The gravelometer machine uses compressed air to spray gravel or other media onto the test sample, simulating the different degrees of damage caused by the impact of stone and sand on the surface of the car’s exterior trim during road driving. Through the gravel impact simulation, the test piece is subjected to different degrees of impact (various gravel types, air pressure requirements, impact time, temperature treatment, etc.) to investigate the adhesion of the coating.
Gravelometer testing equipment is suitable for cohesive failure tests of outer coatings, cohesive failure tests between different layers in coating systems, brittle thickness of hard glass materials, optimal film thickness for resistance to peeling, peeling resistance of plastics and glass , Anti-collision, anti-wear tests and other related tests. It is one of the important tests for automobile inspection by mainstream automobile manufacturers in the world today｜Gravelometer Testing for Car’s CoatingThe Multi-Test Gravelometer is mainly used in the automotive industry to carry out corresponding detection tests on the coatings of automobile shells. It is a comprehensive evaluation of the mechanical properties of the entire coating system. The Gravelometer machine can reflect the flexibility of the coating, the adhesion between the layers and the compatibility, and it is also one of the most important testing items for evaluating the secondary mechanical properties of the coating.
| Equipment Model | DIN-ISO-VDA-Gravelmeter | ASTM-SAE-Gravelmeter | ASTM-SAE-Gravelmeter-30℃ |
| Circulation Time | 0 ~ 30 Seconds | 0 ~ 30 Seconds | 0 ~ 30 Seconds |
| Machine’s Real Photo | Photo of Gravelometer 1 | Photo of Gravelometer 2 | Photo of Gravelometer 3 |
| Spray Times | 1 ~ 5 Times | 1 ~ 5 Times | 1 ~ 5 Times |
| Air Flow Range | 0 ~ 0.08 m3/S | 0 ~ 0.08 m3/S | 0 ~ 0.25 m3/S |
| Working Pressure | 0 ~ 3 Bar ±0.5% | 0 ~ 1.0 Mpa ±2.0% | 0 ~ 6 Bar ±1.0% |
| Air Groove Volume | 136 Liters | 136 Liters | 180 Liters |
| Temperature Range | +5℃~ +60℃ | +5℃~ +60℃ | -30℃ ~ +60℃ |
| Spray Time | 8~12 Seconds, 500g | 30~35 Seconds, 2000g | 30~35 Seconds, 2000g |
| ID of Shooting Barrel | 30.0mm ±0.50 mm(VDA) | 52.6mm ±0.75 mm (SAE J400) | 52.6mm ±0.75 mm (SAE J400) |
| Spray Distance | 10 ~ 500 mm | 10 ~ 500 mm | 10 ~ 500 mm |
| Nosie Level | 130 dB | 130 dB | 85 dB |
| Power Voltage | AC220V, 50Hz, 1.5 kW | AC220V, 50Hz, 1.5 kW | AC380V, 50Hz, 3 Phase |
| Max Test Specimen | W105mm*D20mm*L150mm | W105mm*D20mm*L150mm | W195mm*D35mm*L240mm |
| Impact Media | Gravel and Steel Pellets, 500g | Gravel and Steel Pellets, 500g | Gravel and Steel Pellets, 1000g |
| Ambient Temperature | +5 ~ +35°C | +5 ~ +35°C | +5 ~ +35°C |
| Sample Placement Angle | VDA: 90°, 45°, 25° | SAE: 90°, 45°, 40° | SAE: 75°, 54°, 45° |
| Relative Humidity | 30% ~ 85% RH | 30% ~ 85% RH | 30% ~ 85% RH |
| Exterior Dimensions | W1800*D500*H1250mm | W1800*D500*H1250mm | W2000*D3250*H1850mm |
| Equipment Weight | 145 KGS | 155 KGS | 1850 KGS |
How does the Gravelometer work? The Gravelometer machine is specially designed for the gravel impact test of automotive materials and surface coatings. Use a certain weight of gravel or pebbles to simulate the impact of sand and gravel on the coating surface during driving. It is ejected into the chute feeder by vibration, and then sprayed by jet air to test the paint sample to be tested. After the media hits the paint sample being tested, the media falls into the gravel collection box. This test is used to assess the coating’s resistance to stone impact.
