Ministry of education and science of the republic of kazakhstan

	KAZAKH AGROTECHNICAL UNIVERSITY
	NAMED AFTER S. SEYFULLIN

Methodical guidelines to fulfill practical works

by the discipline «Systems of numerical control of machine tools - CNC machine tools»

for students of speciality

6M072400 «Technological machines and equipment» astana 2016

Recommended and approved for publication on the at the meeting of educational methodical council of KazATU named after S.Seyfullin Protocol №_______ «_____» _________________ 20__

«APPROVED» Head of the EMC of KazATU named after S.Seyfullin ______________A.M. Abdyrov «_____» _________________ 20__

Compliers:

Kanlybaev Orazaly, d.t.s., head of the department «TME»

Kakimov Ulan Kadyrkhauly, k.t.n., senior lecturer of the department «TME»

Reviewer:

Considered and discussed at a meeting of the Department of «Mechanical engineering» protocol №_____ from «____»__________2015

Considered and discussed at a meeting of the methodical commission of the Department of «Technological machines and equipment» protocol №_____ from «____»__________2015

© Kazakh agrotechnical university named after S.Seyfullin

© KazATU named after S.Seyfullin press 2016

Content

INTRODUCTION………………………………………………………… 4 PRACTICAL WORK №1 Characteristics of numerical control systems, stages of software development .………....................................................................................5 PRACTICAL WORK №2 Studying of CNC mill machine, CNC lathe machine ………………………6 PRACTICAL WORK №3 Creating own 2D and 3D design project (on Compass or SolidWorks) with given specifications and tolerances …………………….………………….8 PRACTICAL WORK №4 Programming own project on CAM system (on Esprit or another) ……….9 PRACTICAL WORK №5 CNC programming. Selection of operation for machining ………………10 PRACTICAL WORK №6 Manufacturing project (on CNC machine) …..…………………………...12

Introduction

The abbreviation CNC stands for computer numerical control, and refers specifically to a computer “controller” that reads G-code instructions and drives a machine tool, a powered mechanical device typically used to fabricate components by the selective removal of material. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via software load program.

The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action has been dramatically reduced.

With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved with no strain on the operator. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.

In a production environment, a series of CNC machines may be combined into one station, commonly called a “cell”, to progressively machine a part requiring several operations. CNC machines today are controlled directly from files created by CAM software packages, so that a part or assembly can go directly from design to manufacturing without the need of producing a drafted paper drawing of the manufactured component. In a sense, the CNC machines represent a special segment of industrial robot systems, as they are programmable to perform many kinds of machining operations (within their designed physical limits, like other robotic systems). CNC machines can run over night and over weekends without operator intervention. Error detection features have been developed, giving CNC machines the ability to call the operator’s mobile phone if it detects that a tool has broken. While the machine is awaiting replacement on the tool, it would run other parts it is already loaded with up to that tool and wait for the operator. The ever changing intelligence of CNC controllers has dramatically increased job shop cell production. Some machines might even make 1000 parts on a weekend with no operator, checking each part with lasers and sensors.

These practical works are aimed to get skills in operation of CNC machining, to learn how create designed parts, connect 3D drawings with CNC machines.

Practical work № 1

Title: Characteristics of numerical control systems, stages of software development.

Include on every drawing

1. Your Name

2. Your Section/Box Number (e.g. A01-15, A02-03)

3. Your Drawing Number: Quarter&Year-Section-Box#

• e.g. W13-A02-03 is the number for Winter Quarter 2016, Section A02 box 03

4. Due Date

5. Scale (1:1 required)

6. Material

7. North and South Mates

8. Sheet Size

Avoid

1. Unnecessary dimensions.

2. Cluttered Dimensioning.

3. Overly-complicated designs.

• Our machine tools can only move in certain limited ways. Complicated and complex curves, designs, symbols, are usually not possible. All impossible features must be redesigned to something you can do on the machine tools in the Engineering Fabrication Laboratory (EFL).

4. Turning in your drawings late (late drawings come with a severe penalty).

• When we grade, the TAs check that your totem is both possible to make and that you will fit with your partners. Late drawings therefore affect you and your partner's ability to make quick, accurate revisions, so please keep that in mind.

Basic Requirements

1. Your Totem must be 2.00 inches tall and 1.50 inches in diameter.

2. You must have a minimum 5 machine operations including:

• Two Lathe cuts.

• Two Mill cuts.

• 1 drill operation (using a drill bit, not an end mill).

3. Your totem must connect to 2 other totems, one above and one below you. The totems follow this pattern:

Drawing and Title Block Requirements

Title Block

1. Include all of the above information in an appropriate place.

2. All information is typed.

3. Sheet size: A

   • Very important for maintaining a 1:1 scale.

Drawing

1. Third-Angle Orthographic Projections

• Required views: Top (North), Front, Right (unless symmetric with Front), and Isometric.

• Other views such as bottom are optional but recommended for complicated features and designs.

