gearcutter
Industrial
Hello all,
I need your help. Our 900mm capacity vertical hobber is gradually developing, what I can only describe as, a kind of harmonic vibration when cutting 6 module or larger pitches on blanks larger than half the machine's capacity. The vibration results in chatter marks being left on the tooth form. When it begins to develop the vibration causes the whole machine to develop a resonance that can be fealt right through to the concrete slab you're standing on! To make an attempt to rectify the problem we began by looking at all the obvious things that might cause this eg; work holding, tool holding, tool cutting edge condition, type of material the blank was made from, adjusting gibbs on the head and saddle slide ways, saddle clamping, re tensioning of nuts and bolts located throughout the machine, tool spindle bearings/end & radial float, machine levelling, etc, etc. The only thing we feel that is left to do is determining the condition of the table area. We measured the circular backlash of the table's worm & gear to be around 0.05mm or .002". We were unable to get any radial movement of the table although we were able to get around 0.07mm of axial movement. We're leaving the table's worm shaft bearings until last, although feel that if they were damaged this would reflect in the table's circular backlash. The only way to reduce the vibration is to lower the cutting speed to the point we're its becoming uneconomical to do the job. If anyone has any useful suggestions please post them.
Many thanks, Ron.
I need your help. Our 900mm capacity vertical hobber is gradually developing, what I can only describe as, a kind of harmonic vibration when cutting 6 module or larger pitches on blanks larger than half the machine's capacity. The vibration results in chatter marks being left on the tooth form. When it begins to develop the vibration causes the whole machine to develop a resonance that can be fealt right through to the concrete slab you're standing on! To make an attempt to rectify the problem we began by looking at all the obvious things that might cause this eg; work holding, tool holding, tool cutting edge condition, type of material the blank was made from, adjusting gibbs on the head and saddle slide ways, saddle clamping, re tensioning of nuts and bolts located throughout the machine, tool spindle bearings/end & radial float, machine levelling, etc, etc. The only thing we feel that is left to do is determining the condition of the table area. We measured the circular backlash of the table's worm & gear to be around 0.05mm or .002". We were unable to get any radial movement of the table although we were able to get around 0.07mm of axial movement. We're leaving the table's worm shaft bearings until last, although feel that if they were damaged this would reflect in the table's circular backlash. The only way to reduce the vibration is to lower the cutting speed to the point we're its becoming uneconomical to do the job. If anyone has any useful suggestions please post them.
Many thanks, Ron.