(1) The guide pillar is usually set on the moving mould, whereas the guide bush is set on corresponding part of the fixed mould; sometimes the two pieces are assembled vice versa according to the structure of the mould (such as the runner plate in the fixed mould).
(2) The injection mould is usually provided with four guide pillars and guide bushes, scattering in the margin of four corners of the mould plate, wherein distance between center of the guide pillar and margin of the plate is usually 1~1.5 times of the diameter of the pillar’s retaining end.
(3) Heated guide pillars are usually applied to small moulds or moulds with scarce productivity, while large and medium-sized injection moulds of moulds with rich productivity are mostly provided with shouldered guide pillars. To reduce friction and oil storage tank can be cut on the guide pillar according to the actual use; spiral oil storage tanks can be found in some large moulds.
(4) Straight guide bushes are usually applied to simple moulds or moulds with thin plate; Ⅰ-type heated guide bush is mainly applied to complicated moulds or the guide of fixed and moving moulds of large and medium-sized moulds; Ⅱ-type heated guide bush is principally used in the guide of ejection mechanism. To reduce friction, an oil storage tank can also be cut in the guide bush or use a self-lubricating guide bush (Use Mos2 in the annular groove of steel guide bush and use solid graphite in the side wall hole of high-intensity brass guide bush).
(5) To ensure sound fitting of parting line after mould closing, a cuttings shoot of the guide pillar and guide bush should be made on the parting line: generally one of the sides is cut or chamfered on the orifice of the bush, as indicated in Fig.2-28.
(6) Length of the guide pillar on the working part should be 6~8mm higher than the end plane of the core as indicated in Fig.2-29.
(7) The surface roughness for the working part of the guide pillar takes Ra0.4um (micron order Ra0.2um), and take Ra0.8um or Ra1.6um (micron order of the inner cylinder can take Ra0.2um).
(8) Clearance fit is adopted between the guide pillar and guide bush, with the quality of fit usually as H7/f7 (G6/h5 for high quality of fit and H8/f8 or H9/f9 for low quality of fit) and the slip length usually takes 1.5~2 times of the mating diameter, whereas the remaining parts are countersunk to reduce friction. Transitional fit is usually adopted between the mould plate and the guide pillar and guide bush, with the quality of fit as H7/k6 orH7/m6. In addition, to prevent the straight guide bush from falling off, a retaining groove can be applied to the flank of the straight guide bush, screwed with hexagonal socket head plug.
(9) For moulds with small batch of production and of low precision, the guide pillar can be directly fitted pilot hole on the plate. The hole should be generally made into through hole; when the cavity plate is rather thick, if the pilot hole is a blind hole, a blowhole should be made on the side wall of the blind hole, or a vent groove can be abraded ion the main body of the guide pillar and at the open end of the pilot hole; length and surface roughness of the slide guiding plane on the pilot can be adopted in accordance with the size of guide bush of equal specifications, and the diameter with exceeding length should be expanded so as to shorten the slip surface.