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GB/T 25156-2020: PDF in English (GBT 25156-2020)
GB/T 25156-2020
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.120; 83.200
G 95
Replacing GB/T 25156-2010, GB/T 25157-2010
General specifications and inspection methods of rubber and
plastics injection moulding machines
ISSUED ON: MARCH 31, 2020
IMPLEMENTED ON: FEBRUARY 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions... 6 
4 Models and basic parameters ... 6 
5 Requirements ... 7 
6 Testing methods ... 9 
7 Inspection rules ... 29 
8 Marking, packaging, transportation, storage ... 30 
Appendix A (Informative) Model ... 32 
Appendix B (Normative) Basic parameters ... 33 
References ... 35 
General specifications and inspection methods of rubber and
plastics injection moulding machines
1 Scope
This standard specifies the model and basic parameters, requirements, testing methods,
inspection rules and signs, packaging, transportation, storage of rubber and plastic
injection molding machines.
This standard applies to single-screw plunger, single-station, vertical/horizontal rubber
injection molding machines AND single-screw, single-station, horizontal plastic
injection molding machines (hereinafter referred to as injection molding machines).
2 Normative references
The following documents are essential for the application of this document. For dated
references, only the dated version applies to this document. For undated references, the
latest edition (including all amendments) applies to this document.
GB/T 191 Packaging - Pictorial marking for handling of goods
GB/T 321-2005 Preferred numbers - Series of preferred numbers
GB/T 3682.1 Plastics - Determination of the melt mass-flow rate (MFR) and melt
volume-flow rate (MVR) of thermoplastics - Part 1: Standard method
GB/T 3785.1-2010 Electroacoustics - Sound level meters - Part 1: Specifications
GB/T 6388 Transport package shipping mark
GB/T 13306 Plates
GB/T 13384 General specifications for packing of mechanical and electrical product
GB 22530 Safety requirements of injection moulding machines for rubber and
plastics
GB/T 36587 Rubber and plastics machinery - Terminology
HG/T 3120 The general technological requirements for the appearance of the rubber
and plastic machinery
HG/T 3228-2001 General specifications of painting for rubber and plastics
machinery
3 Terms and definitions
The terms and definitions, which are defined in GB/T 36587, as well as the following
terms and definitions, apply to this document. For ease of use, some terms and
definitions of GB/T 36587 are repeated below.
3.1
Repeatability of mold opening position
After the mold opening action under the same conditions, the consistency of the
actual position of the moving platen, when the mold opening is terminated.
3.2
Repeatability of injection position
The consistency of the actual position of the screw or plunger, at the end of the
injection, after the injection action under the same conditions.
3.3
Dry cycle time
Dry cycle
Without injection and pre-molding action, the time required for the clamping
mechanism to run for one cycle, which includes mold closing time, mold opening
time, conversion time.
[GB/T 36587-2018, definition 3.5.52]
4 Models and basic parameters
4.1 Model
See Appendix A for the model of the injection molding machine.
4.2 Basic parameters
See Appendix B for the basic parameters of the injection molding machine.
working surface of the hot plate shall meet the following requirements:
a) For electric heating (the size of the hot plate is not more than 1000 mm x 1000
mm), steam heating, oil heating, the temperature difference shall be controlled
within 6 °C;
b) For electric heating (the size of the hot plate is larger than 1000 mm x 1000 mm),
the temperature difference shall be controlled within 10 °C.
5.4 Safety requirements
Safety requirements shall comply with the provisions of GB 22530.
6 Testing methods
6.1 General testing methods
6.1.1 Testing of operation control mode
Check whether the manual operation control mode, semi-automatic operation control
mode, automatic operation control mode are available and effective.
6.1.2 Motion detection of moving parts
Set the oil pressure of the system to 25% of its rated value. Perform each of mold
opening and closing, hydraulic ejection and retraction, injection nozzle advance and
retraction, for three times, to check whether the moving parts are crawling, jamming,
or having obvious shock.
6.1.3 Detection of the coaxiality between the center of the injection nozzle hole and
the positioning hole of the template mold
Move the injection nozzle head to the measurable position of the positioning hole of
the fixed platen mold. Use a vernier caliper, to measure the values of the four positions
(A, B, C, D) in Figure 1. Take the difference, between the maximum value and the
minimum value, as the coaxiality tolerance.
