DPT 312/3
METROLOGY
UNIVERSITI MALAYSIA PERLIS
SCHOOL OF MANUFACTURING ENGINEERING
INJECTION MOULD DESIGN
(DPT 321)
STEP FOR INJECTION MOULD
DESIGN USIGN UG NX4
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School of Manufacturing Engineering
DPT 312/3
METROLOGY
LAB 1: 3D DRAWING (CAD)
OBJECTIVES
1. To draw the 3D part drawing using UG NX4 Software.
2. Refresh the student about 3D Modelling.
3. Understanding the concept of the parts that can be use the plastic injection
moulding.
INTRODUCTION
Before starting to decide the part size, the important factor that should be considered
is the plate size of injection moulding machine. If the part is too large, so the mould
will be larger. Mould size also increase when the number of cavities are increase.
Modelling the 3D part is the first steps of designing mould for plastic injection
moulding. The thickness of the part must be considered to prevent from shrinkage and
the cycle time. If the part is too thick, its will encourage warpage, and if the part is too
thin, the short moulding is much easier to occur. But, to prevent warpage or defects,
the holding time (cooling time) must be increase and its increase of cycle time. The
cycle time is determined primarily by the thickness wall section of the part.
PROCEDURES
1. Open the part.x_t on the Desktop. The part is in parasolid format.
2. Draw the 3D part in Modeling window, same with the parasolid file.
3. After finish the drawing, save as (part.prt) in your Sub folder at My Document.
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METROLOGY
LAB 2:
TAPERING, DECIDE PARTING LINE & 2D DRAFTING
OBJECTIVES
1. To draw taper for the vertical part construction
2. To decide the suitable location for parting line.
3. To draw 2D Drafting for the part.
INTRODUCTION
If some construction part is 90 (vertical) from the base, the injection moulding
process cannot be done. It is because of surface contact between mould and part when
mould open and part ejection and provide damage of parts. To prevent this damage,
the part must have some taper (1 - 3 for core side and 3 - 5 for cavity side) to the
vertical plane. It is also depending on the wall section thickness of the part.
A parting line can be define as any part of the mould that parts, and forms part of the
part. There is usually only a single parting line, but there can be two or three or more,
depending on the complexity of the mould.
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DPT 312/3
METROLOGY
PROCEDURES
1. Open the part.prt on the Sub Folder.
2. Click on ‘Draf’ button, select “Draf from Stationary Edge” for Type and select
‘ZC’ axis in Selection Step. Key in 3 for angle for ‘set1 A’ and select the edge that
want to taper. (Refer Figure 2.1)
Figure 2.1
3. Continue drafting for the entire vertical surface both cavity and core side.
4. After finish the draft angle, choose the suitable parting line for parts.
5. Change the display (color) for core side and cavity side to make its different. Click
on the ‘Edit’ – ‘Object display’ – select the surface that want to change (core) –
‘OK’.
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DPT 312/3
METROLOGY
Figure 2.2
6. Click on the ‘Color’ frame and change the color.
7. Repeat the step 5 and 6, and change the cavity side color.
8. Save the project.
9. Draw the 2D Drafting. Enter to Drafting window by clicking on Start and choose
Drafting.
10. Add ‘base view’ for TOP, BOTTOM, and SIDE view and add dimension values.
11. If needed, add the ‘section view’, projected view’ and ‘detail view’.
12. Save the project.
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DPT 312/3
METROLOGY
LAB 3
MAKING CORE AND CAVITY INSERT
OBJECTIVE
To draw core and cavity insert base on part size.
INTRODUCTION
The insert forms both the cavity and the core of the plastic part. The insert is a block
of steel that is machined in a softened condition and then hardened to withstand the
injection pressures and wear of the plastic additives. The two opening plates of the
mold base, A plate and B plate, are machined with a pocket to accept the cavity insert.
The insert is bolted and secured into place with cap screws from the back of the plate.
Ejector pins are located on the core side, B plate, and drilled and reamed through the
support plate. The ejector pins provide a means for mechanically pushing the molded
part off the core side of the mold. Depending on the size and complexity of the plastic
part, the insert can be a single block or multiple blocks of steel.
