Machine Times?

[patricktoomey]

I just got my ShopBot and I'm relatively new to CNC routers. I have a strong background in 3D CAD/CAM and programming so that's going to help but I'm a bit curious about other people's experience with how long it takes to do 3D carving and V Carving. I got the demo for a program called VCarve Wizard that I've seen discussed here and I also just bought Mill Wizard. I know that doing a 3D scan of a piece of carved molding with the probe and then milling a copy of it can take many hours and I can figure out the math pretty easily based on square inches, feed rate, ramp times, tool size, stepover, etc. My question is that with VCarve Wizard I'm getting some shockingly high estimates for machining times. For example, I calculate that a 2 square foot sign may take 6-12 hours to machine in 3D with a 1/8" ball end mill. I had assumed that it would be the least efficient method since it has to raster over the entire surface of the piece. By putting the same design into VCarve Wizard, I though that it would make efficient tool paths, only cutting what needs to be cut and reducing machine time considerably but instead I'm getting estimates of 40-60 hours! The quality would be dramatically higher with VCarve Wizard since it would be using a V bit and the edges would be nice and sharp but it would be hard to ever make any money if a 2 square foot sign takes 60 hours of machine time. I set the .25 inch end mill to a feed rate of 1.5 in/min and the V bit to the same with a rapid move speed of 4.5 inches/min. I'm using a PRT96 so I'm guessing those speed are the most I could hope for? The material thickness is 1 inch with the flat spots (maximum carving depth) at 0.5 inches. Am I nuts or does this sound like realistic times? I'm going to attempt to upload an image of the final sign to give an idea of the file I'm experimenting with.

7730

[scott_smith]

Patrick, Change your settings from inch/min to inch/sec. Keep the 1.5 and 4.5 the same. I think you will be much happier with the run times.
Scott

[paco]

Hi Patrick!

You might to review your toolpath settings, mostly the tool stepover and stepdown and speed for both the Vcarving toolpath and the "pocket" part. Have a llok at the time scale factor too; try something 1.2 to 1.4 which is more what reflect reality. Pay attention to the units used for the estimate...

A such sign as the one you show, I'd say less than an hour with a 1/4" CED "End mill" type tool for the pocket area and the cutout profiling and, say, a 1" CED 90 V tool bit.

This one (about 23" X 15")...


7731

...is estimate for 28 minutes 27 seconds. I used setting that I would use for, say, MDF or softwood.

Please, don't do this kind of work with 3D strategies... life too short!

[patricktoomey]

Thanks for the tip Scott, that was the answer. What a rookie mistake!!!! In my other life I normally work in feet per minute and I got crossed up here and went inches per minute instead of inches per second. Paco, thanks for the tip on the scale factor, I was wondering what to do with that also. You are right on the money with your estimate for my sign, adjusting everything as you say I come up with 53 minutes now so my heart is beating again. I don't intend on being in the sign business but with cutting times like those I should be able to make some decent money on the sign jobs that will inevitably find their way to me. I will be using raster 3D strategies only for duplicated parts, anything I design I'll do with optimized tool paths. I'm placing my order for VCarve Wizard tonight, it's an awesome program!

Thanks again for the fast and thoughtful replies.

[ron brown]

Patric,

I would tend to use a larger flat-bottom bit to ground out the back and clean the corners with a hand tool. One would be surprised a how much time can be saved with just a little hand work.

Ron

[jsfrost]

Patric,

As well as cleaning up with hand tools, consider the clearance strategy in the final design. Often a small tweak of size or shape will make space the clearance tool can fit. Look at the clearance toolpath to see where the tool does not fit, and adjust the design slightly if this does not spoil the appearance.

[joe]

Patric & All,

I've been slowly moving in the 3D direction and am just about to settle down on using it only to make parts that are applied to my signs.

Once I realized the machine time for a3'X8'panel, it was obvious the financial numbers didn't work. I'm allways looking around the country, to see how other artists are working. I've found that most 3D stuff is cut seperately and applied to the finished product. One of my favorite is David McDonald at www.avilasigndesign.com/ (http://www.avilasigndesign.com/). David is frequently featured in Sign Business. Although he doesn't do lots of 3D work, his technique appears to be.

Thanks to Shopbot and all the contributors for a great forum.

[Brady Watson]

Hey Joe,
Does David use a ShopBot to carve these signs?

-Brady

[joe]

Brady,

David is a tried and true Letterhead with plenty of experience in design and hand lettering. I think his creative skills sure come through with a router.

One very interesting technique he often uses on those deliclate outlines, is to combine several individual pieces. Painting each part seperately, then combining them for a finsished piece. You can probably see this in his letters. He's also very good with gold and expecially so with smaltz & Mica Powders.

He uses a Gerber, Sabre.