How To Evaluate CNC Machining Time

How to evaluate CNC machining time

How to evaluate the quality of CNC machining services when quoting CNC machining? When a customer directly asks how many days it will take to deliver the goods, the workshop usually estimates the completion period to be shorter due to various reasons. This phenomenon is indeed not caused by one person's subjective factors alone. The fundamental reason is that there is currently a lack of a set of binding systematic evaluation methods as a basic guarantee.

Determine processing procedures and process parameters

After getting the drawings, the first step is to determine the processing technology. As for whether the material is aluminum alloy or stainless steel, and whether it is a rough machining stage or a finishing operation, these factors will directly determine the specific values ​​of cutting speed, feed rate and depth of cut.

For the case of using No. 45 steel, if rough turning is performed, it is recommended to set the cutting speed vc to 120 meters per minute, and when finishing turning, it needs to be reduced to 60 meters per minute. In this way, the time spent between the two will be approximately doubled.

Once the parameters are determined, you must also pay attention to the condition of the tool. Under the premise of the same feed rate, the life difference between coated carbide inserts and high-speed steel inserts can be as much as three to five times. Because the number of tool changes is very high, the hidden auxiliary time is completely exposed and can no longer be covered up.

Write and optimize machining programs

Program quality can be directly reflected, and this reflection is reflected in idle time. If the design of a tool path is very reasonable, then the tool can reduce the empty tool stroke by about 30%. If two more fast-moving instructions are written inside the G code, the originally required time will be reduced by dozens of seconds.

At present, most people use computer-aided manufacturing software to perform automated programming work. However, after the program is generated, special personnel still need to be arranged to check and review one by one. Overcutting problems are very easy to occur where corners are involved, so the original sharp corners need to be modified into arc-shaped transitions in advance. This can not only effectively save the time required for cutting processing, but also minimize the wear and damage to the tools.

Breakdown of processing time item by item

The total time does not equal the actual cutting time. In a typical turning process, it takes 4 minutes to set up the clamping, then 2 minutes to complete the tool setting, and then enters the cutting stage of 18 minutes, then it takes another 3 minutes to change the tool, and finally it takes 5 minutes to unload the workpiece, which takes a total of 32 minutes. If any of these operations are missed, the delivery deadline will be delayed.

For parts with multiple processes, we also need to include the transit time between processes. When we move to the milling process after the car is finished, we need to replace the machine tool equipment and perform the alignment operation again. Just waiting for this can cause an additional 10 to 15 minutes of time consumption. However, when many people make quotations, they do not consider the time cost of this period at all.

Optimize cutting parameters and shorten working hours

Within the allowable range of the machine tool and tool, the fastest way is to increase the feed speed appropriately. However, in the finishing stage, if the feed rate suddenly becomes too large, deeper lines will be left. In this case, rework will be more time-consuming and labor-intensive, so you must not rush blindly.

How to evaluate the quality of CNC machining services when using different cooling methods such as dry cutting, wet cutting and MQL minimum quantity lubrication? Due to different principles, there is a very significant difference in the wear rate of the tool. If the specific concentration parameters of the cutting fluid and the corresponding flow value can be selected, the service life of the tool can be greatly extended, thereby greatly reducing the frequency of tool replacement, so that the total working hours consumed will naturally be shortened.

Simulate and schedule using software

Most factories today have used APS scheduling software. They input the detailed time-consuming of each process, the actual production capacity of the machine tools, and various shift arrangements into the system. Then the system can automatically generate a Gantt chart. If an emergency order occurs during this period, the operator only needs to manually drag and adjust to immediately and clearly see the specific impact on the final delivery date. This method of operation is obviously more trustworthy than relying on calling the relevant personnel to ask the relevant personnel.

From the perspective of practical application, cutting simulation appears to be more practical.

By using software such as Vericut or Mastercam to run simulations in advance before processing, the operator can detect possible dangerous situations such as tool collisions and overcutting before the machine tool officially starts processing. In this way, it can directly save the time cost of two or three hours wasted during trial cutting operations in reality.

Experience accumulation and continuous improvement

Whenever a machining operation is completed, the actual time spent and the pre-estimated value must be recorded. If you find that the deviation between the two exceeds the range of 10%, you must immediately find the specific cause of the difference. Wait until a quarter of data has been accumulated. Then the standard data about time is stored in the database. Its accuracy will exceed that of any form of operating manual.

As long as new technologies emerge in the industry and how to evaluate the quality of CNC machining services , the evaluation model must be recalibrated. Using five-axis joint adjustment to replace multi-process clamping, and using CBN to replace cemented carbide. Whenever each technology is introduced, all the previous old data will be completely invalidated and need to be calculated again.

In your workshop, does the current evaluation of processing time mainly rely on direct judgments based on the experience of senior employees, or is there a fixed set of standard operating procedures? Everyone is welcome to participate in discussions and exchanges in the comment area. If you find this content helpful, you may wish to like and save it so that you can quickly check it when you need to coordinate the construction schedule in the future.