We are interested in the classification of the characteristics of the assembly work and the reference to the current national power tools, that is, thread diameter M10 or less, with a slot, cross slot, hexagonal hole cylindrical head, semi-circular head or countersunk mechanical thread The pieces are screws.
In this way, it is more reasonable to distinguish the assembly tool, that is, in terms of structure and parameters, in addition to the required tightening torque and assembly efficiency, the electric screwdriver for assembling the screw needs to be advantageous for applying the axial force. The electric wrench with the same specification of the bolt and nut is much larger than the electric screwdriver, because the cross groove and the slot are much less torque than the hexagonal or square screw head.
Therefore, the torque and axial load (tension) during assembly are also smaller than those of the bolt. Of course, it is not excluded to use a power screwdriver to assemble smaller gauge bolts and nuts, and it does not exclude the use of an electric wrench to assemble a larger size hexagon socket head cap screw. The self-tapping screws are generally heat-treated with IJRC50-58. During assembly, the threads can be directly tapped on the reserved holes of the workpiece to complete the threaded connection.
There are three types depending on the use: (1) The thread forming screws have the following four types according to the tail part: Type A: There are 30 corner tips, which can be perforated to join the metal sheets, and sometimes can be used instead of wood screws. Type B: The end is blunt, the pitch is smaller than the A type, and it can be used for heavy metal sheets and non-ferrous metal castings. Type A13: The end is like A, the pitch is B, it can be used for plastic or zinc die casting, and it can also be used as wood screw. Type C: The end is blunt with machine screw threads. The starting part of the thread is a taper thread that can be used for thick sections but requires a large tightening torque.
(2) Thread self-cutting screws are used to replace the thread forming screws to reduce the tapping torque and internal stress. There are six types, in which the sub-doors and four-type all have machine screw threads with a blunt tapered end and a cutting groove at the end. Used in various die castings, cast iron parts, brass parts, plastics and steel plates. Types 13F and 1 have an auxiliary cutting edge and a larger cutting chute at their ends. Can be used in a variety of plastic parts and composite parts.
(3) Thread rolling screws are also called self-tapping screws. It has a curved triangular section of thread that is extruded into a ferrous metal or non-ferrous metal preformed hole and extruded to form a mating thread. The joint strength is improved by extrusion cold work hardening. This special form of screw has a low tightening torque and high locking performance, which has better working performance than ordinary self-tapping screws.
Self-drilling screws have hardened machine threads and special drilling edges at the end for drilling. It can be assembled directly on non-ferrous or ferrous metals without pre-fabricated holes, avoiding the trouble of deviations between the workpiece passhole and the other working pre-cavity axis. Such screws are costly but can reduce other costs.
The wood screws are screwed directly into the wood. For large sizes, pre-made holes can be made on the workpiece in order to reduce its assembly torque and guide the screw axis. Due to the diversity of wood materials, the same wood is also different in nature due to the direction of wood grain and nodules. Therefore, the assembly characteristics and final moment dispersion of wood screws are extremely random and random.
Common screw coupling structure assembly characteristics and basic requirements A wide variety of screws, coupled with the material, rigidity, thickness and other diversity of the connected workpiece, constitutes a variety of resistance torque characteristics during assembly. Therefore, the power characteristics and control functions of the electric screwdriver used in combination with it are various, that is, the electric screwdriver which is not a structure and control can satisfy the assembly of all the screws, so objectively, a variety of typical electric screwdrivers are formed. The user selects the screw assembly characteristics of the assembled product.
If the selection is not correct, the assembly task will not be completed correctly, and sometimes the workpiece will be damaged a lot. This is significantly different from the electric wrench. On the other hand, the difference is that the screws are generally small in size and large in number, requiring a high assembly rate. How to effectively reduce the torque when the torque is controlled? After the power is cut off, the problem of the additional impact torque caused by the kinetic energy of the rotating system is much more important than that of the fixed torque electric wrench.
Of course, the electric screwdriver should be designed to withstand large axial forces without excessively affecting the operation of the motor. This is also different from the electric wrench. We can't discuss the assembly characteristics of many screw joint structures. However, it is beneficial to categorize and analyze a large number of common assembly characteristics.
ZHEJIANG HESHUO TECHNOLOGY CO.,LTD , https://www.hosuocn.com