Then carry out empty injection. After the material is cooled, use the standard weighing
instrument to weigh out its mass W plasticizing (g). Then calculates the plasticizing
capacity G (g/s), G = W plasticizing/2T plasticizing. This testing is carried out as such for three
times. Finally, take the arithmetic mean of the three calculation results, as the
plasticizing ability value.
6.1.11 Testing of injection rate
6.1.11.1 Testing conditions
The testing conditions of injection rate shall be as specified in a) ~ f) of 6.1.10.1.
6.1.11.2 Testing method
Carry out the empty injection. Use a stopwatch or other more accurate timing device,
to record the injection time t injection (s). After the material is cooled, use a standard
weighing instrument, to weigh its mass W injection (g). Then calculate the injection rate q
(g/ s), q = W injection/t injection. This testing is performed as such for three times. Take the
arithmetic mean of the three calculation results, as the injection rate value.
6.1.12 Testing of actual injection volume
6.1.12.1 Testing conditions
The testing conditions for actual injection volume are as specified in a) ~ f) of 6.1.10.1.
6.1.12.2 Testing method
Carry out the empty injection. After the material is cooled, use a standard weighing
instrument, to weigh its mass. Carry out testing for three times. Finally take the
arithmetic mean of the three test results, as the actual injection volume value.
6.1.13 Testing of injection pressure
6.1.13.1 Testing method 1
Set the injection molding machine to the semi-automatic operation mode, without
material. Run the injection to the end. Determine the system's working pressure p0,
according to the pressure gauge. Then calculate the injection pressure p, according to
formula (5).
Where:
p - The injection pressure, in megapascals (MPa);
A0 - The effective cross-sectional area of the injection piston, in square centimeters
(cm2);
p0 - The working pressure of the system, in megapascals (MPa);
AS - The cross-sectional area of the screw or barrel plunger, in square centimeters
(cm2);
n - The number of injection cylinders.
6.1.13.2 Testing method 2
The test raw material is recommended to use polystyrene (PS); the heating temperature
is 216 °C ± 6 °C. Install a pressure detection device, which has an accuracy of 0.01
MPa, at the nozzle. After the machine enters a stable state, set the injection speed to be
less than 20% of the maximum injection speed. Perform cyclically 10 injection pressure
tests. Read the maximum injection pressure value. Calculate the injection pressure
value, which is measured 10 times according to the arithmetic mean, as the injection
pressure of the machine.
6.1.14 Testing of clamping force
6.1.14.1 Testing conditions
During the test, the tie rod to be tested and test block shall not have temperature changes,
which are caused by human factors; the hydraulic system shall be under the rated
working pressure.
6.1.14.2 Testing method 1
The testing method is carried out, according to the following steps:
a) The method of measuring the maximum strain of the tie rod by a strain gauge (it
is also allowed to use a clamping force tester, which has comparable accuracy, for
testing).
b) Install the test block at the center of the fixed platen (see Figure 4). The material
and size of the test block are in accordance with Table 10; the form of the test
block shall be one selected from two. When the inner spacing of tie rods is
inconsistent in horizontal and vertical directions, take the size of the test block
which is corresponding to the smaller value.
c) On each tie rod, paste sensitive strain gauges, as shown in Figure 4. The distance,
between the sensitive strain gages and the fixed template, is less than 1.5 times
the diameter of the tie rod. Paste two or more (even number) stain gauges.
d) Measure the strain εi of the tie rod (under the clamping state of the clamping
mechanism).
Where:
F Clamping - Clamping force, in kilonewton (kN);
p0 - The reading value of the pressure gauge, in megapascal (MPa);
A - The area of the hydraulic pressure acting on the plunger, in square centimeters
(cm2);
n - The number of hydraulic cylinders.
6.1.15 Testing of product quality repeatability accuracy
6.1.15.1 Testing conditions
Test conditions include the following:
a) The material of plastic injection molding machine adopts the unmodified
uncolored polystyrene (GPPS), which has a melt flow rate MFR of 200/5 = 7 g/10
min ~ 9 g/10 min (see GB/T 3682.1), OR the unmodified uncolored high-density
polyethylene (HDPE), which has a melt flow rate MFR of 190/2.16 = 3 g/10 min
~ 4 g/10 min (see GB/T 3682.1). Rubber injection machine material adopts nitrile
rubber (NBR) film.
b) The test mold is provided by the manufacturer or the user.
c) The quality of the test product shall be 60% ~ 80% of the actual injection volume
of the injection molding machine.
d) The injection molding machine shall be in normal working state (including the
mold), after debugging; its injection molding process parameters shall be set
reasonably.
