Re: scaling in LAzyCam

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ebiz_59" <chuckm@...> wrote:

>
> My ignorance is going to shine thru, but I bot a minimill for my science/tech club kids and they know more than I. But they (we) are having some problems scaling stuff in LazyCAM. I think most of what we have done has been Corel or JPG thru LazyCAM to MACH3 to the minimill. So is there some way to check dimensions before cutting?
>
> And we are about to do a dxf that should have appropriate dimensions in the dxf. This should be straight forward, right? or is there a scaling option here too? And do we set the tool size in MACH or prior?
>
> Thanks, Chuck
>

The purpose of CAM is to take a drawing (in DXF format) and define the toolpath (what tools to use, what offsets, how fast, which paths to cut and when) then put it in a G-code format specifically for your control software (MACH3). JPG's are bitmaps and except for "peck" engraving cannot be used for milling. CorelDraw supports bitmaps but is primarily a vector drawing tool. Biggest problem is it's rather poor DXF export filter. It breaks all the nice smooth curves in Corel into hundreds of tine straight line segments.

The dimensions on a drawing will come across on a DXF (maybe). That is not the best way to do it. The drawing should be done 1:1 (full size) and any dimensions on a separate layer you do not export. DXF exports in "units" so your import has to tell it if its' inches or mm. usually there is an option in the import to define that. There should also be a way to define where the drawing origin (0,0) location is (middle, or corners). I use lower left on everything since my table 0 is lower left.

The lazycam you get for free with MACH is limited on functions. I recommend you have a look at SheetCAM TNG (www.sheetcam.com). It's pretty easy to learn and has lots of features. It is limited to 2d and 2.5D milling and cutting operations.

To improve your Corel to SheetCAM exchange download the demo of DXFTools Standard edition (www.CorelDrawTools.com) for the version Corel you have. It gives you 30 days or 30 exports before you have to buy it. The price is reasonable.

MACH is a control program and is designed to take g-code and move the motors and provide operator feedback. Although you can get it to do some toolpath stuff (like scaling) it's a LOT easier if you just do that in the CAM side of the equation.

To see if it's going to cut right you can take the g-code from SheetCAM and either run MACH in simulation mode or get one of the free G-code simulation tools. I've gotten so trusting of the code that I don't check it any more. You can setup the mill and set Z zero up above the work and do a dry run of the code. It will at least point out of the postion is right or if someone has drawn something the table can't cut!

Try out SheetCAM (demo download is limited to 150 lines of code) and DXFtool with CorelDraw. It's a combination we have been using for years and with all kinds of cutting processes. From a cost standpoint it is about the lowest you can go besides free.

Tom caudle
www.CandCNC.com