Need Help!- Alignment problem when machining 2nd side

[jmcglynn]

OK, I'm stumped - I hope someone can help.

I have a part I'm making that uses the same program to machine both sides. The stock is 1.5" x 3" aluminum rectangular bar that I've squared up the cut ends so that the lengths are are the same.

I have X and Y set to the edges of the fixed jaw (brand new Kurt vise). I put the stock into the vise with the squared ends against the jaws and I align the left edge of the stock with the edge of the vise that I set to X 0. Z is set to the top of stock of course.

Long story short, I cut the top side, flip the part end-for-end so that the same face is being used to align with the edge of the vise and I run the same program again.

The part comes out mis-aligned in the X direction every time. Y orientation is always fine. The part is offset at *least* .010". I've tried re-indexing x off the left side of the stock on every part set up, and it still come out offset.

I know that the edge I'm indexing X off of isn't machined square (I'm using the "factory" material edge), that is the only thing I can think of but it doesn't account for the amount of error as far as I can see.

The vise is square, the setup is rigid, it is the same part program on both sides so it seems like it has to be that the stock isn't "square enough", but that doesn't make sense to me.

Help!

[Geof]

Originally Posted by jmcglynn .... The part is offset at *least* .010". .... ....it seems like it has to be that the stock isn't "square enough", but that doesn't make sense to me. Help!

Maybe it does make sense. You say it is offset .01 but you need to remember that each setup can be off by .005 to get the .01 total at the end, and .005 is pretty good for 'square enough' on aluminum extrusion stock.

When you flip the stock do you still have the same face against the fixed jaw on the vise? This is a good practise.

You don't mention your machine type so this suggestion may be awkward to implement without a toolchanger: Put a piece of round stock the same diameter as your cutter in a tool holder and use this as the X direction stop for clamping the bar in the vise. You will have this stop at the + end for the first clamping and then at the - end for the second, but at each position this stop is touching the same point on the bar. This way out of square on the bar end does not matter.

[cam1]

Hi:
Is there a feature that you can index off after you have machined the first face?
If so you would machine all of the first faces, and then do a second setup which would use a simple fixture to align the part on the X.
Another method that I use is to do another operation on the end face that isn't cut square. Let it stick out of the faws (in the X) just eneough to machine it square. This then becomes a known datum. Make sure to use an end stop to accurately locate the part in the X.

hope this helps
PS how's you and SolidCam?

regards

[jmcglynn]

Originally Posted by cam1 Hi: Is there a feature that you can index off after you have machined the first face? If so you would machine all of the first faces, and then do a second setup which would use a simple fixture to align the part on the X. Another method that I use is to do another operation on the end face that isn't cut square. Let it stick out of the faws (in the X) just eneough to machine it square. This then becomes a known datum. Make sure to use an end stop to accurately locate the part in the X. hope this helps PS how's you and SolidCam? regards

I could do that I suppose, originally going to machine a set of vise jaws to locate the part for the second side. Since the program is the same for both sides I thought it would be cheaper to must flip the part and index off of the material edge. Next time I make these I'll try that approach I guess.

SolidCAM and I are getting along OK. I've run into a number of really annoying bugs but I'm able to work around them. I find the way they translate WCS to MCS limiting or at least awkward. MAC-1 in SolidCAM automatically becomes G54, MAC-2 = G55. I'd rather have direct control over this. Plus there is a bug where it tries to make you start with MAC-1 and go up incrementally from there every time.