PROCEDURES
1. Open the part.prt on the Sub Folder.
2. Create a rectangular line 25mm offset from the outer edges of the part. Click
“Offset curve” and select the outer curve of the part – key in value -25 and click
OK. (Figure 3.1)
Figure 3.1
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DPT 312/3
METROLOGY
3. Save as the project in two names (core and cavity).
4. Open the cavity.prt file.
5. Extrude the rectangular curve 50mm thru the part.
Figure 3.2
6. Subtract the part and the rectangular box. If part having holes, it must be close by
adding plugs same size to the holes.
7. Delete the unwanted part after subtracted.
Figure 3.3
8. Open core.prt file.
9. Create rectangular at the outer curve of the part using ‘create line’ or ‘extract
curve’ icon.
10. Extrude the curve until the top of the part.
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DPT 312/3
METROLOGY
Figure 3.4
11. Subtract the part and the rectangular box. If part having holes, it must be close by
adding plugs same size to the holes.
12. Delete the unwanted part after subtracted.
13. Extrude the offset curve, 25mm down of the part and “unite” the two solid bodies.
Figure 3.5
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School of Manufacturing Engineering
DPT 312/3
METROLOGY
LAB 3
SUB-INSERT, COOLING CHANNEL, EJECTOR PIN HOLE,
GATING SYSTEM & VENTING
OBJECTIVES
1. To draw Sub-Insert for core and cavity insert.
2. To make holes for cooling channel and ejector pin base on recommended distance
and sizes.
3. To build a gating and runner system for cavity inserts.
INTRODUCTION
Runners channel the melt from the side of the sprue just above the cold slug well into
the cavity area. Depending on the number and placement of the cavities, the runners
can take the shape of a cross, a tree with several limbs, or fan out like the spokes on a
wheel. Just prior to the cavity wall, the runner stops. Plastics enter the cavity through
a small opening at the end of the runner called a gate. The gate restricts the flow of the
plastics until the runner system is completely pressurized by the molten plastic. When
the pressure is high enough for the plastic to break through the small restriction of the
gate, it jettisons into the cavity, filling it rapidly.
The rapid filling of the cavity displaces and traps the air. A small groove,
approximately 0.003" (0.05 mm) deep provides a point for venting the trapped air. If
the air remains, it can be compressed by the melted plastics. The compression of the
air and the fumes together causes an explosion. A small explosion will produce burn
marks, black char discoloration, on the surface of the plastic part. Vents are normally
machined onto the surface of cavity side of the mold after a prototype is made because
the initial prototype runs help to identify the location and need for vents or its will be
identify from software.
Sub-insert is designed to simplify the complex part machining and in the same time it
will prevent air traps.
The location and size of the gate affects the proper filling of the cavity. If the gate is
too large, the plastic will jettison into the mold and stack up like spaghetti at the back
of the cavity. This forms a discolored and swirled surface part. The molecular
structure around the gate is oriented in the direction of flow. The shear action of the
small constricted gate areas causes the build up of stress; this results in a potential
weakness in the part. Gates should be located in non critical areas of the plastic part.
As the plastic fills the cavity, it flows around the pins and cores. As the plastic moves
around both sides of the core the flow fronts meet again behind the core. Where the
plastics meet is called a weld line. The weld line is generally a weak point in the
plastic part. Weld lines often form where a part is gated at two locations. Gate
location must be designed into the part so that weld lines are not located in a high
stress area of the plastic part.
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METROLOGY
PROCEDURES
Draw Sub-Insert
1. Open the cavity part.prt on the Sub Folder.
2. Sketch rectangular 40mm x 40mm at the bottom of cavity insert, and extrude
10mm through mold insert.
3. Make a cylinders pass through the pin at the center of cavity insert until it touch
the rectangular created.
4. Copy the cavity insert solid body by right clicking at mold insert in part navigator
box. Click transform – translate – delta – OK – copy – cancel.
5. Click intersect icon and click at cavity insert that had copied follow by the
cylinder. Refer Figure 3.1.
Figure 3.1
6. The result that you have is same like the rest pin. Unite this result with rectangular
boxes that had made before. The result is sub insert like Figure 3.2.
