motion guru
Diamond
- Joined
- Dec 8, 2003
- Location
- Yacolt, WA
We are nearing completion of a rebuild of a Surface Grinder with automated controls and the more we get into this thing, the more questions that I am having about the final configuration of the controls and wheel dressing.
1.) Dressing the Magnetic Chucks - our customer provided a grinding "wheel" to dress the magnetic chucks. After rebuilding the gearboxes, all new bearings, shimming the mounts, etc. the chucks ran true to +/- 0.002 inches or so. The grinding wheel seemed only to be effective at polishing the chucks with roughly 1 hour of grinding required for every 0.0005" of material removal. We noted that if we dressed the wheel it seemed effective for about 75% of material removal in the first few revolutions and then went back to polishing. I bet we worked on one chuck for at least 4 hours before we changed approaches. One of my employees grabbed a dressing stick and just held it against the portion of the grinding wheel that was not over the chuck while it was grinding and this made a huge difference. More material was removed in 10 minutes than in the prior 4 hours. We ended up using this approach on both rotary chucks and now they are great
We have a diamond stylus for dressing the wheel mounted to a small hydraulic cylinder with guiding rod bearing for "automatic" dressing operations, but again, this seemed only effective for a minute or so before grinding effectiveness was reduced to almost nothing. We tried chuck rotational speeds from 5 RPM to 45 RPM . . . no real change. Is this normal? Was the grinding wheel loading up with the brass? If it is normal - should we design a dressing stick holder that would press the stick into the wheel at a programmable interval / force to improve grinding efficiency or is this kind of scenario only going to happen when grinding a continuous surface like the magnetic chuck / or when encountering non-ferrous materials like the brass rings on the magnetic chuck?
2.) The original OEM controls had the Spindle Downfeed as (+) to go down and (-) to go up . . . this seems backwards to me. Any reason why a grinder axis direction would be configured like this?
3.) As we consider how to control the downfeed - I am of the opinion that we have the operator set the maximum motor load they want to see (something like 75% or thereabouts) and the downfeed should automatically adjust the rate downward to keep the spindle loaded to this level. Once the acoustical sensor detects that we are within some distance of finish dimension, it would transfer over to finish grind feedrate until the dimension was reached (we are using an acoustical sensor on a linear axis to determine grind wheel position and thus thickness of parts being ground). . . does this seem reasonable? The spindle motor is rated at 40HP, the wheels are 450mm diameter, and typical grinding speed ratings of the wheels is between 28 - 35 m/s
1.) Dressing the Magnetic Chucks - our customer provided a grinding "wheel" to dress the magnetic chucks. After rebuilding the gearboxes, all new bearings, shimming the mounts, etc. the chucks ran true to +/- 0.002 inches or so. The grinding wheel seemed only to be effective at polishing the chucks with roughly 1 hour of grinding required for every 0.0005" of material removal. We noted that if we dressed the wheel it seemed effective for about 75% of material removal in the first few revolutions and then went back to polishing. I bet we worked on one chuck for at least 4 hours before we changed approaches. One of my employees grabbed a dressing stick and just held it against the portion of the grinding wheel that was not over the chuck while it was grinding and this made a huge difference. More material was removed in 10 minutes than in the prior 4 hours. We ended up using this approach on both rotary chucks and now they are great
We have a diamond stylus for dressing the wheel mounted to a small hydraulic cylinder with guiding rod bearing for "automatic" dressing operations, but again, this seemed only effective for a minute or so before grinding effectiveness was reduced to almost nothing. We tried chuck rotational speeds from 5 RPM to 45 RPM . . . no real change. Is this normal? Was the grinding wheel loading up with the brass? If it is normal - should we design a dressing stick holder that would press the stick into the wheel at a programmable interval / force to improve grinding efficiency or is this kind of scenario only going to happen when grinding a continuous surface like the magnetic chuck / or when encountering non-ferrous materials like the brass rings on the magnetic chuck?
2.) The original OEM controls had the Spindle Downfeed as (+) to go down and (-) to go up . . . this seems backwards to me. Any reason why a grinder axis direction would be configured like this?
3.) As we consider how to control the downfeed - I am of the opinion that we have the operator set the maximum motor load they want to see (something like 75% or thereabouts) and the downfeed should automatically adjust the rate downward to keep the spindle loaded to this level. Once the acoustical sensor detects that we are within some distance of finish dimension, it would transfer over to finish grind feedrate until the dimension was reached (we are using an acoustical sensor on a linear axis to determine grind wheel position and thus thickness of parts being ground). . . does this seem reasonable? The spindle motor is rated at 40HP, the wheels are 450mm diameter, and typical grinding speed ratings of the wheels is between 28 - 35 m/s