CNC Plasma Cutting Complex Shapes

Plasma Cutters can be used to make some amazing products & projects. Upload some pictures of projects you've completed using your plasma cutter.
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Tmate
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CNC Plasma Cutting Complex Shapes

Post by Tmate »

I've probably overstayed my welcome with all the pictures of my vintage motorcycle cutouts, but I thought I might provide some information on how I went about creating them. Below is the philosophy I have followed in cutting these little guys out. I realize that not everyone uses the same methods on this kind of work, but hopefully this will be of some use.

The plasma cutting process generally gets bad marks for the lack of detail possible compared to laser or water-jet. This is due to the significantly greater kerf width produced by plasma arc. However, it is possible to create a surprising amount of detail if certain methods are used in planning and creating shapes.

It is natural for us to look for the easiest way of accomplishing anything. There some relatively easy ways to come up with shapes to be cut. They can perhaps be scanned from an image, purchased on-line as a dxf file, or imported as clip art. While these methods may be ok for cutting simple brackets, they have definite limitations when creating complex original shapes.

Many of the dxf files available for purchase on-line were developed by artists with no plasma cutting experience. They may be too complicated for the desired size, they may contain lines and internal that are too close together, or cutouts within cutouts. Even if you can find one that is usable, it is unlikely that it will be exactly what you want.

While bitmaps such as drawings and photos can be scanned and automatically traced by some software, in practice this is easier said than done. The background must be in total contrast with the image. Photos must be very high resolution for the edges to be well defined. Lines should be thin and crisp. Often it will take more work to fix a scanned and traced shape than to create one from scratch. Clip art is usually cartoon-like and originally drawn without any intention of their being plasma-cut.

The bottom line is that if you are going to do complex shapes, you will have to do some drawing. Most drawing and editing features included with CNC plasma cutting table are simplistic, and lack a number of labor saving features. There are a wide variety of top-notch graphics packages available to help you create your own original shapes. Just Google "best drawing and shape editing programs" to get an idea of what's out there. Once you have selected a program and become thoroughly familiar with it, you will be able to create plasma-cut shapes with a surprising amount of detail.

I personally have used CorelDraw for a number of years. It has the ability to auto-trace photos and other bitmaps. It allows you to draw lines of any desired thickness quickly around any contour, and then fine-tune them in seconds to fit precisely. It allows you to easily maintain a given amount of space between lines and shapes (about .150" or 3.8mm for plasma). It also has the ability to let you automatically color lines and fill shapes to give you a near perfect idea of what your cut piece will look like.

The following photos show a fairly complicated drawing created by manually tracing over a photograph. Note the small yellow colored circle which is exactly the right diameter to assure the proper clearance between objects. Lines and internal shapes must be shifted slightly from their photo counterparts to obtain the clearances. The thinnest eternal shape that can be satisfactorily cut is around .150" while slots and internal shapes can be slightly thinner.

The first photo shows a photo with lines and shapes partially drawn over it. The second photo shows the finished outline. The third photo shows the CorelDraw drawing with fill applied to provide a preview of what the finished piece will look like. The fourth photo is the finished shape.
over photo.jpg
Barn Job no fill.jpg
Barn Job fill.jpg
Barn Job 1 mb.jpg
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Re: CNC Plasma Cutting Complex Shapes

Post by Joe Jones »

VERY, very nice work!

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Re: CNC Plasma Cutting Complex Shapes

Post by Joe Jones »

This was a surprisingly thin cut I did with the HyperTherm 85 and fine cut consumables. I didn't think I could cut something that thin without problems.

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Re: CNC Plasma Cutting Complex Shapes

Post by AREA »

What a fantastic explanation and a great looking design, your post has inspired me to put more effort forth in my designs. So just out of curiosity so I can compare to my current ability, how long would it have taken you to complete this drawing start to finish?
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Re: CNC Plasma Cutting Complex Shapes

Post by Tmate »

With the photo already selected and without any interruptions, probably about four hours. Probably a third of that time is moving the little .150 diameter yellow circle around between parts, and tweaking them to make sure I have enough clearance. The circle could be a bit smaller, but I would rather give up a little there than take a chance on ruining $25 worth of steel. So far, I have cut out 19 different motorcycle designs without losing a single piece of material.

The only thing I don't do, that would probably speed the cleanup process, is have the torch move back and forth around the plate to reduce heat concentration on any spot. Tapping off a little extra dross is probably quicker and easier than massaging the G code to change the cut order. Note that the thinner the cross section being cut, the greater the heat buildup, and consequently the dross. Dross is also harder to tap off on the thinner parts without bending them.

On my small machine, I have chosen not to be burdened with a bulky THC. This probably adds to the dross and consumables usage, but at my small production level, I don't mind.

Below are shots of my little machine with an arc voltage THC and with the rack and pinion torch holder I have chosen to use. The third photo speaks for itself.
arc voltage thc on 2x2.jpg
2x2 CNC Plasma.jpg
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Re: CNC Plasma Cutting Complex Shapes

Post by adbuch »

Bill - thanks for a great explanation of your process. That is a great idea using the small circle to check your kerf width.
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Re: CNC Plasma Cutting Complex Shapes

Post by AREA »

Ok, 4 hours. That makes me not feel so bad, I expect it would take me roughly that amount of time also. If you were pulling that off in 20 minutes or something I would have known I was doing something wrong. Awesome work, thanks for sharing your info.
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Re: CNC Plasma Cutting Complex Shapes

Post by adbuch »

AREA wrote: Wed Apr 20, 2022 11:47 am Ok, 4 hours. That makes me not feel so bad, I expect it would take me roughly that amount of time also. If you were pulling that off in 20 minutes or something I would have known I was doing something wrong. Awesome work, thanks for sharing your info.
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Re: CNC Plasma Cutting Complex Shapes

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AREA wrote: Wed Apr 20, 2022 11:47 am Ok, 4 hours. That makes me not feel so bad, I expect it would take me roughly that amount of time also. If you were pulling that off in 20 minutes or something I would have known I was doing something wrong. Awesome work, thanks for sharing your info.
I brought the photo into DesignEdge and went at it, just to test myself. There is a LOT of detail in that photo. At 2 hours 34 minutes, I had the whole thing traced, BUT I had not yet begun to clean up the crossovers, the incomplete paths, etc. I can easily see this as a four hour effort or longer, and only when undisturbed.

