View Full Version : Creating a drawing for CNC. Is this right?

07-24-2010, 08:15 PM
Hi Guys,
I'm using TurboCAD to do my drawing. I've been using it for years and am well acquainted with the UI. I have ver.15.2. I can save in DFX format and have been successful in opening the DXF with Mach2 and Lazycam.
I'm trying to draw my Mooney Bravo panel so that the entire unit (gauge rings, encoder holders, etc) is crafted from a single 3/8" thick piece of PVC sheet. The problem I'm running into is that I can only subtract just so many shapes from the sheet (in the drawing) before a I receive a ACIS error. My question is, Do I have to subtract all of the elements (holes, depressions, etc) of my drawing from the sheet for a CNC to cut it out. Or can I have each element be a separate entity? I hope this makes at least a little sense to someone here.

07-25-2010, 12:37 AM
Hi there, ACIS I believe is a solids thing. So when you say "subtract shapes" are you meaning that you are using solids to do your modeling? If so, you need to have a 2d wireframe .DXF file for most CNC jobs and a 3D .DXF for machining more complex things. And A solid or surface model only for fancy curvy things that can't be cut with standard cutters. This is called "hem stitching" where you can make anything with 1 ballnose cutter.

The way I do cad is to keep seperate in my mind, what is needed for design in the computer, and what is needed to run a CNC. So I will make my designs with 2D wireframe unless I really need to see it in the computer first, But when I know what I want I don't waste time making solid models. I do that all day at work.

So If you are making panels try too keep your cad to a minimum and the real parts you make from it at a maximum..

If you are talking about something else....well....never mind



07-25-2010, 10:45 AM

you could assign each element, or groups of elements, to a separate layer and export the individual layers as separate dxf files. Then run multiple Mach jobs from each of the dxfs.


07-25-2010, 02:44 PM
Thank you very much gentlemen. You each perfectly answered different elements of my question. I used Paint.net for the original drawing to see what the finished product is "supposed" to look like. I'm so glad that it doesn't have to be a solid and I never thought abut cutting it in stages. A co-worker's dad is going to do the cutting for me at his work. I plan on building a CNC but want to get this panel up and running soon as I've dis-assembled the old panel to make the new one.
Thanks again.

07-31-2010, 01:16 AM
I modified my plan slightly. I've found the perfect gauge ring material (PVC tube). The diameter is 3" instead of 3.125" but I think I can live with that. I've made a couple using a circular saw and router. I'll take some pictures. About $.30 a piece. I've decided to use .25" PVC sheet for the panel and mount/glue small .0625" thick "plates" to it to hold the encoders and give some dimension to the attitude and HSI gauges.
It would seem as though a .0625" cutting bit is the smallest diameter bit there is for the material I'm using. Some of the cuts I'm making have "corners" Can I draw them as corners or do I have to incorporate the bit diameter into the drawing? I've attached the DXF of the panel, HSI, and attitude plates. so you can see what I'm dealing with.
I've drawn all of the encoder plates but have not seperated them out from the overall drawing and saved the as DXF files yet. Plus I have the radio panel and gauge stickers drawn up and ready to print out. It's starting to look like this thing might just come together.
Comments and critiques welcome.
EDIT: Oops, just noticed that I don't have the MP and RPM holes in this version of the panel. The "mounting" screw holes are there but not the gauge holes.

07-31-2010, 03:00 PM
It would seem as though a .0625" cutting bit is the smallest diameter bit there is for the material I'm using. Some of the cuts I'm making have "corners" Can I draw them as corners or do I have to incorporate the bit diameter into the drawing?

Hi, you only have to worry about the radiuses if you need them to be exact, for example another panel inside another with perfect fit.
Normally you just use the bit you have availabe and the CNC will leave the bit's radius on the corners.

For panel work i suggest you try sheetCam or Vectric CUT2D, both are great for beginner.

Your panel.dxf has everything on a single layes so in sheetcam it is impossible to make the toolpaths right.


Always design with layers on cad program, because you need different layer for outline routing and hole and inside cutouts.

I normally use just few layers like OUTLINE, CIRCLES, HOLES and POCKETS

07-31-2010, 06:08 PM
Thank you for your response Jylhami. Do you mean more like this?
If I wanted to have a realistic bevel around the flaps and trim gauge would I draw this in somehow or would it be better/easier to make them their own layer and use a 60 deg. bit? I've seen several videos where the CNC is making nice relief type plaques. I can't even imagine the effort that would go into setting up something like that.

08-01-2010, 12:46 AM
Hi John, It's easy to make a bevel (chamfer) to any given line in (circle, rectangle, even text) with Cut2D and you can simulate the toolpath, so you actually see what will come up ! Usually you need 2 different toolpaths: one profile path to take out the center and then other toolpath (with different bit) to machine the chamfer maybe a 45 deg bit.

Get the free demo for Cut2D and play with it and do the tutorials, you get familiar with it in one evening.
I did that and after a week i purchased the lisence.

When you get more experiense with CNC and you need more control for the toolpaths like ramp in or lead out etc. you can switch to SheetCam, only about 85-100 USD. Very nice program, but the simulation only shows the toolpaths not the stock as it is routed out.

I could not open your panel.dxf in cut2d, as it was not in ACAD format, also was unable to open it in ACAD2000, but ACAD2008 and sheetcam opened it without problems...

08-01-2010, 08:16 PM
Your right. What an easy yet powerful program Cut2D is. I couldn't open any of my TurboCAD 15 drawn DXF files. Funny thing is that it will open my TurboCAD 5 drawings with no problem. I'm pretty bummed that I used TC15 to modify and save my TC5 panel files. Now I can't open them with TC5 and resave them to use with Cut2D. I think I may just start over.
Edit: Yeehaa, One of the TC users in the imsisoft forum told me how to save the DXF in an older file format. Cut2D opens the older format. Probably a good thing that i didn't find that out till this evening or none of my chores would have gotten done today.

08-02-2010, 01:51 AM
I have TCad 17. I can probably open and resave them for you. I also have VCarve