CNC used for making moldings

I’m not talking your run of the mill trim made with routers and shapers and molders, I’m talking patterned trim like this:


http://www.rockler.com/bendix-1013-carved-egg-and-dart-moulding

http://www.rockler.com/bendix-gesso-leaf-with-egg-and-dart-crown-moulding

I was hoping someone had done this kind of thing. I wasn’t certain if it would be possible to align a narrow board to a tool path and have it cut accurately or if it would it be necessary to cut it out on a wider board and trim the board back.

I understand the idea of tiling and that it would be necessary, but could it be done seamlessly with intricate cuts.


In woodworking there is always more then one way to accomplish something.

Just for reference...let's do some math to predict cycle time for a custom 3D routed profile.

Lets assume a .025" step over per pass. This will extract a fair amount of detail, yet it will be textured.
Let's say we can use 100 IPM feed rate.

I will work an example of 1" wide section 12" long. From there it is easy to factor it using your actual trim width and length needed.

1" wide / .025" step over = 40 passes required cover that inch of trim width.
40 passes * 12" of trim length = 480 inches the tool will travel making that 1" wide by 12" long piece of trim.
480" of tool travel at 100 IPM (480/100) = 4.8 minutes of cycle time.

Now we can use this number of minutes to calculate the actual cycle time of our trim width*length requirement.

Let's say we are making a piece of crown molding. I like this example because the .025" step over is a perfect balance of cycle time and acceptable finish for the distance the eye is from the trim.

We decide we want a 6" wide trim profile and it is for a 12' x 15' room.
12' + 12' + 15' + 15' = 54' of trim required. For example sake we will not factor in scrap or cut waste.

To simplify the formula we will say 12" of trim length equals 1'. We will call the 1" wide x 1' area a "section"

6" wide * 54' = 324 sections * 4.8 minutes per section = 1555.2 minutes / 60 (minutes per hour) = 25.92 hours of cut time.

That number does not account for setup time, fixturing, and moving the part down if our machine table length is less than the chosen length of trim section we are making at a time.

If the machine is only capable of running 50 IPM for 3D work double that amount of time.
If the machine can run 200 IPM cut that time in half.
If the step over is .0125" (half of the original .025" step over) the cycle time is doubled.

You can see how we can now factor this information to cover pretty much any 3D tool path area, feed rate, and step over.

Math is fun.

Rob

P.S.
I simplified the 100 IPM example. The actual cycle time can be greater than what is reflected in the math above. Different machines have different accel/decel parameters that will affect the actual feed rate. This is really a factor if the trim were programmed to step over the long direction. Always program parts to keep the tool moving the longest distance possible before having to turn around and go the other way. This reduces the number of times the accel/decel parameters affect the cycle time.

To produce 3D moulding you would need Vectric Aspire software or some other 3D modeling software. Here is a video of the preview of the toolpaths cutting a model of my reproduction of the Egg and Dart moulding that Rockler carries. It was modeled in Aspire V9.015


This piece of moulding is approximately 9/16" thick x 1" wide x 8" long.

The estimated cut time for this piece is 1 hour and 6 minutes at 100 IPM. It can be lengthened and tiled for longer pieces. Most CNC machines will cut this at a faster rate, this is a conservative estimate for hobby machines. This is a 3D project and could be redesigned using one of various bit profiles and 2D and 2 1/2D toolpaths to speed up the cutting process.

This is just a simple pattern, some really nice moulding can be made to accent a specially designed project like this grape moulding.

Terry I created these mouldings in Aspire. The re-creation of the Rockler moulding took longer than the Grapes moulding because I had to start from scratch. The Grapes moulding was made using one of the 3D models included with Aspire, I created the rest of the model using the 2 rail sweep in the software. For longer lengths you can just make the model longer and if it is longer than the bed you can tile the toolpath to cut much longer pieces moving the blank on the bed as needed.

I have had Aspire software for several years like John pointed out. I have learned a few tricks and still have a lot to learn. Vectric has upgraded Aspire to include a lot of tools that make short work of some tasks that use to take hours or days to design. I tend to think outside the box at times and it seems that Vectric is designing the software to make project design easier and faster so more people have tools to create those out of the ordinary projects. I use the software almost everyday, I am in charge of the local CNC user group and I do Vectric software demos at some of the local woodworking stores.

The important thing is to use the software, you won't learn anything if you don't use it. I always recommend downloading the trial version of Aspire first and play with it awhile to see if you really want to make your own models. Remember, if you want to you can use other 3D programs to make models. And there are also other software companies that make design software for CNC projects. I like Vectric software and find the tutorials very helpful. I recommend watching all of the videos using the Category feature that should lead you from start to finish. If you try to watch the videos using the Project feature you will be lost because you might be watching videos that are using basic tools that you don't know what they do because you have not watched the video where it was introduced and explained.

If you find that creating models is not for you then you can download models from places like http://www.designandmake.com/ and use creative 2D and 2 1/2D toolpaths to make the mouldings. Remember these models can also be carved directly into the project for accent.
@honesttjohn did not list 6 -- see if you can visit someone that owns a CNC to see how they run in person. (John is from Michigan)

One think to remember is CNC work is 85% to 95% computer work for the design, the rest is cutting the project. If it will be cut over and over then it is easier to justify the time you spend on design.

This one was made in VCarve Pro using the models included with the software.