Step by Step Clock- 2 Sided CNC Wood Surfacing With Shopbot Router

I really like wooden sculpted objects, there is something subtle and refined about wood crafted pieces. I wanted to explore the Shopbot to make 3d surfacing in objects that were designed digitally and then export it to the machine to make the work for me. I decided to start with a clock I designed where I would machine both the top and the bottom. I hope you guys get excited and make stuff on the router, it’s a pretty cool machine to sculpt wood and make beautiful objects.

Here is a preview video of what you will be doing:

I wanted to design a clock that could show the progress of time in a 3 dimensional way. There is something special about how time is relative to humans, sometimes time goes so fast that it “flies” meanwhile to others it “drags” forever.

I was inspired by M.C. Escher’s lithograph “Ascending and Descending” which shows a line of people in an infinite loop stairs, very similar to the Penrose stairs/steps. All of these examples are impossible objects as they are an optical illusion. A person could climb the stairs forever and never get higher, making it impossible to make in 3 dimensions. This made me think of time and space to design the clock. I wanted to divide the 12 hours in a clock and make a spiral staircase of 12 steps but making 6 go down and 6 go up so it would be a useless stairs. In terms of time, this would show how time passes but you are still back where you started.

ShopBot Training Tutorials & Videos are a great resource to dig in before doing any operation. I really wanted to learn 2 sided machining I went and watched their video from the link above: Two Sided Machining [Download Video 75mb] [Propeller File]. Most of my process is taken from that video.

Materials:

• Maple wood: (dimensions at least: 13 x 7 x 2 inches)
• Danish Oil (Natural)
• Satin Wax (Natural)
• Clock moving part: American Made Mini Quartz Movements – Model: MVT7290A
• Sanding paper + File

Machines/Equipment:

• Jointer and Planer
• Chop Saw
• Table Saw
• Shopbot Buddy + software included
• Band Saw
• Belt Sander
• Table Router + 45 ° bit

I designed the clock on Rhinoceros. You can download the STL file you need to make the toolpaths. I will be using PartWorks 3D (free software included in all new Shopbots) to make the toolpaths of the clock. So go ahead, Open PartWorks 3D. Click on Load 3d File and load: clock.stl

Here is where you will see the 3d model and a 7 step process to get your toolpaths for the shopbot.

Step 1: Orientate and Size Model

The model size is in mm: 150 x 150 x 42

As it is a 2-sided part we will need to select:

Sides to Machine: 2 Top and Bottom and hit Apply

You can rearrange the orientation. The clock is squared so it doesn’t really matter. Either way it is kind of a good practice to know which is your X and Y axis in your Shopbot. I’m going to use a Shopbot Buddy and my Y axis runs from my right to left when I’m facing the machine.

Step 2: Material Size and Margins

We need to put in the piece of wood that will be slightly bigger than our clock. I cut down a piece of maple wood with the table saw in these dimensions and it worked fine: 177 x 330 x 44.5

You can now see a few things:

• The model size is the blue box
• The material size is the purple box with black lines
• The cut plane is in gray
• X and Y axis

It is very important to know where your ZERO is. We will put this on the center of the part and on the top surface. It will help us when we do the flipping to machine the other side. Cut plane is where your middle of the cut is, in this case the cut plane position is the middle. In Machining margins around the model use Symmetrical. It’s a good practice to do an overcut bellow the cut plane. In some cases your centre point will not work as a cut plane and you need to cut more material. I put in 6 mm but it doesn’t really need it. Select Apply.

Click on Edit Tabs:

Since we will be flipping the material to do the 2 sides we need to add a tab (or more) so the part does not go flying. A tab is piece that won’t be cut of the material that will keep the material in place. You can put in any dimension you want. In my case I used a square tab of 12 x 12, you then click on Add Tab and you click one more time on the side of the part you want to make the tab. You can then edit the size and location of the tab if you are not satisfied. Next, repeat and put a second tab on the opposite side. I

I didn’t put tabs on the other 2 sides of the square because it was a pretty short piece, If you want have a long rectangular piece you might want to put 4 tabs (1 on each side).

