Stationery Inspection

A pencil is a common writing and drawing tool, mainly composed of a graphite core and a shell. The graphite core is made of a mixture of graphite and clay, and the hardness and color depth (such as 2B, HB, etc.) can be changed by adjusting the ratio. The shell is traditionally made of wood, but there are also alternatives made of plastic or environmentally friendly materials. Pencils are widely used for writing, sketching, measuring and drawing, and their easy-to-erase properties make them an ideal tool for learning and creation.

Classification

• Pencils are divided into graphite pencils and colored pencils according to the materials of their lead cores. Graphite pencils are divided into ordinary and high-end products.
• Graphite pencils are divided into 17 types according to their hardness: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, and 9H.
• Colored pencils (including red and blue pencils) are classified according to the number of colors in a single or complete set of products.

Require

The performance of graphite pencil leads should comply with regulations.

The performance of colored pencil leads should comply with regulations.

The diameter of the lead core should comply with regulations.

The allowable tolerance of the pen shaft diameter is ±0.2mm, and the recommended values ​​of the nominal dimensions are shown in Appendix A.

The pen shaft length should comply with regulations.

Other properties of pencils shall comply with the regulations.

The appearance of pencils shall meet the following requirements:

a) The pen barrel has good sharpening performance;

b) There are no obvious defects on the surface of the pen;

c) The markings are recognizable.

For pencils used by students aged 14 and below, the content of migratable elements in the lead core and barrel coating, the content of migratable elements in the pencil tip (according to the requirements for erasers and accessible plastic parts), and the content of phthalate plasticizers should comply with the provisions of GB21027.

Test conditions and materials

Test conditions

Ambient temperature: (23±5)℃.

Relative humidity: 45%~65%.

The test pen should be stored in an environment with a temperature of (23±5)℃ and a relative humidity of 45%~65% for more than 1 hour.

Test materials

The specifications of 128g/㎡ drawing paper should comply with regulations.

The core tip gauge plate shall meet the following requirements:

a) The diameters of the small end of the tapered hole are 0.6mm, 0.7mm, 0.8mm, and 1.2mm respectively, with a tolerance of 0mm to 0.04mm.

Degree mark selection;

b) Cone hole angle: 21°~25°;

c) Gauge plate thickness: (6±0.1) mm.

The tip angle of a pencil sharpener or pencil sharpener should be (20±1)°, and 20° is recommended.

Test methods

Core tip force test

Instruments and Materials

• Core tip force tester with a resolution of not less than 0.20N.
• Constant temperature drying oven.
• Dryer.
• Core tip gauge plates with apertures of 0.8mm and 1.2mm respectively.

Test steps

• Colored pencils should first be placed in a constant temperature drying oven at 35℃~40℃ for 24 hours, and then placed in a dryer to cool for more than 12 hours.
• Use a pencil sharpener or pencil sharpener to sharpen the test pencil. If you use a pencil sharpener, you need to use a pencil sharpener to trim it. Then insert the lead into the tip gauge and smooth the exposed part with metallographic sandpaper placed on a hard surface. Use a 1.2mm aperture tip gauge for colored pencils and 6B~3B graphite pencils, and a 0.8mm aperture tip gauge for 2B~9H graphite pencils.
• Install the test pen core tip with the gauge tip facing downward on the pen clamp of the core tip force tester which is tilted 45°, align the core tip with the midpoint of the force device, and clamp the test pen.
• Start the instrument and move the pen holder at a speed of (12±1) mm/min. When the core tip on the force-bearing device is damaged (including fragmentation, cracking, breaking, etc.), stop moving the pen holder. The maximum value indicated by the instrument is the force value on the core tip.

Abrasion test

Instruments and Materials

• Abrasion tester [resolution: 0.01 mm, drum diameter: (160 ± 1) mm, rotation speed: 6 r/min, line spacing: 1.5 mm].
• 80.0g/m2 writing paper that meets the requirements of GB/T12654-2018 qualified products.
• Constant temperature drying oven.
• Dryer.
• Core tip gauge plates with apertures of 0.7mm and 0.8mm respectively.

