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Answers to mold design 88 questions

  1. Commonly used plastic engineering materials include ABS, PC, PE, POM, PMMA, PP, PPO, PS, and PET.
    The following is the shrinkage rate of each material:
    ABS: 0.5% (super unbreakable rubber)
    PC: 0.5% (bulletproof glass glue)
    PMMA: 0.5%: (plexiglass)
    PE: 2% polyethylene
    PS: 0.5% (polystyrene)
    PP: 2% (100% soft rubber)
    PA: 2% (nylon)
    PVC: 2% (polyvinyl chloride)
    POM: 2% (steel)
    ABS+PC: 0.4%
    PC+ABS: 0.5%
  2. The mold is divided into several major systems: pouring, ejection, cooling, forming, and exhaust.
  3. During the mold design process, you should pay attention to the following issues:
    (1) The wall thickness should be as uniform as possible, and the draft angle should be large enough.
    (2) The transition part should be gradually smooth and avoid sharp corners.
    (3) The gate and runner should be as wide, thick and short as possible, and the gate position should be set according to the shrinkage and condensation process. If necessary, a cold well should be added.
    (4) The mold surface should be smooth and clean with low roughness. (Preferably lower than 0.8)
    (5) The exhaust holes and slots must be sufficient to discharge air and gas in the melt in a timely manner.
    (6) Except for PET, the wall thickness should not be too thin, generally not less than 1mm.
  4. Common defects in plastic parts include lack of glue, cloaks, bubbles, shrinkage, weld marks, black spots, stripes, lifting, delamination, and peeling.
  5. Commonly used plastic mold steels include 45#, S50c, 718, 738, 718H, 738H, P20, 2316, 8407, H13, NAK80, NAK55, S136, S136H, SKD61, etc.
  6. Use SKD61, 8407 and S136 steel for high mirror polishing.
  7. The mold base has structures such as panels, A plates, B plates, square irons, guide posts, ejector plates, ejector fixing plates, bottom plates, etc.
  8. The basic forms of parting surfaces include straight, inclined, curved, vertical and arc surfaces.
  9. In UG, holding down ctrL+B or ctrL+shift+B is the hidden object command.
  10. Mold processing machinery and equipment include computerized machines, lathes, milling machines, grinders, drilling machines, etc.
  11. 2D refers to the two-dimensional plane, and 3D refers to the three-dimensional space. In the mold part, 2D usually refers to the plan view or CAD drawing, and 3D usually refers to the three-dimensional drawing.
  12. The default accuracy of Pro/e is 0.0012MM, and the default accuracy of UG is 0.0254MM.
  13. The top four global mold base manufacturers are HASCO of Germany, FUTABA of Japan, DME of the United States, and LKM of China.
  14. The default font height of CAD is 2.5MM.
  15. The mating surface of the male and female molds that is parallel to the PL surface is called the penetration surface, and the mating surface of the male and female molds that is not parallel to the PL surface is called the insertion surface.
  16. Strips and wires are both units of length. Strip is a Taiwanese term, 1 strip = 0.01MM. Silk is a Hong Kong term, 1 silk = 0.01MM, so 1 strip = 1 silk.
  17. There are often gaps on the edges of shell plastic parts, which are used to install various accessories. The pillow-shaped parting part formed here is called a pillow.
  18. The glue-reduced part at the root of the BOSS column reflected on the mold is similar to the shape after a volcanic eruption, which is called the mold crater.
  19. Ha refers to Mo Ren, a Hong Kong idiom.
  20. The tiger’s mouth is also called the tube position, which is the part used to limit the position.
  21. The product layout on the mold is called ranking.
  22. The cavity of the product on the mold is called the glue position.
  23. The tendons on the product are called bone locations.
  24. The BOSS column on the product is called the column position.
  25. The gap on the mold is called the virtual position.
  26. The hooks used for connection on the product are called buckles.
  27. The patterns left after EDM are called spark patterns.
  28. The PL surface, also known as the parting surface and the pop-up surface, refers to the part where the front mold and the rear mold come into contact when the mold is closed.
  29. Computer gongs are CNC milling machines and machining centers.
  30. Electric sparks usually use easy-to-process copper materials as discharge electrodes, which are called copper workers, also called electrodes. Copper workers are generally divided into: rough workers, rough and young workers, and young workers. The young workers are also called fine workers.
  31. During the discharge process, the discharge gap between the copper and steel materials is called the spark position. The rough sparks are generally between 10 and 50, and the young sparks are generally between 5 and 15.
  32. The material level is the wall thickness of the plastic product, also called the thickness.
  33. Compared with cutting inserts, original body retention refers to a whole piece of steel that is processed as blank material and is processed together during processing.
