Session 9

Apply CAM to a Practice Piece

The Template Only Knows Its Own Plate

In Session 8 you broke settings on a plate somebody else drew. Every number in that template was chosen for that one plate.

Today the part is yours. Every setting that was right for the sample has to be checked again against your part, because CAM Studio won't do it for you.

Meet the Test Coupon

A plate 120 × 80 mm at your board's real thickness, with a 50 × 30 mm pocket 4 mm deep and a 28 mm button hole straight through.

Meet the Test Coupon

It's small and cheap on purpose. If the program is wrong, you find out on a scrap, not on a cabinet panel.

Shops do this for real: prove the setup on a test piece, then cut the part that matters.

Your Coupon Breaks a Template Number

The template's pocket toolpath stops 6 mm below the pocket's top edge. It doesn't look at the model; the 6 is typed in. Your pocket is 4 mm deep. What happens if you leave it?

Your Coupon Breaks a Template Number

The bit goes to 6 mm anyway. Your pocket floor comes out 2 mm deeper than you drew it, and nothing on the screen warns you.

That number lives under Heights → End height. Today you change it to match your part.

A New Toolpath Starts From Scratch

The template has no toolpath for a button hole, so you'll make one. A new toolpath doesn't copy the template's safe numbers. It gets CAM Studio's defaults.

A New Toolpath Starts From Scratch

Step down: 10 mm. Session 8's snapped bit.

End height: 0, measured from the hole's top edge. The bit never goes below the surface. It cuts nothing at all.

Offset: 0.8 mm. It leaves 0.8 mm of wall on every side, for a smoothing pass we never run.

Predict the Hole

You draw a 28 mm hole. The toolpath leaves 0.8 mm of wall on every side. How big does the hole come out?

Predict the Hole

28 − 2 × 0.8 = 26.4 mm. A 28 mm arcade button doesn't go in.

Set Offset to 0 and the hole comes out 28 mm. In this class, every pocket toolpath gets Offset 0.

A Button Hole Is a Pocket, Not an Outline

An inside profile around the hole would cut a 28 mm disc free and leave it loose, right beside a spinning bit.

A pocket clears the whole circle, layer by layer, down through the bottom. Nothing comes loose, because nothing is left.

Order Is Part of the Program

CAM Studio runs toolpaths top to bottom, in the order they're listed. A new toolpath lands at the bottom, after the outline.

Order Is Part of the Program

The outline is the cut that lets go of the part. After it, only a 0.5 mm onion skin holds the coupon in the board.

Anything that runs after the outline cuts a part held by a skin. So the outline always goes last, and you drag your new toolpath above it.

Verify Shows You the Cut

Verify Shows You the Cut

Verify plays the job on a model of the board, so you can watch the order and see that the hole goes all the way through.

It doesn't measure anything. A 26.4 mm hole looks just as right as a 28 mm one. The numbers you set are the only check for that.

Two Things to Remember

A new toolpath doesn't know the template's rules.

Check Step down, Offset, and End height on every toolpath you make, every time.

Two Things to Remember

The outline goes last.

Holes and pockets first, while the board still holds the part firmly.

Today

1. Model the coupon at your board's thickness
2. Bring it into your Session 8 template copy
3. Fix the template's pocket for your part
4. Add the button hole, then put the order right
5. Verify it

Next Time

Session 10: Post-Processing & Troubleshooting

Turning this job into a file the router runs, and a checklist that catches what Verify can't.

'F' → Fullscreen

Build

Step 1: Model the Coupon

1. Measure the offcut your instructor gives you with calipers, and write the thickness on your sheet. If there's no offcut yet, use 12 mm.
2. Create a new OnShape document named Session 9 Coupon - your name. Set ≡ → Workspace units… → Millimeter first.
3. Model a 120 × 80 mm plate, extruded to your measured thickness.
4. Cut a 50 × 30 mm pocket, 4 mm deep toward one end, and a 28 mm hole, Through all, toward the other. Leave at least 10 mm of plate around each.
5. Right-click the part and Rename it Coupon. Every new part is called "Part 1", and in a minute you'll have two of them.

Step 2: Bring It Into Your Template Copy

1. Open Session 8 - your name, then its CAM Studio tab.
2. Click the Insert button at the far left of the toolbar, then Insert part.
3. Choose Other documents, find your coupon document, open its Part Studio, and click Coupon.
4. If it says "N changes since the last version", click Create a version right there, then click your part. CAM Studio only cuts saved versions.

Step 3: Point the Job at Your Coupon

1. If your coupon is hidden inside the sample plate, go to Components, right-click the sample's row, and choose Hide.
2. Right-click My part → Edit My part… Click the × in Bodies, then click a face of your coupon.
3. Check Stock height. It should change to your coupon's thickness on its own. Then click the green check.
4. Delete the sample: Components, right-click its row, Delete.

Both toolpaths turn red. That's expected: they kept every setting but lost the edges they were cutting, because those edges belonged to the sample.

Step 4: Fix the Template's Toolpaths for Your Part

Two axis rough (the pocket). Double-click it, then:

1. Drive edges: click your pocket's top edge.
2. Offset: set it to 0.
3. Heights: write down the End height before you change it. Then set it to −4, your pocket's depth. Click Ok.

Two axis profile (the outline). Double-click it, then:

1. Drive edges: turn on Toggle loop, then click your coupon's bottom edge.
2. Check the red side arrow points away from the coupon. Click Ok.

The outline's onion skin doesn't need changing. It's measured from the bottom edge, so it follows your coupon's thickness.

Step 5: Add the Button Hole

1. Click Setup, then Create toolpath on the toolbar. Name it Button hole. It opens as Type Edges, Pattern 2-Axis rough: a pocket, which is what you want.
2. Drive edges: click the hole's top edge.
3. Before you change anything, write down the toolpath's Step down, Offset, and End height on your sheet.
4. Set Step down to 1.5, Offset to 0, and End height to minus your thickness: for a 12 mm board, −12. Click Ok.

Step 6: Put the Order Right

1. Write down where Button hole landed in the list.
2. Drag Button hole onto Two axis rough. It moves above it. The list should read Button hole, Two axis rough, Two axis profile.
3. If the list shows a toolpath twice, reload the page. The order is saved; the list just didn't redraw.

Step 7: Regenerate and Verify

1. Right-click Setup → Regenerate all toolpaths.
2. Click the ▶ beside Setup and choose Verify. When "Your verification is ready" appears, click Verify in that message.
3. Press play and watch it run. Write down the order the three cuts happen in, then check: is the hole open all the way through? Is the pocket there?

The outline doesn't show up in Verify. It cuts just outside your coupon, and Verify only draws the block your coupon fills.

Checkpoint

Before you move on, confirm:

• Your list reads Button hole, Two axis rough, Two axis profile, with nothing red
• Every pocket toolpath has Step down 1.5 and Offset 0, and an End height that matches your part
• Verify shows the hole open all the way through, and you watched it run

Reflection

Answer these on your own. Reflections are individual, even when the rest of the session was team work.

1. Your Button hole toolpath started with CAM Studio's defaults, not the template's. Pick one default you changed and say exactly what it would have done to your coupon.
2. Verify showed you a finished-looking coupon. Name one mistake from today that Verify would have shown you, and one it never would.

Submit

Submit your sheet and your reflection. Keep your template copy; Session 10 posts it.

Activity Complete