VR202 - IGP Coating Powder
Coarse-Grained Structures and Hammered Effects
Introduction
This type of coating powder creates surfaces with a relatively coarse, rough, and much more textured structure.
The structure intensity and characteristics depend largely on the coating thickness applied (a thin coating produces finer structures, thick coats produce coarser structures).
These surface characteristics make specific demands of the coater. This Processing Instruction VR 202 was prepared in order to provide users with assistance in fault-free processing of IGP coarse structures and hammer
effects. As IGP hammer-effect powders contain effect particles, they are also classified in the five processing categories. The stars on the label of your powder coating container indicate the processing class of your product.
Project organization
One batch, one application facility
If the components are installed directly adjacent to each other, we recommend determining the required powder amount for the entire order and planning a certain reserve in order to coat the entire application with a single production batch. This minimizes color and effect differences when coating the entire order.
Processing one order in different cabin types should be avoided. Do not make any changes to the coating plant processing or application parameters when processing a single consignment. If you determine that plant
data / application parameters are ideal, document and observe them without fail. This procedure and the parameter settings must also be observed for follow-up orders.
To ensure you achieve the required structure formation, we recommend creating limiting samples before starting the work. Use the limiting samples throughout the entire production to monitor structural characteristics, gloss, and shade. If you coat complex geometries, it may be additionally necessary to coat a mockup in order to ensure a consistent surface characteristic.
Substrate pre-treatment
When coating with structure powders, clean the metal substrate especially thoroughly. Any residues of oil, grease, graphite, or welding agents cause problems resulting in different surface tensions which are visible as large areas of dark contamination on the surface. These residues can also prevent the formation of structure patterns.
Processing groups
The structure characteristic depends largely on the coating thickness. Therefore, during the coating process, ensure a constant coating thickness distribution as far as possible. For an attractive surface characteristic and sufficient opacity, we recommend average coating thicknesses of at least 90-110 μm.
However, the above coating thicknesses can not guarantee complete opacity on the substrate in the case of pale, red, yellow, and orange shades. To ensure opacity on the substrate, we recommend pre-coating with the required shade (2-coat method).
Structure fluctuations are caused above all by edge greasing (coating too thick) or coating that is too thin on inner edges. To prevent edge greasing, we recommend adjusting the high-voltage settings, the lifting movement, and the prespray and respray of the pistols as accurately as possible to suit the workpiece. As the lifting and prespray and respray are strongly influenced by the component geometry and the arrangement of the coating pistols, it is not possible to give any general recommendations here.
For the high voltage, we recommend a setting of 60-80kV. You can also reduce edge greasing by limiting the current to approx. 20 μA. In some cases, after checking the result, you can also use ion-leakage rings.
If the part geometry (deep internal angles) makes it impossible to achieve an even coating thickness, additional manual coating is necessary. You can do this in the form of pre-coating or follow-up coating. Complete manual coating is possible, however you must ensure even coating in this case.
Recycling
Single-color coarse-structure powder coatings are generally suitable for recycling. After first checking the shade, you can also process hammer effect powder coatings with a certain share of recycled powder. In this case, take note of the table below. You must especially ensure thorough cleaning of the entire coating plant. That means thoroughly cleaning the pistols, hoses, powder cabins, etc. before using the coarse-structure powder and again when you change back to other powder types.
When you change from a smooth-finish coating powder to a coarse-structure powder, you must prevent contamination of the structure. Contamination of a coarse-structure powder with smooth-finish coating powder of a different color is especially visible. The reason for this is that, during the melting phase, the contaminating particles of the smooth-finish powder spread out on the structured substrate so that the particle size increases by a factor of 5-10 of its original size.
When you change from coarse-structure powder to smooth-finish coating powder, it is important to avoid surface impairments such as craters, pin-holes or poor flow. Coarse-structure powders contain structure-forming agents which can cause the above problems even in small quantities.
Without fail, thoroughly flush the powder hoses with the new powder after changing between powders (spray the powder in the empty cabin). Additionally, you can reduce flow or cross-linking problems if you use a fine-structure powder before and after the coarse-structure product.
If the contamination of the powder persists even after you have thoroughly cleaned and flushed the powder hoses, it may be necessary to install separate powder hoses in the cabin specifically for coarse-structure powders. Then you must change the hoses every time you change the powder. Depending on the system manufacturer, this is possible in just a few moves.
Plant maintenance and cleaning
To ensure the coating plant achieves reproducible coating results, the maintenance work for replacing parts subject to wear in the entire plant must be performed at the specified intervals, as recommended by the manufacturer. Various functional tests, e.g. checking the high voltage, must be carried out at regular intervals.
Suspension of the parts
The suspension of the parts (horizontal or vertical) must be determined prior to coating. The intermediate spacing between the coating objects within the hangers as well as the spaces between the hangers must be kept as small and regular as possible. If there are large distances between the hangers, it is advisable to automatically switch the guns on and off via a parts detection system. Furthermore, ensure as far as possible that similar parts are always coated together.
Curing
Depending on the mass of the workpieces to be coated and the temperature control in the stoving oven, different and uneven structures can result from the melt viscosity and reaction time.
Matt structured coatings only achieve the required surface and gloss values if they are cured according to the instructions. If the curing time is too short or the temperature too low, this results in surfaces with too much gloss and insufficient mechanical properties. If the curing time is too long and the temperature too high, this can lead to yellowing and surfaces that are too matt.
To prevent problems due to uneven heating of the components, avoid different curing temperatures and do not simultaneously cure thickwalled and thin-walled parts. Observe the recommended range of curing conditions without fail. To ensure the right quality, we recommend measuring the oven temperature when you create the limiting sample.
Grounding
Just like coating with all powder coatings, you must make sure of sufficient grounding when applying coarse-structure and hammer-effect coatings. This helps ensure an even deposit of the powder onto the workpiece and a homogeneous structural characteristic.
Other applicable documents
Observe the relevant technical data sheets of the product groups.
Recommendations for processing IGP coarse-structure and hammer-effect products
The values stated here are recommended values. When processing IGP coarse-structure and hammer-effect powders, you must adjust the processing parameters of the coating plant to the product to be processed.
** Processing category of the effect products according to TI000
** Processing category of the effect products according to TI000
Recycling
Single-color products can generally be processed in recycling mode. However, continuously adding fresh powder is strongly recommended. Group A speckle products (LivingSurfaces product group) can be processed in recycling mode. To achieve stable and even surface characteristics, small amounts of recycled powder amounting to approx. 15% should be added to the fresh powder (automatically where possible).
For Group B pearl mica products (LivingSurfaces product group) and for hammer effects (Mica-Bond effects of category **), we recommend processing in loss mode to achieve stable and even surface characteristics. After checking the shade, you can proceed in recycling mode. For this, constantly check the shade and structure while adding recycled powder not exceeding a share of 15% to the fresh powder (automatically where possible).
We recommend first making limiting samples.
Suspension of the parts
The suspension of the parts (horizontal or vertical) must be determined prior to coating. The intermediate spacing between the coating objects within the hangers as well as the spaces between the hangers must be kept as small and regular as possible. If there are large distances between the hangers, it is advisable to automatically switch the guns on and off via a parts detection system.
Curing
Depending on the melt viscosity, the temperature management in the stoving oven and the mass of the coated component may cause a change in the effect (visually apparent as a difference in shade). This means that varying curing temperatures and heating speeds must be avoided. Furthermore, thick and thin-walled parts must be coated separately.
Resistances and technical data
This information can be found in the respective data sheets.