Figure 3.2
7. Repeat step 4 but choose sub insert to duplicate it.
8. Subtract the copy of sub insert and the cavity insert to get a hole. Refer Figure
3.3.
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METROLOGY
Figure 3.3
9. Mark and unmark at the Part Navigator either to show or hidden the object layer.
10. Save the project.
11. Open core part.prt at sub folder.
12. Make a sub insert by your own step to get the result in Figure 3.4. Save the
project.
Figure 3.4
Draw Air Vent
1. Open the cavity part.prt on the Sub Folder.
2. Make 4 venting system at the bottom of cavity insert 10mm wide and 0.03mm
deep like Figure 3.5. Save the project.
Figure 3.5
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DPT 312/3
METROLOGY
Create Cooling Channel
1. Open core part.prt.
2. Create 10mm diameter of thru holes using hole icon and position it 25mm from
part location and from the sub insert. Save the project.
Figure 3.6
3. Open cavity part.prt and create the holes with same direction of core insert. Save
the project.
Create Ejector Pin Holes
1. Open core part.prt.
2. Create 10mm diameter of thru holes using hole icon and position it minimum
5mm from part location, sub insert and cooling channel. Save the project.
3. Make sure the position of ejector pin holes are symmetric and balance (Figure
3.7). If necessary, add the other size of holes for narrow location or critical
location. It recommended that only two type of ejector pin diameter in one mold.
Figure 3.7
Draw Gating System
1. Create New File and name as Assembly Insert.
2. Make sure Assemblies icon is mark in the Start menu.
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DPT 312/3
METROLOGY
3. Add component core part, cavity part and cover by clicking on Add Existing icon.
Make sure the Positioning in Add Existing Part box is Absolute for all three part.
Refer figure below.
Figure 3.8
4. When all three part were added, its will become as Figure 3.9 below.
Figure 3.9
5. In assembly navigator, activate (yellow) ‘core’ by double clicking on ‘core part’
and unmark ‘core’ and ‘cavity’ layers by click in boxes.
6. Create 7mm x 10mm x 1mm rib at the center front of the part. Draw Sub-Marine
Gate on the rib. The inlet diameter gate is 5mm and outlet is 1 mm. Runner
diameter is 5mm. Unite the runner, gate and rib. Refer Figure 3.10. If the runner
system created outside the core and cavity insert, you need to increase the size of
insert using ‘Offset face’
icon.
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DPT 312/3
METROLOGY
Figure 3.10
7. Activate layer core and subtract the runner system with core insert to make holes
in core insert.
8. Repeat step 5 to 7 for cavity insert.
9. Save the parts.
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School of Manufacturing Engineering
DPT 312/3
METROLOGY
LAB 4
MOULD ASSEMBLY 3D
OBJECTIVES
1. To create assembly all parts in mould construction, including mould base, ejector
pin, sprue, locator ring, sprue bushing, etc.
2. To make holes for cooling channel and ejector pin for mould base plate through
the core and cavity insert.
PROCEDURES
1. Open the ‘mould base assembly part’ on the Sub Folder.
2. Add ‘cover’, ‘cavity’ and ‘core’ by clicking on the Add existing icon. Make sure
the Positioning in Add Existing Part box is Absolute for all three part
3. Add ‘ejector pin’, ‘sprue busing’ and ‘locator ring’ using Add existing icon and
position each of component to their location on the mould base.
4. You can use ‘Mate’ and ‘Reposition’ icon in ‘assembly’s component’ to assemble
the part.
5. Create rectangular pocket for core and cavity insert. Create 20mm diameter holes
at 4 corners in rectangular. Size of the rectangular is same size of mould insert.
6. To create ejector pin holes and cooling channel, make a layer active and work for
the mould plate that want to create.
7. Sketch the diameter on the mould plate where ejector pins cross the mould plate.
Extrude and subtract to make holes.
8. Repeat step 6 for the entire ejector pin and mould plate that it were crossed.
9. For the cooling channel, extend the cooling channel holes in core and cavity insert
thru the mould plate.
10. Repeat step 9 for all channel including water inlet and outlet holes.
11. Plugs the unwanted holes at the mould insert to make water are flow properly.
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