Technical Data
Technical Data In dressing, the surface roughness of grinding wheels is influenced by elements such as: 1. Peripheral speed ratio (Vr/Vs), 2. Infeed per revolution of wheel (Ar), and 3. Dress out (Na).
Design Information for Forming Rotary Dresser
Tolerances of Rotary Dresser Designs (mm)
Dimensional Tolerances of Rotary Dressers Set approx half of the allowable tolerance of the workpiece.
M
W
U
1. Peripheral Speed Ratio ① Influence of Peripheral Speed Ratio on Grinding Wheel Surface Roughness • Control of the grinding surface accuracy by up-dressing is easier than by down-dressing • Higher feed rate creates more open grinding surface (grinding ability increases)
Rotary Dresser Accuracy Limits
Other tolerances available upon request
15
Test Condition
Item Factor
Symbol Accuracy (mm)
Illustration
WA60K #20/30 Vs=29m/s Na=0
Grinding Wheel Rotary Dresser Grinding Wheel Peripheral Speed Dress Out Infeed Per Rev.of Grinding wheel Ar = 0.18μm/rev
L L
Width
L
± 0.005
S
10
U value
W value RZ type ≥ 0.5Z SZ type ≥ 0.5Z SX type ≥ 4Z
Y value M value
Radius
R
± 0.002
RZ type ≥ 10 SZ type ≥ 10 SX type ≥ 3
RZ type ≥ 10
≥ L
Down Dressing
Up Dressing
0.002
SZ type
≥ 10
≥ L
Step
S
± 0.001
R
R
R
5
SX type
≥ 4
≥ 0.5L
= 0.36μm/rev = 0.54μm/rev = 0.72μm/rev
Down Dress
Up Dress
Profile Accuracy
0.002
Prof ile
0 1.5 1.0 0.5 0 -0.5 -1.0 -1.5
P P P
Concave R Convex R Convex R
Peripheral Speed Ratio (Vr/Vs)
0.002
θ
Concave R
Angle
± 1´
② Influence of Peripheral Speed Ratio on Dressing Force • Larger peripheral speed ratio allows higher normal force (increasing in grinding ability • Tangential force shows the same tendency as normal force, but the value is much smaller
8
0.6
ー
Straightness
0.002
nP
0.5
6
P P P
Pitch Accumulative Pitch
P nP
± 0.002 ± 0.004 + 0.005 − 0
0.4
4
P value
*Convex R value *Concave R value
0.3
RZ type
≥ 0.1
≥ 0.03
RZ type
≥ 0.3
φ H
Bore
2
0.2
0.002
SZ type
≥ 0.2
≥ 0.15
Parallel
0.002
0.1
0
0.002
A
SX type ≥ 0.15 *Value depending on diamond grain sizes ≥ 0.2
Pro le
1.0
0.5
0
-0.5
-1.0
1.0
0.5
0
0.005 A
Control
Peripheral Speed Ratio (Vr/Vs)
Body
Peripheral Speed Ratio (Vr/Vs)
Perpendicularity
0.002
0.002
Pro le
2. Infeed Rate ① Influence of Infeed Rate of Grinding Wheel Surface Roughness • Higher feed rates create a more open grinding surface (grinding ability increases) • Longer dress-out time diminishes sharpness of the grinding surface
Runout of Profile
0.005
② Influence of Infeed Rate on Dressing Force • Larger feed rate increases normal force. (Grinding ability increases) • Tangential force shows the same tendency as normal force, but the value is much smaller.
