LABORATORY REPORT

MECT 3360

Fall, 2014

LAB SECTION #3, M/W 7:00pm - 10:00pm

LAB # 3

CNC LATHE PROGRAMMING

Student's Name : Date Due : 10/08/2014 Student's ID : (Peoplesoft Student ID#)Graded by : Group : 03

Objective :

Learn the basics of the lathe machining and CNC programming. Introduce students to

circular interpolation and various canned lathe programs. Manually program and machine

the assigned part (Exhibit 2) on the HAAS lathe.

Equipment Required :

1. PC to type the NC program.

2. USB drive to transfer the program to the CNC lathe.

3. HAAS CNC lathe used to simulate the CNC program, correct it, and cut the part.

4. Polyethylene cylindrical bars (1” Dia. X 4” long).

5. HAAS CNC lathe programming guide including setup and operation.

Procedure :

1st Session :

1. Review the various lathe operations.

2. Learn the basic commands of NC lathe programming.

3. Use the first graph of Exhibit #1, showing the large scale of a sample part with multitapered

steps, to define the coordinates of the points joining the segments delineating the finished

sizes.

4. Use the second graph of Exhibit #1 to define the coordinates of the beginning and ending

points of the roughing and finishing cuts as shown.

5. Write the corresponding CNC program shown on Exhibit #1.The cutting tool is a HSS

or Carbide insert. Both tools have a negligible nose radius. The initial position of the tool

is at X=O. 500”, Z=1.500”; at the end of the program return to that position.

6. Obtain a copy of the program for your report.

2nd Session :

1. Learn circular interpolation and various canned cycle programs of thread cutting,

straight side turning, tapering and boring, end turning, and spine interpolation with

Bezier curve.

2. Refer to Exhibit #2 to program the part shown. Use the same tool as in session #1,

with an initial position at X=1.000”, Z=3.500”. Take 2 or 3 roughing passes, and a

finishing pass. Select the pass depth and length keeping in mind that the finishing cut

must be of about the same depth of cut on all the machined surfaces.

3. Connect your USB drive to the HAAS machine, and simulate the program.

4. If necessary, edit the program using the control panel.

5. When the simulation results are correct, run the program and cut the part.

Discussion :

This third lab was about the CNC lathe and it had two sessions same as the previous

second lab. In CNC lathe, a blueprint of the part was necessary. To understand both the

design and the blueprint, the students needed to write the program with the correct cutting

tools and specific moves which were based on a coordinate system that moved the tools in

two directions: x-direction and z-direction.

The first step was to set the parameter of the tools in the tooling screen. With this

information, the machine would know where the location the tool and the spinning method

for cutting the material. For example, the G codes (also called preparatory codes) would

specify the machine to perform according to the codes such as rapid moving, controlling the

series of feed movement (straight line or arc), setting tool information such as offset,

switching coordinate systems, etc. One of the most common code for feeding during a cut

was linear interpolation. This code would allow the program automatically calculates the

intermediate points to pass through that will yield a straight line (base on the start and end

points). Another important code was the circular interpolation, behaved same as linear

interpolation but the interpolation generates was a circle (not line). This interpolation

translate the linear axis into curve tool motions. Its requirement would include: an endpoint,

feed rate, a center, a radius and a direction of movement.

The second step, the students should know was to indicate the type of material which

would be cut and the maximum rotation per minutes. It was very important to set the

material correctly at the start of the program. The default guideline would be used to

approximate speeds and feeds for the chosen tooling. For instance, aluminum would need

faster speeds and feeds than steel.

The third step was the facing operation. It was critical to command a facing tool to clean

the raw material so that the wourkpiece would have you a consistent spot to start

machining. The reason for this was the raw material was often cut with a metal saw or band,

and these tool would create a rough surface. By adding a facing operation code in the

program, the operator would start machining with a clean surface for a higher end quality

product.

The fourth step was to program the outside turning process. This command would tell

the machine to cut the outside dimension into the final size. It meant that the machine

would first use a roughing bit tool and then come back for a second pass with a finishing tool

for a smooth surface. In addition, if the workpiece had holes for boring bars, the next step

would be the drilling operation to create a hole for the boring process. A series of drills

should be used to remove the material enough to create a follow cylinder (inside diameter),

and a drilling sequence with a roughing pass and rigid bar would create a smooth finish on

the inside.

