Blend Surface Toolpath

[lavrgs]

In the "out of Memory" thread there was mention of using blend surface tool path - I am a reletive newcomer to Mastercam and machining but wanted to learn more about when it would be appropriate to use this blended surface toolpath.
I am working on a pattern to use for making a cast part. It is a shifter link for a motorcycle, it has a parting line in the middle of the part and I have made models of the top and bottom halves. Picture a rectangular section with rounds on the top edge and draft on the sides.
A bit of history on what I have tried; I ran a contour path with depth passes and 2 deg walls, then a contour with a 2 degree cutter, then a finish surface to create the rounds on top - I picked all the surfaces except the bottom. The problem with the finish surface tool path is that I expected that it would not touch the cuts made with the contour tool paths...but it did. I am using a tree J325 to machine the part and it has been "upgraded" to use Mach3 for the control
I attached a file that has a view of the finished part in the upper right. All suggestions would be welcome.
My ultimate goal would be to create the top and bottom and have them meet perfectly in the middle where the parting line is. I do drill two holes for alignment but so far alignment is far from perfect.

Thanks,

Bill

[Superman]

A couple of queries.

What material is the part to bw cast from ?
Why split the part ?, would it not be easier to sink the part 0.24" deep in 1 half, and a flat face on the other side ( you may get flashing dags, is my guess why not )

My ultimate goal would be to create the top and bottom and have them meet perfectly in the middle where the parting line is. I do drill two holes for alignment but so far alignment is far from perfect.

-create a rectanglar solid ( same dims as the 2 dies put together ), the Z zero to represnt the split line.
-place the solid part inside this rectangle, make the split line lay along the Z zero line, and do a solid subtract -rectangle 1st then your lever
-create 2 circles in TOP view, (for the alignment pins ), now solid extrude those circles, ( select the make cavity option, and both directions, through all ), and take them away from the rectangle.
-do a "solid slice" on the rectangle "by plane" at Z0, select "keep all"

result= one top and one bottom die, alignment method done, all you have to do is machine them

[lavrgs]

The part will be sand cast out of aluminum. In sand casting the parts are placed on either side of a board, this lets you make the top and bottom halves of the mold. Multiple parts can be put on the board along with runners and gates and alignment features. There will be some flash but this is limited by alignment.
. I do not need 2 cavities - I think that is where you are going below... I will eventually need multiple tops and bottoms that when put together represent the finished part - these are used to make the cavity in the sand mold.

Bill

[Superman]

Little bit clearer now

I'll assume that you will fix blocks( glue etc ) to your board and then machine 1/2 your part from those blocks ?

Get your part, and solid slice at the split line ( keep both items)
Xform one half, and place a rectangle solid ( ...your board ) between them
use a common XY datum point for both TOP and BOTTOM pieces...the Z plane would be different for both items

Set Z0 to be the upper face of the board, this XYZ position is what you set it in the machine for each seperate piece

You should be using 2 different WCS origins, both having the same XY point, one for the upper part and 1 for the lower

[lavrgs]

I will make the parts out of aluminum and them put them on the board.
My capability in Mastercam is very limited...I have been trying to figure out how to change work coordinates without much success. What I have been doing is creating the coordinate system in ProE and using that to export IGES files so it comes into Mastercam properly oriented.
I have one part (the top) that I machined and it came out as I wanted but when I machined "the bottom" part it was different. Unfortunately I didn't have the file of the top to go back and figure out why.
The difference between the two parts is that the top has the boundary that looks like it was cut with the tapered mill and the bottom looks like it was profiled with a ball end mill. The only thing that I can think that caused the difference is the tool layout- For the part that looks good I had a 0.125 ball end mill and for the part that looks funky I used a smaller diameter tool that was not a library tool. I may have missed something in the parameters(?).
My expectation was that the profiling should not affect the area that was contoured...that is it should not be machining material that isn't there, but since it is perhaps the contours were different...
It may be helpful to see a picture of the two parts to determine my best path forward... I'll try and post some tonight.