With the characteristics of high strength and hardness, good wear resistance and corrosion resistance, high dimensional accuracy, high material utilization rate and small subsequent machining work, die casting aluminum is widely used in LED industry, such as street lights, flood lights, tunnel lights ,downlights, etc. Especially in the integrated design of LED outdoor lights (the shell is not only used for heat dissipation but also the carrier of other parts) , it is popular.
1,Classification from the casting methods: Die castings are the most widely used in lighting, followed by sand castings, metal castings and a small amount of investment castings. 2,Classification from the casting materials: Aluminum castings are the most widely used in lighting, followed by czinc alloy castings, copper alloy castings and a small amount of steel and stainless steel castings.
1, Some non-exposed aluminum and zinc castings are mostly with rough or sanded surfaces, sometimes will do chromated treatment to increase corrosion resistance. Copper and steel castings mainly use rough surfaces, because it mainly plays the role of structural force and does not affect the appearance. Copper castings are sometimes treated with phosphating to improve corrosion resistance. Chromization, passivation and phosphating are sometimes also used as pretreatments for post-treatment. 2,The castings with exposed surfaces are mainly polished, sanding, decorative anodizing, powder spraying, spray painting, electroplating and other relatively beautiful surface treatment for different materials when applied to indoor lights. 3, When the exposed surface of the outdoor lights is made of aluminum die casting, it mainly adopts the surface treatment of powder spraying and painting. The surface of copper and stainless steel castings is mainly polished and vibrated. Sometimes, in order to be consistent with the surface of other parts, the surface treatment of powder spraying and painting can also be used.
1,The dimensions of the castings must be inspected when the mold is confirmed to ensure that qualified molds are used for production.In order to ensure the correctness of the dimensions in each batch of production, the dimensions including fitting size, tolerance and size of the post machining that may vary when production needs to be triple checked. For the matching size, it needs to assembly and check whether appropriate. 2, Regarding the shape and position tolerances, the requirement of most casting parts used in lights are not too strict. Generally, the flatness tolerances need to pay more attention and other shape and position tolerances are not so strict. Of course, for some precise stage light parts, the requirements of flatness, parallelism,verticality coaxiality and other tolerances are relatively strict and need to be controlled during manufacture. Due to the easy deformation of die casting parts, some casting parts need to be calibrated and corrected, or processed by fixtures and CNC machining to meet various requirements. 3, The threading on the casting parts need to be processing by fixture and it requires to guarantee the verticality. At the same time, a tapping machine with relatively high precision will be chosen for processiong. And the screw tapping,drilling rate,tapping speed and whether to add cooling oil should be carried out stipulated in the process. For the sandblasted parts, it will be better to tap the screw after sandblasting to ensure the precision of threading. For the machined threaded hole of parts to be sprayed or painted,it should be protected to prevent powder or dust entering. 4. For the appearance inspection of the casting part, it should not have defects, such as cracks, shrinkage holes,porosity, cold insulantion, pores, bubbles, ballast etc. The pouring risers, flashes, burrs and sharp corners should be removed. Usually, it is neccessary to use 120# or better sandpaper when deburring, so as not to damage the surface of casting parts. For the exposed surface, especially for the surface with electroplating, the apperance should be smooth without any defects and the internal should have no pores to prevent bubbles from bulging during electroplating. For casting parts with powder coating, painting and hand-painted finishing, as long as there are no defects that can’t be covered by coating, it is qualified.Since there is a very thin dense layer on the surface of the casting part, it is usually not necessary to destroy, for it has great benefits to the mechanical properties and surface treatment of the casting parts. 5, Most of the casting parts in lighting is to withstand a certain load, and the material quality also affects the rust protection effect.So most mechanical die casting parts are necessary to do chemical composition analysis, as well as tensile, strength and elongation tests. 6, The powder coated and adhesion of the indoor casting surface must do test 5B, salt spray test and UV protection test. In order to improvde the surface effect, the casting parts need to be sanded or shot blasting before powder coating.
