Prototype Build – Volume 1 Part 2: Plywood Routing

After going out on enquiry with a sample cutting file to five different vendors we have selected CNC Lab in Randburg, South Africa to do our wood routing. We ordered the thirteen sheets of plywood and had it delivered directly to the CNC shop.

Plywood quality

A word on the quality of the plywood. There is a confusing array of grade classifications, including Brazilian, Malaysian/Chinese, Chilean, Finnish, Russian and Swedish amongst others. Here in South Africa we seem to use the Brazilian grade nomenclature. They have an excellent spec sheet which can be downloaded here:

This is an extract from their grading criteria page:

In brief, we use a combination of the letters to indicate quality front and back:

  • C+/C Face knots filled and repaired/reverse open knots
  • B/C No knots in face/open knots in reverse
  • B/B No knots face or back

We have stuck to using B/B grade Pine plywood. This gives a balance between quality and cost. According to the CNC shop we are using Birch ply gives a much better result with less ripping, but that comes at twice the price. Hence it will be fine for us to fill in the areas where some ripping has occurred – it all gets painted in the end anyway.


The routing started today and a number of the 6mm panels have been completed. This work will continue over the next few days and should be completed this week. Initial results are looking great.

Setting up of the CNC Router


Together with the CNC shop we have decided that the easiest and cheapest way of numbering the parts will simply be to scribe the code on the part with a marker pen. We did consider laser engraving but for this it simply is not cost effective. (It is something we are considering on the metal parts that will be plasma cut, but that is simply because we have less control in that process).

The numbering is kept simple, giving the thickness of the ply, the drawing sheet number and the item number on the sheet. That’s easier than having to put in the actual Part Number

6mm parts with the numbering visible
Example of the sheets showing their item numbers unique to that specific sheet

With any luck we will be able to start gluing up over the weekend! 🙂

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