V-Carve flat depth problem

I've been having this problem for awhile now and I can't figure out why this is happening. I don't know if it's human error or machine error. I have included some pictures of the problem I'm having.


I'm using Aspire 8.5. The problem I'm having is when I'm V-carving and I need to put in a flat depth I use a 1/4" or 1/8" endmill to hog out the majority of the material then I use a 45-degree vbit to clean up the areas where the endmill can't reach. I raster with an endmill with a 10% stepover and it's perfect, but when the endmill does its profile pass at the end it seems to dig into the material just a fraction too deep and you can see an outline in the wood of the endmills profile pass. If you look at my pics I circled a couple spots in red where it really showed up but you can see the outline of the profile pass all the way around everything. I have no clue why it does this as the rastering pass is perfect but the profile pass is messed up.


The other problem I'm having is that after the endmill is done hogging out the material I switch to the vbit to get into the areas that the endmill couldn't, but what happens is that when the vbit is clearing out the leftover material it's cutting a fraction too deep in comparison with how deep the endmill cut. If you take a look at the 3rd pic you can see I highlighted how deep the endmill cut in purple and how deep the vbit cut in green. As you can see the vbit cut down deeper than the endmill did. I use an aluminum touch plate to zero out the x,y, and z-axis on top of the workpiece. When I do a tool change I re-zero the Z axis again. I measured the aluminum touch plate with digital calipers to be as accurate as I could.


I don't know if it's me that's getting the Z-axis measurement wrong or something else. I have noticed that when I zero out the x,y, and z-axis then run a program. After it's all done and returns to the starting position everything in Mach 3 looks good except the X-axis reads 0.0006 off. Y reads 0.0 and Z reads 0.4 exactly what I put in Aspire. I don't know if that would make any difference or not.


Any help would be greatly appreciated.


Additional info:


I have Aspire 8.5
My machine is a Romaxx HS-1
I'm using a 2 flute 1/4" upcut or 1/8" downcut endmill
45 degree 1/8" 2 flute vbit
My wasteboard has been machined level
I run the 1/4" endmill at 75 ipm
Router speed #3 or around 18950 rpm