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View Full Version : Got a job - how to do it ? :)



Davek0974
07-04-2016, 10:54 AM
I have a request for a job, not sure yet how to cut it, pretty certain my machine is up to the task, be good if it is :)

Material - 6mm brass or copper plate.
Depth to machine - 1.5 to 2mm

The job requires milling away probably 95% of the surface to leave a raised line or design 1mm wide at the top and with trapezoidal sides, about 2mm wide at the base.

The corners to be sharp as possible, edges to be smooth (no burrs)

Sounds easy and i know what they are for as i use them in the day job - printing blocks for hot-foil stamping machines.

Questions...

Milling away the waste sounds easy - biggest tool and have at it, leave allowance of course.
Cutting the trapezoid shape - not sure what tool here - engraving tool??
Any suggestions appreciated.

They can also be made in softer magnesium plate but there are serious fire risks involved in working with that stuff so I don't think i'll go that way. Aluminium is too soft generally but might be worth a test.

Exciting stuff ;)

magicniner
07-04-2016, 12:44 PM
I'm assuming you need some sharp internal corners on the shapes so I'd use a V-Carve type strategy, the variant in my CAM system allows for the option to rough out all accessible areas with an end-mill then cut only the edge/angled sections and those inaccessible to the end-mill.

- Nick

Boyan Silyavski
07-04-2016, 08:52 PM
Brass is my favourite material. Perfect i would say. Drills, machines,taps like a charm.

Probably 60 degree V cutter will do it best. Now the great thing is that you could grind away the point, measure it and enter its tip size at the program. Voilaa, no need for tool change and avoiding complications. So instead of scratching the point on a V carve path, you will finish the flat space much faster.
Especially if you CAM could not combine properly V carve paths with pocket paths later. Which by the way is not so simple at all as it seems if the result must be perfect. Impossible by not electronically setting the tool height by probing in mach 3. Even then... The problem being not knowing the exact sharp V cutter tip size. If using non brand cutter, especially.

My advice- simplicity. Roughen if possible with bigger tool. Use flat tip V cutter and finish directly. No complications, if a bit more time. Bonus- no tip breakage, faster, simpler.

Davek0974
07-04-2016, 09:03 PM
I see the idea of grinding the tip on a v-bit but i need it to give me sharp internal corners, Sheetcam has a sharpen feature that raises the Z as it approaches a corner and the lowers it again, i think that will work.

magicniner
07-04-2016, 09:10 PM
Wouldn't the required tip size will be determined by how sharp the internal corners need to be at the upper surface of the part?

Boyan Silyavski
07-04-2016, 09:18 PM
Depends what he is doing exactly. But the corner sharpness itself is determined by the angle. The tip size could determine bottom corner sharpness if any. Once you enter the details you could easily spot in the simulation the difference if any, and time difference

Davek0974
07-04-2016, 09:21 PM
Yes, it's all supposition at present.

I did look at some scrap blocks today and it seems anything around what appears to be from a 0.2 to 0.4mm radius is a 'sharp' corner for this stuff so a flat tipped v-bit with a 0.1 or 0.2 tip might work, might even be worth trying some of the 3mm engraving cutters i was gifted on it.

magicniner
07-04-2016, 10:36 PM
Depends what he is doing exactly. But the corner sharpness itself is determined by the angle.

That is geometrically incorrect, if you were right a 15 degree cutter with a 3mm flat will generate really sharp corners?
The size of the flat at the tip of the cutter determines it's effective minimum diameter and directly dictates how sharp an internal corner you can generate with it.

- Nick

Boyan Silyavski
09-04-2016, 06:44 AM
That is geometrically incorrect, if you were right a 15 degree cutter with a 3mm flat will generate really sharp corners?
The size of the flat at the tip of the cutter determines it's effective minimum diameter and directly dictates how sharp an internal corner you can generate with it.

- Nick
I agree, what i was thinking :boxing: