Common defects and solutions for centerless grinder products

Common defects and solutions for centerless grinder products

A centerless grinding machine is a type of grinding machine that does not need to use the axis of the workpiece to perform grinding. It is composed of three mechanisms: grinding wheel, adjusting wheel and workpiece support. Common grinding defects and elimination methods of centerless grinders are organized as follows:

1. The parts are not round

　　cause

　　(1) The guide wheel is not rounded

　　(2) The number of grinding is small or the ellipse of the previous process is too large.

　　(3) Blunt grinding wheel

　　(4) The amount of grinding is too large or the amount of knife is too large

　　Elimination method

　　(1) Re-repair the guide wheel, and the rounding of the guide wheel will stop (generally the repair will stop until there is no intermittent sound)

　　(2) Properly increase the number of grinding

　　(3) Re-repair the grinding wheel

　　(4) Reduce the amount of grinding and the speed of heavy knife

2. The parts have edges (polygons)

　　cause

　　(1) The part center height is not enough

　　(2) The axial thrust of the part is too large, so that the part is pressed against the stop pin and cannot rotate evenly

　　(3) Unbalanced grinding wheel

　　(4) The center of the part is too high

　　Elimination method

　　(1) Accurately advance the center of the part

　　(2) Reduce the inclination angle of the grinder guide wheel to 0.5° or 0.25°. If the block cannot be resolved, check the balance of the fulcrum.

　　(3) Balance grinding wheel

　　(4) Properly reduce the height of the center of the part

[Metal processing WeChat, the content is good, worthy of attention]

3. Vibration marks on the surface of the part (that is, fish spots and straight white lines appear on the surface of the part)

　　cause

　　(1) Machine tool vibration caused by the unbalanced surface of the grinding wheel

　　(2) The center of the part moves forward to make the part jump

　　(3) The grinding wheel is blunt or the surface of the grinding wheel is too polished

　　(4) The rotation speed of the guide wheel is too fast

　　Elimination method

　　(1) Carefully balance the grinding wheel

　　(2) Properly lower the center of the part

　　(3) Grinding wheel or increase the dressing speed of the grinding wheel appropriately

　　(4) Properly reduce the guide speed

Fourth, the parts have taper

　　cause

　　(1) The front part of the part is small because the front guide plate is too low or the front guide plate is inclined in the direction of the guide wheel.

　　(2) The rear part of the part is small due to the low surface of the rear guide plate and the bus bar of the guide wheel or the tilt of the rear guide plate toward the guide wheel.

　　(3) Taper at the front or rear of the part due to the following reasons

　　①The grinding wheel is incorrectly trimmed, and it has a taper.

　　②The surface of the grinding wheel and guide wheel is worn

　　Elimination method

　　(1) Properly move the front guide plate and adjust the front guide plate to be parallel to the bus bar of the guide wheel

　　(2) After adjustment, the guide surface of the guide plate is parallel to the generatrix of the guide wheel and is on the same line.

　　①According to the direction of the part taper, adjust the angle of the grinding wheel in the modification of the grinding wheel

　　② Grinding wheel and guide wheel [Metal processing WeChat, the content is good, worthy of attention]

Five, the part center is big and the two ends are small

　　cause

　　(1) The front and rear guide plates are evenly inclined to one side of the grinding wheel

　　(2) The grinding wheel is trimmed into a waist drum shape

　　Elimination method

　　(1) Adjust the front and rear guides

　　(2) Modify the grinding wheel, and the margin for each modification should not be too large

Six, there is a ring thread on the surface of the part

　　cause

　　(1) The front and rear guide plates protrude from the surface of the guide wheel, so that the parts are scraped by the edge of the guide wheel at the exit or entrance.

　　(2) The support ratio is too soft, and the ground cutting is embedded in the support surface to form a protruding burr, and the surface of the part is carved into a thread

　　(3) The coolant is not clean, there are chips or grit inside

　　(4) Due to the large amount of grinding at the exit, it is scraped by the edge of the grinding wheel.

