Coping crown moulding

[Jerry Scott (Unregistered Guest)]

I have a large job, 5,000 feet of 3 5/8 finished MDF crown. Has anyone tried to cope crown on a shopbot? I thought it would make the job go much faster if the coping was done in advance since all the rooms are the same size.

[kerrazy]

They might be the same size, but are the walls the same angle....Not even a remote chance. I would leave it for the job site.

[ron brown]

Jerry,

I have considerd the process. Contact me off-forum for my thoughts.

Ron

[beacon14]

Pre-coping the sticks is a good idea for a production-style assault on a house full of crown molding. (Dale - unlike mitering, coping inside corners accomodates slight variations in the wall angle. With a uniform product like the MDF crown should be, there should be little handwork required to complete an inside corner once the part is coped.)
Jerry, I see the biggest problem being how to get the backcut required to do a coped corner on crown molding. I suppose you could use the 'Bot to cut the end profile, then back-cut by hand. If you are tricky with the programming, you might be able to use a narrow angle dovetail bit to do a lot of it.
Please let us know if you find a solution.

David B.

[Jim Rabeneck (Unregistered Guest)]

I just started putting up crown yesterday in my own house. Coping the 4 1/4" by hand is going to be quite time consuming. I cut off a thin slice of the crown yesterday and scanned it and inserted the image in to autocad. I then traced the outline full scale as a closed polyline and extruded around a 90 degree bend to make a 3d solid of the crown in a corner. I then sliced the model at a 45degree angle just as you would do the actual cut. Discard one of the solids and align the other so that the piece will be face down on the shopbot table. Use the 3d polyline tool to draw a line where you would make a cope cut in reality. Mirror the 3d polyline so that you have a left and a right cut. Export the drawing as a dxf file. I then use vector cam to process the lines with no offsets. I used a 1/2" 90 degree v bit and cut the file in two passes. My first cuts look like they are going to work quite well.

[Jerry Scott (Unregistered Guest)]

To Jim,
I like what you are doing with this crown moulding. This is pretty much what I envisioned, although I see that I don't have the same tools to work with. I could sure use some help with this project. My E-mail is out of wack right now thanks to a virus gift from a shopbotter, but if you'll contact me by phone (912) 925-3623 we can make a deal good for you and I both.

Thanks,

Jerry Scott

Also thanks to the other comment contributors. It all helps us to get to where we're going.