Introduction: How to Cut Pieces Longer Than Your CNC Router

Picture of How to Cut Pieces Longer Than Your CNC Router

Do you sometimes wish you had a bigger CNC router, to be able to cut larger parts?

Well, now you don't need one! I will show you how you can use your CNC router to cut pieces longer that it's working area.

OK, I know that it's still better to have a large CNC router rather than using this method, but larger machines tend to be quite pricey and take up more space.

I've come up with this method while I was making my own DIY CNC router MkII. Basically I made the first version out of plywood using hand tools, then I used it to cut out all the pieces again with more accuracy. Unfortunately some of the parts (supports running along the Y axis) were longer than the working area of the router so it was time to get creative. (Shortly after finishing MkII, I realised that the plywood is no good and remade it out of metal :-)

This method relies on Locating Holes to find the point X0 Y0 after the stock has been re-positioned.
Basically what we will do is:

  • add Locating Holes to the drawing
  • split the drawing into two pieces
  • cut 1st part of the drawing
  • re position the stock and realign it with the Y axis using Locating Holes
  • cut 2nd part of the drawing

OK, enough talking, here it comes!

Step 1: Add Locating Holes and Split Your Drawing

Picture of Add Locating Holes and Split Your Drawing

In your CAD program add the Locating Holes along the Y axis as in the second picture. The second hole should be near the end of the working area and they should be as far apart as possible (for better accuracy with aligning with Y axis). The coordinates shown apply to my CNC router, which has a working area of 480x 800mm.

Next, split your drawing into two pieces making sure they are overlapping each other (you can extend the vectors to do that). Each of the pieces must be smaller than the working area of your router.

Step 2: Re Position the Second Half of Your Drawing

Picture of Re Position the Second Half of Your Drawing

Generate the toolpaths for the first half of your drawing and the locating holes.

Highlight the second half of your drawing and the holes and bring the centre of the first hole to X0 Y0 as pictured above. The holes and the second half of the drawing should remain in the same position in relation to each other.

Generate the toolpaths for the second half of your drawing, you can ignore the holes this time. Make sure the toolpaths are on the correct side of the vector - some programs may get confused while calculating toolpaths for open vectors.

Step 3: Drill Locating Holes and Cut the First Half of Your Piece

Picture of Drill Locating Holes and Cut the First Half of Your Piece

Go to your router and fasten some stock to the cutting bed.

Drill the Locating Holes and cut the first half of your piece.

Step 4: Reposition the Stock and Align the Stock With Y Axis

Picture of Reposition the Stock and Align the Stock With Y Axis

Reposition the stock so that the first hole (marked blue) is near the Y0 of your router, as in the first picture.

Manually jog the router along the Y axis ONLY to reach the second hole. move the stock carefully to align the second hole with the endmill whilst making sure the first hole stays in the same place.

Jog the router back along the Y axis ONLY to the first hole and if the cutter is exactly above the hole, reset both axes to 0 (x=0, Y=0). Otherwise repeat this step.

Step 5: Cut the Second Half of Your Piece

Picture of Cut the Second Half of Your Piece

Fasten the stock to the cutting bed and cut the second half of your design.

This method can be used to cut virtually infinitely long pieces by splitting your drawing into more parts and adding more holes.

You can get away with just 1 hole if your piece has a straight edge that runs parallel to Y axis. In this case just use that edge to align the stock to the Y axis.

Well done, You made it to the end! I hope I didn't confuse you too much, I tried to be as clear as I can.

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Many thanks for reading and standby for more great Instructables!

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