　　(5) The center of the part is lower than the center of the grinding wheel, and the straight pressure is larger, so that the sand and chips stick to the branch hair

　　(6) Blunt grinding wheel

　　(7) There is too much allowance in one grinding or the grinding wheel is repaired too thick, and extremely fine thread lines occur on the surface of the part.

　　Elimination method

　　(1) Adjust the front and rear guides

　　(2) Replace the branch hair with lubricated surface and higher hardness

　　(3) Replace the coolant

　　(4) Round the edge of the grinding wheel, and finally make the 20mm at the exit of the part do not grind

　　(5) Properly advance the height of the center of the part

　　(6) Grinding wheel

　　(7) Appropriately reduce the amount of wear and slow down the speed of modification

Seven, cut off a small piece from the front of the part

　　cause

　　(1) The front guide plate protrudes from the surface of the guide wheel

　　(2) The front face of the grinding wheel and the guide wheel are not in a straight line, and there is a big difference.

　　(3) Too much grinding at the entrance

　　Elimination method

　　(1) Move the front guide a little bit backward

　　(2) Replace or modify the longest of the two

　　(3) Reduce the amount of grinding at the entrance

8. The middle part or the tail part of the part is cut badly. There are the following kinds of cuts:

　　1. The cut is rectangular

　　cause

　　(1) The excellent guide wheel surface of the rear guide plate prevents the parts from rotating and the grinding of the trekking surface continues to work.

　　(2) The back support pad extends too long, and the polished parts are not dropped, which prevents the polished parts from rotating and advancing.

　　Elimination method

　　(1) Move the rear guide plate back properly

　　(2) Reinstall the support pad [Metalworking WeChat, the content is good, it is worth paying attention to]

　　2. The incision is angular or has many micro-shaped traces

　　cause

　　(1) The rear guide plate is behind the surface of the guide wheel

　　(2) The advancement of the part center is too high, causing the part to jump at the exit

　　Elimination method

　　(1) Move the rear guide slightly forward

　　(2) Properly reduce the height of the center of the part

Nine, the surface brightness of the part is not zero enough

　　cause

　　(1) The inclination angle of the guide wheel is too large, which causes the parts to move too fast.

　　(2) The modification speed of the grinding wheel is too fast, and the modification of the surface of the grinding wheel is not bright

　　(3) The modified guide wheel is too thick

　　Elimination method

　　(1) Reduce inclination

　　(2) Reduce the modification speed and modify the grinding wheel from the beginning

　　(3) Rebuild the guide wheel

　　 Note: It is forbidden to open the coolant when the grinding wheel is not running. If the coolant is opened first, in order to prevent the occurrence of failures, you should adopt intermittent driving (that is, open, close, open, close) and wait for the coolant to dissipate from the surroundings. start working.

　　In addition, the editor of metal processing has collected some precautions for you when operating a centerless grinder for your reference~

Grinding characteristics and safe operation rules of centerless grinder

　　The centerless external grinding is carried out on a centerless grinding machine. The workpiece is placed between the guide wheel and the grinding wheel. One of the grinding wheels is used for grinding and the other is used for transmission, which is called the guide wheel. The lower part of the workpiece is supported by a pallet. The guide wheel is made of rubber bond, and its axis forms an angle θ with the grinding wheel in the vertical direction to drive the workpiece to rotate and feed.

　　When using centerless grinding, the grinding wheel rotates at a peripheral speed that is about 75 times greater than that of the guide wheel. Since the friction between the workpiece and the guide wheel is greater than the friction between the workpiece and the grinding wheel, the tolerance level of the workpiece after the workpiece is driven by the guide wheel and ground is IT6~IT7, and the surface roughness value is Ra0.8~0.01um .

