Looking for help

General MeshCAM Art Questions

Looking for help

Postby RacerJoe » Fri Mar 04, 2016 6:10 pm

Test-Medal.png (48.34 KiB) Viewed 711 times
I have taken on a project that I shouldn't have. But I let youtube convince me that it was all that simple. I purchased MC, GWizard and CutViewer and didn't bother with the trial versions. I am trying to make a couple projects on my Bridgeport CNC mill with EZ Vision. Again, I'm a noob at all of this and not exactly having good success. I have reviewed every tutorial and video out there but still can not get any of my parts to generate a satisfactory code that delivers a quality product in Cut Viewer. Not too mention, every estimate is 1000+ minutes. I need to make 75 of these pieces and don't have that much time. If there's someone out there willing to take a look at these files and take a stab at them, I would be GRACIOUSLY supportive! These medals are supposed to be roughly 4" in diameter and 3/16" thick. I just want to cut .05-.08" deep. Thoughts?
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Re: Looking for help

Postby Randy » Sat Mar 05, 2016 6:42 pm

Hi RacerJoe, and welcome to the forum. You have set yourself a good challenge as your first MeshCAM job!

What format is the original file? Do you have it in vector form, or is the PNG the only format? A couple of aspects of working from a bitmap:

-MeshCAM machines the whole rectangular area of the bitmap--transparency doesn't count (or rather is counted as white) Fortunately you can use Machine Regions even with a bitmap to avoid the corners of the image.
-Ideally the bitmap is as clean as possible--sharp transition between colors rather than shading or dithering.
-The higher the resolution, the better the transitions between colors. For bitmaps, MeshCAM doesn't do vertical walls, but a one-pixel slope between the different colors. This is most important for the text, which even at a 4" diameter medal is pretty small.

This is true whether just doing a height map from the image, or using the Art function to shape areas.

Can you machine the basic medal shape--outline and ribbon hole--separately? That would leave the "embossed" design as the only part to machine. If you can draw just the outline and ribbon hole in CAD and bring it into MeshCAM as a DXF (or even use Illustrator or Inkscape and bring it is as an SVG) you can extrude a solid and very efficiently use waterline and pencil cuts to make the slot and outline.

Assuming the medals are blanked out as above, I did a little image editing to change the rim to transparent (to merge it with the background), and trimmed the image to a square just the size of the outer edge of the medal.

Test-Medal-mod.png (34.25 KiB) Viewed 702 times

I imported the bitmap, scaled to 4.00 inches across and .05" deep, black as Z-.

I drew a Machine Region (after several trials--MC only has center-and-edge circle definition and 3-point circles would be a really nice enhancement) on the rim.

region.PNG (459.22 KiB) Viewed 702 times

For this example I didn't use roughing but used these parameters for the finishing:

parameters.png (89.44 KiB) Viewed 702 times

These are the toolpaths that MC calculated

paths.PNG (299.13 KiB) Viewed 702 times

And this is what the simulation looks like

simulation.PNG (346 KiB) Viewed 702 times

The machining would be a lot cleaner with a higher-resolution, sharp bitmap but this is an indication. The narrow stripes near each edge of the banner won't come through well with the machining in any case and I'd suggest leaving them out. I'd probably also suggest reversing the letters on the banner to be recessed rather than raised.

Do you have a high-speed spindle for your Bridgeport? If I recall, top speed for a typical Bridgeport spindle is only 4000 or so, and you'll be using small cutters for this job. At those RPM's you'll need to be creeping along and the machining times will be long. What material will the medals be? I just pulled speeds out of my ear for the example above, but you could ratio the machining time based on the speeds you'd actually be using.

Is there a possibility of machining one pattern and then casting (or having them cast) from metal-powder-filled resin? A couple of weeks ago I saw a Doctor Who Tardis key prop replica cast from metal-filled resin and I could not tell it wan't metal. It even felt cold in my hand.

Any way, this is at least the beginning of an approach for doing the medal. :)

All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
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