Test steps

• First, place the writing paper in a constant temperature drying oven at (30±3)℃ for 2 hours, then cool it in a dryer for 2 hours, take it out, and then place it tightly in a plastic bag or a dryer without desiccant and use it within one week. When using, the front side of the paper should face up and the ring should be attached to the rotating drum of the abrasion tester.
• Take the pencil with the lowest tip force as the test pencil.
• Bend the test pencil in a pencil sharpener or pencil sharpener, insert the lead core into the core tip gauge, and smooth the exposed part with metallographic sandpaper.
• Colored pencils and 6B~B graphite pencils use a core tip gauge with a 0.8mm aperture, and HB~9H graphite pencils use a core tip gauge with a 0.7mm aperture.
• Connect the clutch of the wear tester, insert the test pen into the pen holder, adjust the weight on the pen holder lever to make it balanced, add a 300g weight to the pen holder, and adjust the counter and dial indicator pointer to zero respectively.
• Turn on the power supply to rotate the abrasion tester drum, and turn off the power supply after it rotates 100 times. The value shown on the dial indicator is the abrasion value of the lead core.

Slip test

Instruments and Materials

• Method A: Slipmeter (rotation speed: 40r/min).
• Method A: Coordinate recording paper.
• Method B: Writing lubricity tester with force sensor resolution not less than 0.001N.
• Method B: Electronic balance with a resolution of not less than 0.01g.
• Method B: 80.0g/m2 writing paper that meets the qualified product requirements of GB/T12654-2018.
• Core tip gauge plate with a hole diameter of 0.7mm.
• Ethanol.

A method

Place the coordinate recording paper with a grid of 1 mm on the recorder of the slipmeter, align one of the horizontal grids of the paper with the 0.15 mark on the scale of the recorder, and use this position as the calculation center line. Wipe the copper plate clean with ethanol.

Take a pencil that is closest to the middle value of the measured tip force as a test pencil.

The test pencil is sharpened in a pencil sharpener or pencil sharpener, and then the lead core is inserted into a 0.7mm aperture core tip gauge, and the exposed part is smoothed with metallographic sandpaper.

Insert the test pen into the pen holder and tighten it, and adjust the weight on the lever of the pen holder to make it balanced.

Adjust the spring so that the pointer points to the zero point of the scale.

Add ink to the record pointer.

Add a 400g weight to the pencil holder, adjust the counter to zero, start the motor, and when the pencil core rotates and rubs on the copper plate for 100 circles, turn on the recorder and start drawing lines. After the recorder rotates one circle, turn off the motor.

Remove the recording paper and calculate the friction factor as follows:

a) Cut off 30mm at each end of the recording paper, find the highest and lowest points in the recording curve, and use the 0.15 scale of the recorder as the

Center line, count the highest point and the lowest point relative to the center line, nh and n1 (the number of grids above the center line is negative,

The number of grids below the center line is positive), and the average number of grids relative to the center line is calculated according to the formula (the average number of grids can be positive

positive or negative value).

b) Each test pen is tested 3 times, and the average of the 3 tests is taken as the final result.

Method B

Take three pencils closest to the measured middle value of the tip force as test pencils, prepare them according to 7.3.2.3 and weigh them one by one on an electronic balance.

Install the test pen on the pen holder of the writing lubricity tester, set the writing load to (3.92±0.1)N, the marking speed to (4.5±0.5)m/min, the writing angle to 90°, and the circle diameter to 100mm.

Set the number of circles drawn by the writing lubricity tester to 3. Turn on the writing lubricity tester. The average value of the 3 circles displayed by the instrument is the friction force of the test pen. Calculate the friction factor according to the formula.

Concentration test

Instruments and Materials

• Reflective photoelectric colorimeter.
• Cross-marking machine (line spacing: 1.5 mm).
• 128g/m2 drawing paper.
• Core tip gauge plates with apertures of 0.6mm and 0.7mm respectively.

