Friday, December 9, 2016

Beyond Plywood 1

7:50 AM Comments 0

CNC & Furniture

One of the great things about having a CNC machine is the ability to exploit its uses for all kinds of other projects besides just cutting up melamine and plywood. We design and build a lot of custom furniture, and it has been so fun to figure out how to use the CNC machine to aid in the creation of some of those projects. With greater experience comes greater willingness to experiment outside the box.

Project: Ambrose Clock

Every year, the private school where my wife teaches has an auction, and many of the classes are required to provide a project to be sold. Each of the projects needs to in some way relate to the material they have studied throughout the year. Last year, I helped out with my youngest son’s 2nd grade class project; we decided to build a clock with a band of copper inset into the face of the outer ring. The copper would have each of the kids’ names embossed in Hebrew characters.

Problem: How to cut a perfect ring, with an outer diameter of 36″ and an inner diameter of 30″, with a 2″ wide, 1/8″ deep recess directly in the middle. The outer and inner diameters could be cut using a variety of tools, such as a jig saw and a band saw, and shaped using an edge sander, a belt sander, and a spindle sander, but the potential for flat spots on the circles would be quite high. The inner 1/8″ deep recess could also be accomplished using a variety of jigs and flush trim bits, but one mistake, and the project is destined for the burn pile.

Ambrose CNC 1

We began by constructing a ring from twelve equally sized pieces of quarter-sawn Sapele, and joined them together using dominoes and glue.

I forgot to take pictures of the CNC operation, so I will try and describe it as best as possible. Since the machine’s vacuum would not be adequately strong enough to hold the wood ring on its own, we made an intermediate layer of 1/2″ melamine. We started by cutting the outline of the ring, only a 1/16″ deep or so, into the piece of melamine. This showed us where the bit would be cutting the Sapele ring (and where we should not put any screws!). We then attached the wood ring through the back side of the melamine plate, which ensured adequate vacuum hold down.

Ambrose CNC 2

The CNC machine cut both outside diameters in multiple passes, removing about a .2″ at a time. The final result from the machine is a perfect ring, in about five minutes of machine time!

liimakkaa

The final clock was assembled using copper numbers sourced from Van Dyke’s Restoration; a large clock movement from the local craft store; and very thin copper sheets, with the kids’ names embossed in Hebrew characters (as aforementioned), that were contact cemented to the inner recessed ring.

Project: Butterfly Keys

Gaughan CNC 2

We have been using a lot of live edge slabs lately, both for commission work and spec work. One of the easiest ways to add a bit of flair to these slabs is to inlay a butterfly key into the cracks and splits. Prior to purchasing the CNC machine, I had purchased a phenolic template with bushings to make the mortise and the butterfly entirely by hand. With the CNC machine at our disposal, I figured it would be easier and faster to use it to batch out the butterflies. We still use the template to cut the mortise, but now we can batch out dozens of butterfly keys in a few minutes!

We started by cutting out the test pieces until we had the size and shape perfectly dialed in.

Gaughan CNC 1

We then took a scrap piece of 1/4″ melamine as our template and cut the outline of all the butterfly keys. We have three columns of the larger keys and two columns of the smaller keys, allowing us to make 17 butterfly keys per round. (If the gigantic circle seen in the spoilboard above looks eerily similar to the clock we previously talked about, you would be correct. See this entry to learn about what happened.)

Gaughan CNC 4

Since the mortise for the keys is routed 1/2″ deep, we mill a piece of wood to just slightly thicker than 1/2″ and screw it to the template.

Gaughan CNC 3

Looking from the back side, you can see that we have two screws holding each butterfly key in place. The melamine template is indexed off the pop-up pins to ensure accurate and repeatable cuts.

Gaughan CNC 5

The solid wood is left with a slight onion skin, which keeps the outer frame of solid wood from moving around during the milling process. The keys are easily removed and installed into the mortise in the live edge slab.

Gaughan 11

The keys are proud of the surface, but once the slab is sent through the wide belt, they are quickly sanded flush with the surrounding surface.

Final 2

Here is the first piece we used these CNC butterfly keys on. Using two 3″ thick Walnut slabs, we constructed a TV stand that ended up being shipped to a client in Albuquerque, NM.

Mid Century Modern Inspired Strike Plates

We have also had a few commissions come our way that have only been made possible to take on through CNC automation. One of the projects in this category was from a local guy who already had a company that sold mid-century modern inspired mailboxes, and was looking to add a line of mid-century inspired strike plates.

We worked up a few prototypes over the summer before dialing in the final design and material.

strikeplates-1

The strike plates were nested and cut from a 4′ x 8′ sheet of 1/4″ Baltic birch core Walnut plywood. We machined each sheet face down, since we had to cut a pocket to accept the outlet on the back side. We were able to array 90 plates on each sheet. In the future, we may try to nest the plates even closer together to get even more yield, but then we increase the risk of having the small parts move during milling.

Even though the CNC machine does all the work of cutting the material, it is only as smart as the programmer who tells it what to do. The challenge for us was to figure out the most efficient and quickest way to cut all 90 strike plates from each sheet. In the end, we settled on this order of operations:

Step 1: Drill a 3mm hole to accept the mounting screw.

Step 2: Machine out the 1/8″ deep pocket for the outlet, using a 3/8″ down cut spiral bit.

Step 3: Onion skin the outline of each plate using the same 3/8″ down cut bit.

Step 4: Cut the outlet hole for the switch or outlet faces, using a 1/4″ down cut bit.

Step 5: Cut away the onion skin left from step 3 using the same 1/4″ down cut bit.

When we started with a freshly milled spoilboard, we had no damaged strike plates due to small part movement. Much of what we do as CNC programmers is to determine the order of operations that will result in the highest quality piece in the shortest amount of time. Sometimes speed is sacrificed in order to ensure quality…sometimes, it’s the other way around.

strike-plates

The final product came out beautiful and can be purchased from the website linked below.

Modern Mailbox