The dimension 12 x 12 work well but you can go slimmer. To be honest, the process of cutting the tabs and sand it down on a straight plane for this clock is pretty easy so if you make a bulky tab if you prefer.

3D machining it is frequently divided into two distinct stages: roughing and finishing. The bulk of the stock material is removed by the roughing toolpath, it is a quick process but leaves poor quality surface finish. Finishing toolpaths remove small amounts of material and give the desired quality. We will begin with the first stage: Roughing toolpath

We will use a ¼ inch End Mill for both the roughing and finishing toolpath. I know some people will not agree with this one but to me it seemed like a waste of time to change the toolbit on this specific job. We are going to select it and change some of the parameters as following:

ROUGHING END MIL ¼ (name and save it for future jobs):

• ¼ end mill
• Stepover 40%
• 14000 rpm
• 2.5 feed rate
• Plunge rate 1
• Tool number 1
• -
• Rapid clearance 5 mm
• Machining allowance 1 mm
• -
• Z Level: Raster X

Now you should hit Calculate for both TOP and BOTTOM. Make sure you do both!!!

• TOP- Estimate time: 8 minutes
• BOTTOM- Estimate time: 7 minutes

If you see the blue bar at the bottom “Calculating xx%” that is moving really slowly you can cancel and check back your parameters. For us, 8 and 7 minutes sounds like a decent amount of time, so lets continue with Step 4.

As I mentioned earlier, we will still use the ¼ inch end mill but we need to change a few things in order to make a finer and detailed pass. In order to speed the process, make a copy of the Roughing Toolpath and name it Finishing Toolpath.

• Stepover 9%
• 1200 rpm
• Feed rate 5
• Plunge rate 5
• Keep Tool number 1 so the machine doesn’t prompt to change the toolbit.

Now hit Calculate for both Top and Bottom. Top: 12 minutes, Bottom: 12 minutes

On Step 5, we are not doing a cutout so we will skip by clicking next.

Step 6: Here is where we can preview and check a simulation of our toolpaths. First, we will preview the top side by clicking on Roughing and then Finishing. Then do the same to check the bottom as well, both roughing and finishing.

Step 7: Save Toolpaths

Since we are using the same bit we can select Save Toolpaths to a single file (maybe its faster). If you might change bits it could be a better option to save it as multiple files.

Click on:

• Save toolpaths to a single file
• Select top
• Save

Do the same for Bottom.

We now need to figure out how to set it on the Shopbot. On step 2 of Partworks 3D we selected the zero origin as the middle top of the part. This is important to know because we are going to put in the indexing pins. These will help us orient the stock material when we flip the piece to machine the bottom side. I found some dowels that worked fine, they are: 3/8-inch diameter, 2 inches long. We will now use another Software that comes for free with any new Shopbot: Partworks.

Open Partworks

We will create a file with the size of the stock material we will use 177 x 330 (it should be the same from Step 2 of Partworks 3D).

• In Job Size type in the same dimensions: 177 x 330 x 44.5
• Remember to Zero to the Top
• Only make 2 holes
• Center them in the material

We are going to put in 2 circles that we will neet to cut on to the sacrificial board of the Shopbot. We will use a cut depth of 15 mm for the pins to fit snugly. To minimize bit changes we will also use the same ¼ inch End Mill. Save the toolpath for the 2 holes.

Turn on the Shopbot and the Shopbot control software.

Jog 2 Axis and move the Shopbot spindle wherever you want to machine it. I recommend selecting a place where you don’t mind making 2 holes on the sacrificial board.

Zero the X and Y axis.

Now use the Z plate to zero the Z axis.

Open the toolpath for the 2 holes and Start the job. Remember to start the spindle.

Once you have the 2 holes on the sacrificial board, grab a pencil and ruler and draw a line that passes through the center of the holes. Draw a perpendicular line from the middle point between them. This will help you align the stock material.

