Centerless grinding machine is a kind of grinding machine that does not need to use the axis of the workpiece for grinding. It is composed of grinding wheel, adjusting wheel and workpiece support. Common grinding defects of centerless grinder and their elimination methods are summarized as follows:

1、 Parts are not round

Occurrence reason

(1) The guide wheel is not rounded

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

(3) Dull grinding wheel

(4) Excessive grinding or cutting

Elimination method

(1) Repair the guide wheel, and stop when the guide wheel is rounded (generally stop when there is no intermittent sound)

(2) Properly increase grinding times

(3) Reworking grinding wheel

(4) Reduce grinding volume and re cutting speed

2、 Parts have edges (polygons)

Occurrence reason

(1) The part center is not high enough

(2) The axial thrust of the part is too large, which makes the part press the retaining pin tightly and cannot rotate evenly

(3) Unbalance of grinding wheel

(4) Part center too high

Elimination method

(1) Precise forward part centrality

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

(3) Balancing wheel

(4) Properly reduce the height of the part center

3、 Vibration trace on the part surface (i.e. fish color and straight white lines appear on the part surface)

Occurrence reason

(1) Machine tool vibration caused by wheel unbalance surface

(2) Moving forward the part center makes the part run out

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

(4) The guide wheel rotates too fast

Elimination method

(1) Carefully balanced grinding wheel

(2) Lower the part center properly

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

(4) Properly reduce the guiding speed

4、 Parts have taper

Occurrence reason

(1) The front part of the part is small due to the excessive low bus of the front guide plate guide wheel or the inclined plane of the front guide plate guide wheel

(2) The rear part of the part is small because the rear guide plate surface and the guide wheel bus are low or the rear guide plate guide wheel is inclined

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

① The grinding wheel has a taper due to incorrect dressing

② The surface of grinding wheel and guide wheel is worn

Elimination method

(1) Properly move in the front guide plate and adjust that the front guide plate is parallel to the guide wheel bus

(2) The guide surface of the adjusted rear guide plate is parallel to the guide wheel bus and in one line.

① Adjust the angle grinding wheel in the grinding wheel modification according to the taper direction of the part

② Grinding wheel and guide wheel

5、 The part center is large and the two ends are small

Occurrence reason

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

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

Elimination method

(1) Adjust the front and rear guide plates

(2) When modifying the grinding wheel, the margin should not be too large each time

6、 There are annular thread lines on the part surface

Occurrence reason

(1) The front and rear guide plates protrude from the surface of the guide wheel, making the parts scrape against the edge of the guide wheel at the exit or entrance

(2) If the support ratio is too soft, the ground cutting is embedded on the support bearing surface to form a convex burr, and the thread line is carved on the part surface

(3) The coolant is not clean and there are chips or sand particles in it

(4) It is scraped from the edge of the grinding wheel at the outlet due to a large amount of grinding

(5) The part center is lower than the center of the grinding wheel, and the straight pressure is large, so that the sand particles and chips stick to the bristles

(6) Dull grinding wheel

(7) Too much allowance is removed from one grinding or the grinding wheel is too rough, resulting in extremely fine thread lines on the surface of another piece

Elimination method

(1) Adjust the front and rear guide plates

(2) Replace the surface lubricated bristles with high hardness

(3) Replace coolant

(4) Make the edge of the grinding wheel into a fillet, and finally make the 20mm at the part outlet not to be ground

(5) Proper forward part center height

(6) Grinding wheel

(7) Properly reduce the amount of grinding and slow down the modification speed

7、 Cut a small piece from the front of the part

Occurrence reason

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

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

(3) Wear too much at the entrance

Elimination method

(1) Move the front guide back a little

(2) Replace or modify the longest one

(3) Reduce the amount of grinding at the entrance

8、 The middle or tail of the part is cut, and the cuts are as follows:

1. The cut is rectangular

Occurrence reason

(1) The excellent guide wheel surface of the rear guide plate prevents the rotation of the parts and the grinding of the traveling surface from continuing

(2) The rear support pad extends too long, and the ground parts do not fall down, preventing the rotation and advance of the ground parts

Elimination method

(1) Move the rear guide back properly

(2) Reinstall the support pad

2. Corner shaped or many micro shaped marks

Occurrence reason

(1) The rear guide plate lags behind the guide wheel surface

(2) The center of the part moves too high, causing the part to jump at the outlet

Elimination method

(1) Move the rear guide plate forward slightly

(2) Properly reduce the height of the part center

9、 The brightness of part surface is not zero

Occurrence reason

(1) The inclination angle of the guide wheel is too large, which makes the cutting amount of the parts too fast.

