Thinking about a CNC router - Can I digitize my existing furniture templates?

[Bob Falk]

My apologies if this is a stupid or already answered question. I am thinking of purchasing a CNC router for various tasks in my shop (carving, signs, etc) and I have existing wood templates for various chair parts I would like to automate the cutting of with the CNC. What is the simplest way to digitize these templates? Some are 4-5' long, so photographing or scanning may be awkward. Do CNC routers come with probes that can be used to trace? If so, are they expensive? thanks, bob

[William Adams]

A touch probe is easily added to most machines so long as the controller software will support it.

Lots of designs around.

[Art Mann]

The control hardware/software for my CNC router is called WinCNC. It provides the ability to record X Y coordinates manually with a test probe or just a pointed bit. A set of these coordinates can then be used to recreate a drawing of the object being probed. I have not yet attempted to do this so I can't say how well it works.

[Doug Rasmussen]

In answer to the digitizing question, this is how I would do it. Keep in mind my machine's controller has the capability built in to do this efficiently and automatically.

Probe the part by specifying to the machine controller the area to probe. The specification would be a rectangular area totally enclosing the part with an incremental distance between points to be probed. The incremental distance between points depends on the amount of detail in the part's contour. As the points are probed the machine controller saves point coordinates to a text file on the controller's hard drive (note: and this is important, some machines can't write to a file or store point files in memory).

The probed point coordinates will be offset from the actual part coordinates by half the diameter of the round probe tip. In a CAD program the probed coordinates would be turned into a line contour. That line contour will be offset half the probe tip diameter from actual part contour. Use the CAD program's offset function to move it to the actual part contour. At this point you have an accurate drawing of the part.

[Bob Falk]

Thanks for the input! Sounds like I should assure that the CNC I buy has the option for a probe. Cheers, bob

[Brad Shipton]

The system on an entry level machine is not an incredibly fast method, but it will work. I suggest you watch some videos on Youtube. https://www.youtube.com/results?sear...y=cnc+scanning Mick Martin made a good video where he digitized his table to install pop-up pins. That will give you a good idea of the speed for the non-auto digitizing system.

I would not be surprised if Doug is talking about a scanning system like this ---> https://www.youtube.com/watch?v=IcVv1So1n_8 If so, that is not your run of the mill setup you get on an entry level machine. He has full blown CNC milling machines. The workflow for most of us using yellow or blue machines will be to measure, model, tool path and then cut. All of this can be quite time consuming, so you need to do some reading.

Before getting keen you need to go thru your expectations, speed requirements, and the level of detail you require. Not all CNC's are created equal. If you are thinking of doing this on a $2k - $10k CNC, sadly, I doubt you will be happy if you have high expectations.

[Bruce Page]

If the geometry of the template is not too complex it might be easier and quicker to draw out the part in a CAD program. Most modern CNC software can then import the drawing file and generate tool paths to cut the final part.

[Gerry Grzadzinski]

My preference is to measure and draw it in CAD. Far faster for me. Even with probing, you'll still most likely need to clean up and/or refine in a CAD program.

[Mark Bolton]

Not coming from the most experience in CNC but in the time I have on our machine I would suggest taking photos of your parts and scaling those photos in your software and matching vectors. Outline digitizing with a probe is a tedious practice at best and as already stated, you will wind up with a file that needs a tremendous amount of editing and tweaking after a painfully long (hours sometimes) digitizing process. The software I use compensates for probe tip diameter and trigger allowances but you can put a precisely machined 2-4-6 block on the machine and probe it and it will-not give you a precise rectangle. The resulting file will have hundreds, if not thousands, of nodes that will then have to be corrected in post processing.

Probing (to me) is most effective on very intricately profiled parts or 3D parts. For simple part outlines its more work than its worth.

For 2D work setting up a camera and tripod and shooting images of your parts from overhead and then importing them and tracing vectors is extremely accurate and allows you the ability to refer to your notes and adjust mortise and tenon sizes, sweeps, radius', ad so on. Its way faster.

[Kevin Groenke]

+1 on photographing and tracing vectors.

Here is an ok tutorial on doing this in Rhino.
https://www.youtube.com/watch?v=5WQ_bLT56Y4

Another possibility is to trace the outline from an actual part or a template (black line on white paper) then use a vectorizing service or software function (like illustrator's live trace) to generate vectors. Some clean-up may be necessary but those should get you close.

[Bob Falk]

Thanks guys..... most of the templates I have are chair legs with long gentle curves....sounds like a probe will be overkill.....after reading the above comments, it seems that redrawing the parts may be faster and cheaper.

[Mark Bolton]

Ive templated several chairs with tracings made in the field. Rolls of rosin or craft paper and lay the faces on the floor and acurately trace them. Parts that aren't flat/traceable I trace whatever curves/angles I can and make lots of notes. Back at the shop I photograph the drawings with a 12" scale in the image and import them, scale, and fit vectors to the drawing. Works very well. You can work graceful sweeps very easily.

[Bob Falk]

Thanks Mark....I'll try that. Cheers, bob

[Cliff Land]

another option that you may explore. aliexpresscom search for stl for cnc. there are tons of models there. if you find one that is close enough that it you can edit in rhino or mesh mixer. for example the search "3d model in STL format for cnc furniture" turned up 7 pages of results. or the shop owner may can make a custom model for you.