If the part needed to cut into pieces, the program would require the cut-off command. It

would be useful to make more than one part from a length of material. A programming of

cut-off tool for cutting finished part and cycling it to run again with new set of dimensions. To

save time for writing CNC code program, the student would have knowledge about how to

perform canned cycles. This operation was useful because it would give the student the

option to do some routine functions with a simple G-code instead of writing many lines of

coding information. The definition of a canned cycle was a sequence of machine operations

initiated by a single G-code. It could act as shortcuts of a simple the program. The purpose of

the canned cycles was save memory because the early CNC machines had a very expensive

limited memory and canned cycles could provide efficient ways to do repetitive complex

actions with small amount of memory. For an example, if the operator wanted to drill a hole

5 inches deep and clear the chip every 0.500, the coding program would take a dozen lines to

perform the drilling. With a canned drill cycles, the program would be short and only contain

the correct G code for the operation to be performed (a few variable and coordinate points

for the holes) and the machine would drill the programmed hole at every program point.

There were many of canned cycles for drilling, taping, boring and counter boring on milling

machines and routers. The lathes would use their own set of canned cycles that make it

possible to very quickly rough and finish turn, thread, bore and contour parts.

There were several errors in the program simulation that encounter during the lab

session. The common error was that the student forgot to set up the workpiece in right

dimension. In addition, the program would have some basic mistake such as the “;” at the

end of each command line, the extra “M” word, and the miscalculating interpolation

coordination.

Program code :

1. Exhibit 01 :

N1 G20 G90;N2 S200 M03;N3 G00 X0.26 Z1.1;N4 G00 X0.25 Z1.1;N5 G01 X0.25 Z0.35 F5;N6 G00 X0.26 Z0.35;N7 G00 X0.26 Z1.1;N8 G00 X0.23 Z1.1;N9 G01 X0.23 Z0.4 F5;N10 G00 X0.26 Z0.4;N11 G00 X0.26 Z1.1;N12 G00 X0.21 Z1.1;N13 G01 X0.21 Z0.44 F5;N14 G00 X0.26 Z0.44;N15 G00 X0.26 Z1.1;N16 G00 X0.19 Z1.1;N17 G01 X0.19 Z0.48 F5;N18 G00 X0.26 Z0.48;N19 G00 X0.26 Z1.1;N20 G00 X0.17 Z1.1;N21 G01 X0.17 Z0.52 F5;N22 G00 X0.26 Z0.52;N23 G00 X0.26 Z1.1;N24 G00 X0.16 Z1.1;N25 G01 X0.16 Z0.53 F5;N26 G01 X0.26 Z0.33 F5;N27 G00 X0.26 Z1.1;N28 G00 X0.15 Z1.1;N29 G01 X0.15 Z0.66 F5;N30 G00 X0.26 Z0.66;N31 G00 X0.26 Z1.1;N32 G00 X0.13 Z1.1;N33 G01 X0.13 Z0.7 F5;N34 G00 X0.26 Z0.7;

N35 G00 X0.26 Z1.1;N36 G00 X0.11 Z1.1;N37 G01 X0.11 Z0.74 F5;N38 G00 X0.26 Z0.74;N39 G00 X0.26 Z1.1;N40 G00 X0.10 Z1.1;N41 G01 X0.10 Z0.75 F5;N42 G01 X0.17 Z0.61 F5;N43 G00 X0.26 Z1.1;N44 M30;

2. Exhibit 02 :

N1 G20 G90;N2 S200 M03;N3 G00 X0.51 Z3.1;N4 G00 X0.50 Z3.1;N5 G01 X0.50 Z1.0 F1;N6 G00 X0.51 Z1.0;N7 G00 X0.51 Z3.1;N8 G00 X0.45 Z3.1;N9 G01 X0.45 Z1.0 F1;N10 G00 X0.51 Z1.0;N11 G00 X0.51 Z3.1;N12 G00 X0.40 Z3.1;N13 G01 X0.40 Z1.05 F1;N14 G00 X0.51 Z1.05;N15 G00 X0.51 Z3.1;N16 G00 X0.35 Z3.1;N17 G01 X0.35 Z1.1 F1;N18 G00 X0.51 Z1.1;N19 G00 X0.51 Z3.1;N20 G00 X0.30 Z3.1;N21 G01 X0.30 Z2.45 F1;N22 G00 X0.51 Z2.45;N23 G00 X0.51 Z3.1;N24 G00 X0.25 Z3.1;N25 G01 X0.25 Z2.5 F1;N26 G00 X0.51 Z2.5;N27 G00 X0.51 Z3.1;N28 G00 X0.20 Z3.1;N29 G01 X0.20 Z2.5 F1;N30 G00 X0.51 Z2.5;N31 G00 X0.51 Z3.1;N32 G00 X0.15 Z3.1;N33 G01 X0.15 Z2.5;N34 G02 X0.35 Z2.3 R.2;N35 G00 X0.35 Z2.0;N36 G03 X0.35 Z1.5 R0.415;N37 G00 X0.35 Z1.1;N38 G03 X0.45 Z1.0 R0.1;N39 G00 X0.51 Z1.0N40 G00 X1.0 Z3.5;N41 M30;

Pictures :