Plastic gear mold design points

Date:2014-07-29

Plastic gear due to its features of lightweight, inexpensive, small transmission noise etc., are widely used in automotive, instrumentation, home appliances, toys and a variety of timing device, not only in many occasions has been replaced by a metal gear, and can be used in many fields of metal gear is not recommended.

The present study about the forming of plastic gear is on the outer gear shaping pull, and for the study of internal gear is less. Small module plastic inner gears in the assembly of small size, transmission products with complex structure, there are obvious advantages. Analysis of internal gear, small module plastic injection molding characteristics

The design of the 1 gating system

Moldflow is a powerful analysis function of the professional injection molding CAE software, analysis and optimal design is widely used in the field of injection molding. Injection mould design of gear in the small module plastic in the first use of Moldflow software, to analyze the best gate location. The surface mesh (Fusion) can be guaranteed at the same time the analysis precision, reduce computer operation time, so the grid type selection Fusion. According to the local minimum size of plastic parts, the average length of the grid is set to 0.2mm. The results show that the software should be located in the plastic parts, gate at mid height of the side or the outer side.

Submarine gate size should not be too large, or between the runner and the plastic parts are not easy to break off, and then affect the normal release condensed material and plastic, the gate size and 0.6mm?. For a mold cavity two cavity arrangement, the overall design of gating system as shown in figure 3.

2 forming component design

Tooth profile of internal gear with small module plastic metal outer gear core small modulus 3 molding. The core of the height of 4mm, the top of the tooth thickness is 0.07mm, slot width is 0.16mm. Because the tooth shaped small core can not be used gear tools for processing; and because of the height of more than 1mm core, also cannot adopt a method of electroforming metal photoetching resin after processing; processing method suitable is the use of wire cut electrical discharge machining. First of all, will die of alloy steel billet grinding plate thickness as required, and then in the NC line cutting machine tools used? Molybdenum wire 0.1mm from the plate cut small modulus of metal gear, get the core required. The use of? 2.5 mm standard top rod as the core fixing rod in the rod part machining threads matched with the nut, M2.5 phase, the core is fixed on a movable mould insert the upper 5.

The overall structure of the 3 mold design

Push rod when the injection molding machine to promote mold pushrod plate moves forward, by the reset rod drives the push board to realize the plastic parts ejection movement. Because the cold material is arranged on the push plate, if pulling rod is like the conventional design that is fixed on the push rod mounting plate, between the pulling rod and a push plate will be no relative motion, also can make the condensed material from pulling rod. This will pull the material rod is fixed on the movable template, pushing plate at the top of a plastic parts at the same time, will be condensed material from pulling rod forced launch. In order to take the condensed material adhesion in under the push plate, push plate on the cold material design into a shallow spherical pits.