RhinoCAM assists in Cello Making Craft

Christopher Dungey of Grand Junction, CO has been hand crafting cellos since 1979. In 2015 Chris purchased a Laguna IQ HHC 3 Axis CNC machining center and RhinoCAM. Chris will readily admit that even with some automation, it still takes 400-600 hours of labor and love to craft a Christopher Dungey Cello with #116 being completed as we speak, within the span of his 40-year career. 
However, cello making is an arduous profession that wreaks havoc on the upper arms, wrists and joints forcing short careers on many of his colleagues. With the help of RhinoCAM, Chris is able to automate the task of bulk material removal that 200 years ago would have been performed by apprentices. Chris has agreed to share with us a few of the RhinoCAM techniques he uses in this process. 
 

Part & Setup

Chris has spent a considerable amount of time reviewing and tweaking his 3D CAD models until they represent the perfect form that make his cellos unique. In image (a) below on the left we see the top side of the cello as a Rhino 3D part model. Notice the curvature in the front elevation. On the right image (b) we see the stock model in RhinoCAM. The holes at the north and south ends are for alignment while those located east and west are for fastening the stock to the table of the CNC machine.
Please note that all dimensions mentioned below are in millimeters.



(a) Cello Top & Front Elevation
 
(b) Stock (600 x 900 x 33.5), Alignment & Mounting


Roughing

It is important to note here that the CNC machine is ONLY used for the bulk removal of excess wood. The final finishing work is all done by Christopher Dungey’s own two hands (see Hand Finishing below). 
Now for the tech talk: In the first image (a) below we see a 2½ Axis Profile roughing operation using a 12.5 diameter Ball Mill with the XY Stock allowance set to 3.0 mm and Cut Direction set to Conventional (Up Cut). The Z depth of this profiling operation leaves a 7.0 mm thickness at the base of the stock and two rectangular bridges (20 long x 7 high) at the north and south locations. Refer to the Rough Finishing section below to see the Bridges & Tabs clearly. 
The next two operations shown in images (b) and (c) are an interesting use of 3 Axis Parallel Finishing, but used as roughing, again with a 12.5 diameter Ball Mill. In the first operation (b) Chris has a stock allowance of 2.0, a Mixed cut direction, a 46% Stepover and then sets the Lowest Z Containment to 23.0.
This is followed by the same operation (c) but with Stock at 1.5 and the Lowest Z set to 13.5. Both (b) and (c) have Engage and Retract motions set to Linear but with zero length and Approach and Departure motions set to 0.6. This allows the tool to start cutting while centered on the inner edge of the stock left from the previous Profiling operation.



(a) 2½ Axis Profile Roughing


(b) Parallel Roughing with Z Limit (Level 1)


(c) Parallel Roughing with Z Limit (Level 2)
 

 

Rough Finishing

In these next series of images we see the final 3 Axis Parallel Finishing operation and the final 2½ Axis Profiling operation. The Parallel Finishing (a) is identical to the two shown above but with Stock and Z Limit both set to 0.0 and Stepover reduced to 12%. In (b) the second Profiling operation is shown, this time with the XY Stock allowance set to zero and the rectangular bridges (north & south) set to 25 long by 6 high. The north end bridge is shown in image (c). Also notice the scalloping of stock material left on the part shown in image (d). This is by design. The final exterior cut is done completely by hand (see Hand Finishing below).



(a) Parallel Finishing


(b) 2½ Axis Profile Finishing


(c) 2½ Axis Profile Finishing w/Bridges & Tabs


(d) Scalloping of Stock is left for Hand Finishing

 

Hand Finishing

Regardless of the use of modern CNC machine tools for bulk material removal, a Christopher Dungey Cello is a finely crafted instrument. The images below show you all you need to know about the quality, skill and craftsmanship incorporated into each and every Christopher Dungey Cello.

 

 

A Christopher Dungey Cello

Here are images of a completed Christopher Dungey Cello.

 

More about Christopher Dungey Cello Maker

We want to thank Chris for allowing us to share his story of a modern day Cello Maker and RhinoCAM! To see the completed handcrafted cello shown above, you’re invited to read more about Chris and RhinoCAM here:

To learn more about Christopher Dungey and his passion and talent for cello making, we invite you to visit his website at www.dungeycello.com and on Facebook. We also invite you to hear a Christopher Dungey Cello at these video links:

 

Don LaCourse

Don LaCourse

Don LaCourse is an Application Engineer with MecSoft Corporation. Don brings over 20 years of experience in CAD/CAM operations in both automotive and mold design applications. Don also has extensive experience in documenting CAD/CAM products and is actively involved with writing the on-line help as well as creating training tutorials for MecSoft's products.
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