Other lathes and turning machines
In addition to the engine lathe, other turning machines have been developed to satisfy particular functions or to automate the turning process. Among these machines are (1) toolroom lathe, (2) speed lathe, (3) turret lathe, (4) chucking machine, (5) automatic screw machine, and (6) numerically controlled lathe.
The toolroom lathe and speed lathe are closely related to the engine lathe. The toolroom lathe is smaller and has a wider available range of speeds and feeds.
The speed lathe is simpler in construction than the engine lathe. It has no carriage and cross-slide assembly, and therefore no leadscrew to drive the carriage.
A turret lathe is a manually operated lathe in which the tailstock is replaced by a turret that holds up to six cutting tools.
As the name suggests, a chucking machine (nicknamed chucker) uses a chuck in its spindle to hold the workpart.
A barmachine is similar to a chucking machine except that a collet is used (instead of a chuck), which permits long bar stock to be fed through the headstock into position. Bar machines can be classified as single spindle or multiple spindle (Fig 5.5).
Figure 5.5 - (a) Type of part produced on a six-spindle automatic barmachine; and (b) sequence of operations to produce the part: (1) feed stock to stop, (2) turn main diameter, (3) form second diameter and spotface, (4) drill, (5) chamfer, and (6) cutoff.
The modern form of control is computer numerical control (CNC), in which the machine tool operations are controlled by a ‘‘program of instructions’’ consisting of alphanumeric code. Today, automatic chuckers and bar machines are implemented by CNC.
References: Gen [1-3].
Assessing questions:
What is turning and their related operations?
What are the main parts of a lathe?
How can be described the methods of holding the work in a lathe?
Describe the other lathes.
What kind operation can be done by using the speed lathe?
Lecture 6. CAM part program creation and data management. Three types of part geometry. Program creation. CNC controls
Boring machines
It uses a single-point tool against a rotating workpart. Boring is performed on the inside diameter of an existing hole of an existing cylinder. Boring mills can be horizontal or vertical. In a horizontal boring operation, the setup can be arranged in either of two ways. The first setup is one in which the work is fixtured to a rotating spindle, and the tool is attached to a cantilevered boring bar that feeds into the work, as illustrated in Figure 5.6(a). The boring bar in this setup must be very stiff to avoid deflection and vibration during cutting.
(a) boring bar is fed into a rotating workpart, and (b) work is fed past a rotating boring bar.
Figure 5.6 – Two forms of horizontal boring:
Drilling and related operations
Several operations related to drilling illustrated in Figure 6.1.
(a) Reaming. Reaming is used to slightly enlarge a hole, to provide a better tolerance on its diameter, and to improve its surface finish. The tool is called a reamer, and it usually has straight flutes.
(b) Tapping. This operation is performed by a tap and is used to provide internal screw threads on an existing hole.
(c) Counterboring. Counterboring provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the hole. A counterbored hole is used to seat bolt heads into a hole so the heads do not protrude above the surface.
(d) Countersinking. This is similar to counterboring, except that the step in the hole is cone-shaped for flat head screws and bolts.
(e) Centering. Also called center drilling, this operation drills a starting hole to accurately establish its location for subsequent drilling. The tool is called a center drill.
(f) Spot facing. Spot facing is similar to milling. It is used to provide a flat machined surface on the workpart in a localized area.
(a) reaming, (b) tapping, (c) counterboring, (d) countersinking, (e) center drilling, and (f) spot facing.
Figure 6.1 – Machining operations related to drilling:
Computer-assisted machining is a power tool for programming that’s also the major change engine in machining.
Axial engagement. Using the side teeth of an end mill.
Feature-based machining (FBM). Mastercam recognizes and creates a toolpath based on window selected solid features.
Post processing. Creating program codes after the toolpath is selected.
Rest milling. Removing the rest of unwanted material after roughing.
Trochodial (toolpath motion). A continuous series of arcing whittles.
Dynamic toolpath. Milling in adaptive, small circular whittles using more axial and less radial engagement.
Radial engagement. The amount of the mill cutters side engagement—how much of its cutter radius is used.
Optimized roughing (Opti-Rough-Mill). Adaptive auto-routines that remove the most effi cient amounts of material per pass.
Spiral entry. A spiral end mill plunge using axial engagement for better cutting, chip ejection, and coolant entry