What is the Plastic Injection Mold Polishing process like?
For Plastic Injection Mold Polishing, it is customary to first roughen the surface of the machined Injection mold cavity using coarse oilstone, then use fine oilstone to remove the grinding marks left by the coarse oilstone, and finally fine sandpaper to remove any knife marks from the machining process. To create a bright mirror-like effect, the surface polished by the fine oil stone is polished before the cavity surface of the mold is polished with polishing paste or grinding paste. This is the Plastic Injection Mold Polishing process. For sure, a more effective method of polishing the mold is to use ultrasonic polishing equipment.
The most crucial factor in getting high-quality polishing results is having high-quality polishing equipment and accessories, such as oilstone, sandpaper, and diamond paste.
The surface state following pre-processing, such as machining, EDM, grinding, and other processes, determines the choice of the polishing program. The following summarizes the general mechanics of mechanical polishing.
The most crucial factor in getting high-quality polishing results is having high-quality polishing equipment and accessories, such as oilstone, sandpaper, and diamond paste. The surface state following pre-processing, such as machining, EDM, grinding, and other processes, determines the choice of the polishing program. The following summarizes the general mechanics of mechanical polishing.
The following is the specific Plastic Injection Mold Polishing
Rough Polishing: The surface can be polished by a rotating surface polishing machine or an ultrasonic grinding machine with a speed of 35000–40000r/min after turning, milling, EDM, grinding, and other procedures. The white EDM layer is typically removed with WA#400 and a wheel with a diameter of 3mm. Then it is manually honed using a whetstone, whetstone strips, and kerosene as a lubricant or coolant. The standard usage is #180, #240, #320, #400, #600, #800, and #1000.
The most critical and challenging process is whetstone polishing. The cross-grinding is done in a balanced manner at an angle of around 70° depending on the various specifications of the processed goods. 40–70mm is the appropriate round-trip range. Work done with a whetstone also differs according to the raw material. To save time, a lot of mold manufacturers start with #400 sandpaper.
Semi-fine Polishing: Semi-fine polishing mainly uses sandpaper and kerosene. After the oilstone operation is finished, it is the sandpaper operation. During the sandpaper operation, attention should be paid to the rounded edges, rounded corners, and orange peels of the inserts and cores.
Sandpaper and a hard wooden stick are used for grinding at an angle of about 70° like a whetstone operation, and the number of times of grinding with one side of the sandpaper is about 10 to 15 times. If the grinding time is too long, the grinding force of the sandpaper will be reduced, which will cause unevenness on the machined surface, which is also one of the reasons for orange peel.
Bamboo chips are generally used for grinding in sandpaper operations. In practice, it is ideal to use a wooden stick with low elasticity or an aluminum stick with low hardness for grinding at an angle of about 45°. The grinding surface cannot use rubber or materials with high elasticity, and sharp angles can be used for shapes that cannot be ground at a 45° angle.
The numbers of the sandpaper are as follows: #220→#320→#400→#600→#800→#1000→#1200→#1500. #1500 sandpaper is only suitable for hardened die steel (above 52HRC), not for pre-hardened steel, because it may cause a surface burn of pre-hardened steel.
Fine Polishing: Diamond abrasive paste is mostly used in fine polishing. The typical grinding order when using a polishing cloth wheel for grinding diamond grinding powder or grinding paste is 9um(#1800)6um(#3000)3m(#8000).
The #1200 and #1500 sandpapers can be polished with polishing cloth wheels and diamond paste to eliminate hair-like scratches. Then polish to a thickness of 1 mm (#14000), 1/2 mm (#60000), and 1/4 mm (#100000) using adhesive felt and diamond paste.
The polishing procedure must be done in a sterile polishing chamber in the mold processing workshop if the precision requirements are greater than 1 um (including 1 um). A spotless environment is necessary for more exact polishing. The highly-precision polished surface you obtain after several hours of work could be damaged by dust, fumes, dandruff, and drool.
Specifications and categories of Plastic Injection Mold Polishing tools:
Sandpaper: 150#, 180#, 320*, 400*, 600*, 800*, 1000*, 1200*.
Gold sandpaper: 0#, 2/0#, 3/0#, 4/0#, 5/0*, 6/0*.
Whetstone: Polished unheated-treated P-20 die steel, using the brand GESSWEIN DF, the thickness of ordinary whetstone is 120#, 220#, 400#, and 600#.
EDM Whetstone: Polished heat-treated H13 die steel with BORIDE EDM 150#, 180#, 320# roughness
Hairbrush: Mirror polishing for polishing some large flat and curved surfaces
Diamond paste: 1#, 3#, 6#, 9#, 15#, 25#, 35#, 60#
Color: White, Yellow, Orange, Green, Blue, Brown, Red, Purple
Table files: Square, Round, Flat, Small, Angular, Curved, and other shapes
Tape reels: Cylindrical, conical, square tip
Flint Aberdeen: According to the handle size, there are φ3/32in, ф1/8in, ф1/4in, ф6mm, ф3mm.
Shapes are cylindrical, conical, or beat with Flint King to the shape and size you need.
Diamond grinding needle: Generally 3/32in shank and 1/8in the shank, there is a round wave, cylindrical, long straight cylindrical, long conical.
Sand and gravel boots: It is used with the front and rear pull heads and double-sided tape to stick to the boots. The size is divided into two sizes: 17mmx28mm, 8mmx17mm.
Copper sheet: ф1/8in, ф1/4in, the handle is flattened to facilitate sandpaper to polish deep bones or flat surfaces.
Bamboo slices: Various shapes should be suitable for the operator and according to the shape of the mold. The function is to press the sandpaper and grind it on the surface of the cavity to achieve the roughness required by the customer.
Fiber Whetstone: 200*, 300*, 400*, 600*, 800*, 1000*, 1200*.
Color: Gray, Light coffee, Orange, Black, Blue, White, Red.
