The Bantam Tools Desktop PCB Milling Machine can mill a wide variety of materials. Below is a list of materials that work great, materials that work great if you're intermediate/advanced, and materials you shouldn't try milling with the Bantam Tools Desktop PCB Milling Machine. Following the lists are in-depth guides for many of these materials. Each guide provides information on attaching the material to the milling machine bed, tips on milling, and suggested feeds and speeds.
Materials that work great:
- FR-1 printed circuit board blanks
- Machining wax
- Brass (for engraving)
- Aluminum (for engraving)
- Silver (for engraving)
Materials that work great if you're intermediate/advanced:
- FR-4 (can be milled safely only if using the the Bantam Tools FR-4 Milling System)
- Hard plastics (e.g., Delrin and HDPE)
- Hardwood (e.g., mahogany)
- Soft stone (e.g., soapstone)
- Leather (for engraving)
Don't mill these materials:
- Steel (stainless or otherwise) — Dull/melts the cutting tool
- Iron — Dulls/melts the cutting tool
- Magnesium — Chips can ignite and are difficult to extinguish
- Titanium — Dulls/melts the cutting tool
- Fiberglass (including FR-4 circuit boards) — Makes unhealthy dust. FR-4 should not be milled unless while using the Bantam Tools FR-4 Milling System.
- Hard stone and precious gems — Dulls/melts the cutting tool and creates dangerous dust
- Glass — Shatters, creating dangerous shrapnel
- Silver chloride or other powdery materials — Very crumbly, doesn’t hold its shape
- Chocolate, cheese, or other food products — Milling machine is not food safe.
Material Tips and Tricks
- If you’re cutting hard materials, shallower cuts will improve the longevity of your cutting tool.
- If you’re cutting a small, deep hole, make sure that the flutes on your tool are at least as deep as the hole. Otherwise, the material will fail to eject, gumming up the cutting tool. This can damage or break the tool.
- To improve milling times on jobs with large areas to clear, use a larger tool in addition to a smaller tool. For example, to mill a circuit board faster, it's typically best to use a use a 0.005” PCB engraving bit to isolate the traces and pads and a 1/32" flat end mill to mill the holes and cut out the board outline.
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ABS, or acrylonitrile butadiene styrene, is a terpolymer, meaning a combination of three polymers. ABS is a versatile, impact-resistant material that's easy to add color to and construct things with. It’s a little finicky to mill because it can melt and gum up your tool, but it’s also less expensive than some other plastics.
Acrylic is a transparent thermoplastic derived from natural gas. It’s more brittle and has a lower melting point than polycarbonate but has better scratch resistance and comes in a variety of colors and textures. It can be tricky to mill because of its lower melting point, but its clarity is very desirable. It’s known commercially by such names as Acrylite, Lucite, and Perspex.
Aluminum is a lightweight, durable, and corrosion-resistant metal that is electrically conductive. It comes in a vast number of different alloys, each with different physical and thermal properties. The most commonly used, general-purpose alloy is 6061 aluminum, which has a great blend of strength and machinability.
Brass is an alloy of primarily copper and zinc. It’s desirable because it has a gold-like luster and color, a low enough melting point to be easily cast, and low friction. There are many kinds of brass alloys, each with different properties that make it suitable for different uses. For milling, we recommend 360 brass.
Delrin is the brand name for acetal homopolymer resin, which is a very hard, high-strength engineering plastic. It can withstand temperatures from -40°C to 120°C (-40°F to 248°F), and it holds its shape well over time. Despite being hard, it mills easily and gives an excellent surface finish with the right settings. It’s also self-lubricating, which allows it to be used for parts that slide against each other without wearing down or sticking.
FR-1 is a hard, flat material that consists of a thin layer of copper over a non-conductive phenolic resin. It’s usually about the thickness of two or three credit cards. FR-1 is primarily used for making circuit boards. The thin copper layer can be milled or etched away, leaving traces to which electronic components can be soldered. Dust generated by milling FR-1 is considerably less dangerous than dust from milling FR-4 (fiberglass).
HDPE stands for high-density polyethylene. It’s an inexpensive, lightweight, chemical-resistant, food-safe plastic that has a high strength-to-density ratio, which makes it well suited for a vast number of applications. It can be blow molded, injection molded, extruded, and milled. You may recognize it as "#2 plastic" by its recycling symbol.
Machining wax, or machinable wax, is wax that has been mixed with plastic to make it very hard, tolerant of high temperatures, and able to retain extremely fine details. This means that it won’t melt when you mill it, and it also won’t droop, sag, or deform like many other soft materials, so you can mill very thin surfaces and tiny features.
Polycarbonate is a set of durable, impact-resistant thermoplastic resins that have relatively high heat resistance and color stability. It’s naturally clear and can transmit light almost as well as glass. It’s commercially known under trademarked names such as Makrolon or Lexan. It has excellent milling properties.
There are many kinds of wood, with many different uses. The milling machine can mill all of them. Softer woods like plywood or balsa are useful for jigs or quick models but may not give a great surface finish due to their long grains and low density. Hardwoods like mahogany, purpleheart, or cherry mill more slowly but can be given a beautiful surface finish.
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