  34. The line formed by the meeting of two strands of plastic is called a weld mark.
  35. After the plastic enters the mold cavity from the plastic inlet, it forms a curved and folded snake-like flow mark called a jet.
  36. LKM refers to Longji mold base. Commonly used mold bases include: LKM, Fudeba, Mingli, Huansheng, Changhui and Desheng.
  37. DME and LKM are both standards for standard parts. DME is American-made and HASCO is European-made.
  38. The parts of the product that cannot be directly demolded by the front and rear molds become undercuts.
  39. Fool-proofing is an idiom, which means to prevent a very simple mistake and to prevent being in a daze! For example: an insert has hangers of the same size on both the ceiling and the ground. During on-site assembly, the ceiling and floor are likely to be installed upside down, but the hanger is made on one side of the insert. At this time, if the ceiling and floor are installed upside down, It cannot be installed, and it is impossible to install it wrongly. This action to prevent errors caused by daze is called foolproofing.
  40. Beer machine is a local idiom, which is what we often call injection molding machine and molding machine.
  41. The stop is the art line of the mouth, also known as the ugly line.
  42. Flying molds are matching molds or standard molds.
  43. The action of CNC finishing is called light knife, which means that it is processed in place based on rough cutting.
  44. The action of processing the position of the mold core on the mold base is called frame opening.
  45. Printing is to put the fonts on the film and then add fonts to the fonts.
  46. The method of opening the mold by inverting the front and rear mold material positions under normal circumstances is called reverse.
  47. The mold ejection method of using small inserts to pop up the local undercut is called Fuhe.
  48. When opening the mold, the product remaining in the front mold is called eating the front mold.
  49. When ejecting, the mold force required is large, and the ejection pin is not strong enough, causing the product to be partially ejected. Viewed from the front of the product, there is an obvious white color called ejection white, which is also called the ejection nozzle.
  50. The marks left by the water entry point on the surface of the point made during diving are called baking marks.
  51. The coder is a clamping tool, a pad with a triangular inclined plane and an opening slot.
  52. Overcutting refers to excessive cutting, that is, when processing the workpiece, the parts that do not need to be processed are also processed. Overcutting is not good.
  53. The school cup is the position where the front mold pops up and opens the mold.
  54. Tapping and thread tapping are called teeth.
  55. When a product contains two different materials or the same material in different colors, design a two-color mold for molding.
  56. The mold design process of the factory is that the customer provides product drawings → analyzes the product → confirms the plastic type → confirms the mold material → converts the engineering drawing → multiplies and shrinks to make a mirror image → completes the assembly drawing → orders the mold blank → orders the mold core material → drafts the mold →3D mold splitting→Determine the runner/gate method→Refer to the ranking diagram for structural design→Remove the inserts→Correct the 3D→Project drawings “Including: mold core/inserts/mold base/parts”→Make BOM list →Proofreading and review.
  57. There are two methods of demoulding: smooth demoulding and forced demoulding.
  58. The glue feeding methods include direct glue feeding, overlapping glue feeding, side glue feeding, circular glue feeding, sheet glue feeding, latent glue feeding, point glue feeding, horn type glue feeding, and fan-shaped glue feeding.
  59. The flow channels include circular flow channels, semicircular flow channels, T-shaped flow channels, and regular hexagonal flow channels.
  60. The standing manuals and books for mold designers include steel books, plastic books, and mold standard parts books.
  61. External use produces rebound force when appearing.
  62. Mold drafting is to prevent the product from being strained when it is demoulded.
  63. Screws mainly play a role in tightening and fixing. The matching length is generally 1.5 to 2 times the diameter of the screw.
  64. The slope of the slider is generally 20 degrees, and the slope of the inclined guide column is generally 18 degrees.
  65. The function of the cold material well is to store the small portion of relatively low-temperature plastic material that enters the mold first.
  66. The function of the positioning ring is to ensure that the correct relative position between the mold and the injection machine is maintained.
  67. Fits are mainly divided into three categories: clearance fit, transition fit, and interference fit.
  68. The function of inserts is to facilitate processing, prevent carbon deposition, facilitate polishing, save materials, help exhaust, facilitate replacement, and reduce the size of the processing machine.
  69. Hardness indicates the ability of a material to resist hard objects being pressed into its surface. Commonly used hardness indicators include Brinell hardness, Rockwell hardness and Vickers hardness.
  70. Curved surfaces cannot be drafted, but assembled surfaces can be drafted, and quilts can be replaced.
  71. To understand the difference between the first angle method and the third angle method, you must first understand their definitions.
