Software for producing CNC cutting files

What software is available for producing CNC cutting files for molds from either a table of offsets, lines drawings, or full scale loftings? I can hand cut molds from the loftings, but if there's a program available for making the CNC cutting files I'd be glad to take the easy way out.

I've not done this before, so it will only be worthwhile if it's straightforward for a new chum.

Thanks!

 

In general, it is not necessary any specific software to generate files for cnc.
You can draw parts and make nestings with any CAD program. Those files in DXF format, for example, can be brought to the most current cutting machines CNC.
File created with AutoCAD :

 

Most Cad programs will produce files suitable for translation to cutting files.

It depends a lot on the CNC cutter and the machinery and controller they are using. For example, one local guy here requires Autocad version 12 dxf files, which my Rhino will produce.

have a talk to the cutter in your local area, and just output your files in the requested format that can be created from the majority of cad programs ( usually by File, Save As ).


The 'easy' way can be expensive, for 6mm ply, the sheet can cost half the price of the whole plywood sheet, so you would only do it by cnc if there was a lot of parts, with very fine tolerances. ( like the attached picture)

Sometimes its more economical to get one sheet cnc cut, and if you have more identical matching pieces to make, you can use the router to copy the CNC 'd item manually, for the other sheets.


Explained here

 

If you are a rhino user, Rhinocam is very very well suited ..........

 

Also be aware that if you use Autocad 12 (or earlier) the ellipses do not conform to those generated by other software.... So if trying to nest with other ellipses from other packages - they won't!.

Rel 13 is OK (same value as most others), the rho value is different on 12 and earlier so watch out. If exported from Rhino, no problem, even in Rel 12 output. Ensure you break down the polylines enough for the CNC to follow sufficiently smoothly, you may preview or test to ensure good enough accuracy.

 

Cutting machines (2 and a half axes) only understand straight lines and arcs of circles. Therefore, in any CAD program, you must replace the ellipses by polylines. The same should be done when the contour of a part is defined by a spline.
The length of the straight sections that replace the splines can be determined by the variables of the system so that once set the value, you do not need to worry anymore.

 

The software that produces the cutting files is normally the CAM software.Before you can use this,you need to have determined the shape of the parts and this is most easily accomplished with a 3D CAD system.

What you haven't described is the material the boat will be built from and consequently it is a bit difficult to suggest a suitable solution.I know nothing about the best CAM software for laser or plasma cutting machines,if metal is your medium of choice.

I tend to agree that having generated the shapes of the components you are likely to achieve success with R12 .dxf as almost every system can cope with them.I slightly disagree with TANSL about what the machines understand as some CAM programs and machine controllers are able to generate and follow splines and those CAM systems that lack the capability normally have a menu that will allow you to specify a chordal deviation that is acceptable for your purposes.This may result in a much larger file for the controller of the machine to work through and may have to be drip fed from a computer if the cutting machine is old or using old software.

If the construction technique requires any parts with bevelled edges you absolutely have to work with a 3D CAD system to extract their outlines.It will require a more sophisticated CAM system to generate cutting files for bevelled edges and as mentioned above,Rhino and Rhinocam integrate very well for the purpose.There is a bit of a learning curve compared to simply creating a polyline for a 2D panel and there is also a tremendous time saving compared to cutting a 2D shape and bevelling it as the hull assembly progresses.If you are lucky enough to have a good 5 axis machine with a smart operator you can save a lot of time once you have accepted their hourly rates.Just be very careful to supply good data to any machine operator,whatever system you adopt.

 

Thanks all, there's great info there. The boat will be strip planked, so I'm looking to go from offsets/drawings to cut molds from chipboard (cheap stuff, and it's only molds, nothing structural). There's a single stringer per side to incorporate, which sounds like a bit of work. I'm currently looking at Rhino, which at this stage looks daunting for a raw beginner in this stuff!

 

I suggest you make up plastic templates for the moulds ( one side only) from the CNC cuts, and transfer them manually to the chipboard.

The slight loss of accuracy in the manual transfer will not be significant, but will cut your cnc costs dramatically, as it will be less than 1 sheet of cutting, and will leave you with a re-usable set of templates.

Rhino has a fair old learning curve, but if you follow the basic tutorials in detail, watch Youtube videos and every other free resource, you can be comfortable with the product in a month or so. Its well worth acquiring the skill despite the pain - you will be able to use it for the rest of your life.

 

I have used this

https://www.buildyourcnc.com/item/control-SOFTWARE-linuxcnc

with this

http://www.probotix.com/FireBall_v90_cnc_router_kit/

to make bulkheaads

 

Not a bad plan,but wouldn't it be easier to use the first side to mark out the second side and then use a jigsaw to cut the parts ~2mm oversize.Then screw the original on the oversize part and use a router with a trimming cutter to make an exact duplicate?

In all likelihood the CNC time for the second side would be about ten minutes.The size of the proposed boat is also a factor.

I agree with the comment about the usefulness of learning to use Rhino.Fifteen years ago I would have thought Autocad was the answer-now the capabilities of Rhino and its integration with a reasonable CAM system its a much better solution.

 

If you have ever tried to Route chipboard, you might find that it turns out a bit rough, and is hard to shape, especially in thicker sizes.

In fact, for ultimate precision, use the template to route an exact copy the shape in thinner high quality ply - say 6 mm, and screw that to the heavy, non flexing chipboard. That has these advantages

1) The thin plywood is easier to get a precision shape
2) You can make outer 'shells' from a small piece of ply sheet from the hardware store, and not use whole sheets for full size moulds.
3) because the outer 'edge' is thinner, you dont have to bevel it to make the planks 'land' evenly.


I did that on a hard chine kayak using thin wood strips. I have attached that photo and a diagram I whipped up in Rhino showing how you could arrange the outer precision edges of the mould, to illustrate the concept.

 

Both those ideas are noted, thanks. I'll check on prices. The plan initially was to use chipboard because it's cheap, and it can be CNC cut cleanly enough for moulds. At this stage I don't have a cost for cutting, so I'll find out. The first step is mastering that software, and loading a bunch of offsets into it. Quite a task. The boat itself is small enough for the material cost of the moulds to be small, and apart from hours of toiling on the PC it looks like the cost making the cutting files is not much more than a few new grey hairs.

I take my hat off to those who build fifty foot boats. Whew!!!

 

On small projects, where you just need bulkhead/temporary frames, it is not too difficult to use 2D drawings from the 3D model. The advantage of the model is you can 'slice' it anywhere, ie have angled bulkheads. If you plot the shape on stable film or paper it can be stuck on to the frame material and shaped to the line/curve. As long as you allow for whether the hull is getting larger one side ie bevel, this is pretty accurate. I tend to use a 2D package to deal with dimensioning the frames etc as it can be easier when offsetting for skin thickness etc.

Register with a good clear CL and a vertical Datum position. I tend to use a 10mm hole on the CL through which I pass a very very tight thin line. If you add a transverse visual mark, ie like a cross hair with the hole in the centre this will give good alignment when you set up the frames. Do not underestimate how to set up the frames, a bit of thought on that can save a lot of time and ensure accuracy. I have yet to find a flat floor.....

 

We use shipconstrucotor