CNC Routing?

[slamman]

I am fairly new to CNC'ing. I have managed to create some 2 signs and cutouts. We have a cnc machine that is used for both plasma cutting and cnc routing. Currently we are using sheetcam and mach3 to convert dxf's, create tool paths and drive the router.

I now have a project that I need to do something a bit different. It seems simple enough, but I am unclear on what we need software wise to accomplish the goal.

The project:

We have a 12" wide by 48" long by 1" tall (actually 2 .5 in thick pieces of mdf glued together) piece of material. In solidworks we have a corresponding design that essentially resembles a piece of molding, in that is has contours. It is actually more simplistic than a piece of molding. The piece is to be used as a mold to bend a light contour into another piece of wood.

Attached is an image that shows essentially what I am talking about.

I could use any suggestions on how to accomplish this, any links, articles or video tutorials would be very helpful.

Software I have looked at and am considering trying:

Sheetcam
Cam Bam
meshcam

[ger21]

You can do it in SheetCAM, with a bit of work. Here's how I layout my toolpath location. You can draw all your lines at Z=0, with each different depth on a separate layer. In SheetCAM, assign the correct depth to each layer.

AutoCAD 2 G-Code macro

[ger21]

Forgot to add that if you use the biggest ballnose that you can, you won't need to may passes and you'll get a better finish.

[slamman]

Thanks for your response.

I am going to have to play around with this to see if I can figure out what you are doing. I dont have much autocad experience and very little solidworks experience. I am willing to learn, but I was hoping that there was software that would be able to take a 3d file from solid works and interpret what toolpaths were needed to make the part.

I am playing with meshcam and freemill, and both seem to be able to do what I am talking about with some work, but I have yet been able to simulate the cut in mach3. There must be a problem in the gcode or something.

Chris

[ger21]

I use MeshCAM too, and it should work well for what you want to do, but it'll take longer to cut then with my other method. Is there an error message in Mach3?

[slamman]

The item being cut is a low volume item in that there may on be 1 piece cut or a couple at the most. Is it an issue of more time on setup vs cut time between the two programs? If so for this item I would opt for ease of setup.

I think I get what you are doing in your tutorial with sheetcam, but it may take me a while to actually figure out how to accomplish it.

I am going to be working on the cnc today. Up till now I have been working on another computer with mach3 that did not have the cnc attached. I will post more after I have had a chance to try some of this on the actual cnc.

Thanks

[slamman]

Gerry,

Thanks for your help in this matter. When I have more time I intend to investigate your technique. For now I am going forward with one of the 3d programs i.e. meshcam, cut3d, freemill etc.

I have a question...I have been reading through many of the posts here and you seem to have alot of knowledge on using the cnc to cut wood. My question has been asked here before, but I wanted to confirm my suspicions as it relates to this kind of project. It has been suggested to me to use and end mill to rough cut, and a ball mill for final cut. Your previous post here suggested a ballnose bit. In reading the posts I believe I recall you suggesting to someone else to use "router" bits that are made for wood and not "mills" which are made for metal. Am I understanding that correctly, that a standard Home Depot type router bit would be acceptable for this project. Like a plunge-able straight bit for instance to hog out the rough cut. If so what would a suitable "ballnose" bit be for the finishing pass? Could a round nose bit be used effectively?

Thanks

[ger21]

Am I understanding that correctly, that a standard Home Depot type router bit would be acceptable for this project

It looks like you're making these from MDF? If so, then definitely. Although spiral router bits will let you cut faster, they also cost a bit more.

If roughing solid wood, you need to be careful to avoid tearout. Cutting direction is important.

AS for the round nose bits, I've always use carbide tipped core box bits with great results, even in hardwood. Remember that the larger the bit, the smoother the finish will be.

With a profile like that, if you use a lager bit, you can probably skip the roughing and do a finishing pass only. Faster, and no need to change tools. The toolpath should start at one of the edges, so it should be a shallow cut. On deeper cuts, the stepover will control the amount of material removed.

Here's the type of bits I typically use.
http://www.eagleamerica.com/product/...groove_forming

For very small tools (< 1/8"), I've used spiral ballnose endmills from Ebay, which ahave worked well and are cheap.

[ger21]

Here's a screenshot from MeshCAM with a guess at what you're doing. 12" wide, .125 stepover with a 1" ballnose tool.

[ERJS2000]

If Gerry's screen shot is an accurate depiction of what you are trying to do, it can be done entirely from Cambam. I made a series of radiused sanding blocks for sanding guitar fingerboards using the information in this thread on the Cambam forum.

http://www.cambam.co.uk/forum/index.php?topic=887.0

It took me a number of attempts to get it right but the information is all there once you understand how it works. There is a step by step tutorial on how to extrude the surface and generate the code to cut it with a lot of screen shots illustrating the process.

[slamman]

Thanks for all the help every one.

I am going to make a run today. machine is warmed up using gcode generated by meshcam. The part is similar to what you have shown Gerry. The bit I am using is a .75" straight bit to do a rough pass and then a .25" round bit for the finish.

My new dilemma is finding the edge of the material. To date I have really only cut objects out a larger sheet...like signs. I have not needed any real accuracy as far as the edge of the stock. I just moved the bit about a quarter of an inch onto the stock...zeroed out and started cutting. Is there a simple method for finding the edge of stock when using the entire piece? Or is it better to use the cutout pass? Right now I have a 2' x 4' sheet that I am going to cut into 2 1' x 4' sheets so that I can make 2 parts from it. I don't need exact tolerances, but I need to be very close...I could use the entire sheet and cut the profile and then run it over the table saw.

Any suggestions?

Thanks