Depending on the test standard, a large number of small steel shot or gravel with sharp edges can also be used to hit the surface of the paint sample in a short time. The whole test is carried out under controlled temperature. After the gravelometer test, use adhesive tape to remove the loose coating to reveal the stone chip marks remaining on the sample plate, and judge the quality of its stone chip resistance by analyzing the degree of damage of the coating｜Structure of Gravelometer Machine
The Multi-Test Gravelometer is assembled from standard parts, and is equipped with easy-to-load accessories: gun assembly, collision box, sample device fixture, feeding funnel device (including vibrator), electric control system, air compressor ( optional) composition. Gravelometer can quickly load and unload test pieces and is equipped with an external gravel collection box, which is convenient and practical. Each part belongs to standard parts and can be assembled and used together. Quick loading and unloading convenient and practical Can meet all major automotive material peeling tests→ Note: Due to the differences in the conditions and technologies required by different standards, the same gravel impact tester for VDA and SAE experiments cannot meet the requirements at the same time.
Depending on the test standard, a large number of small steel shot or gravel with sharp edges can also be used to hit the surface of the paint sample in a short time. The whole test is carried out under controlled temperature. After the gravelometer test, use adhesive tape to remove the loose coating to reveal the stone chip marks remaining on the sample plate, and judge the quality of its stone chip resistance by analyzing the degree of damage of the coating｜Structure of Gravelometer Machine
| 6.1.1 There are two methods available for determining the degree of chipping from gravel on the tested panel (other media will require other evaluation methods.) | 6.1 Test Methods Available → SAE J400 | |
| ln Method I, the exact number of chips in each sizerange is tabulated for the specified test area, while Method II utilizes a visual comparison of the tested panelwith the SAE Chipping Rating Standards shown in Figure 3 which depict various degrees of chipping severityand are arranged sequentially from best to worst according to chipping size and frequency. | ||
| Method I is the most precise and should be used where definitive accuracy is required or as the refereemethod in case differences arise between laboratories; however, it is more time-consuming than the visualcomparison method. | ||
| Method II is much faster and while more of an approximation than the first method, can be used for manyroutine laboratory evaluations where the accuracy of Method l is not required. Method ll also lends itself tofield survey work where the chipped areas can be rated by direct comparison with the chipping RatingStandards. | ||
| 6.1.2 With both methods, the chipped area to be evaluated on the tested panel should be the 10.16x 10.16 cm (4 x 4 in) square that exhibits the center of the chipped pattern. | ||
| Generally, the basic structure of the chip rating system consists of oneor more number-letter combinations in which rating numbers 10-0 indicate the number of chips of each sizeand rating letter A-D designate the sizes of the corresponding chips. A point of failure notation may also beincluded in the rating if more descriptive refinement is desired. | 6.2 Basic Structure of Rating System → SAE J400/ ASTM D3170 | |
| A whole rating number selected from the range of 10-0 in Table 1 is used to indicate thenumber of chips of each size in the 10.16 x10.16 cm (4 x 4 in) test area. | 6.2.1 NUMBER OF CHIPS | |
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| The size of the chip is specified by a rating letter selected from A-D in Table 2. Due to theirregular nature of chipping, the size cannot always be measured exactly so it has to be approximated. | 6.2.2 SIZE OF CHIPS | |
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| The coating layer at which the most predominant chipping failure occurs is designated as the point of failure. The notations in Table 3 can be used to designate this information if desired. Othernotations may be used with agreement between contractual parties. | 6.2.3 POINT OF FALURE | |
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| ► 1. Stick the tape on the surface of the sample coating (if it is a sample treated at low temperature, it needs to be returned to room temperature and then wipe off the condensed water with a dry cloth), and use uniform force to make it stick to the sample surface and avoid Air bubbles, then pull the tape up. | Chips Evaluation Method → SAE J400, ASTM D3170 | |
| ► 2. Use a new tape to stick to the surface of the sample coating, use uniform force to make it close to the sample surface and avoid air bubbles, and pull the tape from the opposite direction to ► 1. | ||
| ► 3. Repeat 1, 2 until the damaged coating is completely peeled off. (Except for electroplating parts, bubbling is regarded as damage point) | ||
| ► 4. Evaluated by the number of points method of Method I. Judge as follows: | ||
| ►5. Cover the sample with a transparent grid, count the number of coating damage points (except impact marks) in the area of 101.6mm × 101.6mm and confirm the size of the area, and grade according to above Table 1 and Table 2, And write down the damage form according to Table 3. | ||
| The advantage of the Gravelometer chip tester is that the obtained results have good repeatability and comparability, Feed rate is adjusted by electromagnetic vibrating feeder. | Equipment Features |
| The flat test sample angle can meet the setting requirements of 20°, 40°, 45°, 54°, and 90°, and the irregular sample adopts a 3D test box. | |
| A large volume storage compressed air tank keeps the pressure and flow rate constant, and the pressure can be controlled by the regulating valve at the spray gun. Multi-function display can display working pressure, test time, vibration frequency and impact times (Total/Current). | |
| Multiple tests can be completed in a short time by means of continuous or intermittent operation. The test spray gun can be changed freely and quickly. It meets the requirements of VDA and SAE and other standards. | |
| Safety Protection Measures: safety power-off device, air pressure safety value protection device, in line with European CE and EMC certification. |
ISO 20567-1 “Paints and Varnishes – Determination of Stone-Chip Resistance of Coatings – Part 1: Multi-Impact Testing” formulated by the Standardization Organization (ISO) is derived from the German industrial standard DIN 55996-1: 2001 “Paints and Varnishes – Determination of Stone-Chip Resistance of Coatings – Part 1: Multi-Impact Testing”, Therefore, in Europe, the German Standardization Association, the French Standardization Association and the Austrian Standardization Association all cited this standard to establish their own national testing standards.
