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
Thank you. We have a PLC based Honing Machine. Slide movement to bring down honing cutter close to component, movement of honing tool inside bore and expansion of tool for finish honing, all these three functions are hydraulic, position feedback thro Servo. Bore length is 200mm, sometimes, we find black marks/rings ( 2 or 3) on top of bore but this mark not effecting surface finish Ra, flow of cutting oil adequate. Unable to understand reason for black mark. After replacing tool, no mark found but we are unable to conclude reason for such mark
Hello Mike, although I know u support immensely on CNC application related issues, was wondering if u can guide on Application related issues of Honing machines as well, please comment
Thanks, sent an invite to u on linked in
Thanks Mike your responses do help me a lot. Yes we are in touch with OEM as well, as u rightly mentioned encoder might well be reason, we would replace and revert. R u on Linked in, if yes please share your coordinates as well as contact details, if u r okay to share as I want to connect with u
Could u please respond to me
It sounds like you've covered pretty much everything I'd suggest. Again, is this a new process or one that has been working in the past but now is not?
Assuming it has been working previously, again, something has obviously changed. If the machine has not been crashed, I'd suspect cutting tool or workholding devices. Also, you say the depth of the bore varies, but what machines the surface into which the bore is machined? Could it be varying? 1.0-mm is a big variance. Are parts coming off the process varying with this from part to part - or do several parts come out okay and then a bad one shows up?
I know you said the cutting tool has been clamped properly, but if it is a straight shank tool held in a collet, I'd check the cutting tool after a variance to see if its length has changed (though you'd think depths would come out shallower - not deeper).