可焊接的结构钢【精品-PPT】.pptxVIP

Lesson 3 Machine Tool Frames;The frame is a machines fundamental element. Most frames are made from cast iron, welded steel, composite, or concrete. The following factors govern material choice.;The material must resist deformation and fracture. Hardness must be balanced against elasticity. The frame must withstand impact, yet yield under load without cracking or permanently deforming. ; frame 床身 cast iron 铸铁 welded steel 可焊接的结构钢 composite 复合材料 govern 决定 hardness 硬度 be balanced against 与…平衡;elasticity 弹性 impact 冲击 cracking 裂纹 deforming 永久性变形;The frame material must eliminate or block vibration transmission to reduce oscillations that degrade accuracy and tool life. It must withstand the hostile shop-floor environment, including the newer coolants and lubricants. ;Material expansion must be understood (in order) to minimize forces needed to move slides. The material must not build up too much heat, must retain its shape for its lifetime, and must be dense enough to distribute forces throughout the machine. ;vibration 震动 oscillation 震荡 degrade 降低等级 tool life 刀具寿命 withstand 耐受 hostile 恶劣的 coolant 冷却液 lubricant 润滑剂 slide 滑动部件(滑块);Pros and Cons Either castings or welded sections can be used in most applications. The decision on which is best depends on the costs in a given design situation.;Cast iron. Almost all machine tool frames were traditionally made of cast iron because features difficult to obtain any other way can be cast in. Castings have a good stiffness-to-weight ratio and good damping qualities. Modifying wall thic