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

(3) The guide wheel is modified too rough

Elimination method

(1) Decrease the inclination

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

(3) Rework the guide wheel

Note: When the grinding wheel is not started, it is forbidden to open the coolant. If the coolant is opened first, in order to prevent the occurrence of faults, intermittent starting (i.e., opening, closing, opening, closing) shall be adopted until the coolant is distributed from all around, and then the work can be started.

In addition, the small knitting machine for metal processing also collects some

Precautions for your reference~

Grinding characteristics and safety operation rules of centerless grinder

Centerless cylindrical grinding is carried out on a centerless grinder. 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 driving. It is called the guide wheel. The lower part of the workpiece is supported by a supporting plate. The guide wheel is made of rubber binder, and its axis is perpendicular to the grinding wheel θ Angle, driving the workpiece to rotate and feed.

When centerless grinding is adopted, the grinding wheel rotates at a peripheral speed about 75 times greater than 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 grade of the workpiece after being driven by the guide wheel and ground is IT6~IT7, and the surface roughness value reaches Ra0.8~0.01um.

1. When grinding the workpiece by hand, the distance between the hand and the grinding wheel should be more than 50 mm. Do not hold it too tightly.

2. When using the pusher bar to feed materials, hold the pusher bar firmly. It is prohibited to use metal bars.

3. When adjusting the grinding amount, the number of test grinding workpiece shall not be less than 3.

4. When correcting the grinding wheel, feed the tool slowly and give sufficient coolant to avoid damaging the diamond.

5. When the workpiece is tilted in the middle of the grinding wheel, emergency stop is required.

6. When grinding the bar material, the center between the support frame, the grinding wheel and the guide wheel shall be in a straight line. It is strictly prohibited to bend materials.

7. When the workpiece is not grinded out from the grinding wheel, it is not allowed to take it out. When manually connecting the workpiece, hold the workpiece quickly and stop its rotation.

8. The workpieces on the material rack shall be placed properly to prevent falling and injuring people.

9. Wear gloves when installing the spiral wheel; Take the inner hole of the end face of the spiral wheel, and do not take the outside of the spiral wheel.

10. The edge of the centerless sharpening plate should be blunt to prevent cutting the hand.

11. Do not add large materials exceeding the specification. Large materials shall be taken out immediately to prevent accidents.

12. The general safety regulations of the grinder shall be followed when replacing the grinding wheel.

Precautions for operation of centerless grinder are as follows:

(1) Before starting the machine, check the surrounding conditions of the machine. No objects shall be placed on the machine, and the workpieces shall be placed in order.

(2) Before starting the machine, check whether the berth of the berthing box is normal, the water level of the cooling water tank, the clearance between the grinding wheel and guide wheel and the support blade is normal, and whether there are working objects or sundries in the machine tool.

(3) Before starting the machine, check whether the switch is reliable and 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 each mooring mirror and each mooring pipe.

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

(6) Before starting the machine, operators must be trained according to the operation instructions to make them understand various work procedures.

(7) The machine can be started only after the above confirmation is correct.

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

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

(10) After the grinding wheel and guide wheel operate normally, turn on the water pump and adjust it to the appropriate water volume.

(11) Adjust the machine to grind 1-3 workpieces. First, check the size and appearance of workpieces, and put the adjusted products into the adjustment box.

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

(13) Batch production can be carried out only after the inspection is qualified.

(14) After starting production, the operator must conduct self inspection and record the first sample according to the operation instructions.

(15) In case of any abnormality in the production process, stop the machine immediately and fill in relevant forms.

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

(17) The grinding wheel and guide wheel shall be idled continuously for more than 5 minutes to stop the water supply, so as to avoid the imbalance of the grinding wheel when the machine is restarted. After the water is drained, turn the power switch of the grinding wheel and guide wheel to the OFF position.

(18) After the grinding wheel and guide wheel are stopped, the oil pressure switch can be turned to the OFF position (do not stop the oil pressure motor first to avoid the wear of bearing bush and main shaft due to oil loss).