A
H
Runout of Control
0.002
(Na=Dress out wheel rotation frequency)
Troubleshooting
6
0.5
Vs Vr Down Dress =0.81
Down Dress Na=0
10
0.4
Corrective Action
8
4
Trouble Details
Cause
0.3
Vs Vr Down Dress =0.16
Grinding wheel, dresser, and facility speci cation changes
Maintenance, change of dress conditions
6
Up Dress Na=0 Down Dress Na=80
0.2
2
Large dressing noise Chatter occurs
Vibrations
Cause of abnormal vibration isn't eliminated
• Check the run-out of the dresser • Check the unbalance between grinding wheel and dresser • Increasing the peripheral speed relative to the grinding wheel Down-dress: Reduce dresser rpm Up-dress: Increase dresser rpm
Vs Vr Up Dress =0.81
4
0.1
Up Dress Na=80
• Reduce diamond concentration of dresser • Increase machine rigidity • Increase the driving force of the dressing device
High dressing Load
0
2
0.1 0.2 0.3 0.4 0.5 0.6
0
0.18
0.36
0.54
0
0.18 0.36 0.54 0.72
Infeed Rate (μm/rev)
Infeed Rate (μm/rev)
Infeed Rate (μm/rev)
• Reduce infeed rate • Increase feed rate • Shorten dress-out
3. Dress Out Influences of Dress Out on Grinding Wheel surface Roughness • Longer dress out time increases roundness of the grinding surface, but reduces sharpness.
Burn mark
Temperature rise of workpiece Grinding wheel is dull
• Use softer grinding wheel • Use larger Grit grinding wheel
10
• Increase total dressing amount
• Reduce diamond concentration of dresser
• Avoid end-face grinding with angular grinding
8
Coolant is not supplied suf ciently
• Increase coolant amount
• Increase the amount of diamond protrusion of the dresser
6
• Adjust coolant nozzle position • Avoid end-face grinding with angular grinding
Down Dress Up Dress
4
Grain shedding due to early bond retreat
Insuf cient evacuation of grinding debris
• Increase coolant amount • Adjust coolant nozzle position • Increase coolant amount • Reduce infeed rate • Shorten dress-out • Check the run-out of the dresser
Abnormal wear
2
Diamond wear
Dresser temperature rise
0
80 150 240 320 Grinding Wheel Rotation Speed During Dress-Out (Na)
Dresser vibrations
• Increase machine rigidity
• Check the unbalance between grinding wheel and dresser
Precautions for Use of Rotary Dressers
Unsuitable Dresser selection
• Increase diamond concentration of dresser • Reduce the size of the abrasive grains
1. Do not directly touch the diamond part of the rotary dresser, which has a small edge angle and edge radius. Use cut-resistant gloves and handle with care. 2. When mounting and removing a rotary dresser on and from the spindle, do not strike it with a hammer. 3. When a rotary dresser is mounted on the spindle, be sure that the runout of the reference surface is less than 2µm in both the radial and axial directions. If the runout is large, turn the rotary dresser by a half turn and set it again. 4. Prior to starting dressing, run the grinding wheel and rotary dresser under no load to check for abnormal noise and vibration. 5. During dressing, keep supplying an ample amount of grinding fluid. This will improve the dressing performance and prolong the life. Make sure the nozzle is located properly and the nozzle is not clogged. Never use the rotary dresser without coolant. 6. When bringing the rotary dresser in contact with the grinding wheel for dressing, exercise special care. Do not hit the rotary dresser against the grinding wheel with a shock. Be sure that the infeed rate will not exceed the setting. The rotary dressers are precision equipment. When using them, be sure to observe the following precautions.
Poor surface roughness
Unsuitable grinding wheel spec Grinding wheel grain size is too large
Workpiece contamination
Clogging of grinding debris
• Increase coolant amount • Adjust coolant nozzle position
Dirty or contaminated coolant
• Clean the coolant path • Replace coolant
Vibrations
Cause of abnormal vibration isn't eliminated
• Check the unbalance between grinding wheel and dresser • Increase machine rigidity • Check the run-out of the dresser
Poor grinding wheel roundness Insuf cient grinding wheel forming • Check the run-out of the dresser
• Increasing the peripheral speed relative to the grinding wheel Down-dress: Reduce dresser rpm Up-dress: Increase dresser rpm • Reduce infeed rate • Apply longer dress-out
For safe use of the rotary dresser, read and understand Rotary Dresser Instruction Manual thoroughly.
5
6
Made with FlippingBook flipbook maker