Test steps

• Take the pencil with the highest tip force as the test pencil.
• Roll the test pencil into a pencil sharpener or a pencil sharpener, insert the lead into the tip gauge, and smooth the exposed part with metallographic sandpaper.
• 6B~B graphite pencils use a core tip gauge with a 0.7mm aperture, and HB~9H graphite pencils use a core tip gauge with a 0.6mm aperture.
• Place the drawing paper on the smooth metal plate of the cross-marking machine, insert the test pen into the pen holder and tighten it, adjust the weight on the pen holder lever to balance it, add a 500g weight, and make the lead core mark on the drawing paper at a speed of (45~55)mm/s. Mark 15 lines at a time, each line is 60mm long and the spacing is 1.5mm. After marking 15 lines each time, rotate 45° and continue marking, for a total of 4 times. Take a square with a side length of (25±1)mm in the middle of the trace as the sample paper.
• Adjust the photoelectric colorimeter, select the interference filter with a central wavelength of 450nm, place the sample paper in a dark box, and open the shutter. After the measurement, rotate the sample paper 90° and measure again, measure 3 times in total, record the value on the "-logT" scale line each time, and calculate the average value as the final result.

Hardness test

Test equipment

Microhardness tester (magnification not less than 200 times, resolution not less than 0.1μm).

Test steps

Take a section of the lead core with the highest and lowest tip stress as the sample. Use a core grinding fixture to grind the end surface of the sample flat on metallographic sandpaper, and observe it under the measuring microscope of the microhardness tester. The fineness of the end surface texture of the sample is the standard.

Select the load and set the load holding time to 10s.

Clamp the sample lead on the fixture and adjust its position.

The longer diagonal direction of the indentation shall prevail.

Press the load button to load the specimen and hold it for the selected time.

Eliminate the indentations with large and small head defects. Load each section of the sample 5 times, and move the position of the sample relative to the indenter after each loading.

Adjust the workbench and reading knob, and observe through the eyepiece to make the reference line and measuring line in the field of view of the measuring microscope tangent to the longer diagonal line of the indentation.

Note the value k of the reading knob, and when the magnification is 200 times, calculate the length of the longer diagonal line of the indentation.

Take the three closest values ​​of the diagonal length of the indentation in the five tests and calculate the average value. If the difference between the three values ​​exceeds 10μm, the test should be repeated.

Calculate hardness according to the formula

The calculation result is accurate to an integer.

Lightfastness

Instruments and Materials

• The light fastness tester that complies with GB/T8427 is recommended to use an irradiance of (42±2)W/m2 (wavelength of 300nm~400nm) or (1.10±0.02)W/(m2·nm) (wavelength of 420nm).
• Rating light box using D65 (artificial daylight) light source.
• Blue wool standard sample that conforms to GB/T8427.
• Gray scale for evaluating color change in accordance with GB/T250.
• 200g/m2~250g/m2 lead drawing paper.
• Light-proof covering (thin steel sheet, aluminum sheet, or cardboard covered with aluminum foil, etc.).

Test steps

Place the lead drawing paper on a hard flat surface, and use a test pen to repeatedly and evenly paint a square color block with a side length of 50 mm in the left and right and up and down directions as a sample.

Put the sample and the grade 2 blue wool standard sample on a special rack, and cover the sample and 1/2 of the blue wool standard sample with an opaque cover. Put them in the light fastness tester for exposure. When the color difference between the exposed part and the unexposed part of the blue wool standard sample is obvious, and the gray sample card for color change is rated at grade 2, the exposure is terminated. Take out the sample and the blue wool standard sample and put them in a dark place for 30 minutes, and then perform the rating.

In the rating light box, compare the fading degree of the sample with the corresponding fading degree of the blue wool standard sample. If the fading degree of the sample is less than or equal to the fading degree of the blue wool standard sample, the light fastness is in compliance, otherwise it is not in compliance.

