In addition to the BT40 and BT50 toolholders, what types of toolholders do you know when playing CNC machining
November 14, 2022
Now CNC machine tools have been widely used in factories. These machine tools and tools used come from all over the world, with different models and standards. Today, I would like to talk about the knowledge of tool handle of machining center.
The tool handle is the connection between the machine tool and the tool. The tool handle is a key link that affects concentricity and dynamic balance. It must not be regarded as a general part. Concentricity can determine whether the cutting amount of each cutting edge part is uniform when the tool rotates for one circle; When the spindle rotates, the dynamic imbalance will produce periodic vibration.
1、 According to the taper hole of spindle, it is divided into two categories
Tapers of tool mounting holes on the spindle of the machining center are generally divided into two categories:
1. SK universal tool handle with a taper of 7:24,
2. HSK vacuum tool handle with a taper of 1: 10
SK universal tool handle with a taper of 7: 24
7: 24 refers to that the taper of the tool handle is 7:24, which is positioned for a single cone, and the taper handle is longer. The cone surface plays two important roles at the same time, namely, the accurate positioning of the tool handle relative to the spindle and the clamping of the tool handle.
Advantages: It is not self-locking and can realize rapid tool loading and unloading; As long as the taper angle is processed to a high precision, the connection precision can be guaranteed when manufacturing the tool handle, so the cost of the tool handle is relatively low.
Disadvantages: When rotating at high speed, the taper hole at the front end of the spindle will expand. The amount of expansion will increase with the increase of the rotating radius and speed. The taper connection stiffness will decrease. Under the action of the pull rod, the axial displacement of the tool handle will also change. After each tool change, the radial size of the tool holder will change, and there is a problem of unstable repetitive positioning accuracy.
The general tool handle with a taper of 7:24 usually has five standards and specifications:
1. International standard IS0 7388/1 (IV or IT for short)
2. Japanese standard MAS BT (BT for short)
3. German standard DIN 2080 (NT or ST for short)
4. American standard ANSI/ASME (CAT for short)
5. DIN 69871 (JT, DIN, DAT or DV for short)
Tensioning method:
The NT type tool handle is tightened by the pull rod on the traditional machine tool, which is also called ST in China; The other four tool handles are tightened on the machining center by the pull pin at the end of the tool handle.
generality:
1) At present, DIN 69871 type (i.e. JT) and Japan MAS BT type tool handles are mostly used in China;
2) The tool handle of DIN 69871 can also be installed on the machine tool with ANSI/ASME spindle taper hole;
3) The tool handle of international standard IS0 7388/1 can also be installed on the DIN 69871 type and ANSI/ASME spindle taper hole machine tools, so in terms of universality, IS0 7388/1 type tool handle is the best.
HSK vacuum tool handle with a taper of 1: 10
The HSK vacuum tool handle relies on the elastic deformation of the tool handle, which not only makes the 1:10 taper of the tool handle contact with the 1:10 taper of the machine tool spindle hole, but also makes the flange face of the tool handle closely contact with the spindle face. This double-sided contact system is superior to the 7:24 universal tool handle in high-speed machining, connection rigidity and coincidence accuracy.
HSK vacuum tool shank can improve the rigidity and stability of the system and the product accuracy in high-speed machining, and shorten the tool replacement time. It plays a very important role in high-speed machining. It is suitable for the spindle speed of the machine tool to reach 60000 rpm. HSK tool system is widely used in aerospace, automotive, precision mold and other manufacturing industries.
HSK tool shank has a variety of specifications such as type A, type B, type C, type D, type E, and type F, among which type A, type E, and type F are commonly used on machining centers (automatic tool change).
The biggest difference between Type A and Type E:
1. Type A has a drive groove while Type E does not. Therefore, relatively speaking, A-type transmission torque is relatively large, and it can be used for some heavy cutting. The torque transmitted by the E type is relatively small, and only some light cutting can be carried out.
2. In addition to the transmission groove, there are also manual fixing holes, direction grooves, etc. on the A type tool handle, so the balance is relatively poor. The E type does not, so the E type is more suitable for high-speed machining. The mechanisms of E type and F type are identical. The difference between them is that the taper of E type and F type tool handles (such as E63 and F63), which are also called, should be one size smaller. That is to say, the flange diameters of E63 and F63 are φ 63, but the cone size of F63 is only the same as that of E50. Therefore, compared with E63, the speed of F63 will be faster (the spindle bearing is smaller).
2、 Tool mounting form of tool handle
Spring collet tool handle
It is mainly used for clamping straight shank tools and tools such as drills, milling cutters, taps, etc. The elastic deformation of the circlip is 1mm, and the clamping range is 0.5~32mm in diameter.
Hydraulic collet
A - Tighten the locking screw with an Allen wrench;
B - Lock the piston and press the hydraulic medium into the expansion chamber;
C - expansion chamber, pressure generated by liquid extrusion;
D - thin expansion bushing, which makes the center of the tool clamping rod locate and evenly envelop during the locking process.
E - Special seals ensure ideal sealing and long service life.
Heating tool handle
Apply induction heating technology to heat the tool clamping part on the tool handle to make its diameter expand, and then put the cold tool shank into the hot tool handle. The heating tool handle has large clamping force, good dynamic balance and is suitable for high-speed machining. High repeated positioning accuracy, generally 2 μ Within m, the radial runout is 5 μ Within m; Good anti pollution ability and anti interference ability in processing. However, each specification of tool handle is only suitable for installing tools with one handle diameter, and a set of heating equipment is required.
