Five keys to improve the maximum productivity of t

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It can be said that many mold factories do not adopt the latest processes and products available in the market, because they are satisfied with the existing system and do not believe that they need to receive re education that can improve efficiency. While those factories that are investing only make partial improvements, they will be disappointed because they do not see the expected results

improve one process at a time

when trying to improve factory productivity, we need to improve one process at a time from the evaluation of existing processing processes. The following are two cases to illustrate this process

case 1

challenge: a factory processes a mold with a hardness of 66rc and uses a double slot replaceable blade milling cutter. With a processing speed of 12 inches/minute, it takes two blades to complete the processing of a groove

solution: replaceable blade milling cutter and application program are recommended. The feeding, rotating speed and programming path were changed. The test was completed at a speed of 36 inches/minute, and nine grooves were machined with a blade

case 2

challenge: a factory encountered the problem that the required surface finish could not be achieved in the application of finish milling

solution: after evaluating the application and process, it was found that the machine controller filtered out most of the code. Simply put, the program tolerance is set to 0.0001 and the controller tolerance is set to 0.0004. After changing the controller tolerance to match the program tolerance, the finish is greatly improved (see Figure 1)

Figure 1: DM milling cutter for high-speed machining and hard milling

thank horm USA for providing pictures

this paper will discuss the five elements that mold manufacturers must consider when adopting the "one process at a time" method to achieve the maximum factory productivity: finish machining parts through hard milling rather than EDM; Unattended processing; Understand the difference between HSM and ordinary processing; Replace coordinate grinding with hard milling; And know when to use high-speed machining before hard milling. Based on the examples established by the above two cases, here are five keys that readers can start to evaluate the productivity of their factories and improve it

1. Finish machining parts with hard milling instead of EDM

hard milling is the process of machining part accuracy and tolerance. With the help of the technological progress of machine tools, tool holders and milling cutters, the efficiency of EDM machine tools can be achieved by 10 times. In the time of electrode processing, you may have processed parts. Although hard milling cannot completely replace EDM in all occasions, it can reduce the number of electrodes used on components and improve efficiency

The global competition requires us to adjust our processing process to reduce our manufacturing costs and compete with low wage countries all over the world. One way to reduce costs is to use hard milling instead of EDM for finish machining

people have made great progress in machine tools, tool holders and end mills, so customers can achieve 10 times the efficiency through hard milling. In terms of parts finishing, when turning from EDM forming processing to hard milling, let us make full use of these advances and the important role of appropriate machine tools, software, cutters, tool holders and training

taking advantage of the latest technological advances in mold manufacturing will always keep you ahead of your competitors

◆ taper and surface contact spindle connection

one area where great progress has been made in machine tools and tool holders is taper and surface contact spindle connection. The taper and surface contact of this connection can achieve almost three times the tool life in rough machining. When machining with taper and surface contact, a negative "Z" motion will be seen as the spindle temperature rises. This heat will force the tool holder down, and at the same time, the cone will open, allowing the tool holder to move up

in the experiment, it is found that for these two-way forces, a tool holder with multidirectional motion is needed. These tool holders have an integral cone to ensure tight and accurate TIR, and a moving flange to ensure face contact at all times

cat 40, BT 40, HSK 63A and BT 40 FF (face and flange contact) tool holders with moving flanges are tested. The tool life of cat 40 is 1.3 hours, BT is 1.6 hours (because the protrusion of BT is shorter than that of cat), HSK is 2.0 hours, and BT40 FF is 3.6 hours. (see figures 2 and 3)

Figure 2: compared with BT 40 and BT 40 flange contact tool holders, the tool life of cat 40 is 1.3 hours, BT 40 is 1.6 hours, and BT 40 flange contact is 2.9 hours

thank HPI USA for providing pictures

Figure 3: comparison between BT40 flange contact and BT40 flange contact tool holder with movable surface

the service life of the former is 2.6 hours, while that of the latter is 3.6 hours

◆ coating technology, geometric structure and accuracy

another area of progress is the coating technology, geometric structure and accuracy now provided by end mill manufacturers. One particular area of progress is the provision of geometry in a standard way to replace coordinate grinding with hard milling. The use of this process will not only reduce the processing time by half, but also improve the quality of parts

suitable machine tools, software, tools, tool holders and training are very important, so before we investigate the tools, we must first ensure that the machine tools, software and tool holders are in place

