Thread processing isCNCOne of the very important applications of machining centers, the processing quality and efficiency of threads will directly affect the processing quality of parts and the production efficiency of the machining center.
withCNCWith the improvement of the performance of machining centers and the improvement of cutting tools, the thread processing methods are also constantly improving, and the precision and efficiency of thread processing are also gradually improving. In order to enable craftsmen to reasonably select yarn processing methods during processing, improve production efficiency and avoid quality accidents, this will now be put into practiceCNCSeveral thread processing methods commonly used in machining centers are summarized as follows:
1. Faucet processing method
1.1 Classification and features of tap processing
Using a tap to process threaded holes is the most commonly used processing method. It is mainly suitable for small diameters (.D《30), threaded holes that do not require high hole position accuracy.
exist20century80In the 1990s, flexible tapping methods were used for threaded holes, that is, a flexible tapping chuck is used to hold the tap. The tapping chuck can perform axial compensation to compensate for the feed error caused by desynchronization between threaded holes. axial feed of the machine tool and the spindle speed, guaranteeing a correct pitch. Flexible tapping chuck has complex structure, high cost, easy damage and low processing efficiency. In recent years,CNCThe performance of machining centers has gradually improved, and the rigid tapping function has becomeCNCBasic configuration of the machining center.
Therefore, rigid tapping has become the main method of thread processing at present.
That is, a rigid spring-loaded chuck is used to hold the tap, and the feed and spindle speed are controlled by the machine tool to keep them consistent.
Compared with flexible tapping chucks, spring chucks have a simple structure, are cheap, and have a wide range of uses. In addition to holding taps, they can also hold end mills, drill bits and other tools, which can reduce tool costs. At the same time, rigid tapping can perform high-speed cutting, improve the efficiency of machining centers and reduce manufacturing costs.
1.2 Determining the bottom hole of the thread before tapping
The processing of threaded bottom holes has a great impact on the life of the tap and the quality of thread processing. Usually, the diameter of the threaded hole drill is selected close to the upper limit of the tolerance of the threaded hole diameter.
For example,M8The bottom hole diameter of the threaded hole is Ф6.7+0.27mmselect drill bit diameter as Ф6.9mm. In this way, the machining allowance of the tap can be reduced, the load of the tap can be reduced, and the life of the tap can be improved.
1.3 Press selection
When selecting a tap, you must first select the corresponding tap according to the material to be processed. Tooling companies produce different types of taps depending on the different materials to be processed, so take special care when selecting.
Because taps are very sensitive to the material being processed compared to milling cutters and boring tools. For example, using a cast iron processing tap to process aluminum parts can easily cause thread loss, random buckling, or even breakage of the tap, resulting in the parts being scrapped. Secondly, it is worth paying attention to the difference between through taps and blind taps. The front end of the through tap has a longer guide and the chips are discharged from the front. The front guide of the blind hole is short and the chips are discharged from the rear. Using a through tap to process blind holes cannot guarantee the processing depth of the thread. In addition, if a flexible tapping chuck is used, attention should also be paid to the tap shank diameter and square width, which should be the same as those of the tapping chuck.;The diameter of the tap shank for rigid tapping should be the same as the diameter of the spring collet. In short, only a reasonable selection of taps can guarantee smooth processing.
1.4 CNC programming for tap machining
Programming take processing is relatively simple. Nowadays, machining centers usually have a solidified tapping routine and only need to assign values to each parameter. But it should be noted that different CNC systems have different subroutine formats, and the meaning of some parameters is different.
For example,SIEMEN840CControl system, its programming format is:G84. When programming, simply change this12setting.
2. thread milling method
2.1 Features of thread milling
Thread milling uses thread milling tools and the three-axis linkage of the machining center, i.e.X、YesCircular axis interpolation,ZThreads are machined using spindle linear feed milling.
Thread milling is mainly used to process large-hole threads and threaded holes in difficult-to-machine materials. It mainly has the following characteristics:
⑴ Fast processing speed, high efficiency and high processing precision. The tool material is generally carbide, and the cutting speed is fast. The tools are manufactured with high precision and the threads are therefore milled with high precision.
