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Discussion Starter · #1 · (Edited)
I have a Chinese CNCEST 6090, running on Mach3.

At the bottom, the machine keeps moving the tool inward on each pass making an angled edge.

The top of the carve is fine.

I never had this happen with my previous machine, this is the 2nd job that cut this way.

Can anyone tell me what is happening here?

It seems like the material is moving with each pass, but is tightly clamped down.

I have an aluminum slotted spoil board.

I am going to get 3/4" MDF and clamp it to the bed, resurface it, and screw down my material like I did in the past.

I never had any problems doing it that way before.

I need to seek the advise of of and experienced CNC operator for some advise with this problem.
 

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David - Machinist in wood
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First impression is that your stepover is too great. Reduce it to something small, like 0.03125" and see what it looks like. If the setting is percentage then go with 10% or less.

David
 

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Discussion Starter · #4 ·
No it is not like that in the design.

I use Vcarve Pro.

I preview the tool paths and it runs perfect.
 

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What type of tool path is it? You could also upload the Vcarve Pro file, if is not proprietary, so others can take a look. The other thing I was told early on is that if it looks OK in the preview but it does look OK when cut it is most assuredly the machine, which is what your initial post suggested.
 

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Discussion Starter · #7 ·
Problem solved.

I use Vcarve Pro, and the roughing tool strategy has 2 options: (zlevel) or (3D raster) along "x".

I had it set at (zlevel), then changed it to (3D raster), recalculated and re-ran the tool path.

I cut correctly.

I am a newbie at this still and will make mistakes that I will learn from.
 

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Discussion Starter · #9 ·
The other thing I was told early on is that if it looks OK in the preview but it does look OK when cut it is most assuredly the machine, which is what your initial post suggested.
I will run a couple of small jobs to see the problem is with the machine.

I am going to get the mdf as a spoil board and resurface it because it seems the bed of this machine is a wee bit lower on one side. When doing a vcarve graphic, it seems to barely touch the surface one one side. I even plane the wood to be smooth and equal which usually corrects the problem. I think it's the aluminum T-slot table.

I am beginning to get a little frustrated with this no-name CNC. There is NO support for it either!
 

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David - Machinist in wood
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It's a given that whatever you use for a spoilboard needs to be leveled with the machine. I surface my spoilboard every few months just to clean it up a bit - 0.015" to 0.020" clean-up pass.

David
 

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" ... I think it's the aluminum T-slot table..."

I have a 6040 with essentially the same design slotted table as you have. I discovered rather quickly that the provided slotted table is not anywhere near stiff enough and that it is not flat. You can quite easily "flex" it with finger pressure.

In desperation I put a piece of 3/4 Baltic Birch ply under the slotted table and secured the table to the ply at several points. This made it OK but at some point I need to replace the ply with something sturdier - maybe thick aluminum plate.

What I typically do is clamp a spoil board to the reinforced table and then run a surfacing program to true it up. Work pieces are then attached (either with screws or double-sided tape) to the spoil board. Seems to be working fine with minimal runout and variability.
 

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Discussion Starter · #13 · (Edited)
I resurface every few months too.

I applied the mdf today and will resurface it tomorrow.

I will be screwing my work material to the mdf, I have been doing it that way for a long time. I find it easier than messing around with clamps.

I also use center of material for the zero position.

I finally received my dust shoe, I will be trimming some of the brush length.

After all is done, I will post a pic.

I have an electrician coming here this week to install 3 more outlets in my garage.
 
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Same here, Karen; I resurface as needed and that turns out to be every few months and I also set my XY zero in the center of the work piece probably 99% of the time.

David
 

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I checked the step over for the tool.

It is 0.0006 at 0.3%

So that is not the problem.
It is not the problem but is drastically increasing the cut times. For a 3D finishing pass using a tapered ball nose bit, 8-10% of the bit diameter is what is normally recommended. For a 6” carve .0006 stepover would require 10,000 passes and will burn up bit (chips cool the bit). Try for .004-.006” stepover.

I think your initial problem may have been loose stock - the anodized aluminum bed and clamps are slippery, if you don’t have some type of stops, stock will move. You need to secure stock down and keep it from shifting sideways.

I never need to resurface my spoilboard, use 1/8” hardboard as a sacrificial spacer when cutting through. A 4x8 sheet of hardboard is both cheaper and much lighter than a 3/4” sheet of MDF. I buy and move sheets of it as seldom as possible.
 
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