Where am I going wrong with my Z axis?

[sebago_signworks]

I am pretty new to using a CNC. The issue I am having is this... I am using V-Carve Pro (Screen Shot attached of my setup). I am routering out Alumalite (6mm / .239"). I am "Z"ing off the top of the material. I set the depth in V-Carve Pro to cut just a tad deeper then the material (.27") with 1/8 tabs. When I cut, it cut through the material into the sacrifice board. Its hard to tell, but it seemed to cut into it about .27"..... Just before this job I ran the table surface. Im sure I botched it up... however I cant figure out where..

Thanks in advance:)


http://i949.photobucket.com/albums/ad336/dmfahie/20120328_200350.jpg

[Ajcoholic]

Are you zeroing the cutting bit, after it is installed into the chuck? With the aluminum plate and battery clip that comes with the machine - and the zeroing routine...

AJC

PS you show a cut of .26", and material thickness of .27"... you shouldnt be cutting through at all.

[bobmoore]

It almost sounds like you zeroed your z to the table top instead of the material top.

[sebago_signworks]

I did zero my Z on top of the alumalite with the alligator plate, with the bit in.

[myxpykalix]

is it possible that there is some type of "shorting" (for lack of a more appropriate term) going on since your z zero plate is aluminum and you material is also aluminum?
Also like he said you need to make your depth set to the same thickness as material or a tad less, so as not to cut thru all the way and into your spoilboard.

[feinddj]

An easy way to check. If your zero is set to the top of your material. MZ to 0 with your material out of the path of the bit. Then check your material against your Z. Also look at the toolpath description when you highlight the toolpath. It will tell you max depth of cut. I have learned, the hard way, more than once to check it every time.
David

[steve_g]

Devin
You say you are new CNC so I have to ask...Has the z-zero routine worked before? I'm wondering what the programmed thickness of your aluminum Z-zero plate is.

Steve

[sebago_signworks]

Jack, great advice.. I will check. Steve, I did verify it in the setup menu. Great stuff guys, much appreciated.

[jerry_stanek]

In your shopbot set up what do you have for the thickness of your zero plate?

[road_king]

This is what I would try.

On the left side you show material setup "thickness" at .27"... You stated your "actual material thickness is .239"... I would use .239" for the material setup (left side). Also, you stated you wanted to go "slightly" through the material... On the right side you have "cut depth" set to .26"... I would set the "cut depth" (right side) to .24"... This will cut .001" beyond the material into the sacrificial board. I would leave the tabs as set...

You can do this and then preview it. I hope this helps..

Gerald....

[curtiss]

Say your z plate is .125 inches thick / When you run the C2 command, the instant the bit touches the plate the z read out should change to .125 / IF this is not the case something needs adjusting.

[hh_woodworking]

Just by chance you did start the cut depth at 0 and not the thickness of the material in the software? We had this problem at the school before took forever to figure out what was wrong worked on the machine all day for a software mistake:)

[paul_z]

Use notepad or word pad and look at the shopbot toolpath code. It's almost trivial to read. See what is happening in the Z axis.

Paul Z

[sebago_signworks]

Great stuff. Think it was a fluke or maybe the bit dropped as I ran a small file this morning with no issues. Want to thank you all for your advice as I learned allot.

[sebago_signworks]

Follow up question. Some of you stated the if I am routing a .25" board and I want to cut through it that should be my depth. What about flex in the board? Do you compensate for that? Alumalite seems to sit pretty flat, but 1/8 sintra, and many other boards bow up in the middle. Depending on the size I am not be able to screw or clamp the center. How are you folks without a vacuum table handeling this?

[steve_g]

Double stick tape...

Steve

[sebago_signworks]

Do you have a preference in brand/model? The only stuff we have in the shop is 3M VHB, but that is to thick.

[steve_g]

Devin

Many ShopBotters use Double stick carpet tape available anywhere. Myself... I've found that it's too sticky for me. I don't like to destroy my project trying to remove it from the table... For large beefy projects it's likely fine. I prefer Golf Grip tape for my more fragile projects. http://www.spectape.com/double.asp The down side of this product is it must be bought a full case at a time (72 rolls) however, last time I bought a case the per roll price was about $3.00 ea.
my preference is the ST501 1/2"

Steve