⑵ Milling tools have a wide range of applications. As long as the thread pitch is the same whether left-handed or right-handed, only one tool can be used, which will help reduce tool costs.
⑶ Milling is easy to remove chips and cool, and has better cutting conditions than taps. It is particularly suitable for processing threads of difficult-to-machine materials such as aluminum, copper and stainless steel. large pieces and pieces made from precious materials. It can guarantee the quality of thread processing and the safety of parts.
⑷ Since there is no front guide of the tool, it is suitable for processing blind holes with short threaded bottom holes and holes without undercuts.
2.2 Classification of threading tools
Thread milling tools can be divided into two types, one is machine type carbide insert milling cutter and the other is solid carbide milling cutter. Machine clamped tools have a wide range of applications. They can process holes with thread depth less than the blade length and holes with thread depth greater than the blade length. Solid carbide end mills are typically used to machine holes where the thread depth is less than the tool length.
2.3 CNC programming for thread milling
Programming thread milling tools is different from programming other tools. If the processing program is compiled incorrectly, it is easy to cause tool damage or thread processing errors. The following points should be considered during preparation:
⑴ First of all, the threaded bottom hole should be treated well. Small diameter holes should be processed with a drill, and larger holes should be drilled to ensure the accuracy of the threaded bottom hole.
⑵ The tool should adopt an arc path when cutting and removing, generally1/2circle to cut or cut out, whileZThe direction of the axis must move1/2not to guarantee the shape of the thread. The tool radius compensation value should be entered at this time.
⑶ X、YesCircular interpolation of axes during one cycle the spindle movesZThe axis direction must advance one thread pitch, otherwise the threads will deform randomly.
⑷ Specific program example: The diameter of the thread milling cutter is Φ16the threaded hole isM48×1.5the depth of the threaded hole is14。
The processing procedure is as follows:
(Threaded bottom hole procedure is omitted, the hole needs to be drilled)G0 G90 G54 X0 Y0G0 Z10 M3 S1400 M8G0 Z-14.75 Feed to the deepest point of the wireG01 G41 X-16 Y0 F2000 Change to feed position and add radius compensationG03 X24 Y0 Z-14 I20 J0 F500 used when cutting1/2Arc cutG03 X24 Y0 Z0 I-24 J0 F400 Cut all the threadG03 X-16 Y0 Z0.75 I-20 J0 F500 used when cutting1/2cut arc of circleG01 G40 X0 Y0 Return to center and undo radius compensationG0Z100M30
3. button selection method
3.1 Characteristics of the pick-and-button method
Sometimes large threaded holes may be encountered on housing parts. In the absence of taps and thread mills, a method similar to lathe tapping can be used.
Install the thread turning tool on the boring tool bar to drill the thread.
The company used to process a batch of parts and the threads wereM52x1.5the degree of the position is0.1mm(see photo1), because the positioning requirements are high, the threaded holes are large, taps cannot be used for processing, and there is no thread milling cutter. After testing, the tapping method is used to ensure the processing requirements.
3.2 Things to note when selecting buttons
⑴ After the spindle starts, there should be a delay to ensure that the spindle reaches the rated speed.
⑵ When retracting, if it is a hand-sharpened threaded tool, since the tool cannot be sharpened symmetrically, reverse retraction cannot be used. The spindle should be oriented, the tool moves radially, then the tool is retracted.
⑶ The tool holder should be manufactured precisely, especially the position of the tool groove should be consistent. If they are inconsistent, multi-tool shank processing cannot be used. Otherwise it will result in random deductions.
⑷ Even if it is a very thin button, you cannot cut it in one cut, otherwise it will cause tooth loss and poor surface roughness. You need to cut it into at least two cuts.
⑸ The processing efficiency is low and is only suitable for small batches of single parts, special pitch threads and situations where there are no corresponding tools.
3.3 Examples of specific procedures
N5 G90 G54 G0 X0 Y0
N10Z15
N15S100M3M8
N20G04X5 Delay to allow the spindle to reach rated speed
N25 G33 Z-50 K1.5 Choose buttons
N30M19 Pin orientation
N35G0X-2 Leave the knife
N40 G0 Z15 Remove the knife
source:UG Momo programming
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