6.1.15.2 Testing method
The number of test products, which are continuously injected by the injection molding
machine, shall be not less than 50. After the material is naturally cooled, weigh the mass
of each product. Take the average value, as the test result of the product quality.
Calculate the repeatability of the product mass, according to formula (8).
Where:
δw - The repeatability accuracy of product quality;
wi - The mass of the ith product, in grams (g);
- The average mass of the product, in grams (g);
n - The number of test products.
6.1.16 Testing of dry cycle time
6.1.16.1 Testing conditions
Testing conditions include the following:
a) The injection molding machine is set to a fully automatic cycle mode, which has
only mold opening-closing action.
b) Install the test block at the center of the fixed platen. The material and size of the
test block are in accordance with Table 10. The form of the test block is selected
from two. Load a force, which is equivalent to 70% of the rated clamping force.
c) The measuring stroke is 70% of the inner spacing of the larger tie rod. If this
requirement is not met, it shall make special instructions. The end position of
mold opening can be set accurately to 10 mm.
d) In addition to cooling, vulcanization or recirculation time, the switching time,
between the other actions, shall be included in the dry cycle time.
6.1.16.2 Testing method
Carry out 10 automatic cycles continuously. Use a stopwatch or other more accurate
timing device, to record the total time of 10 cycles, including mold opening time, mold
closing time, conversion time. Take the average time of 10 cycles, as the dry cycle time.
6.1.17 Testing of diameter of positioning holes on the template
The diameter of the positioning hole is tested, by the use of an inner micrometer.
6.1.18 Testing of other parameters of injection molding machine
6.1.18.1 Testing of inner spacing (horizontal, vertical) of tie rods or length of hot
plate
Use a length ruler, which has an accuracy of more than 1 mm, to measure the inner
distance of the tie rod, in the horizontal and vertical directions, OR the length and width
of the hot plate.
6.1.18.2 Testing of mold opening stroke, maximum mold thickness, minimum mold
thickness (three items are tested together)
shown in Figure 6. When the hot plate is completely closed, hold the pressure for
1 min. Take out the flattened fuse. Use a micrometer, to measure the thickness of
the middle of each fuse. Take the difference, between the maximum thickness and
the minimum thickness, as the parallelism measurement result of the two adjacent
hot plates.
6.3.2 Pressure drop testing of mold closing system
Put the test block, in between the adjacent hot plates. Pressurize with the rated pressure.
After the mold is completely clamped, start timekeeping. Record the reading of the
pressure gauge, after 1 minute. Record the reading at the interval of 1 minute after that.
When the time reaches 10 minutes, that is, after taking 10 records, calculate the
difference, between the maximum reading and the minimum reading, as the pressure
drop of the clamping system.
6.3.3 Testing of the maximum temperature of hot plate
For the steam-heated rubber injection molding machine, heat it by saturated steam at a
pressure of 0.8 MPa. For the oil-heated and electric-heated rubber injection molding
machine, connect the hot oil source and power supply, to heat the hot plate to a stable
state; then use a spot thermometer of the corresponding range, to make measurement at
two points nearby the center line. Take the average value, as the maximum working
temperature of the hot plate.
6.3.4 Temperature uniformity testing on the working surface of the hot plate
Heat the hot plate to 150 °C. After the temperature reaches a steady state, use a spot
thermometer, to make measurement:
a) When the length L of the hot plate is ≤ 1000 mm, make measurement according
to the arrangement as shown in Figure 7;
b) When the length of the hot plate is 1000 mm < L ≤ 6000 mm, make measurement
according to the arrangement as shown in Figure 8;
c) When the length of the hot plate is L > 6000 mm, make measurement according
to the arrangement as shown in Figure 9.
Calculate the temperature difference, in accordance with formula (12).