For example, the standard adopted by German automobile companies is DIN EN ISO 20567-1 “Paints and Varnishes – Determination of Stone-Chip Resistance of Coatings – Part 1: Multi-Impact Testing”. The test equipment is the 508 model Gravelometer machines of Germany Erichsen Company. Please refer to the table below for the size and model selection of different test media such as chips and gravel used in the test.
For example, the standard adopted by German automobile companies is DIN EN ISO 20567-1 “Paints and Varnishes – Determination of Stone-Chip Resistance of Coatings – Part 1: Multi-Impact Testing”. The test equipment is the 508 model Gravelometer machines of Germany Erichsen Company. Please refer to the table below for the size and model selection of different test media such as chips and gravel used in the test.
| Chips Gravel Types | Ink Road Gravel (Cobblestone) | Chilled Cast Iron Gravel | #6 Granite Stone | #7 Granite Stone |
| Size of Chips Gravel | 9.5~15.9 mm | 4.0~5.0 mm | 4.8~14.3 mm | 3.2~9.5 mm |
| Testing Standards | SAE J400 GMW 14700 ASTM D3170 GM 9508P DIN 55996 ISO 20567 | FLTM BI 157-06 FLTM BI 107 PSA D24 1312 | NES M0141 NES M0007 | NES M0141 NES M0007 |
The SAE J400 “Surface Vehicle Recommended Practice Test for Chip Resistance of Surface Coatings” formulated by the Society of Automotive Engineers (SAE) is mostly adopted by automobile companies such as General Motors and Ford in the United States. The anti-stone impact method adopted by Japanese automobile companies is similar to SAE J400 “Surface Vehicle Recommended Practice Test for Chip Resistance of Surface Coatings”, but it is different in the specifications of crushed stones, test temperature and evaluation methods. Because there are many joint ventures with Japanese automobile companies in China, the stone shooting method of JIS is also relatively common.
Here are two test examples to let you understand how to carry out the test of spraying pebbles or steel sand. Wear protective goggles and noise-proof earphones before the experiment. Then connect the air tank and the Gravelometer Machine’s power source. According to the test standard, select the impact box (angle-adjustable impact box or 3D impact box), if you choose the angle-adjustable impact box, adjust the impact angle according to the standard requirements. For example, 45°, 54° or 90°
Here are two test examples to let you understand how to carry out the test of spraying pebbles or steel sand. Wear protective goggles and noise-proof earphones before the experiment. Then connect the air tank and the Gravelometer Machine’s power source. According to the test standard, select the impact box (angle-adjustable impact box or 3D impact box), if you choose the angle-adjustable impact box, adjust the impact angle according to the standard requirements. For example, 45°, 54° or 90°
| Before the test starts, the sample is placed in the environmental chamber to reach the required test temperature and kept for at least 15 minutes. | Method A: Spraying Pebbles (SAE J400 Requirements) | |
| Video Guidance for Gravelometer Installation Teaching and Training | ||
| After taking it out, it is immediately installed on the gravel impact testing machine for stone impact. | ||
| After the impact is completed, the damage point of the sample paint film is evaluated according to SAE J400 The area, depth, and measure the diameter of the damaged point. | ||
| SAE Gravel System Evaluation Card｜Gravel Impact Test Card | ||
| Step 1: Set the air pressure of the test to 2 bar, and impact 2 kg of steel sand within 30 to 35 seconds. | Method B: Spray Steel Grit | |
| Step 2: Immerse the tested sample in water at a temperature of 40°C for 72 hours, then take it out and repeat step 1 within 1 hour. | ||
| VDA Standard Gravel Impact Rating Card｜Gravel Impact Test | ||
| The post-test evaluation is carried out, and the coating damage (paint film damage rate) grade is evaluated by comparing the coating damage level diagram in SAE J400 with the sample surface after the test. | ||
| Video Guidance for Gravelometer Installation Teaching and Training | ||