I did not save the drawing or the video I made of the process. I was so tired last night, I just shut the PC down without saving anything. :Sad The final piece you made came out fantastic. Just imagine what you could do if you made it with a laser table instead!

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Re: CNC Plasma Cutting Complex Shapes

Post by Tmate »

Joe:

The problem with doing it in laser is that a significant part of the shape comes from the light shining through the gaps created by the kerf (about .050"). If the kerf were only .005" or so, as with a laser, the bike would lose much of its appearance.
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Re: CNC Plasma Cutting Complex Shapes

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Tmate wrote: Thu Apr 21, 2022 9:47 am Joe:

The problem with doing it in laser is that a significant part of the shape comes from the light shining through the gaps created by the kerf (about .050"). If the kerf were only .005" or so, as with a laser, the bike would lose much of its appearance.
You are right about that. Our old, failing human eyes cannot see tiny detail that today's machines can produce.

I bought a laser to play with. The seller demonstrated it by burning a logo onto a piece of anodized metal, about 3/4" square. I was impressed, but I asked him how accurate the laser was. so he did some adjustments to the program and said, "Watch ..."

I looked at the aluminum plate, and there was the briefest flash of light. I told him it didn't do anything. He smiled and handed me a jewelers lens and told me to place it over the spot where the light flashed. There it was, as crisp as ever, the logo about .05/1000" inch tall, and just as crisp! He told me he can put the entire Bible onto two sides of a standard metal business card, with illustrations! Needless to say, I bought the laser and it sits here now, mocking me :cry: daring me to find the time to actually USE IT.

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Re: CNC Plasma Cutting Complex Shapes

Post by adbuch »

Tmate wrote: Thu Apr 21, 2022 9:47 am Joe:

The problem with doing it in laser is that a significant part of the shape comes from the light shining through the gaps created by the kerf (about .050"). If the kerf were only .005" or so, as with a laser, the bike would lose much of its appearance.
Not to mention the high cost of a laser compared to plasma. I could see where the file could be modified to achieve the same result, but what would be the point. It's dollars per unit fun, and not the other way around.

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Re: CNC Plasma Cutting Complex Shapes

Post by Tmate »

I also bought a laser to play width. It was a 65 watt Synrad air-cooled unit that was powerful enough to cut paper, cardboard, etc., but not metal. I found the main advantage was being able to put a given amount of detail into a much smaller space than plasma. One of my bikes could have been done in a playing card easily. Laser kerf width when cutting steel would be larger, but still much smaller than plasma.

The first photo below shows the laser mounted on an identical machine to another I was using for plasma at the time, so the only difference was the cutting process. The second photo shows a piece cut in 3/16" thick mild steel with plasma, and the same shape and a couple of others cut in card stock with the laser.

IMG_1042.JPG
IMG_1043.JPG
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Re: CNC Plasma Cutting Complex Shapes

Post by Tmate »

The photo of the CNC machine with the laser got left out of the above post.

laser1.jpg
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Re: CNC Plasma Cutting Complex Shapes

Post by Tmate »

Another photo of the same laser cut shape.

eagleflag.jpg
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Re: CNC Plasma Cutting Complex Shapes

Post by acourtjester »

I to have adapted a diode laser to my CNC table, still learning the technique (speed and power) bumping up the fun factor with different projects.
Picture of my table (4X4)
FHD0001.JPG

video from another site with another guys work, etching on white tiles, procedure can be done with similar materials.
https://forum.v1engineering.com/t/more- ... tile/32389
DSCN5135.JPG
DSCN5131.JPG
I will share the info to those that would like it.
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Re: CNC Plasma Cutting Complex Shapes

Post by Joe Jones »

Yeeeeaaahhhhh ..... I need to start working on those Christmas ornaments with my laser. I figure I can get it set up for ONE TASK, and then create typical plasma style (black and white) files using photos of the customers' grandkids, pets, etc.

If I can just get my a** in gear and START on this! I think there is money to be made in creating a "dozen pack" of laser cut Christmas tree ornaments out of this colored foils, or other materials. People could by the pack, and send them out inside of Christmas cards, etc.

So much to do ... so little time or energy. :Sad

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Re: CNC Plasma Cutting Complex Shapes

Post by adbuch »

Nice work Tom! That table looks brand new. Is this one just for laser or will you add some slats and water table and start getting it dirty?
David
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Re: CNC Plasma Cutting Complex Shapes

Post by acourtjester »

That is maybe after I built it, I have a water table the replaces the spoil board, and it dirty. Cut lots of part on it and used it for sign vinyl with the drag knife I printer, along with the Pen Plotter, diamond scribe, and a utility blade cutter. I think I have run out of optional attachments.
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Re: CNC Plasma Cutting Complex Shapes

Post by adbuch »

OK. They all look great when they are nice and shiny! But it's pretty hard to keep them looking that way.
David
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