2 sided with limit planes - cutting air

[jmcmaster]

Hi there,

I just finished carving the 2 sided Marlin in the tutorials – it turned out well (VCarve Desktop 9.012).

I did the top side then turned the material over and started the bottom side. After the first pass I noticed that the tool (1/8” flat end) was being sent into areas of the material that had been removed when the top side was being done – it spent a lot of time cutting air.

The job setup has significant limit planes set on each side.

I’m wondering if the toolpath generation logic for 2 sided jobs takes into consideration the material that it removed on the other side, particularly material removed between the zero plane and the limit plane. I suspect not and this is adding much needless time to the job.

[martin54]

If you had cut the job using a ball nose cutter rather than a 1/8" endmill then I am guessing that there wouldn't have been anywhere near as much air cutting

[garylmast]

If one side undercut is greater than the other side, in the Component Properties, you can change the amount of Limit Plane's negative base height for each side. ie. If one side undercut is 3/4" and the other side is nothing, set the one amount at minus .75" and the other side at zero. Never go to a positive number. That way, you won't be cutting air on the one side that don't need it. However, after saying that, I don't use zero, but a least a minus 1/8" so it will cut through without having to do a profile cut. A zero plane for each side will leave an onion skin thickness.

Gary

[jmcmaster]

Thanks for the reply … with the model centered in the material, the marlin has features on each side (fins) that are below the zero plane. Adjusting the base height of the limit plane on both the top and the bottom sides to -0.25” allows those features to be cut.

The thickness of the material is 1”; the zero plane is at 0.5” and the limit plane is 0.25” below that or 0.75” below the surface on each side.

So after the top side is cut, a lot of material is removed down to 0.75”.
The material is then flipped over and the bottom cut is started. It would appear that the toolpath is calculated as if the material is still a solid block. Once the first 0.25” of material is removed, the areas removed previously start to show up and the tool is directed to cut them again.

This is particularly noticeable when the boundary offset (model level @ 0.25”) is being cut. The top side has already cut it 0.75” deep and the bottom side cuts it again to a depth of 0.75”, so the bottom 0.5” of the cut is overlapped and is in air.

I’m pretty new to this, but it looks to me that the toolpath generation ignores the fact that some material has already been removed by a previous operation and tries to remove it again. If I’m right, is there a way to optimize the toolpath to avoid this situation?
John

[garylmast]

John,

You are correct in what it is doing. On a similar situation, where I had a deep undercut on both sides, on the back side, the toolpath cycle was only half way done when it was obvious I didn't need to let it finish, so I stopped it and changed to the next tool. If you have an automatic tool changer, I'm not sure how that work. Maybe that's something Vectric can address in a possible update.

Gary

[jmcmaster]

Thanks.

How do I get Vectric's attention?

Do they read this forum?

John

[adze_cnc]

How do I get Vectric's attention?

Do they read this forum?

You could stand on one leg, flap your arms, and bay at the moon... that would get my attention

The easier way would be to go to: vectric.com and under the "Company" menu item select "Contact Us". Pretty standard for contacting any company nowadays.

Company reps apparently do read what's here but as it is a user-to-user forum, specifically, taking the vectric.com route would be the quickest way to get an answer.

I wonder if a "sticky note" at the top of each forum titled "How to contact Vectric?" would be a good idea as this question comes up regularly.