Depth issue

[Xxray]

Am having a maddening problem, am trying to determine if its a machine issue [likely] or perhaps settings.
As you can see in the pic, nice carving, until it comes to the high points. The hair, nose and eyebrow are all trashed, bit doesn't touch them.
So I set it to carve a bit deeper, better but still no joy. Set it again to cut still deeper, and it still won't touch these high points.
Here are some relevant settings used on this piece:
material is .80 thick
Set to cut z depth, at first, around .40, increased it to .50, then .70
.09 tapered ballnose used, FR 100, PR 30IPM
8% stepover
Machine is CAMaster Stinger 1, machine properly initialized, bit & material properly measured with Z pad.

Any suggestions appreciated

[Bob Reda]

Try starting your a couple hundredths under the top. When you set up your toolpaths you can position the model in the wood, I usually set it around .02 below the surface to start so those things don't happen.

Bob

[Xxray]

You can position your model in the wood with 3d machinist ?

[Bob Reda]

I'm sorry, you didn't mention that you were using machinist. I don't know if you can do that there. You can in aspire, not sure about vcarve. Maybe I should ask more questions before I answer

[JamesB]

Ray,
It certainly looks like part of the model is above Z zero. Although I am not sure how that could be set within the software. Can you zip up and email the Machininst setup file to jamesb (at) vectric (dot) com so I can take a look please?

Thanks
James

[Gc3]

why not "fool" z-zero by setting it .02-.04 below what machine marks as zero.....quick, easy work around this problem

[COWBOY1296]

James would know better then anybody but i am on the same page with him and GC3. increasing the depth wont change the flat spots, its appears to be a z zero issue and cutting below the surface should handle that.

[tmerrill]

No need to "fool" anything. 3D Machinist allows the model to be positioned in the material and a negative value for Gap Above will raise the model above the surface as shown in the pictures. This should be easy to check and correct if wrong.

However, my guess in this case is a z-zero setting problem which can be corrected or a positive Gap Above value added to add a safety margin as Bob suggested above.

Also, as it has been mentioned before - if you don't see it in the preview, it is not a software issue and you need to look at your machine and it's setup.

Tim

[Turtle49]

I think the replies above should get you well on your way. But I did have a couple of ideas or things to check anyway.

Have you verified that your z plate is configured properly. Pick a spot, zero to the plate and then run the bit back down to zero at that spot to see if the bit is right on the material or above it, etc.

A good practice that I have adopted is to zero at the high point of the carving when possible. That way if there is a slight curve or bow in the wood, at least the high points get set properly.

Good luck!
Tim

[Xxray]

Thanks for the suggestions. Never tried a gap, sounds like that might work, but that would still only be masking the underlying problem of the inaccuracy.
I did save the file, since I still have the piece fastened in place, hoping I can salvage it, so I'll mail it later on, thanks again.

[Xxray]

Well, the - gap sure solved the problem. Thanks for the tip, I thought this one might be destined for the firewood pile.
So I guess now is to figure out if this is caused by a flaw in the machines accuracy, or if I should just simply position all 3D models down a bit to avoid flat high spots.
BTW, tried to mail the machine file 3 times, kept timing out even though its only 4mb. Comcast severely throttled my bandwidth, and I am far from happy about that.

[JamesB]

Xxray - the files did get through to me - 4 times so I guess the email is working OK.

I took a look and the only thing I can see of any note is the fact there is no gap-above as previously discussed in this thread. Certainly on a board which is not very flat you would see the problem by setting Z zero on a part of the board lower than the middle. The gap above would help that or as Tim mentioned using a high point on your board for Z zero would also alleviate this.

If that is not the cause then it would point to something in the Z Zero setup being out - such as the zero plate settings being wrong or something perhaps to do with Z length offset in the control. Again as mentioned doing some simple tests setting Zero then checking if its at the surface when indicating a value of zero after being moved up and down should perhaps show if there is an issue with that.

Thanks
James

[Xxray]

My bad James, every one of them said they timed out and were undelivered.
Anyhow, thanks everyone for the tips and thoughts, I'll see if I can determine any inaccuracies in the Z process.

[Bob Reda]

It might not just be z z problem. It could be the table, wood or whatever you are using. It could be a combination of things. That's why I always set the model a couple hundreds under the wood surface.

Bob

[Xxray]

This is not a one off problem.
I have been having flat high points and nasty missteps which leave depth lines happen with increasing regularity.
http://www.vectric.com/forum/viewtopic.php?f=9&t=12106
So its not wood, not the model, highly unlikely its the table.
Nonetheless, the Z positioning capability is a great thing, it was staring me in the face and I never noticed it before, glad to have it.