Plastic Mold CNC Machining Process

A high-quality plastic mold not only requires advanced CNC machining equipment and skilled mold makers, but also crucially depends on excellent mold design. Especially for complex molds, design quality contributes over 80% to mold quality. An excellent mold design aims to meet customer requirements while minimizing machining costs, difficulty, and time. What are the processes involved in plastic mold CNC machining?

I. Plastic Mold CNC Machining Process

1.Material Preparation: (If the mold factory directly purchases refined materials, this step may be skipped.)

   Front mold material, back mold material, insert material, positioning material, angled top material;

2.Pin Screw Holes:

   Drill guide holes, needle holes, ejector pin, screw holes;

3.Cooling Channels:

   Machining of cooling channels in the front and back mold cores;

4.Frame Cutting: (If the mold is purchased with a fully machined frame, this step may be skipped.)

   Front mold frame, back mold frame;

5.Rough Machining:

   Rough machining of the front and back mold cores;

6.Finish Machining:

   Finish machining of the front and back mold cores;

7.Copper Electrodes:

   Front mold copper electrodes, back mold copper electrodes, parting line cleanup copper electrodes;

8. Wire Cutting:

   Cutting of insert parting lines, copper electrodes, angled top pillow blocks;

9. EDM (Electric Discharge Machining):

   Rough machining of the front mold, copper electrodes, cleaning corners of core parting lines, back mold core and pillow blocks;

10. Slider Machining:

   Positioning, positioning pressure poles;

11. Angled Tops:

   Angled tops, angled top seats, angled top guide blocks;

12. Mold Accessories Machining:

   ①Sprue, mold module, garbage nails (limiting nails);

   ②Water outlets, support heads, springs, water conveyance;

13. Mold Polishing:

   Polishing of front mold, back mold core and pillow blocks, sliders, angled tops, inserts;

14. Additional Hard Mold Processes:

   Quenching, nitriding of positioning surface;

15. Mold Accessories:

   Mold surface engraving, sliders, angled pins, insert engraving, mold nameplates, etc.;

16. Mold Fitting:

   Matching of front and back molds;

17. Mold Assembly:

   Overall assembly of the mold.

II. How Plastic Molds are CNC Machined

1. Principles of Plastic Mold Machining Allowances:

   ①For workpieces requiring heat treatment, add 0.25mm grinding allowance per side before heat treatment;

   ② For mold cores and inserts requiring CNC rough machining, leave 0.2mm allowance per side;

   ③ For workpieces to be rough milled on milling machines, leave 0.3-0.5mm allowance per side; for parts to be ground after wire cutting, leave 0.05mm machining allowance per side, and 0.1mm grinding allowance per side for rough shaping;

   ④ For CNC finishing and EDM processes followed by mirror polishing, leave 0.03mm polishing allowance per side.

2. Precision Requirements for Plastic Mold Machining:

The manufacturing accuracy of mold dimensions should be within the range of 0.005 to 0.02mm; perpendicularity should be within 0.01 to 0.02mm; coaxiality should be within 0.01 to 0.03mm; parallelism between the upper and lower planes of moving and fixed mold parting surfaces should be within 0.01 to 0.03mm after mold closure, with the gap between parting surfaces smaller than the flash value of molded plastic. The parallelism requirement for other template mating surfaces should be within 0.01 to 0.02mm; the mating accuracy of fixed parts generally ranges from 0.01 to 0.02mm; for small cores without mutual insertion requirements or minor size impacts, a 0.01 to 0.02mm bilateral fit gap is acceptable; the fitting accuracy of sliding parts generally adopts H7/e6, H7/f7, H7/g6 fits.

With the continuous development of technology, the dimensional precision requirements for injection molded products are increasing. In plastic mold CNC machining, plastic molds, injection molding machines, plastic materials, and molding conditions are the four indispensable elements of injection molding.

Lori has advanced CNC equipment that can meet various mold machining requirements. Please contact us if you are interested.