How to calculate position of cut area?

I’m about to build a torsion box as a base and plan to raise the MPCNC feet on either side to allow a removable spoil board between. I’m aware the working cut area is not centered on the machine foot print. Is there a diagram or some way to calculate where the cut area sits relative the overall foot print so I can work out how wide I can make the feet support strips on either side? I’m going with the default workspace of 450 x 330 x 81, and will be using a 65mm diameter router.

If no one answers your question by tomorrow, I can physically measure the offset using my machine (I’m currently out of town). But I suggest an alternate design. Either extend the leg length by your spoil board thickness and mount the legs directly to the base board, or put your feet on minimal blocks (i.e. not much bigger than the feet). Make the spoil the size the calculator defines for the working area of your machine.

At some point you are likely to surface your spoil board. If you go with the design implied by your question, the surrounding area will be higher than the spoil board, making it difficult to work with oversized stock. If you go with my alternate design, you can wait until you have the machine built and use the router to find where to position the spoil board.

Here is a picture of my machine just after I completed my Primo upgrade. Notice how the spoil board floats on top of the base board.

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As someone with the design you suggested I can tell you it is going to be exactly like Robert said. :slight_smile: I will snap a picture for you later.

Thanks for the info that’s a pretty slick setup you have there I like the display display pedestal.

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  • Using Ryan’s Makita mount (65mm)
  • Measuring from the outside of the feet
  • Core pushed against the trucks (so absolute minimum offset).

I measured 92mm offset for both X and Y. You will want a bit of additional offset since you want the endstops to trigger before the core hits the trucks.

Using the " Table Size" and “workspace” calculations from your calculator, you can calculate the values you seek for any machine size.

Thanks for taking the time to measure the offset @robertbu .
Since I’ve already cut the leg tubes I think I’ll go with your suggestion of minimal blocks. I was thinking full depth blocks and shortest possible legs would give maximum rigidity, but I suppose if I glue and screw on small blocks under the feet there won’t be much of a difference.

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