    ① Any drawing method that places an object in the first quadrant and projects the view in the relationship {viewpoint} (observer) → (object) → (projection plane) is called the first angle method, also known as the first quadrant. Law.
    ② Any drawing method that places an object in the third quadrant and projects the view in the relationship {viewpoint} (observer) → (projection plane) → (object) is called the third angle method, also known as the third quadrant method. .
    Note: The difference between the first angle drawing method and the third angle drawing method is the position where the view is placed.
    How to draw the first corner: put the left view on the right, the right view on the left, the top view on the bottom, and so on…
    Third angle drawing method: put the left view on the left, the right view on the right, the top view on top, and so on…
  72. Commonly used methods for transporting water include straight-through type, wrap-around type, water tower type and spiral type.
  73. The basic principles of three views are: length is aligned, height is equal, and width is equal.
  74. Injection machines are divided into vertical and horizontal types according to their appearance. The two most commonly used injection molding machines are divided into ultra-small injection molding machines, small injection molding machines, medium-sized injection molding machines, large injection molding machines, and super-large injection molding machines according to the injection molding volume. That is to say, the injection volume ranges from a few milligrams to tens of kilograms, and according to the mold clamping force, it ranges from a few tons to several thousand tons.
  75. The clamping force of the injection molding machine must be greater than the mold supporting force, otherwise the mold will be stretched open by the pressure inside the mold.
  76. There are two types of positioning methods for male and female molds: one is: template positioning, and the other is: mold core positioning.
  77. The suitable wall thickness of ABS is 1.8-3mm, the suitable wall thickness of PC is 2-3.5mm, the suitable wall thickness of POM is 1.5-2.5mm, and the suitable wall thickness of NoryL is 2-3.5mm.
  78. The overflow value refers to the gap under which the plastic product will overflow (that is, the burrs will appear). The overflow value of ABS is 0.04mm, the overflow value of PC is 0.06mm, and the overflow value of PA is 0.04mm. The edge value is 0.015mm, the overflow value of PBT+15%GR is 0.03mm, the overflow value of PBT+30% is 002mm, the overflow value of PMMA is 0.065mm, the overflow value of PVC is 0.07mm, and the overflow value of AS The overflow value is 0.05mm, the overflow value of PS is 0.05mm, the overflow value of PP is 0.03mm, and the overflow value of PE is 0.02mm.
  79. Commonly used picture frames include A0, A1, A2, A3, and A4. The size of the picture frame of A0 is 1189mmx841mm, the size of the picture frame of A1 is 841mmx594mm, the size of the picture frame of A2 is 594mmx420mm, the size of the picture frame of A3 is 420mmx297mm, and the size of the picture frame of A4 is 297mmx210mm.
  80. Each company has different standards for planning mold sizes, but the common standards are as follows: 15-30 series mold bases are classified as small molds, 30-50 series mold bases are classified as medium molds, and 50 series mold bases are classified as medium molds. The molds of the above mold bases are listed as large molds.
  81. When an object deforms under the action of an external force, when the external force disappears, the object can return to the deformation before deformation, which is called elastic deformation. When the external force disappears, the object cannot return to the deformation before deformation, which is called plastic deformation.
  82. Ace steel (called in Hong Kong) is commonly used for mold bases. Ace steel is medium carbon steel and 45 steel.
  83. Model space is a space for graphic entities, and layout space is a space for drawing layout.
  84. The function of water transport is to control the temperature of the mold core.
  85. In industrial production, various presses and special tools mounted on the press are used to make parts or products of the required shape from metal or non-metallic materials through pressure. Such special tools are collectively called molds.
  86. Molds can generally be divided into plastic molds and non-plastic molds. Non-plastic molds include: casting molds, forging molds, stamping molds, die-casting molds. Plastic molds are further divided into: injection molding molds, blow molding molds according to different production processes and products. Air molds, compression molding molds, transfer molding molds, extrusion molding molds, thermoforming molds, and rotational molding molds. Molds can be divided into three categories according to the different types of pouring systems: large nozzle molds, thin nozzle molds, and hot runner molds .
  87. The plastic flow channel from the injection machine nozzle to the mold cavity is called the gating system. The gating system includes the main channel, the runner, the gate and the cold well.
  88. Reverse engineering is to use a high-speed three-dimensional laser scanner to accurately and quickly scan existing samples or models to obtain their three-dimensional contour data, then use reverse engineering software to perform curved reconstruction, and conduct online accuracy analysis of the reconstructed surface. , evaluate the structural effect, and finally generate IGES or STL data, based on which rapid prototyping or CNC processing can be carried out.
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