If you work with a jigger machine and use plastic clay molding, these tips will definitely be interesting to you:
1) These factors cause deformation:
Improper plasticity of the body (too little or too much)
When the clay is placed on plaster mould, the direction of extrusion is not considered properly
Presence of moisture gradient in extruded clay
Bending the clay slice after cutting and before placing it on the mold
The small amount of clay placed on mould
Not placing the clay slice in the center of the mold
Low mold water absorption
Plaster mold, roller or spindle is out of center
Too much difference between roller and spindle rotation speed
Dirt or failure of the jigger cam or any other factor that makes the movement of the roller uneven
Uneven drying
Uneven surface in the second dryer or any place which leatherhard plates are placed
Not fixing the whole device on the ground by the bolt
2) These factors cause cracks:
The presence of air in the clay
Edge cutter not set
The cutter is not sharp enough
The roller is too hot
Very low mold water absorption (at least 3.5 mm2 per second)
Low humidity in the dryer
High temperature of the dryer
Too much air blowing on the part in the first stages of drying
The amount of clay is not enough in forming
The moulds are new
Fast drying of the mold in molding shop
3) These factors cause sagging of plates:
The tip of the roller is not hot
Low difference between roller and spindle speeds
Low density in the middle and non-uniformity of moisture in extruded clay
4) The RPM of the roller and spindle and the difference in their rotation speeds depends on the following:
The shape of the piece (deep or flat, round or square)
The diameter of the piece (in larger pieces, both the circumference speeds of the roller and the spindle and the difference between them are less)
Adjusting the sagging bottoms of plates (because the drying method is also effective on the sagging and the drying method depends on the season, in different seasons, the correct RPM of the roller and spindle should be obtained by testing)
Moisture of clay
5) These factors cause foot cracks:
Low clay humidity
High roller temperature
Improper design of plate foot
Too much forming time when the roller is at its lowest point
Quick drying at high temperature
6) These factors cause staring botoms of plates:
Some of the adjustment screws of the device are loose
The setting ring of the mold have too much clearance and the mold slides on the spindle
Low humidity of the clay
Too much difference between roller and spindle speeds
The shaping process takes too long.
7) These factors cause mold breakage:
High temperature and low humidity of mold dryer
The long stay of the mold in the warehouse at a temperature higher than 45 degrees Celsius
staying the mold in the dryer with no clay formed on it
Rapid removal of the mold from the dryer while the mold is still hot (due to thermal shock)
The low ratio of plaster to water during mold making (the mold must have a bending strength of at least 8 MPa)
Excessive locking of the mold in the spindle
The edge of the spindle is sharp or the curvature of the place where the base of the mold is attached to the mold is low
8) These factors affect the quality of the piece:
The diameter of the clay slice should be almost equal to the diameter of the foot of the piece.
The weight of the clay slice should be 30% more than the weight of the formed part.
The forming time should be longer for large parts that are formed at a slower speeds (when the roller reaches its lowest point, the roller should rotate 6 times)
Be careful not to reduce the speed of the roller and spindle due to the slipping of the belts during forming.
The existence of vacuum under the mold is necessary both to keep the mold on the spindle and to prevent the clay from flying, and it helps to prevent deformation.
9) These factors affect the shape of the piece:
The graph and design of part
The ratio of roller to spindle revolutions or the difference between roller and spindle revolutions (parts with long edges need less revolution difference)
Roller and spindle speed (how much the speed of the roller and spindle is depends on the size of the part. For example, for an 8 in. plate, the speed of the roller 350 and the spindle 430 seem suitable to begin with. First, you should experiment with some different speeds. When the desired result is achieved you should work on rotation speeds to get the best result.)
Forming time (spindle must rotate at least 6 times during forming)
The humidity of the clay, the humidity of the plaster mold, the humidity of the dryer and generally the drying process.
Roller temperature
Firing resistance of body
