Wikihouse Build - Cutting & Assembling Calibration Test

What We Use

1. Araucoply AC Exterior Plywood 4’x8’x23/32” S252. ShopBot PRS Standard 96x48 w/ Porter Cable Router3. SuperZero Fixture4. Raptor F/15-150 1.5” Polymer Finishing Nails5. Porter Cable #7310 Laminate Trimmer6. Onsrud Two Flute Straight Trim Bit

Resurfacing

Since we’re starting a new project where accuracy is a factor, we start by re-surfacing our spoilboard. With a 1.125” diameter bit, this process takes about 20 minutes. Since our first layer is MDF, we do this more often than other shops and will never use MDF again. MDF expands and contracts a lot with humidity so our cutting surface is unstable for cutting very thin materials.

We simply place the plywood on the ShopBot table and make sure it is flush to the (0,0) so it is as square as possible.

Changing the bit

We start by setting up a 0.25” upcut end mill in the collet and doing our zeroing routine. We use a SuperZero so the process is mostly automated with all 3 axises being zeroed in about 30 seconds.

Cutting the Parts

Out of software habit, we break up the part cutting into multiple files so there are a number of natural pauses in the machining. If something needs redone, a tool needs changed, or we need a snack, there are a number of stopping points. Probably unnecessary but a hard habit to break.

Our ShopBot doesn’t have a vacuum hold-down system so our cutting Step 0 is marking the material. Small, shallow pockets are cut around the material where it is safe to attach the material to the spoilboard. Marking should be heavy enough to see, but light enough to not shift the unsecured material when being marked. For attaching to the spoilboard some people use drywall screws. We use Raptor polymer nails that have hold down power but are easily sliced through by the router if we put one in the wrong place.

For Step 1, we cut the main parts. This process takes about 15 minutes.

In Step 2, we cut labels on the parts. We just use a series of circles to show part numbers instead of taking the time to carve actual fonts.

Finally, we cut some extra parts to use up the left over material. We added some more lock pieces since they are small and probably wear more.

Manually, we had the ShopBot cut our full sheet of plywood in half. We will save the extra half sheet to recut the Calibration Test if we don’t pass. This also makes it easier to move the half around with our parts since we have to flip it over to remove the tabs, freeing the parts.

Remove Parts from Material

To remove the parts we machined in the material held in place by the tabs, we use a Porter Cable Laminate Trimmer. We flip the machined material over so the tabs are now face up. The bit is setup so it cuts deep enough to remove the tab but shallow enough to not go through the material. The trim bit does not have a live cutting edge on the tip so when you place the router into the groove, it won’t grab the material if you touch any. This is an important fact for safety. If there is a live edge and it grabs the material when you try to enter the groove, the torque of the router will easily rip it out of your hands and likely hurt you.

Determining where to place tabs and how many per side is a matter of practice with different bits and materials. On large parts, we try to place at least one tab per side placed away from corners. Sometimes we do more tabs on sides of the part that won’t be exposed in the final assembly.

Assembling the Parts

We end up with seven main parts and a few small locking pieces. Since we couldn’t find any assembly instructions, we pulled the model of the Calibration Test up in SketchUp. After rotating the model around and removing parts, we figured out how everything goes together. The first problem is that we are missing a part. A locking component that holds the vertical spine together wasn’t exported from the Wikihouse Plugin. We think it may have been a grouped object so the plugin didn’t know how to render it to the SVG.

The next problem is that the parts are machined very accurately so they are a little too tight of a fit. We used a small orbital sander on many of the part edges. After about 30 minutes our build is complete.