Getting started with injection mold making and maintenance!

Time：2020-04-29 09:03:14 / Popularity： / Source：

Purpose:

In order to reduce cost of mold making and maintenance operations, shorten manufacturing cycle, ensure life of mold, and ensure product quality.

First, making mold number:

1. Mold number must be processed by a milling machine above outer end face of mold blank (square iron), character height is 40mm, depth is 0.5mm, and font is contour.
2. Each template must be marked with mold number and direction is uniform.
3. All screws, ring holes and mold parts of mold must be metric specifications, and additional tooling accessories must be standard specifications. Self-made is prohibited.

Second, skid position

1. Each set of molds is skid-milled at four corners on B-plate (moving plate) for FIT mold and mold repair.

Third, code pit:

1. Non-I-shaped mold embryos need to be milled in front and rear molds, and specific size depends on design size of mold.

Fourth, code screw hole:

1. Each set of molds must have code holes on bottom plate of moving mold and fixed panel.
2. Hole size needs to be determined according to injection model.

Fifth, top stick hole

1. Bottom of movable mold must be provided with a large enough top stick hole with a diameter of 25 ~ 40mm.
2. Small molds only need to open one top stick hole, medium molds must open more than three top stick holes, and large molds need to open five holes.
3. Diameter and position of top stick are based on actual size (design size) of injection machine.

Sixth, positioning circle

1. Each set of mold must be equipped with a positioning ring (a positioning flange) to facilitate positioning of mold.
2. Size of positioning ring should be determined according to wall diameter of injection machine.
3. Tolerance of diameter of positioning ring is 0.2 ~ 0.4mm, and height of protruding mold panel is at least 8 ~ 10mm.
4. Standard size of positioning ring (flange) of mold and plate is 100mm-0.20 ^ -0.40mm.

Seventh, reset device

1. When ejector cylinder interferes with ejection device of row position, a resetting device must be provided on mold, and ejector plate is not reset by relying on spring to prevent spring from failing in the future and row position (core pulling) colliding with ejector barrel.
2. A travel switch must be installed between ejector plate and movable template to ensure that device can be reset before power is turned on and mold is closed.

Eighth, thimble plate guide post guide sleeve

1. Thimble plate is 12 or more in length, or mold is in middle position.
2. There are more small thimbles and diameter is less than 2mm.
3. There are more tubes (more than 10).
4. In above three cases, four guide posts and guide sleeves must be added to ejector board to ensure that ejector pin ejects plastic parts in a balanced and stable manner.

Ninth, thimble plate spring bow

1. All molds must be equipped with four reset slingshots on ejector pin plate to help ejector pin retract evenly.
2. Special blue slingshot for plastic mold is used, both ends of reset slingshot are smoothed.
3. Reset slingshot cannot be compressed more than 40% of free length. Four ejection limit pins must be made on ejector panel under condition that plastic part is effectively ejected.
4. To fix slingshot, counterbore must be fixed at both ends. Unreliable method of grinding counterbore at one end and grinding the other end is prohibited.

Tenth, automatic dehydration device

1. Small nozzle mold (three-plate mold) must be equipped with tie rods, pull bars or return pins to ensure that nozzle plate, A plate move to nozzle and fall off automatically.
2. Thickness of drawstring material is 10mm or more.
3. Diameter of tension screw must not be less than 8-14mm.
4. It adopts 4 nylon plastic nails (nylon drawing machine) on the surface of B-plate (moving template), which is safe and reliable, economical and practical.

Eleventh, thimble action

1. It should be ensured that plastic parts is ejected reliably in any occasion, and it is reset without interference with other mold parts before mold is closed.
2. During ejection, plastic parts cannot be deformed, ejection and jamming phenomenon can be ejected quickly, traces of eject pin will not affect appearance quality of plastic part.
3. Ejection should be balanced and smooth, ejector plate should not tilt, and there should be no noise in ejection.
4. After ejection is completed, ejector pin should retract automatically (except for special molds).

Twelfth, position action

1. Slider (row position) should be smooth to ensure that shape is not deformed, no dead movements, unevenness, looseness, etc.
2. Guide surface of large slider must have an oil groove;
3. Large slider must have a cooling water channel;
4. HVE6 is used in cooperation with slider and slide part, it should not be too loose;
5. When sliding stroke length of slider is too long, it must be guided on mold base. Generally, length of sliding part should be about 1.5 times width. When core is pulled, mating part of slider in guide groove must have 2/3 of sliding part of slider in guide groove.
6. Clearance between oblique guide post hole and oblique guide post must leave a clearance of more than 0.2mm, and same size is forbidden;
7. Angle of inclined guide column is less than inclination of row clamping surface by 2 degrees. Clamping block of large slider must extend into lower mold 15-20mm, interlock and back pressure with a 10-degree inclined surface.
8. For cavity of round surface slider combination, angle between vertical and clamping surface of slider in the direction of slider and angle of slope column are 2 degrees. Final positioning of slider above mold must be pushed or pulled with a slingshot. Formally, wave beads can not be used to prevent slider from hitting clamping block and oblique guide post during mold clamping.
9. Rubbing surface of all rows must be equipped with a wear-resistant plate. Length of rubbing surface is ≥30mm and width is ≥50mm. Fine line position and line position press plates need to be hardened above 52 degrees, large line position should be nitrided or hardened according to requirements before mold opening.

Thirteen, hanging hole

1. Small and medium molds A and B are provided with screw holes for upper and lower plates;
2. All plates of large molds are made with screw holes for hanging molds, or both sides are required.

Fourteenth, CAV NO .:

1. One-mold multi-cavity parts must be marked with CAVNO on non-exposed surface, and matching surface should be marked before the first trial.
2. It is advisable to contact design engineer with word CAVNONO.

