CNC Carving

Why Use A CNC Machine?

CNCs or Computer numerical control Machines allow a level of accuracy that is hard to achieve by hand. They also allow you to start a carving and walk away to work on another project or carving. It is like having a second set of hands. Finally, you can reuse programs, so frequently made carvings can be easily reproduced. However this comes at a price. Price is the most obvious, depending on the size and quality the can be anywhere from $20,000 – $50,000+. You also need a freezer large enough to operate it in. The main manufactures of CNCs for the ice industry are Ice Monger, Shopbot, and Leguna

Software

CAD vs CAM vs Control Software – All CNCs have some form of Control Software. This is what translate the code to make the machine move. This is not the design software. Most machines use G-code, though some like Shopbot also have custom code that may be more user friendly to read. This will decide what file format you use (the extension on the file name

The actual design software is either CAD (Computer Aided Design) or CAM (Computer Aided Manufacturing). Most people used CAM software such as CarveCo, Aspire, or V-Carve. CAD software such as AutoCAD Fusion or FreeCAD are for advanced full 3D designs and are not need for most ice carving applications. Most CAM software includes the features you need for a basic carving, with more advanced like CarveCo allowing use of 3D models and more advanced toolpaths such as Smart Engrave that will tell the machine how to have to eliminate the little pieces of ice that Area Clear misses (Area Clear is for quickly clearing large areas and is therefore not as accurate

Bits

You want to have a variety of bits. Depending on the skill of your operator you may even be able to use multiple bits in the same area to make engraving faster. We recommend the the Following Bits

1/2″ Shank Bits
1/2″ bit 6″ OAL – If yo are doing logos, this is your workhorse bit. Able to cut through a 4″ slab without putting too much strain on your spindle
1/2″ bit 8″ OAL – Good for larger block up to 6″. Runout and chatter can become an issues causing a finish that is not as nice as the 6″ OAL bit
1/4″XL – Great bit for cutting out cubes and engravings that are are large but that a 1/2″ may not be able to get too
3/8″ CNC Endmill Holder – Allows you to use 3/8″ shank bits without having to change out collets

3/8″ Shank Bits
1/8″ – Your workhorse engraving bit. Good for both cubes and logos, especially text. In the case of logos we try not to go smaller than 1/8″ as it get hard to pour in color in smaller lines. We have a variety of sizes depending on preferences. Longer ones are tapered which can cause issues with blow out such as breaking the middle of As and Bs. Shorter ones are straight but can only go a max of about 1″
1/16″ – Great for cubes. OK for logos, but we try to use this one only when absolutely needed, as it is hard to clean out the snow for color
Budget Vee and Costic Vee – Great of adding Details and swirls

Flutes

The number of flutes on a bit can change how it cuts dramatically. There can be 1-4 flutes, most bits we sell are 2 or 3 flute. The biggest difference is in what is called the Chip Load. This is the size of the scrap material removed (Or in our case, how bit the snow particles are) Large snow particles are easier to clean out. 2 flute bits will create larger chips, while 3 will create smaller. However 3 flute bits are stronger over all. More flutes also create more friction, which can cause your ice to melt instead of cut. This is why we do not recommend using and 4 or more flute bits. Our CNC operator also works with wood on the side, and has seen 4 flute bits off of Amazon catch the wood on fire from friction while 2 flute worked fine (You get what you pay for! Our bits are tested for ice)

Bit Speeds

There are 3 speeded related to CNC Bits – RPMs, how fast it spins, Feed Rate, the travel back and forth and left and right, and Plunge Rate, the speed in move down into the ice.

RPMs – Faster is not always better. In the flutes section I mentioned friction, here is another source of friction. Ever seen a person start a fire by spinning a stick on top of a piece of wood? Same concept. Just because you machine can do 25,000 RPS does not mean you should run it at that speed. You also risk bending the bit and breaking it if it is off center (Runout) and flinging it across your freezer. We recommend 10,000 RPMs for most bits. If you want to increase your chip size to make clean out easier, consider 8,000 RPMs. Some longer bit such as out CUTOUT Bits require even lower RPMs such as 4,000. Then you have specialty bits such as our Sphere and Shot Glass Bits that are 1,200 because of how side they are

Feed Rate – This is the speed of the bit cutting through the ice. Depending on the machine you ay be in Inches, Feet, or Millimeters, and per second or minute. Our machine is Inches a second and that is what all our numbers will be in. When in doubt 1″/sec is a magic number. Nearly every bit can run at this speed. 1/4″ and bigger can run faster, with our 1/2″ running at 3 inches a second. Running faster is better to a point, You do not want to run so fast as to push your ice on the table, or break your bit, but if you run too slow you will rub instead of cut the ice and create friction.

