[ViperTX]

I center the part in the X and Y in MeshCAM, so when I flip the part in the Y-Axis the top and bottom cuts should line up correctly. I'm using the SW corner for the XY Offset, I don't enter any values the software seems to figure it out.

Since I'm using minimum stock, I broken a few end mill bits trying to figure this out. They don't like cutting brass and then being asked to cut the steel clamps.

In the Y-Direction I move from the middle of the stock until the outer periphery of the end mill reaches the outer edge of the stock. I zero Mach Y-Axis at this time.

In the X-direction I move from the middle of the stock until the outer periphery of the mill reaches the outer edge and then I move past the edge 1/2 the diameter of the end mill and zero Mach X-axis. The cut is shifted to the right by an amount that is 1/4 the diameter of the end mill.

So, a little help would be wonderful.

Thanks,

Paul

[Eurisko]

Paul, I'm a little confused. You're zeroing the Y axis at the periphery of the end mill, then zeroing the X axis at a distance of 1/2 the diameter of the mill past the periphery?

You really should be using positive stops to locate the part on the table. This can be as simple as three dowel pins: Two to square the x axis and 1 to locate the Y. Or vice-versa.

Just remember to remove the dowels before machining

[ViperTX]

I am using positive stops, makes flipping the part over and keeping it in perfect alignment quite easy.

Which is the reason that I center the work on the stock.

Paul

Regarding the zeroing...I don't really know what MeshCAM expects. I've tried zeroing both the x and y on the center of the mill and the part is not centered on the stock when the cutting is done.

[ger21]

I center the part in the X and Y in MeshCAM, so when I flip the part in the Y-Axis the top and bottom cuts should line up correctly. I'm using the SW corner for the XY Offset, I don't enter any values the software seems to figure it out.

I don't quite follow you.

In MeshCAM, how are you centering the part? I think you need to use Geometry>Translate geometry and for Translation XY use "Make center of part zero".

Then, under program zero, choose "Center" for the XY Offset.

Then, if you center the tool on the stock, you should be good.

[ViperTX]

ger21,

I'm sure you are somewhat correct, however in MeshCAM when I enter the size of the stock there are also some checkboxes...which indicate if I want to center the part on the x and center on the y and if I want the part centered in the z.

It is quite difficult to center on the middle of the stock, as I'm sure you are aware of.

So, the edge of the stock is the easiest to use for zeroing the x and y-axis in Mach3. I have no problem with the z-axis...using the Big-Tex modification of the Aussie SW.

All I need to know is what MeshCAM is expecting. All the tool diameters are selected in MeshCAM.

Paul

[ger21]

I'm sure you are somewhat correct, however in MeshCAM when I enter the size of the stock there are also some checkboxes...which indicate if I want to center the part on the x and center on the y and if I want the part centered in the z.

That centers the part in the stock, but I think you need to set zero correctly for your stock. I'll take another look tonight when I get home.

[ViperTX]

Well, let me ask this question in another way.

If I'm using the SW location, is the intersection of the x and y on a rectangular piece of stock the x=0 and y=0 point and is that the centerline of whatever end mill I'm using?

Thanks,

Paul

[ger21]

Yes, it should be. It's a bit hard to see, but the origin crosshairs will be the 0,0. With double sided, there are two crosshairs. One on top, and one on the bottom on the other side.

[ViperTX]

Well, I have had more time to try and figure this out.

The stock is a specific size and I center the geometry on the stock.

I'm using the SW corner for the origin of the axis.

To get the part to cut correctly in the x direction I zero the X-axis in Mach3 when the edge of the mill barely touches the edge of the stock.

To get the part to cut correctly in the y direction I zero the Y-axis in Mach3 when the center of the mill is directly over the edge of the stock.

Then when I mill the geometry it is centered on the stock.

So, the question is: What am I doing wrong? Is MESHCam the problem?

Paul

[ger21]

Can you save the job and post it here? You'll need to .zip it.

The center of the tool should be the SW corner of the stock for both X and Y. Not sure why you're seeing something different.

