How we control the quality of ceramic media?
Ceramic media is the key element in surface finishing. Therefore, Inoavtec takes care media quality for each production process. Bellow, we show you how we control ceramic media quality from raw material to ready-to-ship goods.
1. Incoming Material Inspection:
The raw material act as an essential factor to decide media performance. Therefore raw material incoming inspection and testing is our first stage of quality control.
Kaolin is the most important raw material in ceramic media. It takes about 60-80% of the weight of the total raw material. In ceramic media, Kaolin functions as a bonding agent to hold the abrasive. Because of the importance of Kaolin raw material, we have our owned Kaolin raw material mine to control the quality.
The sample is taken from each batch number. If the order quantity is larger then 10 Mt, then we take 1 sample from every 10 Mt raw material.
1. 1 The chemical composition of Raw materials testing should meet the following standard.
Aluminum Oxide (Al2O3) and Silica Oxide (SiO2) is the key index to control, while the other index is for reference.
|Composition||Al2O3 *||SiO2 *||TiO2||Fe2O3||CaO||MgO||K20||Na2O|
Testing device: Panalytical Composition Analyzer (photo)
Panalytical Composition Analyzer
1.2. Size distribution:
Particle Size Distribution D50, it is the value of the particle size at 50% in the cumulative distribution. For example, if D50 = 6.5 um, that means 50% particles are larger than 6.5 um while resting 50% smaller than 6.5 um
Testing device: Malvern Particle Size Analyzer
Testing device: Malvern Particle Size Analyzer (photo)
Malvern Particle Size Analyzer
1.3. Whiteness value
The whiteness value is important for the aesthetic appearance of media. For user and reseller, the appearance of media is the first image to see. When the color is different from one batch to another, they will have a bad feeling of quality control even the performance of media is good.
Test equipment: DN-B Whiteness analysis
DN-B Whiteness analysis
DN-B Whiteness analysis
1.4. Water Content
Water content is another important factor to be controlled in Kaolin. If the water content is too high, it will take a longer time to fermentation and remove water content during the backing process. If the water content is too low, it will affect the mixing process. As a result, the abrasive and bonding agent cannot homogeneously mixed together.
Free water content testing schedule:
Take a certain amount of Kaolin material sample (about 500g), measure as M1. Put the sample in 100 celsius Degree temperature Oven for 2 hours. Then measure the weight as M2. Calculate the moisture content of Kaolin sample：
The moisture content of Kaolin Raw material should be lower than 5%
The raw material sample is reserved for future tracking. To control the quality of the machine, a small sample of each component is served for 6 months.
Sample keep for future quality tracking
2. Raw material prepare:
When the order sends to the workshop, operators in the raw material mixing workshop receive the requirement firstly. They will prepare the raw material according to order quantity to decide the amount of raw material to prepare for each type. Each type of material will be weighted and calculated according to recipe date sheet. The amount of raw material will be double checked by two operators.
Raw material preparing the workshop
3. Material Mixing:
The material mixing process including mixing of bonding agent (kaolin and others) and abrasives.
The mixing process should follow a certain schedule. As each raw material is different particle size and specific gravity, light material firstly transport into mixing tower and heavy material later transport into mixing tower. After mixing of bonding agent, abrasives are added to the pre-mixture. The above process takes place in 30 minutes while stirring not stop. After gradients added, mixing machine continue works another 30 minutes.
Water is consistently adding to the mixture during stirring.
Ceramic media mixing tower
4. Forming and Cutting:
To make a rigid and strong ceramic media, a vacuum system is required to remove air content in ceramic media. The media ceramic is formed into a certain shape with high pressure so the shape and internal structure are compressed. After forming, ceramic rod delivers to an automatic cutting machine and cut at a specified angle according to order requirement. For North America market 22°and 68°is more popular, while still there is some customer prefer 45°. Customers in Europe and Asia prefer 30°and 60°angle cut ceramic media.
5. Drying and Calcination:
Ceramic media need completely remove water content because water is disastrous for ceramic quality. If water content not removed during the drying process, when temperature increase, water will vaporize and ceramic media will crack from the middle in the calcination kiln. Consequently, the whole production batch will be in loss.
The calcination process also called sintering process. It is the most important stage of ceramic media manufacturing. During production, ceramic media keep in high temperature up to 1300 ℃ and stay for 36 hours.
The temperature control is monitored and recorded by computer and keep at least for 6 months for future tracking.
The clean and stable natural gas ensuring consistent and stable production running of the kiln in 24 hours. The calcination kiln temperature is controlled by computer PLC programme with a deviation of ±5℃.
Media calcination kiln with temperature control
6. Self Grinding:
The self-grinding process effectively removes the dirt, wear debris, and small impurities. For ceramic media, self-grinding can round the sharp edge which will hurt delicate workparts. Besides, self-grinding can make the surface smooth and polished.
Self-grinding is required especially for porcelain media and zirconia ball. Because a shiny surface means better a polishing performance.
According to media type and size, we have to make the internal control regulation for media self-grinding time and type of machine to use.
For most ceramic media and plastic media we use vibratory finishing machine to do the self-grinding process. For high demanding high-density media and superfine porcelain media, we use a high energy system.
Tumbling media self-grinding for better surface
7. Visual Inspection:
During the backing process, a small fraction of media is stick together during the backing process. Some of the ceramic media is cracked during transportation. Our experience worker is employed to remove the defect media before packaging.
Those oversize media and undersize will be size out use vibratory sieve machine. The size variation will be precisely controlled in a certain range before shipment.
8. Outgoing Inspection:
Over 10 years experiences in tumbling media manufacturing, we have our experience and reference of wearing and cutting performance of each type of media. The reference coming from media testing result from the different manufacturer, including Rosler and Walther Trowal from German, Washington Mills from the USA, Tipton from Japan.
9. Quality Tracking and Recording System
Two parameters are very important for the customer: wearing rate and cutting rate.
The wearing and cutting rate of media need to be well controlled in a certain range for the specific type of application. Usually higher the cutting rate of metal, higher the wearing rate of ceramic media. The wearing rate and cutting rate of media can be customized with abrasive content, calcination temperature and type of Kaolin used.
The chart for cutting rate is tested according to stainless steel material
Chart of wearing rate tested in centrifugal barrel finishing machine for 2 hours
When the testing result of wearing and cutting is within our reference value, the goods are allowed to ship to make package and ship to the customer. Otherwise, we will keep the goods not ship to the customer and keep it for our own testing laboratory use.