November 29, 2021

Cutting Plywood with a CNC

CNC plywood cutting products are as popular as plywood. It works just like the MDF board and particleboard. Plywood sheets are a result of coIt comes with unique characteristics and structure. This article gives you an introduction to types of plywood and how you can use the Best CNC Wood Carving Machine on it.

What is plywood

Plywood is a three-layer or multiple-layer board material manufactured from thin layers or plies of wood veneer glued together. The number of layers is odd, and the wood grain direction of the adjacent layers is perpendicular to each other. 

Plywood has its advantages and drawbacks. Plywood comes in multiple versions according to different criteria. Based on the wood veneer it uses, plywood includes bamboo plywood, spruce plywood, birch plywood, walnut plywood, oak plywood. It also falls into softwood plywood, hardwood plywood, aircraft plywood, marine plywood, flexible plywood, decorative plywood.

Why cutting plywood with a CNC is a bad idea?

  • It is not affordable when compared to MDF and particleboard.
  • You get a splinter from edges during transportation.
  • It is difficult to cut.
  • It emits toxic, organic compounds. 
  • It is difficult for users to judge which kind of wood veneer is used.

What are the risks

There are chances of making splints that cut through your skin. Those are hard to get rid of, and they cause injuries. 

When cutting, plywood produces sawdust. It happens to all woods, not just plywood. However, plywood has its own distinctive toxic with sawdust. It contains glue that makes plastic compounds. These are more flammable than just wood sawdust. Always practice good housekeeping to keep plywood sawdust to a minimum.

Many of the glues used to make plywood emit formaldehyde gas. If you are a hobbyist who occasionally works with plywood, this hazard might not have implications for you. However, a professional carpenter or builder, exposed to plywood, becomes a victim. 

It becomes worse if you work in unventilated areas. Make sure you wear a respirator to decrease the risk. Cutting plywood creates dust. Inhaling dust particles from plywood causes respiratory issues, from mild throat irritation.

How to cut plywood with a CNC

There are many plywood cutting tools, such as cutting plywood with a jigsaw or electric saw, cutting plywood with the router, or with a plywood laser cutter. When running plywood workshops, the best way can be cutting plywood using a plywood CNC machine. 

The CNC plywood cutting machine includes a plywood CNC router, oscillating knife plywood CNC router, and plywood laser cutter. For cutting plywood sheets with a plywood CNC machine, you may need plywood router bits. 

There are spiral upcut or downcut compression plywood router bits made of solid tungsten carbide. They cut with a shear action when cutting plywood by pushing the chips and cuttings towards the center of the cut so that the outer edges do not get the hairy look.

How to avoid tear-out

There are things that you can do to prevent tear out in plywood. Use a zero clearance insert on your table saw. It supports the wood fibers at the cut line, and that improves your cut quality. You can buy insert blanks for your saw, or make your own from plywood or MDF.

Another thing you can do is use a high-quality, high tooth count blade. Using a 40 tooth blade works just fine. If the tear-out continues, try a plywood blade with 60-80 teeth. More teeth yield a smoother cut and less tear-out. When the plywood blade is at an alternating bevel, meaning the teeth on the plywood blade are milled at a high angle for more effective scoring of the plywood. That is how a less tear-out is created.

Allow the dado blade to come down to sharpness and the properties of your dado stack. Beware of some budget-friendly dado sets that give tear-outs. The dado blade has to balance price and performance.

Another way is to use blue tape. Run a strip of blue masking tape along the cut line on the side that you expect a tear-out. The tape holds the fibers in place during the cut. Expect to see a clean, crisp line. But with a zero clearance insert and a high-quality blade, this step can be unnecessary.

If the above solutions do not work, make a scoring cut by raising the blade about 1/32 inches and making a light, initial pass. That serves the fibers on the face of the plywood. You can make a second pass with the blade extended and end up with a tear-out free cut. Several larger saws out there are outfitted with a second blade that lives in front of the main plywood blade, to make this type of scoring cut.

How do I make cuts in the middle of plywood without cutting in from one of the edges?

  1. Install the cutting bit on the multipurpose tool or the blade on the jigsaw. 
  2. Insert the bit or blade into the hole. 
  3. Hold the tool firmly and turn it on. 
  4. Follow the pencil lines that outline the square from corner to corner to cut out the shape.

How do you seal the edges of plywood?

Fill gaps on the outside layer of plywood by inserting enough putty to cover the void. Use a putty scraper to smooth the putty flush over the hole and wipe away any excess. Rub the outer surface using sandpaper. 

Blend the filled hole to make a smooth surface and sand the edges for a smooth finish. Plywood is a durable material for projects, but it has to be sealed to protect it against water damage and rotting. That gives it a long-lasting finish. Once sealed, you may finish your project with paint or polyurethane.

Alternatives to using a CNC

Rapid molding process

A rapid casting process is an economic alternative to CNC machining, die and investment casting, and sand casting with machining. It uses permanent graphite molds to produce parts from ZA-12, a zinc-aluminum alloy, with typical turnaround times of four to six weeks from finished CAD design to first article samples. 

It is a practical alternative to machining parts from blanks and die casting. For the mold maker, keep up with alternative technologies that can improve the manufacturing process and help you serve your customers.

David D. Hughes
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