Cutting out letters , around the outside of the letter.

[garylgreco@adelphia.net]

I am trying to cut some letters out for a student that wants to inlay them in the top of a jewelry box he has made. I use corel and i am trying to make them a negative,or inverted ? I havent figures out how to export this so it will cut in shopbot. Can anyone give me a hand on this?

Thanks Gary

[kerrazy]

you need to save it as a DXF file, autocad 12 will work when it promts you.

If you have the orginal file in Corel set to the size you want send it to me and I will set the file up for you.
Dale

[artisan]

Since Corel is not actually a machining software, you have to be a bit creative. There is an "Interactive Contour Tool" on the left tool bar, that you can use to create offsets. If you are using a .25 bit, you can offset by .25 to either side, then use the "separate" command in the "Arrange" tool fly out to create two separate versions of your letter. Make two sets of the letters, (one larger, one smaller). When you cut them both, the cutout from the larger letter should fit neatly in the hole from the smaller letter cutout. It's not perfect, but will work well on most simpler letter styles.
Tip #2....make your work page in Corel, the same size as the material you are going to cut from. In other words, if you are cutting the letters from a sheet of plywood, make your page size 96x48. It makes layout a snap. Convert to DXF and feed it to the Bot....D

[donchapman]

Good info in the last message, except that I think you offset by only half the diameter of your bit if you want to keep the letter the same size as in your drawing.

[artisan]

Actually no, Don. Try it and you'll see. You can offset by half the distance first to the inside, and then half the distance (.125) to the outside, but, that is adding a step and you still have a cumulative offset of .25. Since a quarter inch bit will remove the full .25 on a pass, you must make up the entire amount or your fit will have a gap of .125 ....hope this makes sense....D

[donchapman]

I must be dense Darrel, but it still seems to me that offsetting by half a bit diameter from the design is the way to get a final routed letter to be the same size as the design.
I haven't inlaid letters using my Shopbot, but I've designed and routed dozens of signs using raised or incised letters. I always offset my raised letters by half the bit diameter to the outside of my design. My incised letters I offset half a bit diameter to the inside of my design. The routed letters always come out exactly the same size as my designed letters.
If I were to offset by a full bit diameter, then all my raised letters would be half a bit diameter larger than the design and all my incised letters would be half a bit diameter smaller. You can see some of my signs and read my method by going to the Shopbot home page, clicking on Applications, and then clicking on Model Signs. I wrote that four years ago and have done a lot more signs since.

[gerald_d]

Don, I think that Darrell is adding/subtracting a full bit diameter to/from the first toolpath to get the second toolpath. You are using the design outline as a reference for the second toolpath.

[artisan]

Hi Don, I knew what you were thinking and maybe should have jumped ahead a bit. You're exactly right, in that "Sign" software requires you to halve your bit diameter...as does any machining software. Corel is NOT maching software, but can be tricked or massaged in doing it.

If I wanted an inset letter to be "exactly" 6 inches tall, then I would first offset my bit .125 to the INSIDE to cut the hole in my material (negative)....which would leave me with a hole exactly 6 inches tall....but a cutout piece that was 5.5 inches tall (positive and not used). To create the positive from a different material....a 6 inch tall letter insert.... you then offset .125 to the OUTSIDE. This will leave you a 6.5 inch hole (negative and not used), and a 6 inch positive that you can then inlay into your first cutout. The result is till a cumulative offset of .25. I was simply trying to save a step, because the more calculations you make, the more your accuracy often suffers...(more chances for distortion and mistakes). If you use a program such as Artcam or Enroute....this is a no brainer. If, however you want to use Corel....which is much less expensive, you can accomplish it in this way. I hope that's a bit more clear...D

[artisan]

Yup Gerald....precisely....D

[garylgreco@adelphia.net]

Ok guys i'll give i try and let you know .
Thanks again for your help and suggestions.

Gary Greco
garylgreco@adelphia.net (mailto:garylgreco@adelphia.net)

[donchapman]

Thanks Darrell and Gerald. Now that I know your offsets, Darrell, were from an original toolpath rather than an original design outline, I understand and agree with your full bit diameter offsets. Sorry I didn't understand that from your original description. When I design in CorelDraw or a similar program I usually just export an eps file of the design into my LetterArt signmaking program where I scale it to whatever size I want and then generate the offsets and export dxf to the ShopBot software. I'm glad I was just confused instead of nuts.