What are the characteristics of 3D printing resin materials?

Although SLA resin is similar to general light-curing resin in main composition, similar to paint before curing and similar to general plastic after curing, but the uniqueness of SLA process makes it different from ordinary light-curing resin.

The manufacturing of prototype parts by SLA technology requires fast and accurate, and the precision and performance requirements of the parts are relatively strict, and it requires easy operation in the molding process.

SLA performance requirements are special and should generally meet the following requirements:

The viscosity of the resin before curing, photosensitive properties, the accuracy of the material after curing and mechanical properties.

So this material must have the following characteristics.

(1) stable performance before curing, easy to transport, storage, basically no dark reaction occurs

The photosensitive resin used for SLA is usually not taken out once injected into the resin tank, and will be added later with the continuous consumption in use.

Therefore, the use time of the resin is generally very long, i.e., the resin is required not to undergo thermal polymerization under normal circumstances, and it should have high stability to visible light. In order to ensure the stable performance of the resin during the long molding process.

(2) Low viscosity

The SLA manufacturing process is a layer-by-layer molding process. When a layer is completed, the surface tension of the liquid makes it difficult for the resin to automatically cover the surface of the cured layer.

Therefore, it is necessary to use automatic squeegee to scrape and coat the resin surface once after one layer is made, and only after the liquid surface is leveled and stabilized can scanning be performed, otherwise the parts will have defects.

Therefore, the viscosity of resin becomes an important performance indicator. Under the condition that other properties remain unchanged, the smaller the viscosity of resin, the better.

(3) Small curing shrinkage

The main problem of SLA is the manufacturing accuracy, the shrinkage during molding will not only reduce the accuracy of the parts, but also lead to warpage, deformation and cracking of the parts.

In serious cases, the part will be moved by the scraper during the molding process, resulting in complete failure of the molding. So the resin used for SLA should try to use a smaller shrinkage of the material.

(4) A high degree of curing

Some SLA resin can not be directly applied after the parts are made, need to be cured in the UV box, but the curing process is impossible to ensure that the light intensity received in all directions and on all sides of the same. This will make the overall deformation of the parts, seriously affecting the accuracy of the parts.

(5) Small swelling

In the molding process, the curing product is infiltrated in the liquid resin, if the cured material swells, it will not only affect the strength of the part, but also make the cured part swell and produce the overflow phenomenon, which seriously affects the accuracy.

After forming the surface of the part has more uncured resin needs to be cleaned with solvent, when washing, we hope to remove only the uncured part and the surface of the part is not affected, so we hope that the cured material has good solvent resistance.

(6) Fast curing speed

The wavelength of 355 nm light has a larger absorption and faster response rate.

SLA generally use UV laser, laser energy concentration can ensure that the parts have a high degree of accuracy, but the laser scanning speed is very fast, generally greater than 1m / s. So the action of light on the resin is extremely short, the resin only for the wavelength of light has a greater absorption and faster response speed, in order to quickly cure.

(7) High strength of semi-finished products

To ensure that the parts in the post-curing process does not deformation, expansion, no bubbles and layer separation.

(8) Cured products have better mechanical properties

such as higher fracture strength, impact strength, hardness, resistance to chemical reagents, easy to wash and dry, and have good thermal stability.

Among them, precision and strength are two of the most important indicators of rapid forming, the strength of rapid forming parts is generally not high, especially SLA parts, generally brittle before, it is difficult to meet the requirements as a functional part, but in recent years some companies have also introduced toughness and strength of higher materials.

(9) less toxic

The use of toxic oligomers, monomers and photoinitiators should be avoided as much as possible to protect the health of operators and avoid environmental pollution.

The future of rapid prototyping can be done in the office, so it is more important to consider this point when designing formulations.

The above 9 points are the characteristics that a well formed 3D printing photosensitive resin material should have.