Going the long way round!

[puffernutter]

All, some help please from very much a plasma virgin!

OK, the set up! I have a Planet CNC set us and I'm using a R-Tech plasma cutter (their 13A smallest!). The initial word "Clumber" is drawn using Inkscape, then modified in ViaCAD to retain the centres of the B and R when it's being cut. The machine is a home brew job that I have built.

I create a DXF which is then converted to GCODE by Planet CNC and I end up with the plasma taking a very scenic route on the "B" (less so on the "R"). I have tried using DXF2GCODE software, but that just seems to end up missing chunks of the L and has an additional cut on the "M"!

Can anybody suggest what I am doing wrong? I group the individual letter then group the word and export as a DXF.

Bear in mind I am a hobby user and won't be spending out on expensive software- the ViaCAD is on a 14 day trial, but I may buy a licence if I can sort this problem out!

Pictures follow!

Thanks in advance for any help!

Cheers

Peter

Here's the original word in Inkscape

As modified in ViaCAD

And this is the path I see on Planet CNC (importing the DXF and letting Planet CNC do the GCODE conversion

and a close up

 

[James1979]

Not familiar with any bar Inkscape. Why don’t you use that to remove the bits from the letters? It’s quick and easy. I’ll see if I can find a YouTube video about it.

 

[puffernutter]

The YouTube I had found suggested Inkscape for the initial letter, the copy it to ViaCAD! As a total amateur I followed the video frame by frame :-)

 

[awemawson]

Down load a copy of SheetCAM - excellent program, widely used and well supported. Import your DXF, run your chosen post process and spit out the G Code. I think that you can download a free trial.

 

[Agroshield]

The post processor (that turns the dxf into G-code) will process the vectors in the order in which they appear in the dxf file. Some of the vectors making up the 'B' and 'R' are the original ones from Inkscape and some of them are the new ones from your tweaking.

Everything that follows is written in AutoCAD terminology, so you may need Google translate to change into ViaCAD.

I think the way to overcome it is to make sure each letter is represented in the dxf as a closed polyline*. Then when it is post-processed, each letter will be cut in its entirety.

* To do this, select any vector of the letter, convert to polyline and then join the subsequent ones to it. Once you have done that, you can query the properties of the polyline and there should be a field that affirms it is 'closed'. If it won't close, it means the ends of adjacent vectors are not co-incident. I suspect you can influence the cutting order by choosing which letter you make into the first polyline. It is good to purge the dxf multiple times before sending it any further down the processing chain.

 

[puffernutter]

That make a lot of sense. Struggling to find "polylines" in either Inkscape or ViaCAD!

 

[gerrymoore]

I use to use Drawplus8 ... very easy to learn and I think very cheap (although mine was free ) ..then buy sheetcam for about £100 or so ..fantastic prog, doddle to use, and money very well spent....Gerry.

 

[puffernutter]

Yes, I think I may have to bite the bullet and buy some software if I am to progress. Polylines and Z axis are all things I need to consider!

A whole (brave) new world! I have a limited version of Sheetcam from their website, but it keeps on throwing up errors I don't understand!

More time in front of the computer and Googling I think!

Cheers

Peter

 

[Agroshield]

You will not find polylines in Inkscape. They make sense only really in a CAD environment.

Is this forum post any help?

Polyline vs Spline - Beginners Question - 2D Drafting - Punch! CAD

Polyline vs Spline - Beginners Question: There are times when I want to join a punch of line segments, curves, etc and I DON'T WANT the software to mush them up and average them out. Often I want to leave these elements exactly the way I drew them, but join them together to make other...

forums.punchcad.com

A great deal of your difficulty is due to picking a font as the thing you want to cut. It is not the toolchain you are using but the particular challenges of cutting letters. Most letters are made up of curves and they have to look good to the eye. It is reasonably difficult to get a machine to move in a way that produces good looking text.

Your CNC machine only knows (the mathematical definition of) two things: straight lines and circular arcs. So any curve you cut in G-code will be made up of one or both of these. You can think of the G in G-code as GCSE level maths. It means that if the post-processor is given a dxf file with any higher maths in it, it has to reduce it to arcs and lines.

At the CAD (dxf) level, there is an additional way of representing 'free-form' curves: polynomial splines. But there is no G-code to cut a spline. CAD is therefore somewhere like A-level maths.

At Inkscape level (a vector graphics package, not a CAD package), the 'free-form' curves I think are represented as non-uniform rational B-splines (abbreviated to NURBS). That mathematical curve representation seems to be what all the good stuff uses. NURBS are perhaps degree-level maths, and way too advanced for poor old G-code. So if a NURBS-aware program has to output dxf, it has to convert the NURBS to something the dxf will comprehend.

I do not know what Inkscape does, whether it converts to splines or arcs and lines. But to do degree-level stuff with GCSE level knowledge is tricky.

Another way to solve your immediate problem is to trace over the 'B' section-by-section (on a different layer). Then delete the original one underneath and change the layer of the new one to the same as the other letters. This should create new items at the end of the entities section, all adjacent to each other so the post-processor should then do what you want with them.

Have a look at LibreCAD. It is free and open-source.