　　1. When the workpiece is sent by hand to grind, the distance from the hand to the grinding wheel should be more than 50 mm, and don't hold it too tight.

　　2. When using push rods to feed materials, the push rods must be held firmly, and metal rods are forbidden.

　　3. When adjusting the grinding amount, the number of test-grinding workpieces should not be less than 3.

　　4. When correcting the grinding wheel, feed the knife slowly and give sufficient coolant to prevent damage to the diamond.

　　5. When the workpiece is skewed in the middle of the grinding wheel, stop urgently.

　　6. When grinding rod materials, the center between the support frame, the grinding wheel and the guide wheel is required to be in a straight line. It is strictly forbidden to grind the material.

　　7. When the workpiece is not ground out of the grinding wheel, it is not allowed to take it out. When picking up the workpiece, hold the workpiece quickly and stop its rotation.

　　8. The workpiece on the material rack should be put away to prevent it from rolling off and hurting people.

　　9. When installing the spiral wheel, wear gloves; hold the inner hole of the end surface of the spiral wheel, not the outside of the spiral wheel.

　　10. The blade of the unintentional sharpening board should be blunt to prevent cutting the hand.

　　11. Do not add an aniseed material that exceeds the specification. When you find an aniseed material, take it out immediately to prevent accidents.

　　12. The replacement of the grinding wheel should comply with the general safety regulations of the miller.

Note the following when operating a centerless grinder:

　　(1) Check the surrounding conditions of the machine before starting the machine. No objects should be placed on the machine, and the workpieces should be placed neatly. [Metal processing WeChat, the content is good, worthy of attention]

　　(2) Before starting the machine, check whether the berth is normal, the water level of the cooling water tank, the gap between the grinding wheel and the guide wheel and the supporting blade is normal, and whether there is work or debris in the machine tool.

　　(3) Check whether the switch is reliable before starting the machine, and confirm whether the safety protection of the protective cover is effective.

　　(4) Turn on the power supply, start the hydraulic switch, observe whether the pressure of the hydraulic gauge of the machine tool is normal, and then check whether there is oil flowing through the berthing mirrors and the berthing pipes.

　　(5) Before starting the machine, the grinding wheel and guide wheel dressing seat must be wiped clean, and the berth cup must be filled with oil.

　　(6) Operators must be trained in accordance with the work instructions before starting the machine to make them understand the various work operation procedures.

　　(7) After the above confirmation is correct, the machine can be turned on.

　　(8) Turn on the main power to the ON position. 09: Turn on the hydraulic switch to the ON position.

　　(9) Check the parking mirror of the hydraulic system and start the grinding wheel and guide wheel only after the oil gauge is stable.

　　(10) After the grinding wheel and guide wheel are running normally, turn on the water pump and adjust to the proper water volume.

　　(11) Adjust the machine to test grind 1-3 workpieces, first check the size and appearance of the workpiece, and put the adjusted product in the adjustment box.

　　(12) Adjust the machine to test grind 1-3 workpieces, first check the size and appearance of the workpiece, and put the adjusted products in the adjustment box.

　　(13) Mass production can only be carried out after passing the test.

　　(14) After starting production, the operator must conduct self-inspection and record the first sample in accordance with the operating instructions.

　　(15) In the event of an abnormality during the production process, report the shutdown immediately and fill in the relevant form.

　　(16) When shutting down, switch the water pump motor to the OFF position to stop the water supply, and take out the work that is stuck in the machine tool.

　　(17) The grinding wheel and guide wheel should be idling for more than 5 minutes to stop the water supply, so as to avoid imbalance of the grinding wheel when the machine is turned on again, until the moisture is dried, the power switch of the grinding wheel and guide wheel to the OFF position.

　　(18) After the grinding wheel and the guide wheel are stopped, the oil pressure switch can be turned to the OFF position (the oil hydraulic motor must not be stopped first, so as to avoid losing oil and wearing the bearing bush and spindle).