CAD system of the hottest small module gear hob

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Small module gear hob CAD system

1 introduction

because the module of small module gear hob is small (m ≤ 1mm), the size of hob is relatively small and the accuracy requirements are high, so its design is different from the design of ordinary gear hob, and its structure has the following characteristics: ① small module pre shaving gear hob is difficult to process because of its small convex angle. If coal enterprises want to get out of the dilemma of coal dominance as soon as possible, they need to adopt small pressure angle, Reduce wear in the form of uneven shaving; ② The hob adopts an integral structure rather than a gear insert or assembly structure; ③ No keyway is required; ④ The chip holding groove adopts the straight groove type

when designing small module gear hobs with traditional methods, there is a large amount of calculation and drawing, and there are many tedious repetitive work. The AutoCAD system developed with ObjectARX application tool as the carrier, vc++ dialog box and database management technology is used in the design of small module gear hob, which can greatly simplify the design and calculation of small module gear hob and automatically check the shovel back curve

2 characteristics of parametric design

autocad is an application program with open architecture. Users can use it for customization and programming. It is a common development platform for parametric design. Its main development systems include AutoLISP, ads and ObjectARX. AutoLISP is a programming language in the early version of CAD. It is an explanatory programming language. It does not need to be compiled and is easy to understand, but its disadvantage is that it runs slowly; Ads (AutoCAD development system), which is composed of C language and C library provided to developers to create applications, has been integrated into ARX in the form of adsrx with AutoCAD R11 being recognized by us. ObjectARX application program is a dynamic link library (DLL), which runs fast, can share AutoCAD address space and call AutoCAD functions directly, and can provide an object-oriented c++ application design interface. It is a new generation of secondary development tool launched by AutoCAD. Therefore, the system program adopts ARX application program for parametric design, and its program structure has the following characteristics:

using ARX development tools, it is convenient to use MFC to develop ObjectARX applications; It provides the data structure of AutoCAD internal entities and other objects, which makes the application and AutoCAD fully integrated

objectarx environment provides a set of classes that enable developers to create MFC based user interfaces. Its appearance and built-in are exactly the same as AutoCAD user interfaces, so it has good man-machine dialogue function

3 hob outer diameter parameter optimization and shovel grinding possibility check

hob outer diameter parameter optimization

generally, the hob outer diameter can be calculated according to formula (1)

(1) where:—— The tooth surface waviness of the gear to be cut (? M)

s0 -- the feed rate of the hob along the axial direction of the workpiece every revolution of the workpiece (mm/n)

afn -- the normal tooth shape angle of the hob graduation circle

bf -- the spiral angle on the graduation circle of the gear to be cut

Figure 1 the influence of the outer diameter of the hob on the tooth surface waviness of the gear (afn= 20 °, bf= 15 °)

the relationship curve between the tooth surface waviness of the gear to be cut and the outer diameter of the hob can be obtained from equation (1) (see Figure 1)

it can be seen from Figure 1 that with the increase of the outer diameter of the hob, the waviness of the gear to be cut along the tooth surface will gradually decrease. Therefore, the horizontal tension testing machine for precision shackle lock meets the parameters: for gears with high requirements, the hob with larger outer diameter should be selected. However, the increase of outer diameter should not be too large: on the one hand, when machining small module gears, the axial feed is generally not greater than 0.5mm/r, and excessive increase of hob outer diameter has no significant effect on reducing tooth surface waviness; On the other hand, when the outer diameter of the hob is greater than 50mm, the influence of the outer diameter on the waviness has been very small. Therefore, the outer diameter should be controlled between 25 ~ 63mmm

the initialization procedure of outer diameter is as follows:

void initgundao {...

(if M fmodule> 0 & & M fmodule

else (if M fmodule> 0.15 & & M fmodule

else (if M fmodule> 0.4 & & M fmodule

else (if M fmodule> 0.6 & & M fmodule

else (m fmodule>0.8 & & M fmodule


Figure 2 checking process of relieving grinding

checking of relieving grinding possibility

when designing hobs with traditional methods, the human working diagram method is usually used to judge the relieving grinding possibility of hobs, and its accuracy cannot be guaranteed, which often leads to the interference between the grinding wheel and the next tooth when relieving the back of hob teeth. Therefore, in the small module gear hob CAD system, it is necessary to prepare a program to automatically check the possibility of relieving and grinding, and its flow is shown in Figure 2. When in use, the parameters are modified interactively through the dialog box to complete the shovel grinding check. The specific procedures are as follows:

void check {...

bool flag = true;

while (flag) {flag = false;

for (len = 4/7*len1; len

...//drawing to prepare for the check

(if dist1>dist2) break;}//Is there any interference? If there is no interference, jump out of the loop

(if dist1

canshudlg. domode (L);//Dialog box interactively modify the shovel back amount K and outer diameter ded

flag = true;}}...}

Figure 3 information model of object-oriented hob CAD system

4 analysis of CAD program structure of small module gear hob

hob CAD system is composed of modules such as parameter input of tool drawing title bar, tool selection, parameter input of cut gear, tool parameter input, etc. Through the object-oriented analysis method, the hob CAD system is analyzed, and the information model shown in Figure 3 is established. On this basis, object-oriented programming language is used to analyze the relationship between objects

in order to expand the universality of gear tool design, the commonness of gear tools is taken as the base class through induction. This basic class is attached to each specific gear cutter, and there is no need for a specific entity, so it can be set as a class that has been proved by a wide range of mechanical experimental data. Some of its attributes are as follows:

class cutter {

string cutter_id;//tool number

string cutter name;//tool name

string material;//tool material

string product_id;//corresponding product number

string designer;//designer

string designdate//design date

hob class is a derived class of tool class, which automatically inherits all the attributes of the tool, and has modulus, number of teeth, number of heads, and front corner, rear corner And other unique properties, Some of its attributes are as follows:

class gundao:public cutter{

float gd_module;//hob module

uint gd_number;//hob tooth number

uint gd_toushu;//hob head number


void oncalculation();

void ondraw() ;

machining machine tools and tools contain several data items with internal relations, which are summarized into a structure to explain some basic attributes of hob machining, In order to define in the hob class:

struct machine{

string machine_id;//machine tool model

string machine_name;//machine tool name

string machine_cutter_id;//machining tool number

by establishing the objects of the above classes and defining the structure, you can start to compile the software according to the following steps:

define the object.

define the calculation function:

void guid ndaodlg:: oncalculation()

[updatedata (true);

dlg.m_f and the determination of water content will also be restricted by different conditions and environments gdpmodule = m_fgearmodule;

dlg.m_fgdpyalijiao = m_fgearyalijiao;

dlg.m dgdpuojiao = (180*fengyuanloujiao Ca (L)/PI);

dlg.m_fgdpuojiao pzhouchixingjiao = m_fgearyalijiao;

dlg.m_dgdpzhouchiju = zhouxiangchiju Ca (L) ;

dlg. m_ dgdpzhouchihou = ZhouXiangChiHou Ca(l);

int ret = Moda(l);

message link

call the Object ARX global function in the Object ARX environment to write the drawing function

the AutoCAD system of small module gear hob adopts full parametric design to realize parameter optimization and automatic verification of tooth back curve, which can significantly improve the scientificity and reliability of the design; At the same time, the surface roughness and geometric tolerance can be directly inserted and marked, which greatly reduces the workload and improves the design efficiency

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