How would you draw this?

Hi All,

Just wanted to get some advice/opinions from you all.

I work in a Joinery/furniture company who provide bespoke items (Reception desk, tea points, credenzas etc)

From time to time i get some curved pieces of furniture with complex geometry.

My question is when starting the drawing would you try draw with arcs or curve: interpolate points?

If i had a piece of joinery which had a radius i would definitely draw in Arcs, however these items are typically free flowing type of shapes.

These parts will be going to Mastercam to be 5 or 3 axis CNC’ed (So they prefer Arcs)

Just wanted to get some thoughts



What are your tolerances? I probably would just bring the pdf of this in Rhino, scale it and traced general lines with InterpCrv. Go from there.

To be honest I don’t really think we know as a company - but as it’s high end furniture/office fit out joinery we tend to work with small tolerances, around 0.2mm

I was talking more of an overall sizes of the object, like does it matter if that curvy desk is 5mm wider than shown in the drawings. Or is just a concept pic and you are the one creating the drawings?

ah i see, generally we receive drawings from architects and have to follow them as close as possible. A few mm may not be a problem, unless they clearly state on their drawing a dimension they require.

You can always adjust your curves to match the drawings closer after the initial trace. But I’d not use arcs and lines on curves like this.

I drew this using splines in the end, however our CNC department prefer to work with arcs, but i managed to get around this by exporting the 3D parts out as a DWG CAM metric file.

That’s another subject which i’m not 100% sure on as well. The best way to get my 3D parts to our CNC guys. I know Rhino files open in mastercam, but I’m not sure this is the best way to transfer the files, do you know much about this Asterisk?

Btw thanks for your help :slight_smile:

Yeah, CNC software hates splines, 'cause the G or NC code doesn’t do splines. They get converted into lines and arcs by CNC software that generates the code for the machines and sometimes the conversion fails, so the production comes back to you asking to convert the geometry into simple arcs and lines. We use Panel Builder here. It’s AXYZ software if I’m not mistaken and it deals with splines nicely or is it our Rhino exports that are already fixed?.. Don’t know. :slight_smile:

You can make Rhino export splines as arcs and lines into DWG. It’s in the Export scheme settings.

Would you be able to view your export settings just in case it is that and let me know?

Would be much appreciated!

Thanks again

That depends entirely on the quality of your “CNC Department” personnel, their software and their machines. I’ve been CNC’ing spline-based curves for over 20 years with no problem. Decent CAM software will do the conversion to line segments in the background based on tolerance, decent CNC machine controls and motor circuits will not stutter even with lots of relatively fine line segments.

True, it usually comes down to them (business owners) not wanting to spend money for a competent software and pay people who actually know what they’re doing.

This setup seems to work for us. (this is in inches)
You can change splines to this too.

We use Mastercam x9, which i believe is quite old? It would be perfect for me if the CNC guys could convert my 3D parts with spline lines in their software. Maybe its worth us upgrading?

Thanks Asterisk,

I’ll give it ago and see how they get on with the file.

Below is the file which i created, not sure if anyone could have a quick look at it within a CAM software just to see if there’s any obvious issues?

Solid Capping Test.dwg (167.1 KB)


Oof, seems like you were rebuilding lines and arcs… :stuck_out_tongue: familiar picture.

We do wall cladding, so all our CNC stuff is 2D.

I started with Surfcam 7.0 which is even earlier than that (I think). It handled splines just fine back then. The problem is probably not the CAM software, but rather the (older) machines and CNC controls which can’t handle lots of fine line segments (approximating a spline) in the G-Code.

We have old KOMO machine sitting in the shop (still works, but not really used). It’s got whooping 64KB of RAM. If G-code file is larger than that - it has to be split just so machine could actually load it. XD

My 1998 Haas had 1Mb RAM. But I could DNC with it. I routinely sent it 25Mb (1 million lines+) G-code files for 3D machining (via RS-232).

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That’s ADVANCED. That’s like quantum level of CNC in comparison to our stone age 2D troglodyte.

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Yeah, I did some pretty cool stuff with it way back then…


We check exported dwg files in Autocad LT or Draftsight before sending to a supplier. Normally splines is ok for export to Lasers and punching machines. We only had issues with dwgs, that were converted to small polylines. Wrong export parameters can lead to funny results! Too many points, and some Cam Softwares stop working…