◆ machine tools, software and tool holders

first of all, the selected machining center needs to be evaluated. The first test is the ball stick test, which measures the accuracy that the machine tool can achieve when machining circles. The user's local machine tool dealer or service center should be able to carry out this test

after testing the machine tool, some parameters can be adjusted on the controller to improve the quality of the circle. In some cases, there may be mechanical problems or problems with the setting of the controller

the second is the programming of parts. For hard milling these holes, a spiral tool path is required. This operation requires x, y, Z, I or j codes on the same line. The screw interpolation function needs to be turned on in the controller. If you use programming software, you need to develop a 3D model of the area to be processed. The diameter, depth and position of the hole will be accurately developed according to the part drawing

another method to develop the code required in this process is to use macro program B programming, through which the machine operator can make various adjustments to the simple program in the controller, so that the hole of any size and depth can be processed at any position without using 3D model. The user needs to turn this option on in the controller

after checking the machine tool and programming the parts, the third step is to select the tool holder and end mill. The tool holder is required to keep the tool TIR less than 0.0004 inch to ensure the tool life and surface quality. Usually, high-quality milling chuck or shallow taper spring chuck can achieve this runout accuracy. Thermal shrinkage is another option

the last but equally important step is to choose the right end milling cutter. Multi slot end mills with a maximum runout of 0.005mm are recommended. In addition, the groove of the tool must be very short to reduce the contact area when entering the machining hole (see Figure 4)

Figure 4: short slot end milling cutter

2. Unattended processing

since you can achieve better results by providing enough time for the machine tool to process, why do you spend all day manually processing the required accuracy on the parts? In some factories, people use machine tools to process for one hour, but manually process for four hours, because they don't let the machine run for a longer cycle time. Night processing is a way to increase the processing time of machine tools. In this way, you can also keep the mold tolerance from being polished by hand

unattended processing is a way to increase the processing time of factory machine tools. It can also help keep the mold tolerance from being destroyed by manual processing. If there are parts that need to be processed on the machine tool for several hours or spent several days in the polishing department, you can consider unattended processing

the reasons why factories have not taken this step are that many factories do not carry out unattended processing. Here are three representative ones:

◆ our tools can't process for 8 hours. I have to use three tools to process a part well

this is actually a misunderstanding. Today's machine tools, tool holders and tools have this ability

◆ we bought these expensive end mills. When I started machining, I cut at zero point, but when I finished cutting, it cut at positive 0.001. "

your spindle is hot, but this is not considered in the program, which will cause this problem

◆ it seems that I cannot obtain the required surface roughness without polishing

one factor that may affect this may be the software used and the ability to generate sufficiently accurate code to finish machining a part

how to implement the unattended processing strategy? First, you need to evaluate each of the above reasons, and then identify possible solutions to help realize unattended processing

◆ our tools can't process for 8 hours...

first, you must check the tool holder used. Check the taper. If excessive wear is found on the tool holder, it indicates that the spindle needs to be reground. If the spindle looks good, check the quality of the tool holder used. It is ideal to use high-quality milling chuck for rough machining and flat taper spring collet or heat shrink fit for finish machining

if these are all good, check the milling cutter. Many times, customers buy the best priced products instead of the correct end mills suitable for relevant materials, hardness and applications. If all the above items are correct, the milling cutter will be able to run for the required cycle time

◆ we bought these expensive end mills. When I started processing, I cut at zero point, and when I finished cutting...

after the machine tool is preheated, you will find that the tool tip will move in a positive or negative Z mode due to the thermal effect (changing the steel taper between the spindle and the tool holder). If the spindle is cat or BT type without surface contact, you will see that the knife clamp is sucked into the spindle. If you use a taper spindle with surface contact, you will see that due to the downward growth of the end of the spindle, the infrastructure protection and water supply and electricity transfer cost of the worker's residential area each year is up to 30million yuan. This growth will lead to positive or negative growth of parts

you can see the growth of machine tools through the following simple test. If there is a tool probe on the machine tool, you can generate a program to run the spindle for five minutes, and then check the tool length. Run for another five minutes, and then check the tool length. Do this for an hour and chart the results. You will see a characteristic curve that shows how long it takes for the machine tool to stabilize Z growth. Once the machine tool reaches this point, the spindle cooler keeps it in a range suitable for long-time processing. If the spindle speed is changed or the tool is changed, stability will be lost. At this time, in view of this new change, the tool must be stabilized again. Once you know your machine tool, you need to consider this characteristic curve in your programming

◆ it seems that I can't obtain the required surface roughness in

part of the factor in this regard is whether a sufficiently accurate generation can be created

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