated with these defects not only compromise part quality but also promise to drive up costs, since after defects occur, the parts must be straightened (if they can be straightened), and reworking (if possible) on them must also be accomplished before any cutting force can be applied to them while they are still in the clamps, and before the next step in the programmed set of instructions is reached.
To guarantee dimensional precision, it is necessary to perform the programming and tool-setting operations accurately and to ensure that these operations are completed correctly before part processing. It is essential to check the machine tool's precision regularly, make adjustments as needed, and carry out maintenance tasks. Moreover, it is extremely important to use high-precision measuring instruments to inspect the parts exhaustively and to use measuring instruments that are appropriate for the kind of part being processed. In the early stages of my processing experience, I pay little attention to the kind of material being machined; I did not study the characteristics of the material thoroughly; and I did not do the preprocessing that is appropriate for the material being used, which resulted in parts that were deformed and that did not meet the desired tolerances. After this experience, I learned to pay much closer attention to the material being processed and to study the mechanical and physical properties of the material much more thoroughly.
I replaced the carbide tool and set the cutting parameters sensibly, and the problem was well resolved. During the programming process, I made some mistakes, such as incorrect coordinate settings and unreasonable cutting parameter settings. These mistakes caused a lower processing quality of the part and even led to scrapped parts. I later learned to check the program carefully before programming, to perform simulation processing, and to observe closely the running state of the machine tool during processing so I could discover and correct mistakes in a timely manner.
In parallel, adopting suitable programming strategies, such as layer slicing and contour crafting, can curtail tool wear and processing deformation. It is essential to grasp the fundamentals of heat management because the machining of plastic generates heat. If the heat is allowed to build up without control, it can cause part deformation and a drop in accuracy. Consequently, a primary heat management strategy in Machining 101 is to select an appropriate cooling medium and method. The types of cooling methods and mediums that are most appropriate for plastic are air, water, or spray mist. Also, because plastics and the tools that work them tend to have "sticky" characteristics when both are heated, it is essential to apply lubricants to the tools to encourage their long life. A superior lubricant is one that, in an experimental setting, produced the most consistent results. Finally, different plastics behave differently in terms of their shrinkage characteristics, moisture absorption, and other significant factors. Consequently, setting the parameters for Plastics 101 Part I and II requires a clear understanding of the significant characteristics of the undergoing material.
Selecting the proper tool and setting the correct cutting parameters are essential to avoid excessive tool wear, which can significantly impair the quality of manufactured parts and escalate production costs. Regularly monitoring the wear condition of cutting tools is fully as important for ensuring high quality as is the much more commonly practiced regular adjustment of machine tool settings.
In the case of producing parts from plastics, it is also necessary to set the cutting parameters sensibly at first, because if the cutting force is too great, the part being worked can easily twist or bend, particularly if it is extremely thin or large. Processing errors associated with these defects not only compromise part quality but also promise to drive up costs, since after defects occur, the parts must be straightened (if they can be straightened), and reworking (if possible) on them must also be accomplished before any cutting force can be applied to them while they are still in the clamps, and before the next step in the programmed set of instructions is reached.
To guarantee dimensional precision, it is necessary to perform the programming and tool-setting operations accurately and to ensure that these operations are completed correctly before part processing. It is essential to check the machine tool's precision regularly, make adjustments as needed, and carry out maintenance tasks. Moreover, it is extremely important to use high-precision measuring instruments to inspect the parts exhaustively and to use measuring instruments that are appropriate for the kind of part being processed. In the early stages of my processing experience, I pay little attention to the kind of material being machined; I did not study the characteristics of the material thoroughly; and I did not do the preprocessing that is appropriate for the material being used, which resulted in parts that were deformed and that did not meet the desired tolerances. After this experience, I learned to pay much closer attention to the material being processed and to study the mechanical and physical properties of the material much more thoroughly.
I replaced the carbide tool and set the cutting parameters sensibly, and the problem was well resolved. During the programming process, I made some mistakes, such as incorrect coordinate settings and unreasonable cutting parameter settings. These mistakes caused a lower processing quality of the part and even led to scrapped parts. I later learned to check the program carefully before programming, to perform simulation processing, and to observe closely the running state of the machine tool during processing so I could discover and correct mistakes in a timely manner.
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