  1. Use good judgment on where to place extra views.

2. Include TWO Isometric views. Each view shows off either the North or South end.

Note: You do not need to include any of the labels in the above picture as long as you stay in standard third-angle orthographic projections. They are there as an example for this document only.

Decimal Places and Tolerances

Non-Fit Dimensions

ALL of your DECIMAL dimensions are going to be to two decimal places.

Examples:

• 0.20

• 1.00

• 0.125 → 0.13

Your tolerance for these two decimal dimensions is going to be ± 0.02 inches. This means every dimension can be machined larger or smaller by 0.02 inches and still be acceptable.

Examples:

• 2.00 dimension means anything machined from 1.98 to 2.02 inches is acceptable.

• 0.50 dimension means anything machined from 0.48 to 0.52 inches is acceptable.

Precision-Fit Dimensions

THERE ARE TWO EXCEPTIONS to the above two decimal place rules. For ONE dimension on your north end, and ONE dimension on your south end, we require:

• Three decimal place accuracy and an allowance of .002 inches.

• You and your 2 partners totems MUST connect at the precision-fits specified.

• You may only have ONE precision fit on each end.

  • e.g. If you have a pattern of 3 or 4 extrusions or holes, label one of them as a precision fit, and the other 3 as non-fit (two decimal place)

• You get to choose your North End precision dimension.

  • Your south end precision dimension MUST connect to your partner's north end.

• Unilateral Tolerances

  • Guidelines:

    • Holes can be larger, but not smaller than the dimension.

    • Extrusions can be smaller, but cannot be larger than the dimension.

Circular Dimensions

• For circular dimensions, such as a diameter turned down on a lathe, the corresponding hole must be made by an end mill, and not a drill bit.

  • Therefore, you must stick to standard end mill sizes.

Non-Circular Dimensions (end mill cuts)

• As a general rule, your precision fit needs to be a dimension between two flat surfaces.

Try to think of it as something you can measure with calipers easily (see above example of flat extrusions).

Examples of INVALID Precision Fits

More Examples of INVALID Precision Fits

Use Standard-Size Tools

End Mills

• End mills come in standard sizes and have FLAT ends.

  • Your drawings MUST show the flat bottom of any holes made by end-mills.

• The maximum depth cut you can make with an end mill is 1.5*(Diameter of the tool).

• The dimensions for end mill cuts will be in DECIMAL form.

Note, depending on your tolerance, you can round to 2 decimal places if necessary.

Drill Bits

• Drill bits come in standard sizes and have POINTED ends.

  • Your drawings MUST show the pointed bottom of any holes made by drill bits.

  • The smallest drill bit size allowed is 1/8 inch and you can find the rest of the sizes in the shop on the wall next to the drill presses.

• There is no restriction on maximum depth and thru-holes are allowed.

• The dimensions for all holes made by drill bits will be in FRACTION form.

Parting Tool

• The parting tool is 1/8 inch (.125) wide and the maximum depth of cut is 1/4 inch.

Miscellaneous Tips

• Dimension features from the North end, and/or South end when necessary.

• End mills are round. Think about whether your cut will leave a straight or rounded corner.

  • Escpecially important, think about whether round corners will mate with straight corners! Usually they will not and modifications must be made to remove the corners, such as drilling a hole at all four corners.

  

• The mill only moves up, down, right, and left, so think of a design that uses only these movements.

• Dimension whole circles and large arcs as diameters, small arcs as radii.

References: 3 gen. [106-109]

Assessing questions:

1. How to create parts?

2. What is Decimal Places and Tolerances?

3. What kind of drill bits do you need to use?

Practical work № 2

Title: Studying of CNC mill machine, CNC lathe machine.

Task: To study Tormach PCNC mills.

Solution:

Tormach PCNC mills are intended for use as general purpose CNC mills. Pictured below is a typical PCNC 1100 mill set up, including several options.

Figure 2.1 – Tormach PCNC 1100 mill

Item #	Component	Item #	Component
1	Electrical Cabinet	6	PathPilot™ Interface
2	Serial Number Plate Main Disconnect Switch	7	Keyboard Table
		8	Machine Arm (2)
3	Red E-stop	9	Path Pilot Controller Compartment
4	Green Start Button	10	Storage Compartment
5	Operator Panel	11	Coolant Compartment

Specifications (PCNC 1100)

Operator Panel

The Operator Panel is located on the door of the electrical cabinet (see Figure 2.2). It contains physical buttons that control the following functions:

• Start

• E-Stop

• Controller On/Off

• Coolant On/Off/Auto

• Spindle Manual/Auto

• Spindle Start/Stop

• Spindle Forward/Reverse

Figure 2.2 - The Operator Panel

PathPilot Interface

PathPilot is a sophisticated CNC controller for Tormach products. All aspects of the Tormach PCNC 1100 or PCNC 770 are controlled via the on-screen PathPilot interface. There are four primary ways for the operator to interact with PathPilot:

• Keyboard

• Mouse

• Jog shuttle (optional)

• Touch screen (optional)