CNC Final Exam Study guide for EDMT 103

Should CNC program blocks be numbered? If so, how?

Blocks should be numbered 10, 20,30,40 or 100,200,300, and so on.

What is the difference between a CVD and PVD coating?

CVD is a coating produced at a high temp (1850F); it is used in heavy roughing operations where high stresses are encountered. In contrast, PVD is produced at less than 750F with no dimensional changes to the tool being coated. PVD usually retain shaper edges and are for lighter cuts.

Describe coding for circular interpolation.

Circular interpolations are called by G02 and G03 with arc centers defined by I J or R codes.

What is an M code?

Codes are miscellaneous function codes

What is a G code?

Codes are perparatory function codes

What is conversational programming?

Conversational programming uses standard machining sequence menus or prompts such as milling a shape or drilling a hole pattern.

What is cutter radius compensation?

Cutter radius compensation is used to compensate for the cutter radius and permit programming drawing dimensions directly without having to build cutter radius into program dimensions.

Which process might be used for debuting applications?

ECM and ECDB

Which process are essentially depleting?

ECM and ELG

Which process utilities a dielectric fluid?

EDM

Give an example of a G code.

G90 G91 G00 G01 G02 G03 G49 G81

What is the difference between chip thickness and feed per tooth?

If less than half the diameter of a milling cutter is engaged in a cut, the chip thickness is less than the per per tooth.

Discuss the difference between incremental and absolute positioning modes.

In incremental positioning, the current location is always zero. In absolute positioning, each current position is measured from the absolute zero start point.

How is incremental positioning coded in the program?

Incremental positioning is called by the G 91 code.

Name some advantages of using indexable drills.

Indexable drills can drill almost any material because of the great variety of tool grades available. If used on a turning center, they can make holes larger than the drill diameter.

What is a linear interpolation and how is it coded in the CNC program?

Linear interpolation is used for straight-line cutting. It is called by the G01 code.

Give an example of an M code.

M00 M02 M03 M05 M06

What is a model command?

Modal commands place the CNC into a certain mode of operation, where it remains until the mode is changed or canceled. The mode continues to successive blocks until changed or canceled.

Of incremental and absolute, which is better dimensioning system to use?

Neither is better. Both have unique applications in CNC programming.

What is a block or sequence number?

One complete line of CNC instructions is a block or sequence number.

What is a PCD tool used for?

PCD-tipped tools are used to machine nonferrous, highly abrasive materials.

What are the point values in quadrants 1,2,3,4?

Q1 is X is + and Y is + Q2 is X is - and Y is + Q3 is X is - and Y is - Q4 is X is + and Y is -

How is rapid traverse coded in the CNC program?

Rapid traverse is called by G00.

What are some benefits of using roll-forming taps?

Roll-forming tapa produce no chips, run at higher cutting speeds, and leave a smoother, stronger thread than cut threads.

Describe single-point threading on the CNC lathe.

Single-point threading is accomplished by feeding the threading tool at a rate equal to the lead of the thread. Several passes may be required to produce rhe required thread depth.

What do the I and J words do in the program?

The I and J words define the arc center in a circular interpolation. I is the X axis dimension and J is the Y acis dimension as measured from the start of the arc to the arc center.

Why are TiN coatings applied to tools?

TiN coatings give high lubricity to tool surfaces, which helps pervent a bulid-up edge during machining.

What is the primary function of the grinding wheel in ELG?

To maintain the gap between work and wheel

What provides the energy in ultrasonic machining, and what does the cutting?

Ultrasound vibrations provide the energy. Abrasive materials do the cutting

What is an indication of a correct feed rate when a boring tool is used?

When the tool is withdrawn after a finishing cut, the spiral lines on the surface should be barely visible.

Which process would be used for die making?

Wired-Feed EDM

How is a canned drill cycle coded in the program?

With Drill Cycles. G81 would be an example of a canned drill cycle. Variations permit full or partial peck drill cycles.

Axis a is rotation about the _____ axis.

X axis

Axis b is rotation about the _____ axis.

Y axis

Axis c is rotation about the _____ axis.

Z axis

What is a canned cycle?

A canned cycle is a complete maching squence such as drilling ,tapping, or boring.

What is a cermet?

A cermet is a combination of titanium carbide and titanium nitride with a metallic binder such as nickel or colbolt. Cermets are often used in finishing operations.

What is the advantage of using a drill with a self-centering drill point?

A self- centering drill point eliminate spot drilling, reduce cutting forces, and give a good surface finish.

G90 mode invokes______ positioning.

Absolute

G91 mode involves________ positioning.

Absolute

How is the absolute positioning coded in the program?

Absolute coding is called by the G90 code.

How does angular linear interpolation differ from straight-line linear interpolation?

Angular interpolations require simultaneous dimensional entries in two or more axes.