The files included in this step are attached:

position.crv - is the Partworks file with the material dimension and the 2 circles

holes in table 1-4 ball 15 mm.sbp - is the Shopbot toolpath for 1/4 inch ball nose and 15 mm depth

Cut a piece of wood with these dimensions: 177 x 330 x 44.5. I'm not going to cover how to cut this to these measurements but I used the Chop Saw, Jointer, Planer and Table Saw to do this.

Once you have it to the desired dimensions, mark the middle point of the 4 sides of the maple. Align it over the lines you draw in the sacrificial board and hold it down with screws to the sacrificial board. If things aren’t perfectly aligned no worries.

Now we will make the holes on top of the stock wood. Use the Z plate and Zero the Z on top of the wood. Run the same Toolpath file. You will now have 2 holes on the piece of wood and 2 holes on the sacrificial board exactly bellow.

The file included in this step is attached:

holes in material 1-4 ball 36 mm.sbp - is the Shopbot toolpath for 1/4 inch ball nose and 15 mm depth

Now we are ready to run the Clock toolpaths! Load the file, do the top first. It will start doing the roughing pass first and once it finishes it will start doing the finishing pass.

Once the top is done, unscrew the piece and clean up all of the table bed. Make sure you vacuum and blow all of the wood chips and dust away. Any small piece that gets in the way will make the height of the piece change.

Put the pins in place and flip the wood placing the pins over the 2 holes on the sacrificial board. You still need to screw the piece down to the sacrificial board because the pins only align it correctly. Zero the Z using the Z plate and start the Bottom toolpath. It will do the roughing and then the finishing toolpaths.

Unscrew and remove part.

Once you have the part machined of the Shopbot you need to cut the tabs that are holding together the piece. This is pretty easy if you have a band saw. My biggest advice is be careful and don’t get the saw too close to your piece because you might cut it and need to start over with the Shopbot. Align the material to the saw and make a straight cut. Repeat this step with the other tab. Next step will be sanding the tap out so don't be too aggressive on the cut.

We should have a pretty nice clock by now but with a little more sanding we take it to a next level. First we will start by sanding down the 2 tabs. Since the clock has flat surfaces we will use the belt sander. Be careful and don’t but too much pressure with your hand because you might get the maple wood burned.

As we used a ¼ inch end mill some of the surface finish is not as I would have desired. I can see some minor steps made by the end mill that I would like to flatten out in the inside perimeter of the clock face. To sand this off I used a file and a piece of sand paper as shown in the photos.

The clock now looked pretty nice but I was still not happy with the edges. I decided to do a 45 ° chamfer with a table router along the front edges. The process for this is pretty straightforward: select the router bit, put it the router table, adjust the height and finally practice with a test piece. On the left of the photo you can see my test material and the final clock. It is now time to do some finishing work.

I prefer a natural finish on small objects so I picked two products that I know work fine. Both products are liquid so you can wipe it with a cloth or a brush:

• Danish Oil (Natural)
• Satin Wax (Natural)

First you start with the Danish Oil and give a wet coat, leave it rest for a day. Then grab a cloth and wet it with the Danish Oil again and leave it for a few hours. You can put in as many coats as you want. I recommend doing 3.

Now grab another piece of cloth and use the Satin Wax. I also recommend doing 3 coats with 2 hours in between each coat.

Putting in the clock-movement parts:

I looked online for a clock-movement part that had the longest shaft and this is one that worked with my design:

American Made Mini Quartz Movements – Model: MVT7290A

They are pretty simple and work with a single AA battery. Go ahead and order 1 for your clock. Assembling is easy, the only thing that you will need is to cut with a scissors the 2 hands of the clock. My advice is to cut the minute hand first as long as the clock face permits and then cut the hour hand 2/3 of the way. No measuring is needed, just eyeball it.

Yes, you made it this far and now you can enjoy a beautiful clock in your home. Show it off to your friends whenever they come for dinner and let them know you made it.