Fifteenth, shape shape

1. In principle, an O-shaped (round) channel is used;
2. Trapezoidal material channel is adopted in special cases;
3. Section size of sprue mouth usually depends on size of product and number of faces of mold cavity, specific size depends on mold design drawing;
4. Shape of spout opening is various. Usually there are flat style, flat style, spot pouring type, submersible type, and three or four claw point pouring type. Size of specific spout opening is positive or negative with actual product size. When opening sprue mouth, flow should be evenly distributed. Usually farther away from mainstream, material inlet gradually increases. For thin-water nozzle pouring type, in principle, it is necessary to keep navel eye and generally open inclined position of material channel when entering water, so as not to increase auxiliary manual workload after product glue leaves water outlet.

Sixteenth, special-shaped thimbles and inserts

1. When special-shaped thimble insert is rotatable, anti-rotation devices must be made.
2. Anti-rotation device must be reliable, with a single orientation, positioning in two directions is prohibited (including bevel of barrel needle)

Seventeenth, barrel

1. All holes of barrel must be hinged and cannot be drilled directly, so as not to burn shaped part of barrel, it is necessary to process plastic handle, and polish to avoid circles or dragging rubber powder.
2. Standard barrel is preferred. It is strictly forbidden to use as large a size as possible for diameter of forming part. Size of barrel can be smaller than outer diameter of forming column.
3. In order to avoid eccentricity of coordination between barrels, cutting amount of head of barrel cannot exceed 10 mm in length, and size must be considered in the design purchase.

Eighteenth, exhaust trough

1. Exhaust grooves must be milled on the back of guide plate of fixed template (plate A) to avoid formation of vacuum affecting plastic mold and FIT mold, hydraulic energy of unlocking mold will damage parts;
2. In order to ensure high-speed injection, all mold parts must be opened at last welded part and end of sprue mouth must be vented.
3. See parameters of exhaust groove depth: ABS, AS, PS: 0.03mm, PC, PE, PP, POM: 0.02mm, PA nylon 0.01mm.
4. For precise exhaust position, exhaust groove can be processed after first trial. Exhaust groove must be processed with a hemp or milling machine. It is forbidden to grind with a grinder.

Nineteenth, tool rust

1. All processed parts in mold manufacturing process must be coated with anti-rust oil after processing is suspended to avoid rusting;
2. After mold is removed, outside of mold embryo should also be sprayed with anti-rust oil to prevent rust.
3. There should be no rust marks when new mold is manufactured.

Twentieth, needle burns

1. New mold must not have defects such as thimble barrel welding.
2. Thimble hole must be lighter.
3. Bottom of counterbore fixed by top pin hole and top of counterbore must be a flat bottom.
4. Tolerance of hole diameter between ejector cylinder and core is H7.
5. High-temperature thimble oil must be sprayed between thimble barrel and hole.
6. Ejector pin must be 0 ～ 0.5mm above cavity surface.

Twenty-first, cooling water access mark

1. Cooling water outlet must be marked with "OUT" or "O", and inlet must be marked with "IN" or "I"

Twenty-second, thimble mark

1. Thimble fixing plate must be marked. Marks should be same and in same direction in order to modify mold.
2. Marks must also be marked between insert and fixing plate to prevent incorrect installation.

Twenty-third, parting surface is higher than mold surface

1. Parting surface is usually 0.1-0.5mm higher than mold surface.

Twenty-fourth, slider, oblique top block demagnetization

1. Moving parts (slide fast, oblique top block, tightening block) must be demagnetized after grinding, so as not to burn moving part and under effect of magnetic suction, slider will return to original position after leaving, and slider will be injured when second clamping is set.

Twenty-fifth, runner polishing

1. Runner must be polished. It is strictly forbidden to bump runner to avoid affecting injection fluidity and appearance of plastic part;
2. Length of mainstream track is less than 60mm under condition of structural permit.

Twenty-sixth, is flow path and water entering reasonable?

1. Flow channel should be set to ensure water inlet balance and reduce nozzle material. Turning point of flow channel must be provided with a cold material cavity;
2. Hot runner diving port is preferentially used to save material of nozzle, water supply guarantees that product requires as little auxiliary labor costs as possible.

Twenty-seventh, plane of inner and outer molds must be parallel, height of four return needles must be same.

Twenty-eighth, movement of nozzle plate must be balanced and evenly opened, stroke is reasonable.

Twenty-ninth, provincial mold must ensure that it is not sticky, not white, and must meet product requirements.

Thirty, auxiliary column (die top, support head)

1. Mold should be equipped with auxiliary columns as far as possible, in the center and larger than diameter.
2. Auxiliary column must be fixed on bottom plate of movable mold with screws;
3. Length of auxiliary column should be longer than 0.1-0.25mm of height of square iron of mold.

Thirty-first, frozen water

1. All cooling water must be uniform and sufficient, diameter of cooling water cannot be less than Φ8mm or Φ3 / 8 ″, unless structure does not allow it;
2. Sealing rubber ring must be 0.5mm higher during processing;
3. Do a water pressure test. Under pressure of 8Kg, it will not leak for 5 minutes.

Thirty-second, nitriding

1. Except for all steel materials before mold opening, after all projects are completed, surface must be nitrided. Nitriding has following two requirements:
1) All moving parts (including row position, inclined top, wipe-through position, inclined shovel), etc. These parts need to be nitrided for fixing.
2) Individual molds need to be fully nitrided (including PC, nylon plus iron, etc.), and these molds must be specially prompted to be fully nitrided before opening.

Thirty-third, first trial

1. When new mold is tested for the first time, shape of mold must be on company's mold model and name;
2. The first test mold of new mold must be equipped with standard positioning parts of movable fixed mold, one on each side.