Where:
ΔT - Temperature difference, in degrees Celsius (°C);
Tmax - The maximum reading of the spot thermometer, in degrees Celsius (°C);
items in 5.1.2 ~ 5.1.3, 5.1.6, 5.3, during the running test. If a failure occurs during the
test, the test time or number shall be recalculated, after the failure is eliminated.
7.3 Type test
7.3.1 Type test shall be carried out, for all the requirements in Chapter 5 and the basic
parameters of Appendix B, which are specified in this standard.
7.3.2 The type test shall be carried out in one of the following situations:
a) Trial type identification of new products OR old products after trans-plant
production;
b) After formal production, where there are major changes in structure, material,
process, which may affect the performance of the product;
c) After the production is restored, after long-term suspension;
d) When there is a big difference between the exit-factory inspection results and the
last type test;
e) When the national market supervision department puts forward a request for type
test.
8 Marking, packaging, transportation, storage
8.1 Marking
Each product shall have a product label, which is fixed in an obvious position. The label
shall comply with the provisions of GB/T 13306 and include the following contents:
a) Manufacturer's name and trademark;
b) Product name, model, implemented standard number;
c) Product number and date of exit-factory;
d) Main technical parameters, including at least clamping force and injection
capacity.
8.2 Packaging
The product packaging shall comply with the provisions of GB/T 13384. The following
technical documents shall be packed, in the product packaging box (in a waterproof
bag):
a) Product certificate;
Appendix B
(Normative)
Basic parameters
B.1 Parameters that shall be provided in the sales contract (agreement) or product
instruction manual:
a) Clamping force (kN) is recommended to select the specification parameter value,
from the priority number R10 or R20 series, in GB/T 321-2005;
b) Theoretical injection volume;
c) Plasticizing ability;
d) Injection rate;
e) Injection pressure;
f) Actual injection volume.
When expressing plasticizing capacity, injection rate, actual injection volume in
technical documents, it shall state the material to be used, which is generally expressed
in the following format, such as: plasticizing capacity (GPPS): 100 g/s.
B.2 Parameters that the manufacturer shall provide to the user:
a) Spacing (horizontal, vertical) within the tie rod or the length of the hot plate;
b) Diameter of mould positioning hole;
c) Mould-opening stroke;
d) The maximum die thickness (or the maximum opening distance of the formwork);
e) Minimum mould thickness;
f) Minimum mould size.
B.3 The installation parameters that the manufacturer shall provide to the user:
a) Motor power, heating power;
b) The weight of the whole machine AND the overall dimensions of the machine.
B.4 Parameters that the manufacturer can provide to the user:
......

BASIC DATA
Standard ID GB/T 25156-2020 (GB/T25156-2020)
Description (Translated English) General specifications and inspection methods of rubber and plastics injection moulding machines
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard G95
Classification of International Standard 71.120; 83.200
Word Count Estimation 23,251
Date of Issue 2020-03-31
Date of Implementation 2021-02-01
Drafting Organization Haitian Plastic Machinery Group Co., Ltd., Yuyao Huatai Rubber and Plastic Machinery Co., Ltd., Donghua Machinery Co., Ltd., Shenzhen Lingwei Technology Co., Ltd., Zhejiang Shenda Machinery Manufacturing Co., Ltd., Guangdong Yizumi Precision Injection Technology Co., Ltd., Tairui Machinery Co., Ltd., Bochuang Intelligent Equipment Co., Ltd., Ningbo Bona Machinery Co., Ltd., Guangdong Jiaming Machinery Co., Ltd., Ningbo Haixing Machinery Manufacturing Co., Ltd., Shandong Tongjia Intelligent Equipment Co., Ltd., Ningbo Lijin Machinery Co., Ltd., Foshan City Shunde Zhende Plastic Machinery Co., Ltd., Ningbo Ramada Machinery Manufacturing Co., Ltd., Beijing Rubber Industry Research and Design Institute Co., Ltd., Dalian Plastic Machinery Research Institute, National Plastic Machinery Product Quality Supervision and Inspection Center, China Plastics Machinery Industry Association
Administrative Organization National Standardization Technical Committee of Rubber and Plastic Machinery (SAC/TC 71)
Proposing organization China Petroleum and Chemical Industry Federation
Issuing agency(ies) State Administration for Market Regulation, National Standardization Administration