What machine do I use?

i believe its a merrowing machine. it only does a merrowing stitch from my understanding.

About the patches on the uniforms, first, embroidery on twill , then cut each of patch down, overlock if your require,

For the finished patch, they can have plastic backing or iron-on backing or non backing.

Plastic backing just make the patch smooth and stiff, if heated, it will not sticky to unfirms, it can be sewn on the unfims, so the plain backing /non backing patches.
if it is iron-on backing, if heated with iron, it can be ironned on the unfirms,

These are how the patches made.

Thanks
Anna

why dont you buy patch blanks the blanks are already made and you just sew on the blank,

Are you talking about name badges???? Or the entire patch that says like "Boston Police Department" with the shield and crest?

If you want a full custom patch, it is sewn out in "sheets" on tackle twill, (usually 100% nylon) then it is heat cut.

We use 100% polyester fabric. The edges are merrowed. We can also make FR patches, which most fire departments require.

Also, I'm guessing those departments that require FR would require sew on backing. Heat Seal would melt under intense heat.

Depending on what you need, buying blanks is not a bad idea. The cost of a merrowing machine is generally prohibitive for most embroidery shops.

With my long experience in Embroidery field, I tell you the patches is the simplest embroidery, because you can embroidery it on any kind of embroidery machine, just flat machine, or even shuttle machine for mass production and more professional, if you don't have shuttle machine make sure you adjust the thread tension to not shrink the fabric after you get it out of the hoop, you should embroider the face, interlining and backing all together, make sure interlining is heavy enough and hard material like fabric laminated with plastic to not shrink with embroidery stitches, the backing use iron on to fix on the suite or without iron on to sew it on suite, all design inside the patch simple to embroider as digitizing and lettering, the hard part it the edge, there is two ways, simplest is embroider whole patch with the edge to cut and that's it finished, second way to make the edge on the overlook edge machine, this need more experience also thicker thread than embroidery thread, embroidery thread usually 120/2 rayon thread, but with overlook edge use 300/2 or higher, the view will be more great than embroidery, but in some situation, we can not use overlook edge, like complex edge design, my advice to you, just use embroidery with whole patch if you are just a starter patch embroidery.
At the end I want to tell you every one can do the patches, but with experience the finish work view will be more acceptable and faster in production, so you will gain more profit.