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CNC mold processing technology 12 standards

October 18, 2023

1. Craftsmen compile craft cards
1) When the craftsman compiles the process card, he must specify the processing reserve amount, the direction of the reserve amount, roughness requirements and precautions in the process card.


2) Principles for writing processing process flow cards: On the premise of ensuring accuracy and quality, priority is given to using equipment with high processing efficiency. The processing efficiency of milling machines, CNC, and grinders is faster than that of wire cutting and electric pulse. In particular, the processing efficiency of electric pulse is the slowest. The dimensions on the drawing cannot be changed at will (only technicians can change it).

 

2. Principle of processing reserve amount
For workpieces that require heat treatment, a grinding machine allowance of 0.25mm should be added to the outline preparation dimensions before heat treatment. For mold cores and inserts that require CNC rough machining, a allowance of 0.2mm should be reserved on one side. The rough milling outline of the fitter milling machine should be preset on one side. Leave a margin of 0.3-0.5mm. For workpieces that need to be processed by a grinder after wire cutting, leave 0.05mm on one side of the forming part, and leave a grinding allowance of 0.1mm on one side of the roughened shape, mirror surface after CNC finishing and electric pulse Polishing, leaving a polishing allowance of 0.03mm on one side.

 

3. Processing accuracy requirements
1) The manufacturing accuracy of the mold size should be within the range of 0.005~0.02mm, the verticality requirement should be within the range of 0.01~0.02mm, the coaxiality requirement should be within the range of 0.01~0.03mm, the upper and lower parting surfaces of the movable and fixed molds, the parallelism of the two planes is required to be in the range of 0.01~0.03mm.


2) After the mold is closed, the gap between the parting surfaces is less than the overflow value of the molded plastic. The parallelism of the rest of the template mating surfaces is required to be within the range of 0.01~0.02mm, the mating accuracy of the fixed part is generally within the range of 0.01~0.02mm, for small cores, if there are no requirements for insertion or little impact on the size, bilateral 0.01~0.02mm is recommended clearance fit, H7/e6, H7/f7 and H7/g6 are generally used for the fit accuracy of the sliding part.


Note: if there are inserts on the mirror surface that are attached to the steps, the fit should not be too tight. Otherwise, when the insert is knocked backwards from the front, the tool used for knocking may easily damage the mirror surface. If the size of the product is not affected, it can be 0.01~ on both sides. 0.02mm clearance fit.

 

4. Principles of CNC electrode disassembly
1) The main body electrode of the mold cavity core should be removed first, then the other main body electrodes, and finally the partial electrodes, the overall processing of the fixed mold appearance electrode should be considered, and wire cutting should be used to clean the corners that can't be cleaned by CNC. The exterior surface of the fixed mold is complete and has no joints, the reinforcing ribs, ribs, and columns with similar depths in the movable mold can be processed together and made on one electrode as much as possible, the deeper ribs need to be made as inserts, and the electrode side must be made separately to prevent carbon deposition during electric pulses, try not to wire-cut the movable mold electrodes after CNC milling. If necessary, the electrodes should be disassembled or wire-cut directly, the ribs and ribs of the movable mold or If the distance between pillars exceeds 35mm, they should be made separately to save copper materials.

 

2) The spark position for roughing of large electrodes is 0.3mm per side, and the spark position for finishing is 0.15mm per side, the spark position for roughing general electrodes is 0.2mm per side, and the spark position for finishing is 0.1mm per side, the roughing of small electrodes the spark position is 0.15mm per side, and the finishing spark position is 0.07mm per side.

 

5.CNC machining principles
Mold cores and inserts need to be roughened by CNC, leaving a margin of 0.2mm on one side. Workpieces that need CNC finishing after heat treatment. If the product appearance allows, CNC can finish the mold cavity core in place, CNC is preferred. Processing, if the electrode cannot be processed in place, use electric pulse processing.

 

6. Dynamic and static mold core processing technology
1) Prepare materials.


2) Milling machine processing: drilling water holes (the distance between the deepest part of the water hole plug and the horizontal water hole is 3-4mm), threading holes, drilling and tapping screw holes, drilling and reaming pin holes, mold number, reference angle , the hanging platform gives way.


3) CNC machining: rough machining.


4) Heat treatment processing: indicate the hardness requirements.


5) Grinding machine processing: grind hexagonal ruler, and grind the shape according to the size of the frame (if the mold core is one piece, the outer size is 0.03mm-0.05mm less than the drawing size. If the mold core is two pieces, the two pieces of mold core will be put together. The sum of the overall dimensions in the upward direction is minus 0.03mm-0.05mm)⊥0.01, ∥0.01 compared to the drawing size. The parts that can be formed by grinder must be ground and formed.


