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Bakelia material fluidity is very poor, and the general plastic material is different, it is extremely easy to fill the situation is not full, the following is the mold development failure, reverse mold flow analysis, the results are completely consistent with the actual situation, the traditional experience of developing and manufacturing mold of the old method is obviously unreliable, the use of scientific computer-aided software tools, so that the manufacturing has evidence, this is scientific manufacturing.

Bakelite material products do mold flow analysis can predict what problems:

Predict melt front states to assist in part design and gate location selection to optimize cavity filling for most reaction processes.

Calculate the transition (degree of solidification) over time at any location in the mold during the filling and post-filling stages.

Determine the required injection pressure and clamping force to select the appropriate injection molding machine.

Shows the injection pressure at any point in the cavity at any time during the filling phase.

Graphically displays temperature changes due to reaction curing dynamics at any point in time within the mold.

Detect short bursts due to pre-solidification conditions.

Accurately determine the fuse lines (sutures) based on the part design and gate location.

Accurately determine the position of the cavitation, so that the mold can be correctly vented.

For RTM and SRIM analysis: Allows the user to define multiple anisotropic felts with different orientations within the cavity.

Predicting part warping (for reaction molding and chip package analysis).

Bakelite material properties

Bakelite chemical name is bakelite plastic, it has high mechanical strength, good insulation, heat resistance, corrosion resistance, so often used in the manufacture of electrical materials, such as switches, lamps, headphones, telephone shell, instrument shell, "bakelite" from which the name. Phenolic plastics are based on phenolic resin. English name: Phenol-F ormaldehyde (PF) Specific gravity: 15-2.0g/cm3 Molding shrinkage: 0.5-1.0% Molding temperature: 150-170℃.

Bakelite's characteristics are non-absorbent, non-conductive, high temperature resistance, high strength, used in electrical appliances, and because of high insulation like wood and good plasticity, it is called "bakelite". Bakelite is made of powdered phenolic resin, adding sawdust, asbestos or clay, etc., after mixing, at high temperature with a mold to press the finished product, of which phenolic resin is a synthetic resin in the world.

The difference between bakelite molding process and conventional thermoplastic material

1. The formability is good, but the shrinkage and directivity are generally larger than ordinary plastics, and contain water volatiles. The molding should be preheated before, the molding process should be vented, and the molding pressure should be increased if not preheated.

2. Mold temperature has a great impact on liquidity, generally more than 160 degrees, liquidity will decline rapidly.

3. The hardening speed is generally slower than that of ordinary plastics, and the heat released during hardening is large. The internal temperature of large thick wall plastic parts is easy to be too high, and it is easy to have uneven hardening and overheating.

Bakelite injection molding process introduction

If the application process of injection bakelite powder can be controlled according to its performance characteristics, it can improve the rate of finished products; Reduce the working load of the injection machine; Reduce the wear of the screw barrel; Shorten the molding cycle; Improving the appearance of the parts will help a lot. Reasonable use of injected bakelite powder can extend the service life of general nitrided steel screw to 8-12 months, and improve the damage to the mold.

I. Concept:

The material must be fully melted and plasticized in the barrel by screw under appropriate temperature conditions, so that it presents a good melting state and fluidity, so that it has a better injection molding process. The injection bakelite powder has good thermal stability of the barrel, which can be kept in the barrel for more than 10 minutes at 120℃, and present a better molten flow state at 85-100 ℃, and the barrel holding time can reach 20 minutes.

Second, the recommended cylinder temperature setting conditions:

one Two sections of temperature control cylinder: first 90-95 ℃, after 75-85 ℃;

2. Three stage temperature control cylinder: the first 90-100 ℃, 80-90 ℃ in the middle, 70-80 ℃ after;

3. According to the requirements of the process, the flow of the material can be adjusted by appropriately raising or lowering the temperature of the front barrel.

Third, the relationship between back pressure:

The injection bakelite powder is basically granular, and the back pressure must be adjusted to complete and perfect the pre-plasticization of the material in addition to the melting of the temperature, so that the flow is good and the dosage is uniform and stable during the injection process.

The adjustment of back pressure can generally control that the nozzle has the appropriate material outflow when the feed is loose, and the adjustment of the feed is stable during the injection process, depending on the different machine in about 3-5 ㎏/㎝2

4, pressure and injection (injection) speed:

Because the material is fully melted and has good fluidity, the cavity can be filled without high injection pressure, which can greatly reduce and reduce the load of the machine tool, generally about 60㎏ can meet the requirements of injection molding. Rapid friction between injection and nozzle, runner, gate, mold will produce too high temperature and aggravate the wear of the screw barrel. Especially the injection machine controlled by the single proportional valve, the high pressure and high speed damage to the screw mold is more serious, so the shooting speed should not be too fast. Too slow will affect efficiency and is not advisable. Generally, depending on the size of the parts and the form of the gate, it is controlled at 10-25 grams per second. It is better not to produce hard bubbles and gas and not to end.

Five, mold temperature and mold preservation time:

The injection bakelite powder has a faster molding speed, and can meet its molding requirements under the condition of 170℃. The retention time is 14 seconds per millimeter and the increase of time decreases with the increase of thickness. Generally, the cycle of each mold is 60-80 seconds.