Processing of counter-balance weight of hermetic reciprocating compressor

Stamping Process
The stamping layout of a counter-balance weight base is divided into eight stations and the operations performed in each station are indicated as hatch area. The detail of each operation is discussed as follows:

a) Station 1: Piercing & Notching
In this station, two pilot holes are pierced to provide accurate positioning of the stock for the subsequent operations. Notching is also performed to make marking on the counter-balance weight base, which will be used for positioning during assembly onto the crankshaft.

b) Station 2: Piercing
The hole for assembly onto the crankshaft is pierced in this station. Stringent but achievable roundness specification has been added to this hole to ensure firm grip with the crankshaft after assembly.

c) Station 3: Piercing
The cavities of the counter-balance weight base are pierced in this station. These cavities are required to control the center-of-gravity position of the part thus providing the necessary balancing force required.

d) Station 4: Chamfering
The hole for assembly onto the crankshaft is chamfered on the reverse side of the stock in this station to facilitate easy insertion during assembly.

e) Station 5: Piercing
The cavity for controlling the heat transfer rate during the assembly process of the counter-balance weight base is pierced in this station.

f) Station 6: Piercing
In this station, the front and the back profile of the design are pierced.

g) Station 7: Nipple
The dimples on the counter-balance weight base are made in this operation to facilitate resistance welding to be carried out later.

h) Profiling & Parting-off
This is the last station of the progressive die, which performs both the profiling and parting off operations. During profiling operation, the top and bottom portion of the stock strip is cut off, revealing almost the complete shape of the counter-balance weight base. At this stage, the part remains attached to the scrap skeleton until the parting-off operation where it is cut off to produce the complete work piece.

Cleaning Process
After the stamping process, the parts are covered with oil, dirt and other contaminants. To remove all these unwanted substances, they will need to undergo a cleaning process. This section is intended to describe the cleaning process of not only the counter-balance weight, but also for all other compressor parts at the end of the fabrication process.

Equipment Used
(a) Aqueous Ultrasonic machine
(b) Baskets to contain parts to be cleaned

Parameters
Cleaning Agent : Petroleum Solvents [3]
Temperature : Room Temperature
Spraying Pressure : 0.2 ~ 0.25 MPa
Cleaning Time : 1.5 ~ 3 minutes
(Actual cleaning time may be adjusted depending on the parts cleaned.)

Procedures
(a) The parts to be cleaned are placed inside the baskets.
(b) The baskets are then placed on the conveyor system that will travel through the Power Washer machine, which includes soaking, rinsing and drying stations.
(c) After going through the ultrasonic machine, the parts are cleaned and ready for compressor assembly.

Process Control
In order to ensure proper cleaning of the parts, the following process control must be adhered:
(a) The direction of spray nozzle must be adjusted to obtain best cleaning effectiveness.
(b) Parts to be cleaned must be placed such that they can be sprayed directly onto the metal surface.
(c) Set up a magnet near the filter of a cleaning bath and spray clean petroleum solvents to the parts at all times.
(d) Care must be taken to clean parts with “Hard to reach area” such as grooves or holes,
(e) After cleaning, the petroleum solvents must be changed if oil films or dirt are remained on the cleaned parts.