6) If you need CNC finishing of the mold core, arrange CNC finishing. If the cavity has fonts and mold numbers, they need to be engraving.


7) Wire cutting processing: medium wire processing insert holes, inclined top holes, thimble holes, spout holes, etc.

 

8) Electrical discharge machining: processing according to drawings and pulse instructions.


9) Polishing processing: write the roughness and requirements of polishing on the process flow card. Use a marker to mark the polished area on the workpiece. If there is a mirror surface requirement, if the cycle is too late, rough polishing can be done first and then the test mold can be finely polished.

 

10 )assembly.


11) Trial mold.

 

7.Main body insert processing technology
1) Preparing materials: the craftsman determines whether to process a single piece or multiple pieces together based on the size and shape of the workpiece. If multiple pieces are to be processed together, the craftsman needs to draw a drawing of the processing sequence of the workpieces.


2) Milling machine processing: the fitter performs processing according to the workpiece drawing or the ranking chart produced by the craftsman, drilling the water hole (the distance between the deepest part of the water hole plug and the horizontal water hole is 3-4mm), threading holes, drilling, tap the screw hole, drill and ream the ejector pin hole, roughen the molding area, number the mold, and make way for the hanging platform.


3) CNC machining: if the workpiece requires CNC rough machining, arrange CNC rough machining.


4) Heat treatment processing: indicate the hardness requirements.


5) Grinding machine processing: when grinding a hexagon square, the part that can be formed by a grinder must be ground into shape.


6) If the workpiece requires CNC finishing, arrange CNC finishing. If the insert has fonts and mold numbers, it needs to be engraving.


7) Wire cutting processing: medium wire processing insert holes, inclined top holes, thimble holes, etc.


8) Electrical discharge machining: processing according to drawings and pulse instructions.


9) Polishing processing: write the roughness and requirements of polishing on the process flow card. Use a marker to mark the polished area on the workpiece. If there is a mirror surface requirement, if the cycle is too late, you can rough polish it first and wait for the test mold before fine polishing.


10) Assembly.


11) Trial mold.

 

8. Special-shaped insert processing technology
Craft 1:
1) Wire cutting processing: the outer diameter of the wire is cut accurately (A/B view), the tab is pulled, the thickness is left with a grinder, and the forming part is roughened.


2) Grinding machine processing: grinding thickness, slope, and shaping.


3) Electrical discharge machining.


4) Polishing processing.


Craft 2:
1) Wire cutting processing: the shape, insert hole, and ejection pin hole are cut by the middle wire, and the size is cut accurately (C view), and the hanging table and the forming part are roughened.


2) Grinding machine processing: grinding height, hanging table, slope, and shaping.


3) Electrical discharge machining.


4) Polishing processing.

 

9. Simple insert processing technology

1) Wire cutting processing: fast wire cutting contour allowance grinding machine (A/B view), pulling plate, thickness allowance grinding machine.

 

2) Accurate grinding of external dimensions, grinding of hanging platform, inclination, and shaping.

 

3) Electrical discharge machining.

 

4) Polishing processing.

 

10. Machining process of circular inserts

1) Centerless grinding: accurate grinding of external dimensions.

 

2) Grinding machine processing: angle cleaning at the hanging platform.

 

3) Wire cutting processing: fast wire cutting length (with 0.1mm grinding machine allowance on one side), cutting top pinholes and exhaust holes.

 

4) Grinding machine processing: grinding length and forming.

 

11. Oblique roof processing technology

1) Wire cutting processing: in the shape of the wire cutting, the head is ground with allowance for the insertion surface, and other dimensions are ground accurately. The thickness of the pulling plate is left with allowance, and the I-shaped groove is rough with allowance for grinding.

 

2) Grinding machine processing: grinding thickness and I-groove.

 

3) Assembly.

 

4) Pulse.

 

5) Polishing.

 

6) The milling machine opens an oil groove.

 

12. Processing technology of inclined top seat

1) Bench workers prepare strip materials: 1.5mm is reserved on both sides of the height dimension, 0.5mm is reserved on both sides of the width dimension, and 5mm is reserved on both sides of the length direction for convenient wire cutting and clamping.

 

2) Milling machine processing: drilling and tapping screw holes.

 

3) Heat treatment processing.

 

4) Grinding machine processing: grinding hexagonal square, grinding width dimensions accurately.

 

5) Wire cutting fast wire processing I-shaped groove accuracy, pulling plate, thickness allowance grinding machine, with a height dimension of ± 1.2 mm.

 

6) Grinding machine processing: the overall dimensions of the grinding machine are equipped with a needle plate, and the height dimension is 1mm.