Injection molding techniques are reigning the world of plastics. Various other procedures are used to add value to the finished product. Laser marking on plastic injection molded parts is one of them.
Using laser marking within the plastic molding manufacturing operations has multiple advantages. The article will take you through some key benefits of using laser marking systems, the list of ideal plastics and the popular laser marking techniques being used in the industry.
Benefits of Laser Marking
Laser marking systems bring in multiple advantages for industries which use them along with their injection molding operations.
Following is the list of key benefits offered by laser marking techniques:
- The tooling equipment gets less wear and tear. This is because there is no contact with it. The process instead uses focussed laser beams.
- The process is more efficient due to its ability to reach difficult (hard to access) areas. As an example, engraving on convex and concave designs can be difficult to achieve using standard techniques. However, the ability of laser beams to reach all areas makes it extremely easy.
- The process provides sharp resolution due to the precision of the technique. The accuracy of results makes it a very trusted technique for use in essential part making and marking.
- Superior production speed can be achieved as compared to conventional engraving methods. This means that the process is both time saving and cost efficient.
- There is no need for “last step hand polishing” of plastic parts. This is because the laser marking process results in smooth surface materials which do not require any further polishing.
- Laser marking is considered as an eco friendly process. This is because the technique does not result in any toxic by products that are seen in conventional techniques. The use of laser beams for engraving makes the process completely free of waste products and hence environmentally safe.
Ideal Plastics for Laser Marking
Laser marking technology offers an impressive versatility when it comes to choosing materials for engraving. However, laser etching can sometimes be difficult for certain types of plastics. That said, it can still be achieved by changing the laser parameters being used for the marking process.
It is important for a laser beam to burn only the top surface layer of the plastic to achieve optimum contrast levels. This is often accomplished by reducing the power of the laser. Laser beams of low frequency are moved at high scan speed to get the results. Any defect in the laser frequency, scan speed or the power used can easily melt the material resulting in poor contrast.
Laser engraving can be applied to various plastic resins like:
- ABS (Acrylonitrile Butadiene Styrene)
- Polyethylene (including Low Density Polyethylene (LDPE) and High Density Polyethylene (HDPE))
- Glass filled plastics
- Polycarbonate
- Various other plastics
Laser Marking Techniques
Several common laser marking techniques are employed by plastic injection molding operators to get the desired results on their essential plastic parts. Each technique has its own pros and cons. It is hence important to choose a technique based on the type of material being used and the type of engraving being considered.
Following are some commonly available techniques:
Laser Marking
This technique involves the use of a laser beam to discolor the surface of the plastic material. The surface is discolored to a shade of black or dark grey in the form of the chosen graphic or text. Marking is achieved by moving a low powered laser beam on the surface of the plastic material through the discoloration process that creates high contrast marks.
While some oxidation also occurs beneath the surface layers, the finished product remains smooth and undamaged with an intact surface.
Four common types of laser marking technologies in use are:
- Annealing- Oxidation process wherein heat is applied to the plastic surface creating a black mark with a smooth finish.
- Carbon migration- The process is more commonly used for metals and metal alloys where the surface is heated to create chemical bonds within the molecules. The bonding results in dark black laser marking.
- Foaming- This technique is most commonly used in plastics. The process produces light markings. Hence, the technique is highly suitable for plastics where the material is darker and the effective markings are light colored.
- Coloration- This technique is used for both metals as well as plastics. Using controlled laser beams on the surface with variations in pulse, speed and width results in multiple colors and hues.
Laser marking technique is best suited for bar codes, logos, ID codes, etc.
Laser Engraving
Laser engraving involves physical removal of a section of the plastic surface using the laser beams. The removal of some part of the material hence results in a cavity which comes in the form of a graphic or text as desired.
Due to the high level of heat being generated by the laser beams, the selected portion (text or graphic) gets immediately vaporized on contact.
Depending on the type of surface and the extent of surface removal required, laser engraving has the following subsets:
- Etching
- Deep laser engraving
- Laser ablation
Laser engraving a very fast way of marking using laser beams and is commonly used for marking serial numbers, company logos, etc.
Laser Etching
The process of laser etching is similar to engraving or rather a part of it. Laser etching is conducted by melting the plastic surface (on the areas marked for engraving) which then expands and creates a raised marking on the plastic surface.
Foaming
Foaming is also known as color change technique. This technique utilizes the controlled burning of the plastic surface.
This results in a smooth surface finish after the marking and leaves behind a mark (white, black/dark grey or tan colored) on the surface of the plastic
Final words: Irrespective of the type of industry that you represent, marking and identification of parts is extremely critical to its operations. Laser marking technology is one of the most versatile innovations in the world of engraving.
Laser marking of plastics is an art. The process is delicate and requires careful adjustment of multiple parameters to achieve the right levels of accuracy and contrast. The balance of power, frequency and scan speed to create the correct amount of heat on the plastic surface needs high levels of expertise.
