FETTLING

DIPLOMA IN FOUNDRY TECHNOLOGY FETTLING

Introduction to Fettling

1.1 What is it and why do we need such a Labour Intensive Activity?

Fettling is the means by which a crude casting is turned into a cost effective quality component that meets all the standards required by the customer.

We need to fettle the castings to ensure all the indiscretions caused thus far by the foundry process are rectified in accordance with the standards set by such bodies as ISO 9001 accreditation for international suppliers of castings.

The G.I.F.A. exhibition in Dusseldorf Germany, every four years, is recognised as the show case of technology world wide in the Foundry Industry. At the only seminar on Fettling held at G.I.F.A. in June 1994, Doctors of Engineering from all over Europe and North America gave paper after paper on world developments in Fettling.

The summary paper of all these leaders in the industry was as follows:

“Until people realize the importance and costs of a modern fettling department in the foundry industry, people will continue to spend money on bigger, better methods to manufacture more complicated high technical castings only to find no money has been spent world wide on Fettling developments to keep pace with the rest of the industry. The foundry industry must take stock of world trends and be prepared to spend on fettling developments in order to save the industry from its plastic competitions”

SESSION 1 : GRINDING WHEELS

1.1 Introduction

Grinding of castings has become a labour intensive, high consumable cost necessary evil of our industry.

However, it need not be so with modern machines and dramatic improvements in wheel materials, bonds and compositions. The only remaining problem is the lack of understanding by the end user of what he really needs.

“I guarantee it will last longer”.

This very familiar statement has been the selling point for more years than our industry can afford. With a full appreciation of how and why a grinding wheel works the end user can, in conjunction with a reputable supplier, obtain grinding media which can radically improve output, reduce labour costs and consumable cost with no detrimental effect to the quality of the casting.

1.2 What Is A Grinding Wheel?
1.3 The Product
1.4 Abrasives
1.5 Characteristics of a Grinding Wheel
1.6 Manufacturing Process
1.7 How Is a Grinding Wheel Defined?
1.8 Common Grinding Wheel Applications
1.9 Guidelines for Wheel Selection
1.10 Wheel Dressing and Truing
1.11 Wheel Safety
1.12 Basic Recommendations
1.13 Cost-Effective Selection of Grinding Media
1.14 What of the Future?
1.15 Resinoid Fettling Wheels
1.16 Self Assessment Questions: Week One and Two – Grinding Wheels

SESSION 2 : WELDING OF CAST IRON

2.1 Introduction

Why the Myth and Mystery?

If you ask any major manufacturer of cast iron “do you weld any castings?” the usual answer is “Most definitely not, its too risky for our quality product”.
The truth unfortunately is far from that statement. The reason being that the myth still exists that welding of cast iron is very “hit and miss” with little or no guarantee of repeatability or success.

The techniques for welding cast iron are well tried and proven with guaranteed repeatability and success when the process is defined and adhered to.

Reclamation or “cosmetic” welding of castings has become an essential part of most automotive foundries for the following reasons:

The cost of remanufacturing another casting
Lost capacity due to remanufacturing
Small inclusion defects, once acceptable, are now just not good enough
Quality conscious customers
Thin-walled castings
Repair surface defects to otherwise a sound saleable casting
However, no two castings or two defects are the same. We therefore use different techniques for different types of castings. We shall investigate the three most commonly used techniques which are:

1. Gas welding with a fluxed filter rod
2. Powder spray welding
3. Arc welding with fluxed electrodes

2.2 Benefits and Concerns of Each Technique
2.3 Gas Welding
2.4 Welding Techniques
2.5 Powder Spray Equipment
2.6 The Multifont Torch Set
2.7 Arc Welding Equipment
2.8 Gas Safety
2.9 General Safety Precautions
2.10 Selection and Care of Equipment
2.11 Method of Assembling Welding Equipment
2.12 Self Assessment Questions: Week Three – Welding of Cast Iron

SESSION 3 : ABRASIVES

3.1 Abrasives
3.2 Steel Shot
3.3 Efficient Use of Steel Abrasive
3.4 Brinell Hardness check
3.5 Operating Mix
3.6 Glass Bead Media
3.7 Impact Treatment Techniques
3.8 Glass Beads
3.9 Ceramic and Plastic Media
3.10 Product Information on Vibratory Cleaning
3.11 Expendables
3.12 Manufacture of Chilled Iron or Steel Shot and Grit
3.13 Blasting Using Compressed Air Equipment
3.14 Self Assessment Questions: Week Four – Abrasives

SESSION 4 : MODERN BLAST CLEANING

4.1 Introduction

The most universally applicable machine for this task is a manipulator-type shot blast system, type DS or DV. Such a system is illustrated in Figure 4-1.

Figure Error! No text of specified style in document. 1: Manipulator-Type Shot Blast System

The castings arrive automatically on roller conveyors or slat conveyors and are transported to the manipulator by a transfer unit. The manipulators then index the castings through the individual blasting stations via a turntable driven by a cam gear for full exposure of all sides to the blasting stream and continuous removal of the abrasive from the casting interiors.

No shot blasting occurs in the last station. In this station the castings undergo thorough abrasive removal and are then positioned for unloading and pickup from the manipulator by a transfer unit that places them on conveyors for further handling.

The main advantages of the DS are:

All operations, including loading and unloading are fully automatic
Automatic blast cleaning of castings of different sizes and configurations without the need of special setting up
Thorough blast cleaning of ports and internal passages
Evacuation of abrasive within the machine and during a blasting cycle
Easy integration of the DS into existing production lines
High capacity for up to 35 tons per hour of castings weighing up to 500kg each
This new system is a major departure from most of the previous concepts of the automatic blast cleaning of mass-produced castings
The main feature of the DS systems is manipulators that automatically seize and handle the uncleaned castings. Depending on the size used, a DS blast cleaning system may be equipped with 2, 4, or 8 manipulators with the corresponding number of partitions, attached to a rotary table
During a pre-selected work cycle, the rotary table with the manipulators and partitions then indexes through the segment blasting chamber
The manipulators are capable of seizing castings of different shapes without the need for special tools or setting up
Figure 4-2 illustrates the operational principle. The manipulators are mounted on a turntable that indexes them from one station to the next. The manganese steel partitions, which separate one manipulator from the next, move through the machine together with the manipulators. This ensures that all blasting stations and vestibules are hermetically closed during shot blasting
4.2 Abrasive Blasting
4.3 Automatic Shot Blasting of Heavy and Fragile Castings
4.4 Modern Blast Cleaning Technology
4.5 Blasting Processes
4.6 Automation in Blast Cleaning Technology
4.7 Pangborn Air Blast Machines
4.8 Self Assessment Questions: Week Five – Modern Blast Cleaning

SESSION 5 : SHOT BLASTING

5.1 Basic Component Parts
5.2 Shot Recovery Systems
5.3 Extraction Units
5.4 Adjustments and Settings
5.5 Monitoring the Process
5.6 Cost-Effective Controls
5.7 Self Assessment Questions: Week Six – Shot Blasting

SESSION 6 : MECHANICAL ASSISTANCE

6.1 Introduction
6.2 Hand Machines
6.3 Mechanical Grinding
6.4 Modern Trends and Future Prospects
6.5 New Developments
6.6 The “Wedge”
6.7 Shotblasting
6.8 Conclusions for the Future
6.9 Self Assessment Questions: Week Seven – Mechanical Assistance