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CNC Tech Talk Forum

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  • Hello Mike Pl refer to photo showing 4 step reamer. We have a HMC for doing 6 injector bores in cylinder head (which is a casting component) thro 4 step reamer of diameters 8.5,17.23,21.26 and 26.076 mm respectively. There is an observation that after changing tool, we find chattering randomly in any of the 6 bores for dia. 26.076 mm for about 2 to 3 components and then gets ok on its own. Bore depth is approximately 100mm Can you please advice for this random behavior as well as for chattering? Regards Rishikesh
  • Hello Sir We have HMC, which is used for making 24 holes ( it is a combination of 4X6 holes) of same size on face of a casting component by using standard combination boring bar - in which initially a small hole, concentric with one of the big 4 holes, is made and then feed changes to make big hole. . Cycle time is close to 30 minutes Component is rested against 6 rest pads on Fixture, there is air seat check to ensure positive butting all along between job and fixture Say 1 st component is alright and may be next component, depth of hole is found to be increased by upto 1mm scrapping the job We have checked relevant CNC parameters for In-position, acceptable tolerance between commanded and actual position and compared with other similar machines for similar components - found same Tool clamping force checked and found alright Z axis repeatability in Auto cycle checked and found OK as per readings on Dial Compared program with another similar machine - found no change Tooling and cutting parameters are same between this and other similar machines Now we have decided to check "Distance to Go" along Z axis and only then allow feed to start, to see if "Distance to go" itself is appearing more than required, which is unlikely in a semi closed loop CNC system Request your advice
  • Hello Everyone We have got a HMC , to do boring on two different diameters of connecting rod We are having waviness issue in small bore As shown in PPT, there are 3 components loaded on locations A, B, C of fixture, while waviness on A is by and large within limits barring few cases, generally it is out for B and C Please find couple of actions from our side thus far related to fixture 1. Accumulator charged to 85 bars to ensure adequate clamping pressure of components 2. Rest pads checked and ensured tightness. Blue seating of brass rest pads checked and found ok – although we have no issues with regard twist and bend. 3. Replaced locator for fixture B 4. In the original program, at the end of boring, spindle moves to 180 deg then retracts, blocked this block and retracted in feed till boring bar leaves component 5.Boring bar replaced with new one, Feed rate reduced from 126mm/min to 100 mm/min 6. Dia of small bore is 40.026 for length of 40mm, whereas dia of big bore is 73 7. Coolant pressure, tool clamping pressure found alright 8. Axis Z1 is master having linear scale along with direct motor encoder with it, Axis Z2 is slave with only direct motor encoder Request your advice to overcome Waviness of small bore Regards
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