[Jambolero]

Hi all,


I'm really out of ideas what could be wrong. I'm trying engrave aluminium 1 mm thick plate by 0.2 mm diameter conical cutter into 0.04-0.07 mm depth. So far so good, but in engraved text is visible trace of tool.


Any possible combination of spindle revolution and cutting speed doesn't solved it. 50000 rpm - 2 mm/sec cutting speed, 6000 rpm - 8 mm/sec sutting speed, etc., etc... Nothing can remove tool trace.


Please take a look at the picture.




Any ideas? Thanks.


Michal.

[dhruva]

what tool trace? you mean the line below the arrow inside the sim? what program are you using? how the the code looks like?

[Jambolero]

Hi,

you can see too trace inside of engraved text and symbols. It's like small dots or circles. In best case all engraved symbols should be glossy.

I'm using CAM software Cenon from VHF. This kind of software has no any output option. Just saving with its own format. It even doesn't support G-code, so you have to make all programing in Cenon or import dxf or eps files.

Best results was when spindle rpm was set to 50000 and cutting speed to 2 mm/sec. But at this moment aluminium plate produce black dirt into text.

Michal.

[grg12]

I saw similiar marks when using ball-end tool. The problem was lowest part of the tool that has zero cutting speed - it merly "rubs" the surface. Books suggest using spindle on angle head to make the "ball" at tool end touch the surface with "equator" not "south pole" - but in my case it was easier tu buy proper engraving cutter

[Jambolero]

Hmm, it's could be that problem.

But I can't use angle head so only option is correct tool with correct parameters.

Now I'm using tool on picture below. It's have 0.25 mm flat tip.

[grg12]

The tool looks ok to me. Do you use any coolant? Some aluminium alloys tend to "weld" on cutting edge ruining finish (and sometimes tool) - few drops of alcohol or a bit of WD40 may help.
I don't have much experience with engraving tools - i only heard that they are very sensitive to runout due to extremly small clarence - you may try to rotate the tool in collet (pure speculation on my side).

[Jambolero]

Now I'm using alcohol. Before also Spray lubricant ALU-N oil. Still same results.

Welding become with high spindle revolution and slow cuting speed.

[bhurts]

Is your z moving as you cut? It almost looks like it's making dots to create lines. Also is everything mechanically sound. It's not bouncing as it cuts is it?

Ben

[Jambolero]

Hi,

nope, Z-axis is stable and doesn't engraving by "dotting". It's classic process "go down, go forward, go up" and so on... No bounce at all.

You can watch it on this video, which I make today morning:

https://drive.google.com/file/d/0B3R...ew?usp=sharing

Michal.

[silyavski]

I'm trying engrave aluminium 1 mm thick plate by 0.2 mm diameter conical cutter into 0.04-0.07 mm depth.

Michal.

Whats wrong is your Z or your material hold. So if you are sure its not the Z , then its vibration of the thin material. How you hold it down?

[Jambolero]

Aluminium plate is placed on vacuum table made from metal block with 0.2 bar vacuum. No sign of vibration or shaking.

Michal.

[silyavski]

From the looks of it it seems like made using Exact Stop mode instead of Constant Velocity, in Mach3.

What if you go to your CAM and before generating the tool paths, smooth them and convert the letters to curves? The check if mach3 is in CV mode. Then check if you have enabled backslash compensation, it should be off.

[Jambolero]

Hi,

sorry for late reply.

I'm not using these kind of software. Engraved text is made in Galaad and exported as dxf into Cenon. That's mean text is imported as pure lines and curves. So letter "I", for example, is made as one straight line and letter "S" as one straight curve.

Michal.

[Routerfiend]

Hi from your video it looks like you ally plate is sitting on a foam mount and I can see that there is some movement. This may be your problem. Try mounting on some plywood or plastic sheet.

[Jambolero]

Hi,

in this case aluminium plate is placed on vacuum fleece, but this clamp is strong. No movements at all. In other cases plate is placed directly on vacuum table, but no luck. Trace is still visible.

Michal.

[Lasersolution]

This is my machine cutting
Check this out on YouTube!
http://goo.gl/H52FVJ

[magicniner]

How is the tool held in the spindle, is there any freedom of movement at all for the tool?

[Jambolero]

Hi,

no, holding is strong. It's high frequency spindle. But for now I find optimal spindle rpm and cutting speed. It's 8000 rpm and 2 mm/s. So faar so good. But any others faster combination make tool trace visible.

Michal.