 

[puffernutter]

Again very helpful - and when the new plasma CNC operator trying to understand all this has only just passed the 11-plus (or is it getting a good grade in SATS these days? )that's where the fun starts!

Cheers

Peter

 

[Ped]

Sheetcam is the way to go. I use inkscape and sheet cam exclusively for my cnc plasma stuff and never have any issues.

Sheetcam reads and converts the Inkscape svg files fine. You can use the layers feature to use different toolsets for different parts of the cut which is very handy when it comes to lettering (adjusting speeds and thc functions etc). There's another option called Ikocad that's worth a look...

https://www.youtube.com/channel/UC7vdgwoOrSB16zpcX8M12Mw/videos

 

[Ped]

Also, if you've made any errors in Inkscape Sheetcam will automatically delete overlapping lines etc and clean up the svg file for you as you import.

 

[Fraserb]

If im doing certain fonts in inkscape I just cheat, write out the text and just draw a white box to add the holding tabs.

 

[puffernutter]

I'll try that Inkscape to Sheetcam when I get a chance - I may even look at buying Sheetcam, you're giving it good reviews.

For the moment, using LibreCAD I seem to have been able to create a polyline for the "B" and my CNC software (Planet CNC) when importing a dxf seems to have a degree as it makes a good fist of cutting logically!

Once again, many thanks. You lot are a fantastic source of knowledge and experience!

Cheers

Peter

 

[gerrymoore]

Have to say..I'm no good at maths, and never even heard of a polyline ..... but made a good living for 8 years without this 'knowledge' I found using Drawplus for my fonts..just 'convert to curves' and export as a DXF worked every time. Also I used a drawing tablet with Drawplus ... I would insert a drawing or a picture and literally draw around it using the 'pen' on the tablet.... copy the outline to a new drawing, convert the scale if needed, and export as a DXF and then into sheetcam ...the most easy of processes - no maths involved. I would have done this for your doggy outlines Peter...would have taken 10 minutes from file to cutting out on the CNC......it is definitely NOT rocket science or I could not have done it!!!

Look at this 'sculpture' I did a few years ago. I saw the picture on the internet and loved it. Copied the image and sliced it into 4 parts (my CNC was only 600 x 400). I then imported each 'part' into drawplus and traced around the image using the pen and drawing tablet (was a bit fiddly!!) ...probably took me 20 minutes for each slice. I exported them as DXF files (in Drawplus) and cut each part out using sheetcam. Welded them together and 'voila' a lovely sculpture with no maths, poly lines or Parrots involved!! Maybe 2 hours start to finish....... it's 3mm steel and roughly 1050mm long x 260mm high. Been asked many times to sell it but swimbo will not let me

 

[julianf]

If any of your software has a join function, try that. I suspect a poly line conversion would be needed first, but you might get lucky.

Join normally has a tollerance - just set it to somthing sensible like half a mm or so and it should just join what you want rather than the whole job.

 

[Agroshield]

I found using Drawplus for my fonts..just 'convert to curves' and export as a DXF worked every time.

And it is likely that the 'convert to curves' function that you speak of is what is missing from the toolchain that the OP is using.

It works for you because you have chanced on or paid for a set of tools that work for you. There are many ways to skin the CNC cat. If the OP understands what is going on in the software he has chosen, the small issues he is having can be overcome.

Look at the replies to his question: most of them take the form of 'change your software' rather than trying to solve his actual problem.

 

[Brad93]

Try Fusion360. Write your text out, explode, put in some bridges, export sketch to dxf. You can put that into any processor to output a G-Code or use Fusion360 internal processor which i believe is what @Hood does.

 

[Hood]

Try Fusion360. Write your text out, explode, put in some bridges, export sketch to dxf. You can put that into any processor to output a G-Code or use Fusion360 internal processor which i believe is what @Hood does.

Yes, I use Fusion360 from start to finish now and love it. Still have SolidWorks and BobCAD but don't think I have used the former since I started with Fusion and only used the latter once or twice to vectorise images.
Regarding exploding texts and adding the bridges, I don't even do that, I just do my text, cut it from the model (sheet) and then sketch bridges and extrude on the model.

Fusion costs though, I think you can still get the free version but the functionality is being reduced for the free version, especially the CAM side (Rapids/Toolchanges etc) but for anyone using it for their work the £400/year is peanuts in comparison to all other decent CAD/CAM out there especially when you can go from drawing to model to CAM all in one package and in fact all in one file.

 

[Brad93]

Yes, I use Fusion360 from start to finish now and love it. Still have SolidWorks and BobCAD but don't think I have used the former since I started with Fusion and only used the latter once or twice to vectorise images.
Regarding exploding texts and adding the bridges, I don't even do that, I just do my text, cut it from the model (sheet) and then sketch bridges and extrude on the model.



View attachment 275635
View attachment 275636


Fusion costs though, I think you can still get the free version but the functionality is being reduced for the free version, especially the CAM side (Rapids/Toolchanges etc) but for anyone using it for their work the £400/year is peanuts in comparison to all other decent CAD/CAM out there especially when you can go from drawing to model to CAM all in one package and in fact all in one file.

You'll have to do a video on how you do that text you've lost me there.

Have you drawn each side as a component then brought them together in an assembly?