444 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. SAFETY NOTE SAFETY NOTE when rapid traverse power is used. Never activate this feature while making a cut. Vertical-Spindle Milling Machines On a vertical-spindle milling machine, e Figure 26-6, the 6 cutter spindle is in a vertical position, at a right angle to the top of the worktable. The cutter head can be raised and lowered by hand or by power feed. The cutter head can also be swiveled for angular cuts. A vertical spindle mill- ing machine may also be called a vertical milling machine. 26.1.2 Fixed-Bed Milling Machines Fixed-bed milling machines, often referred to as s bed-type milling machines, have a worktable that is mounted to the s bed of the mill at a fixed height, instead of being supported by a knee. This construction restricts the worktable to lon- gitudinal movement. Vertical and traverse movements are obtained by moving the cutter head. The cutter heads on fixed-bed milling machines may be horizontal or vertical. A planer mill is the largest type of fixed-bed mill- ing machine. Variations of the planer milling machine include gantry and bridge milling machines, Figure 26-7. 7 7 Both types are capable of five-axis/five-sided machining. This reduces part refixturing and setup time. 26.1.3 Methods of Control The method used to control table movement is another way of classifying milling machines, and all machine tools in general. The four basic methods of control are: • Manual. All control movements are made by hand lever controls. • Semiautomatic. Movements are controlled by hand and/or power feeds. • Fully automatic. A complex hydraulic feed arrange- ment follows two- or three-dimensional templates to automatically guide one or more cutters. Speci- fications can be programmed to guide the cutters and table. • Computerized (CNC). Machining coordinates are entered into a computer using a programming language. The computer activates electric stepper or servo motors connected to the machine’s Acme or ball lead screws that move the table or cutters through the machining sequence. The milling machines shown in Figure 26-2 are CNC machines. Many manually operated milling machines can be retrofitted for CNC operations. The power feed on smaller machines may only be available for longitudinal table movement. On larger machines, automatic or power feed is available for all table movements. A rapid traverse movement feature is available on many milling machines, Figure 26-8. To use this fea- ture, first engage the power feed lever to start the work moving in the correct direction. Then activate the rapid traverse switch or lever to move the work quickly. Rem Sales, Inc. Figure 26-6. A vertical spindle milling machine. Motor feed Quill f lever e Worktablea Base Swivel Sw Sw Sw Sw Sw Sw Sw S Sw S Sw S Sw w Sw S S w S S w S S S S iv iv iv iv v iv v v el e e e el e el Cross traverse handwheel Vertical movement crank Longitudinal L d d d d feed handwheel h Saddle Swivel S Overarm Spindle Quill Q Q Quill feed handwheel d Fives Cincinnati Figure 26-7. This gantry mill is considered a rail machine because rails are used to move the gantry (bridge) longitudinally. Traverse movement is obtained with the saddle on the cross rail. The cutter head can also be moved vertically. Cutter head Cross rail Saddle Rail Worktable Bed