Sprocket design and processing
Sprocket design: For the sprocket with 12.7-38.1 pitch standard chain, all manufacturers have adopted the standard hob to produce on the gear hobbing machine.
When processing, users only need to provide the number of sprocket teeth, pitch and roller diameter to produce. Sprocket design according to GBl244-85 design. Non-standard sprocket on the basis of the user to provide the necessary data, do the following calculations: indexing circle diameter: d points = P/sin180 degrees / Z = P · K, P-pitch, K-number of teeth can check the table. Tooth groove arc radius: Rmin = O.505d, d = roller diameter. Pressure angle Qmin=l20 degrees-90/2; Qmax=140 degrees-90/2. Generally choose Qmax.
The tooth surface arc radius Remin = O.008d; (Z · Z + 180); Remax = O. 12 (Z · Z + 2). Remax is generally used. The position Do of the tooth surface arc radius is on the d-division 0.2P circle. Tooth groove separation S: machine, Smin = 0.08d; non-add, Smin = O.04P. General choice of machine plus tooth groove separation. Pitch angle a=360/Z. Tooth thickness: 0.95 for a single row with an inner section width, and 0.93 for a double row with an inner section width. The tooth tip circle can be determined based on the drawing, or 0.85 to 0.95 times the diameter of the roller can be added on the basis of the pitch circle. The above data is an important parameter of the sprocket design. of course. The sprocket design of a special chain is different from this and needs to be calculated according to the sprocket formula of the relevant manual.
The sprocket tooth processing sprocket processing is the most important tooth processing. As has been said before, the standard chain sprocket is mostly machined with a hob on the gear hobbing machine. The processing methods for large-size and non-standard sprocket are different due to the limitations of equipment, tools, and quantity. At present, the most widely used method is still the form milling sprocket and Fan Cheng method sprocket. The tooth profile of the roller chain sprocket cutter is designed according to the shape of the sprocket tooth slot. In order to save the tool, the tool is usually grouped according to the number of sprocket teeth. Each group is designed according to the number of teeth, and the number of teeth can be calculated as follows: Zc=2Zl·Z2/Zl+Z2 Where: Zl is the smallest number of teeth in the group. Z2 is the maximum number of teeth in the same group.
(1) Machining tooth profile of a forming knife: Using a forming disc cutter or using a finger-shaped milling cutter, machining a tooth groove on a horizontal or vertical milling machine equipped with a dividing head is a commonly used processing method. Suitable for batch processing of large pitch sprocket.
(2) Hobbing process tooth profile method: The tooth groove is processed on the hobbing machine with a hob and is suitable for sprocket processing with a standard sprocket pitch of P=38.1 or less. high productivity. Good accuracy.
(3) Saddle-shaped milling cutter machining method: Using a saddle-type milling cutter on a horizontal milling machine equipped with a dividing head, simultaneous milling of two teeth on two adjacent tooth slots is the current toothed sprockets Commonly used processing method. Suitable for medium and small batch production.
(4) Sprocket Machining Tooth profile method: The sprocket spline is machined on the gear shaping machine with a circular disc cutter or a comb cutter. Suitable for single-piece production in small quantities.
(5) The larger sprocket can also be used for marking, drilling, machining or inserting the tooth profile. It is also a processing method. Obviously, this method is relatively backward, but the large sprocket is limited by the processing equipment and quantity. This method can also be used.
(6) Recently, some units have used the profiling machine to cut the tooth shape to solve the problem of large-scale sprocket processing and are very creative.
Profile cutting cutting process is as follows:
A. The sprocket to be added to the machine is placed on the index plate, and the sprocket is fixed by the pressure plate and bolt on the mandrel. The gear ring surface must be flat.
B. At any position on the gear ring that has been machined, the depth of cut of the model tooth profile is smaller than that of the design tooth profile by 4-5 mm, and then the squareness of the ruler surface is measured with a square.
C. Measure the distance H between the cut edge of the cut shape and the edge of the finished shaft hole.
D. The depth B needs to be processed. B = measurement size - distance between the edge of the shaft hole and the edge of the index circle.
E. Adjust the size of the connecting rod of the cutting machine, that is, extend a deepening amount on the basis of the original size, and then adjust it to cut according to the template.
F. After cutting a tooth, index with a dial. After cutting three teeth, measure the same side of the same distance. After cutting the fourth tooth, follow the same method to move the same tooth with the same side measurement, and so on.
G. If the difference in the measurement size is greater or the width of the top of the teeth is larger, the wider side can be cut and welded to the other tooth surface for trimming.
H. The tooth surface after cutting is surface-quenched after grinding with a hand wheel. L. Perform other processing.
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