[ViperTX]

Gerry,

I have it zipped...tried to post it earlier, but did not see a way to post it.

Paul

[ger21]

Click the Go Advanced tab and Manage Attachments.

[ViperTX]

Gerry,

Here is the zipped file.

Thanks,

Paul

[robgrz]

I'm not sure I understand the exact problem. Can you post any photos of what happens when you machine the part?

-Robert

[osphoto]

For simplistic sake. The 0,0 reference of the stock should pretty much mimic the same 0,0 reference in the CAM software for your stock.

When doing a multi-side cut, you need consistent reference points. And I'm not reading how you are being consistent in doing this off the stock.

You mentioned you are getting reference points from the actual stock but my question would be, is your stock squared up enough to allow to do so? Is the stock prepped in order to get a consistent 0,0 reference?

Meaning, if you 0,0 side A at the SW (South West corner) of the stock, move the bit to X2,Y2 cut a hole half the depth of the stock, flip the stock 180, and do another 0,0 at the SW, move X2,Y2 cut a hole half the depth of the stock, will the holes match up? if they don't match, obviously, you can't make references off your stock for the next sided cut.

Some CAM software can create the references pieces need to make multi-sided cuts.

Hence, the Peg method for multi-sided cuts.

You ask what are you doing wrong in you CAM software, I'm not so sure it's the CAM software since it's virtual and doesn't care where it starts cutting. It just knows to move from a reference point starting at 0,0,0.

You just have to be consistent in how you setup up your stock/machine to be at 0,0,0 for the next side of the part cut. Where 0,0,0 has to be in reference to the part of the next sided cut and NOT the stock.

Side 1: 0,0,0 of stock
Side 2: 0,0,0 of PART in the stock.

[CanSir]

I hope I'm not confusing the issue, but I think ViperTX and I are experiencing the same thing.

Attached are the top and bottom .NC files (see sample_cut.zip) for a 4" x 4" x 4" cube cut from a 5" x 5" x 5" piece of stock. I have set zero to the top of the stock in the SW corner in both MeshCAM and on the machine.

If you watch what happens to the origin from the top cut to the bottom cut in the attached screenshots, you'll see how things get messed up. The origin moves from the top of the material, SW position to the bottom of the material, NW position.


The best way I can come up with to compensate is (after cutting the top half) to move my machine back to it's zero (g0 x0 y0 z0) and then I perform:
g0 z1 <- move up one inch from the top of the stock so I can flip the workpiece
< physically flip the workpiece >
g0 x0 y5 <- in this example my stock is 5 inches long in the Y direction so this moves my cutter to the NW corner of the material
g0 z0 <- move the cutter back down to the top of the material
g92 x0 y0 z5 <- Z is set to 5 because my material is 5" thick in this example and the cutter is now directly hovering 5" above where MeshCAM will set the origin to be when I load the bottom.nc file. This g92 command sets my machine offsets to match what MeshCAM seems to expect.
< load and run the bottom.nc file >

[ger21]

Gerry,

Here is the zipped file.

Thanks,

Paul

I didn't want the g-code, I wanted you to save the job in MeshCAM and post that. File>Save Job

[ViperTX]

Gerry,

Here is the zipped stl file.


Robert,

NewCenter001 is my setup on my mill.

NewCenter002 is the stock machined. The geometry is center in the Y-axis, but is off center in the X-axis. This was the center of the end mill zeroed on the X-axis and the Y-axis.

[ger21]

Is your stock exactly 3.0110 in x 2.2475 in?

It needs to be if it's not.

I'd make it 2.25x3, and check "Lock Stock Dimensions" in the define stock window.
Check Center X and Center Y, and then try it.

I think the only way I could find out what's happening would be to try and cut it, and I can't for a few weeks.

[ViperTX]

Gerry that particular block was exactly those dimensions.

I'll cut another block tomorrow and try it, I'll adjust the dimensions to the new block and "lock stock dimensions."

My understand of "lock stock dimensions" is all the blocks had the same dimensions then I would "lock stock dimensions."

Thanks,
Paul