Mechanical design taboo

2019-03-15 12:25:47 3

Structural design to increase strength and stiffness


1. Avoid too far between the force point and the support point


2. Avoid cantilever structure or reduce cantilever length


3. Do not ignore the beneficial effects that the working load can produce.


4. Parts subject to vibration load avoid frictional force transmission


5. Avoid imbalance in the organization


6. Avoid considering only a single route of transmission


7. The influence of part deformation on the force distribution during work should not be ignored.


8. Avoid the tensile stress of cast iron parts


9. Avoid bending stress on thin rods


10. Impact load parts avoid excessive stiffness


11. Subjects with variable stresses to avoid rough or scratched surfaces


12. The surface of the stressed stress part should avoid residual tensile stress


13. Parts subject to variable load should avoid or reduce stress concentration


14. Avoid local structures that are too close to the intensity


15. Avoid pre-deformation and the same direction of deformation caused by the workload


16. The diameter of the pulley and the reel of the wire rope should not be too small.


17. Avoid too many bending times of the wire rope, pay special attention to avoid repeated bending


18. When lifting, the wire rope and the reel must have a margin


19. Intermediate parts that can not transmit force should try to avoid stress


20. Try to avoid the additional force generated by the misalignment of the axis during installation.


21. Minimize the force acting on the foundation

Structural design for improved wear resistance


1. Avoid the same material as a sliding friction pair


2. Avoid the white alloy wear layer thickness is too large


3. Avoid increasing the requirements on the entire part in order to improve the wear resistance of the surface of the part.


4. Avoid local wear of large parts and cause the entire part to be scrapped


5. When using white alloy as bearing lining, attention should be paid to the selection of bearing material and the structure design of bearing bush.


6. Lubricant supply is sufficient, full of working surface


7. The oil tank should not be too small


8. Do not filter the filter from the additives in the lubricant.


9. The size, position and shape of the oil groove of the sliding bearing should be reasonable.


10. The amount of grease added to the rolling bearing should not be excessive


11. Add a certain amount of wear margin to the wearable surface of the part


12. Pay attention to the adjustment after parts wear


13. The speed and pressure difference between points on the same contact surface should be small


14. Use dustproof device to prevent abrasive wear


15. Avoid the formation of step wear


16. Sliding bearings cannot be used with contact oil seals


17. Protect the wearable parts


18. Automatically compensated wear structure for wear parts




Structural design for improved precision


1. Try not to adopt a structural scheme that does not conform to the Abbe principle.


2. Avoid overlapping the errors caused by the amount of wear


3. Avoid processing error and wear amount superimposed on each other


4. The driving force action point of the guide rail should be applied to the pressure center of the frictional force of the two guide rails, so that the moments generated by the frictional forces of the two guide rails are balanced with each other.


5. For guide rails with high precision, it is not advisable to use a small amount of ball support.


6. In the deceleration drive chain that requires motion accuracy, the final stage gear ratio should take the maximum value.


7. The number of nut buckles for measuring spirals should not be too small.


8. The axial movement of the helical bearing must be strictly limited


9. Avoid unreasonable matching of bearing accuracy


10. Avoid unreasonable configuration of radial runout of bearings


11. Avoid tightening screws affecting the accuracy of the rolling guide


12. When the gap between the push rod and the guide is too large, a sinusoidal mechanism should be used, and the tangential mechanism should not be used.


13. The accuracy of the sinusoidal mechanism is higher than the tangential mechanism


Considering the ergonomic structural design problem


1. Reasonably selected operating posture


2. The ratio of the height of the table to the size of the human body should be a reasonable value.


3. Reasonable resettlement adjustment to enhance the applicability of equipment


4. The mechanical control, control and display devices should be arranged in the most reasonable position in front of the operator.


5. The display device is in a reasonable form"


6. The lettering on the dashboard should be clear and easy to read.


7. The size and shape of the knob should be reasonable.


8. The button should be easy to operate


9. The force required to operate the handle and the range of motion of the hand should not be too large.


10. The handle shape is easy to operate and exert force


11. Reasonably design the size and shape of the seat


12. Reasonable design of the material and elasticity of the seat


13. Do not have excessive noise in the working environment


14. The illumination of the operation site should not be too low


Structural design considering heat, corrosion, noise, etc.


1. Avoid using low-efficiency mechanical structures


2. The size of the oil tank should be large enough


3. The return fluid of the split system is cooled


4. Avoid high pressure containers, pipes, etc. exposed in the hot sun


5. Parts exposed to high temperatures are not allowed to be rubber, polyethylene plastic, etc.


6. It is not advisable to arrange the fuel tank inside the box parts of precision machinery to avoid thermal deformation.


7. For long mechanical parts, it is necessary to be able to freely deform when dimensional changes occur due to temperature changes.


8. Hardened material working temperature can not be too high


9. Avoid moisture condensation caused by high pressure valve deflation


10. The large thermal expansion box can be supported at the center.


11. The flanges connected by bolts are used as the joints of the pipes. When one side is exposed to sunlight, the two sides are different in temperature and elongation, resulting in bending.


12. Structures in contact with corrosive media should avoid slits


13. The liquid in the container should be cleaned out.


14. Take care to avoid mechanical chemical wear (friction wear) on the contact surface between the shaft and the hub.


15. Avoid corrosion-resistant screw structures


16. When the steel pipe is connected with the copper pipe, it is easy to produce electrochemical corrosion, and a section of pipe can be regularly replaced.


17. Avoid using structures that are susceptible to corrosion


18. Take care to avoid the impact fretting wear of the heat exchanger tubes


19. Reduce or avoid impact and collision of moving parts to reduce noise


20. High speed rotor must be balanced


21. The quality of the impacted parts should not be too small


22. In order to absorb vibration, the part should have strong damping.