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General Mach Discussion / Re: Guideway compensation/mapping?
« on: May 04, 2007, 02:29:18 AM »
There is another way. Now I haven't had time to play with this yet but would like to look into it soon.
Look for Formulas under Function Con-figs. It is my understanding that this could be used to correct for this error.
My machine does exactly what you were describing. I have about 1/8 of an inch difference between the middle and the edges of travel on the y (the bridge). Essentially the 1/8 error is on the tangent of around a 500 foot circle (guessing). Unfortunately I am maths handicapped so i am going to enlist one of my friends who is much smarter than i am to help me figure it out.
After we finish some stuff at the shop i am going to spend some time on the big machine. I have a new 5 axis head in the works and I will be building a new y bridge that will be beefed up to hopefully get rid of the twist problem.
As for keeping things totally straight and and square i have struggled greatly with this. I have found at this scale it is very much a chicken and egg problem. It is really difficult to build really flat and paralell things without something that is big and flat and parallel to use as a reference. Or a machine big enough to machine said surfaces.
All in all i am not too worried about it. The machine has already paid for itself in the molds we have built with it. and nothing is off more than .1 on the final molds. For our purposes that is entirely acceptable. Aerospace tolerances it ain't, but for home brew for us it is fine and will be getting better soon.
Chad
Look for Formulas under Function Con-figs. It is my understanding that this could be used to correct for this error.
My machine does exactly what you were describing. I have about 1/8 of an inch difference between the middle and the edges of travel on the y (the bridge). Essentially the 1/8 error is on the tangent of around a 500 foot circle (guessing). Unfortunately I am maths handicapped so i am going to enlist one of my friends who is much smarter than i am to help me figure it out.
After we finish some stuff at the shop i am going to spend some time on the big machine. I have a new 5 axis head in the works and I will be building a new y bridge that will be beefed up to hopefully get rid of the twist problem.
As for keeping things totally straight and and square i have struggled greatly with this. I have found at this scale it is very much a chicken and egg problem. It is really difficult to build really flat and paralell things without something that is big and flat and parallel to use as a reference. Or a machine big enough to machine said surfaces.
All in all i am not too worried about it. The machine has already paid for itself in the molds we have built with it. and nothing is off more than .1 on the final molds. For our purposes that is entirely acceptable. Aerospace tolerances it ain't, but for home brew for us it is fine and will be getting better soon.
Chad
