Somebody hands you a photo of their logo. It is a JPG off their Facebook page, it is 400 pixels wide, and they want it three feet across on the side of a shop building. Your plasma table cannot cut a JPG. It needs vector paths.

Inkscape has a tool that does this conversion, called Trace Bitmap. It is free, it takes about a minute, and it works well enough that most of the metal art you see on Facebook Marketplace started life inside that dialog box. It also has about a dozen settings and the defaults are wrong for plasma almost every time.

Here is what each setting actually does and where to put it when the end result is going to be cut out of steel.

A bitmap is a grid of coloured dots. A vector is a set of mathematical outlines. Tracing looks at the grid of dots, decides where the boundary between light and dark falls, and draws a path along that boundary.

That is the whole trick. Everything you are about to adjust is really one question: where does the software decide the edge is?

This matters for plasma more than it does for a sticker or a T-shirt, because you are not printing the result. You are cutting it. Every wobble in the traced path becomes a wobble the torch has to physically travel, and every tiny speck the tracer picked up becomes a pierce, and every pierce costs you consumables and adds a chance for a blowout.

Ninety percent of a bad trace is a bad source. Before you open Trace Bitmap:

Get the biggest version of the image you can. Ask the customer for the original file. A vector logo from their sign shop is even better and skips this whole process. If all you can get is what is on their Facebook page, right click the image and open it in a new tab first, because social sites serve you a small thumbnail on the page and a larger file behind it.

Crop out everything you are not cutting. Background, watermark, the white box around the logo, the edge of the T-shirt it was photographed on. The tracer will faithfully trace all of it.

Convert to black and white before you trace, if the image is busy. Any photo editor will do it. A high-contrast black-and-white source gives the tracer an obvious decision to make instead of a hard one.

Import the image into Inkscape with File then Import, select it, then Path then Trace Bitmap, or Shift+Alt+B.

The dialog has a live preview panel. Use it. Change one setting, hit Update, look at the preview, decide. Do not change four things and then wonder which one helped.

This is the simple mode and for logos, silhouettes and monograms it is usually the right one. It converts every pixel to a brightness value and asks: is this pixel darker than the threshold, yes or no. Everything darker becomes part of the shape.

The threshold slider defaults around 0.45. Move it and watch the preview:

For a clean logo on white you can usually leave it near the default. For a photo of a sign taken in a shop with uneven lighting, you will be nudging this around a lot, and that is your signal to go clean up the source image instead.

Edge Detection traces the boundaries between light and dark rather than the dark areas themselves. It produces outlines, not filled shapes. That sounds useful and it almost never is for plasma, because you end up with double lines around everything and the torch cuts both of them.

Colour Quantization reduces the image to a set number of colours and traces the boundary between them. Useful when a logo has two or three flat colours and you want them as separate pieces — a two-layer sign, for instance, where one colour gets cut from steel and the other from copper.

Multiple scans produces a stack of traced layers, one per colour or brightness band. This is how you get a layered piece. It is also how you accidentally get twelve overlapping copies of the same shape if you leave it on by mistake. Check your layers panel after any multiple scan.

Speckles. Raise this. It throws away any traced shape smaller than the number you set. Every speck of JPEG noise the tracer picked up is a closed path, and every closed path is a pierce your torch will do. Set it to 5 and go up from there until the junk is gone. On a rough phone photo I am often at 20 or higher.

Smooth corners. This rounds off corners in the traced path. Push it up a little and a jagged staircase edge turns into a curve. Push it too far and sharp corners in the design go soft — the point of a star stops being a point.

Optimize paths. This merges the thousands of tiny line segments the tracer produces into longer smooth curves. Leave it on. It makes the file smaller, it makes the toolpath smoother, and it makes the cut faster.

Hit OK. The traced vector appears directly on top of the original image. Drag it off to the side so you can see what you actually got, then delete the bitmap.

Then do these, in this order:

A trace is only as good as the resolution you fed it. If the customer sent you a 200-pixel-wide logo, the traced result will have soft, lumpy edges no matter what you do in the dialog, and at three feet across those lumps will be an inch deep in the metal.

At that point you have two honest options: ask for a better file, or redraw the logo by hand over the top of the image using the bezier tool. Redrawing a simple logo takes twenty minutes and gives you a file that is genuinely clean, and it is a service you can charge for.

Tracing is not a shortcut around knowing how to draw. It is a shortcut around drawing the easy ones.


[Watch: How to Trace Bitmaps in Inkscape and turn images into CNC cut files](https://www.youtube.com/watch?v=VqhU2q2x1m4)

If you want clean, correctly built vector files to compare your traces against, the [free CNC plasma cut file library](https://www.tinmanmetalworks.com/blog/free-cnc-plasma-cut-files) has cut-ready SVG and DXF in every category. Opening a properly drawn file and looking at the node count and the bridging teaches you more in five minutes than an hour of reading.

If you want the whole Inkscape workflow in order rather than in pieces, the [Tin Man Metal Works masterclass](https://www.tinmanmetalworks.com/start-today) walks through design, tracing, bridging, toolpathing and pricing as one process, aimed at people running a plasma table for money.

Fix the source image first. Use Brightness Cutoff for logos and silhouettes. Turn Speckles up until the junk disappears. Leave Optimize Paths on. Then delete the bitmap, simplify if the node count is silly, bridge the islands, and set the size in inches before it ever reaches your CAM software.