Cutting depth problems

[zac]

Hi guys,
I am having the same problem as Larry, i.e. inconsistent cutting depth.
I have just run a pocket toolpath program to cut 4mm deep in 1mm passes.
The first run was on a 12mm thick piece of timber which cut the pocket to 4mm.
I ran the same program on 73mm thick timber and the cut depth was 9.7mm, the first cut on the thick timber was approx. 6mm but only showed 1mm on the control panel display.
So it seems the higher up "Z" is, the greater the error.
I hope this helps in trying to solve this issue.
Wayne

[hdtheater]

I found this thread after in posted my own. The difference I am seeing is that the depth changes from one pass to the next correcting itself.

Here is my full post from the other thread:


I recently worked on a piece and as the pockets were cut there were differences in the Z depth as it carved it. I have included a couple photos for reference.







I thought by table might not be the same height across the length and width, but that particular path is the same depth throughout the piece and then it goes back to normal depth on the next pass. The differences happen on the same toolpath. The first and third pieces are a good example of this.

I used 1/4" downward spiral end mill for the larger bit and then a 1/16" single flute for the smaller bit. There are no differences in height from the 1/4" to 1/16" toolpaths.

Can this be remedied though maintenance on the Shark or should I set my software differently? This has happened on other pieces as well.

Thanks,

Eric

[REG]

Eric, strictly an observation; but I think what you have going on there may have been created in your project design. The depth difference I see follows the profile cut by an inch or so. It appears to follow around turns as well which leads me to believe it is not the bit or the table - both of those would be more random. I would check your project if it was built in V-Carve or Aspire and see if you have an offset accidently set. Also check for a vector line that might have been a reference for your profile. If you "selected" that vector in your toolpath, the software will trace it but you may not be able to see it in the toolpath finished preview.

[jeb2cav]

Hi Reg - I agree that what you describe might be causing or contributing to this. I have some other ideas as well. Eric actually created a new post last night - in addition to posting it on this thread. For reference, that thread is http://www.cncsharktalk.com/viewtopic.php?f=2&t=499. We may see different posts on the same discussion - so I'm listing the other post here for reference.

[hdtheater]

Thanks Joe for the suggestion on the offset. I am running that now.

[hdtheater]

I switched my job from Offset/ Clim to Offset/ Conventional and it did the same thing. I don't know how to describe it, but watching VCarve animate the drawing and seeing it on the Shark itself there is a correlation where the depth changes and to how it calculates the order of how to carve the piece.

I am rerunning the same job using raster conventional now. I will post my results.

Eric

[REG]

I see what Joe is describing in the other post noted and I recall a setting issue I was having with the Z axis on a particular project. On the project I had 6 pieces to cut/carve with a simple pocket. In V-carve I typically set my tool clearance for 1 inch which means after the carve the Shark returns to my starting point (in my case it is X - 0, Y - 0) and raises the bit 1 inch. I proceeded to the next piece and noticed that the bit went deeper than the 1st piece. I thought to myself that I should have set the Basic Controller to 0, 0, 0 thinking the 1" raised Z axis messed things up, though it shouldn't but it was the only reason I could come up with at the time.
I did my 3rd piece this time I zeroed my tool in Basic Control Panel, but again it cut slightly deeper than the very first piece. Finally on the 4th piece I witnessed what was happening. The bit I was using was 3 inches long which meant I had a higher than normal tool height. Then I noticed that when the tool returned to 0, 0, +1" (1" rise for clearance of Z axis set in V-Carve), that the Z axis was up against the very top of the Z axis travel. Normally I would have had about 1" from the top at 0, 0, 0 but the clearance setting in V-Carve forced the tool 1", but it couldn't go 1". What ever was lacking of the 1" (say a 1/16" of an inch or less) was not accounted for therefore the starting of the next piece - the tool was lower than my very first cut. Point is, make certain that the Z axis path is not close to the limits of travel in your project.

I hope my text explanation made some sense. I don't have sufficient visual aids to describe what I expereinced.

Bobby

[hdtheater]

I went with Joe's suggestion and that corrected my problem.

Thanks,

Eric

[OakBrook]

Hi I'm no expert but what about the material your working with? Is it fine grain wood or does it have hard spots that may catch the cutter and pull it into the the wood? Or perhaps a wrong angle specified on the cutter itself? just a thought.

[hdtheater]

This is just MDF. I have run the same toolpath over and over. The outcomes is the same on all pieces. Unfortunately, it is not the wood. Thanks though. I have looked at it over and over and I think it is an issue in the software or how the controller is interpreting the tool path.

-Eric