CNC'ing multiple patterns from same stock

I would like to cut at least four different patterns from the same stock…at the same time…setting the CNC up only once. Is this possible? If so could someone point me in the right direction with a link or advice? I use Sketchup, Estlcam and Repetier. Thanks!

They will need the same origin. Then you can just play the gcode file one after the next.

I can think of three different approaches, and a number of variations on each approache. What approach to suggest will depend on a full understanding of what you need to accomplish. Questions:

  • Is this a one-time thing, or are you looking for general approaches?
  • Do you have dual endstops?
  • Is the part saved a contour cut creating individual parts, or are you applying four different patterns to the same piece?
  • Will the patterns vary in size, or can you layout the cuts in quadrants?
  • Will the patterns vary? In other words, are the four patterns selected from a much larger set of patterns?

Note all my approaches result in a file that cuts one pattern and then moves on to the next. None cut at the “same time” like would happen if you authored all the patterns in the same EstlCAM file. Also, all my approaches will involve a bit of hand editing/combining of g-code. I cannot think of an automatic way to make this happen.

No…this is a thing I will do routinely…a commercial project.
I have dual endstops MPCNC Primo my bed is 24" x 36"
The parts are three circles and one rectangle with 1/8" holes in each…as many as 12, as few as 1. The circles are 5 1/2", 4 1/4" and 3 1/4"…the rectangle will vary…doubtfully any larger than 8" x 10". Ideally I would like to cut one of each at the same time but I could cut, say, 4 of the 5 1/2" circles…4 1/4", etc. I am learning metric…I know it is easier.
To start each device consists of 4 different patterns (as above). I’m not sure what you mean by laying them out in quadrants…I will be using ether Baltic Birch plywood or some hardwood…walnut to start. I want to economize on wood as much as possible. I could cut each pattern separately and do the job 4 times per device.
To start I am making two devices with only a small difference in size…
I am thinking that if I have all the parts laid out in the same toolpath…and designate a starting point…would it not cut all the parts? I mean the CNC doesn’t know wastewood from what I will use. I am no expert though…still learning. Thanks for your help!

I am thinking that if I have all the parts laid out in the same toolpath…and designate a starting point…would it not cut all the parts? I mean the CNC doesn’t know wastewood from what I will use. I am no expert though…still learning. Thanks for your help!

Ok. This is simpler than I thought.

This is exactly what the CNC does. You will need to use CAD to make the design of what you want. Then use CAM to decide what shapes to cut out and which ines to keep. Then the gcode file can be played by the machine to cut all of it at once.

I wrote a primer on the software workflow.

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Of course this works. I read between the lines and came to a different conclusion of what you were attempting to do. I imagined you had a variety of some item you were trying to manufacture, and you wanted to decide ad hoc (and without re-authoring to a single file) what items would be cut from some stock. I was thinking of something like keychains or coasters.

Thanks guys…this worked VERY well. When cutting the tabs that hold the piece in the kerf I am getting burn marks on either side of the tabs (brand new bit)…the full depth of the workpiece even though the tabs are 3mm tall. It makes me think the 1/8" bit is being flexed when cutting the circles even though there is no apparent truth to that as the cuts are clean and smooth when cutting out the circle.
One solution that occurred to me is to use double sided tape under the project and not use tabs. Is that feasible…otherwise how do I remedy the burn marks? Thanks again for all your help!

Burning is usually caused by the bit grinding rather than cutting. When I first starting using the MPCNC, I thought I could solve any problems just by cutting slower. That is not the case. In order to avoid burning, each cutter must shave off a slice of wood. In a lot of situations, increasing the cutting speed and/or reducing the RPM and/or selecting a cutter with less flutes and/or selecting a cutter with a smaller diameter will solve the problem. Here is the link to the first video I saw where the concept clicked. There are other videos on this subject.

Your problem is more difficult. When cutting tabs, the router comes to a complete stop, lifts up, accelerates and cuts across the top of the tab, comes to a stop, descends down for the rest of the cut. it is difficult to maintain the speed to avoid burning when the router needs to stop twice at each tab. Fusion 360 has a “Triangular tab” that ramps up to the middle and then back down to the far edge. The router does not need to stop to cut this kind of tab. I don’t know if EstlCAM has this kind of tab. You could also try some of the other items I list that impact burning like slowing down the RPM of the router or selecting a bit with less flutes.

The only problem I find with double-sided tape is that my bit can get gummed up.

A popular choice for double sided tape is to put boue painters tape on the cnc board (the spoil/waste board) and the workpiece and then put some CA glue to stick them together. It is very strong and a putty knife can separate them. Then just peel off the tape.

You could also try adding a full depth finishing pass. This will do a roughing pass while leaving 0.1mm. Then the bit come around again at the full depth to remove that 0.1mm and give a cleaner, more accurate finish. But you have to balance that against the time it takes to sand the piece at the end.

Thanks for the advice…I will see if Estlcam has such a tab…it doesn’t by default. I have never used Fusion360…I will also check that out.

That is an excellent idea! I have seen it done but it didn’t occur to me. Thanks!

Cool I did not know f360 had a triangle tab option. That sounds like a great idea. Besides less burning it also means no “drilling with end mills”.

I think estlcam has the option to plunge at an angle in the tool settings, maybe that could help?