Plunge Rate – How quickly the bit drills into your ice. Once again typically 1″/sec for us, 2″/sec for the half inch. Specialty bit can be much slower sometimes only .25″/sec. If you are doing full block 3D carvings, then on the finishing path your feed and plunge should be the same

Bit Depth

The rule of thumb for bit depth normally is go 1 to 1 1/2 as deeps as the bit is wide. So a 1/2″ bit should only cut 1/2″ to 3/4″. However Ice is much softer than metal or wood. A good quality bit can go up to 4 times the depth of the bit or more. So for us we run the 1/2″ at 2 inches deep. 1/4″ at 1 inch deep and 1/8″ at 1/2″ deep. I have successfully ran smaller bits like the 1/8″ and 1/16″ bit at 1 inch deep, but this does put strain on the bit and should only be done with tapered bits.

Images

You have your Machine, software, and bits, you are now ready to make logos and engravings. Here is the spot that you can lose your mind though. Quality is the most important thing here. Most people that will send you a logo or other item to engrave and not designers or marketing, they are just average people who may not understand that you need a high quality image. Ideally you want vector based line art. Most common formats for that are DXF, EPS, and SVG. Occasionally you can get a PDF with line art, but some people do not understand that when you ask for a PDF, and will just take a normal image and covert it to PDF leaving you with more work to convert it back. If a person does send you a JPG or PNG, you want it as high resolution as possible. A 4K image is great as your software’s auto trace can follow curves much easier than a low resolution one where it will create a more zig-zag line as it tries to trace the individual pixels (which are square) rather than smoothing them out. If you are doing a color image, you will want to mirror image it

Engraving depths

You now have your artwork ready, but how deep should you engrave it into the ice? We start at 1″ deep. It allows us to put in color and still snowpack it, and last though the entirety of a normal 6 hour set up. After the first layer we typically make each layer 1/4″ deeper. Using the YouTube logo as an example, a red square of a white play button, the red would be 1″ deep, and the white would be 1.25″ deep. Always try to find a way to minimize the number of layers, after all the deeper you go, the more gelatin, sand, or glitter you will need to use, and the thinner the ice is between the logo and front of the ice, decreasing how long the carving will last

Other Tips

Sensors are your friends! – Most machines have some form of location sensors for the X and Y axis. They may be magnetic induction proximity sensors that trigger when they pass over a bolt. The advantage here is that the bolt can be easily adjust and moved (You can still set an offset in your software usually) and you can move past them if needed but if the bolt moves it will throw off your alignment. The other option is physical contact switches. While cheaper and more reliable over all, you can not move past them, once they are hit they stop the machine. The main advantage of well maintained sensors is that if something goes wrong, as long as your ice does not move you can re home you machine to the sensors and restart the program. Also can allow you to easily run the program multiple times to help with cleanout

Get a Touch Pad – Most machines have a plate and clip that you can use to set your bit’s height above the table. The problem is that snow build up, inconsistent slab thickness, and human error can lead to incorrect heights, leading to the bit not completely cutting out the carving, or cutting too deep and cutting the table. This makes most carvers scared to do cutouts on their machine. However a touch pad that is permanently mounted will allow you to have a consistent height after alignment (Ours is 4.5″ above the table) allowing to to easily set the Z height

Blowers – Helps clean out the carving. We use a hand blower that we mounted over our spindle and then have a adjustable tube to direct the airflow. Most machines have some sort of relay, either built in or as an accessory. You can use that to have the machine turn on and off the blower for you, even mid program.

Extra Parts – Have 2 (or more) of everything! Collets start to slip over time, usually after about 4000 hours of use. Belts and gears become worn and the machine may start to slip (Circles become ovals for example). Sensors might get hit too hard and break. You could catch a cord with a shovel while clean out your freezer. Power surge may damage a motor or driver. Spindle bearings wear out requiring you to send the spindle out for repair. Bit become dull and break. Always have a back up ready, especially larger parts like the spindle and motors that may have a lead time of a week or more, leaving you machine down the entire time