Lead diameter, pen diameter and pen length test

Test gauge

• Micrometer with a resolution of not less than 0.01 mm.
• Vernier caliper with a resolution of not less than 0.02 mm.
• Steel ruler with a resolution of not less than 0.5 mm.

Test methods

Use a steel ruler or vernier caliper to measure the length of the pen. Use a micrometer to measure the lead diameter and a vernier caliper to measure the pen diameter. Measure 3 points on each lead or pen and find the average value as the final result.

Sliding core test

Test equipment

Sliding core tester (the diameter of the ejector pin is selected according to the hardness mark, tolerance: ±0.05mm).

Test steps

6B~B graphite pencils use a 1.3mm diameter thimble, HB~9H graphite pencils use a 1.5mm diameter thimble, colored pencils

Use a 2.0 mm diameter ejector pin. Place the test pen vertically on the groove of the slide core tester, align the lead core at one end with the ejector pin, apply a load of 39.2N to the ejector pin, and observe whether the lead core moves in the rod.

Eccentricity test

Test equipment

• A measuring microscope with a resolution of not less than 0.01 mm or a measuring instrument with a resolution equal to or higher than that.
• Digital vernier caliper with a resolution of not less than 0.01mm.
• Special fixture.

Test steps

Fix the pen shaft with a special clamp, use a measuring instrument to measure the thinnest part of the pen shaft as the eccentricity, and measure the lead core diameter. Use a digital vernier caliper to measure the pen shaft diameter along the axis at that point, and calculate the eccentricity base according to the formula.

Checks whether the eccentricity is greater than or equal to the eccentricity base.

Leather head tensile test

Test equipment

• Tensile force gauge or heavy hammer type tensile force gauge.
• Stopwatch.

Test steps

Fix the test pen on the clamp of the tensile tester (device), clamp the leather head with the clamping claws, add a load of 9.8N to the leather head, start the stopwatch, keep it for 10s, and check

Check whether the leather head and aluminum hoop are falling off.

Pen coating test

Test equipment

• Constant temperature drying oven.
• refrigerator.

Test steps

Place the test pen in a constant temperature drying oven at (45±2)℃ for 30 minutes, then take it out and place it in the test conditions specified in Chapter 6 for 30 minutes. Then put the test pen in a plastic bag, tie the bag tightly, put it in a refrigerator at (-10±2)℃ for 30 minutes, then take it out and check whether the pen coating has fallen off or cracked.

Penholder bonding strength test

Immerse the test pen in (30±2)℃ water for 1 hour and then take it out. Twist the two ends of the pen in opposite directions with both hands to check whether the pen has come apart.

Rod core break test

Use a blade to scrape off the coating at the seam of the test pencil, remove the leather tip and aluminum hoop of the leather tip pencil, then put the test pencil into boiling water until the glue breaks, and check whether the lead core is broken.

Appearance test

Use a pencil sharpener or pencil sharpener to sharpen a test pen and check whether the sharpened surface is smooth.

Visual inspection under 200lx~250lx illumination.

Marking and packaging requirements

Logo

Each pencil should be marked as follows:

a) The name of the manufacturer or its abbreviation or trademark;

b) Product model (except for sets of colored pencils);

c) Graphite pencils should have hardness markings.

The pencil sales package should have the product name and trademark, product model, implementation standard number, number of pencils, manufacturer name, address, quality grade and other marks. Ordinary products are allowed not to be marked with quality grade, and high-quality products should be marked with "high-quality products". Pencils used by students aged 14 and below should comply with the marking regulations of GB21027.

The pencil transport packaging should have the product name and trademark, product model, implementation standard number, manufacturer's name, address, quality, volume, quantity of products inside, production date or batch number and other marks.

Various signs should be clear and obvious, and the graphic signs on the transport packaging should comply with the provisions of GB/T191.

Package

The sales package should be accompanied by a product certificate or conformity mark.

The packaging materials of transport packaging should be adapted to the needs of long-distance transportation.