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General Mach Discussion / Re: CNC porting cylinder heads - options?
« on: June 30, 2008, 05:55:49 PM »
Hi vmax549,
Glad you chipped in because it was your post on the guitar thread (quoted above) that prompted my enquiry.
The port design of the heads I work with means there's no way you can gain access to the entire port from a single fixed position - it'd probably take at least four static positions to probe the entire port. I've been looking at ways of implementing 5 axis but suspect it may involve a lot of time and expense to achieve something less than satisfactory. I'd happily sacrifice a little time having to reposition the head a few times than have inaccurate machining due to backlash in a rotary table (or two) giving inconsistent co-ordinates. I understand the need for absolute repeatability in respect of positioning the heads on the mill table.
I've yet to carry out the CNC upgrade to my mill. Still trying to decide which route to take eg servos or stepper. Also need to either fabricate or buy a ballscrew Z axis, in addition to the ballscrew upgrade for X&Y. I'm sure this is essential as I'll be relying on accurate control of the Z axis. Pretty much ruled out motorizing the knee.
I've been trying to work out if a rotary 4th axis might be a step in the right direction. I'd still have the issue of dealing with backlash but if I can sort out a decent rotary table with minimal backlash, maybe it'd make additional probing and machining setups easier. Maybe not? From what you say, I suspect 3 axis with some accurately machined fixtures might be the way forward.
I guess I then need to find a reliable and accurate way to digitize the port and use some software that's capable of combining arrays or the creepy crawly method you mention. This is an area of which I have zero knowledge (so far!). Can Mach3 handle either or both of these digitizing methods? I've got a copy of the program but I know I won't start to fully understand and learn its capabilities until I actually start using it for real.
Thanks again for taking the time to share your knowledge. It's much appreciated.
Glad you chipped in because it was your post on the guitar thread (quoted above) that prompted my enquiry.
The port design of the heads I work with means there's no way you can gain access to the entire port from a single fixed position - it'd probably take at least four static positions to probe the entire port. I've been looking at ways of implementing 5 axis but suspect it may involve a lot of time and expense to achieve something less than satisfactory. I'd happily sacrifice a little time having to reposition the head a few times than have inaccurate machining due to backlash in a rotary table (or two) giving inconsistent co-ordinates. I understand the need for absolute repeatability in respect of positioning the heads on the mill table.
I've yet to carry out the CNC upgrade to my mill. Still trying to decide which route to take eg servos or stepper. Also need to either fabricate or buy a ballscrew Z axis, in addition to the ballscrew upgrade for X&Y. I'm sure this is essential as I'll be relying on accurate control of the Z axis. Pretty much ruled out motorizing the knee.
I've been trying to work out if a rotary 4th axis might be a step in the right direction. I'd still have the issue of dealing with backlash but if I can sort out a decent rotary table with minimal backlash, maybe it'd make additional probing and machining setups easier. Maybe not? From what you say, I suspect 3 axis with some accurately machined fixtures might be the way forward.
I guess I then need to find a reliable and accurate way to digitize the port and use some software that's capable of combining arrays or the creepy crawly method you mention. This is an area of which I have zero knowledge (so far!). Can Mach3 handle either or both of these digitizing methods? I've got a copy of the program but I know I won't start to fully understand and learn its capabilities until I actually start using it for real.
Thanks again for taking the time to share your knowledge. It's much appreciated.