A snapshot of CNC

Share your secrets for building safe, durable planes that kick butt!

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THend
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A snapshot of CNC

Post by THend »

Ok, well, the easiest part to make on a CNC machine is a flat part. Or so they say! I think the 3D is easier, but what the heck do I know!

To make basically flat parts, you will need some sort of CAD program. There are many programs out there that can do this particular kind of drawing, and many of them are free or very inexpensive.

Under a student license, and yes ALL of us should go back to school at one time or another, I got Rhino 2.0. In the years, I have gone back to school, and upgraded to Rhino 4.0. It is worth it, first you get your crusty old brain back in gear by attending a class, and second you get a GREAT CAD program at a very good cost.

Or, just come up with a CAD program....

So, I have drawn a fire wall in CAD... this is for a Bob Wallace Ki 64 Rob kit I bought many years ago. I didn't go into too much detail on the CAD. This is a "sampler" if you will of what goes on when I design a plane, or plane parts as it is someone elses design.

We may want to look at having the image size increased on the gallery. I guess I could upload the images to my service provider web space..
Image

Ok, well the Rhino drawing is now loaded into the CAM software. This is Visual Mill Basic, it is a low end CAM yet I think it is pricey. You open the Rhino drawing into the CAM software.
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One of the first things you do is to define the "stock material" you are going to cut the part from. This is a complete write-up on its own, but for now just go with me here. You define the stock from which the part will be cut.
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These images are too small....[V] In this image, I am trying to show you guys the tools available, ie.. the cutting tools that I can put on the router. You need to select the tool you are going to use. You can switch between tools, but you need to halt the cutting program in order to change out tools. So, it is important to think about the sequence you want to do things. The list of items on the left in the white window are tools.
Image

Well, these images are kinda crap, so I guess I'll have to find a better way to get you an image large enough to appreciate.

Here, I have selected two "regions" to cut, they are the 8 mm holes for where the fuel and pressure lines will feed through to the fuel tank. You bladder boys will only need one. [:o)]

Once the regions are selected, and the parameters set for the operation in that additional window that opened up, I select generate, and the tool path will be displayed. Here is a 3D view of the tool path. I look to see if the tool is cutting in the area I want it to.
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Here the image shows the toolpath..
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I'm gonna stop here. I need to give you guys larger photos so you can see what is going on. Granted, nobody is following along step by step with their software... but you should be able to see what I am trying to show you.

We are not done yet....[:D]
draftman1
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Post by draftman1 »

Very informative Terry. I use autocad, So all I have to do first is draw it up. I take it that metric is the best for this. Im assuming that the piece doesnt need to have anotations on it such as dimensions. am I correct? the once it is all dranw up in cad, then it has to go to the CAM program for the 3d work and tooling, is that right so far?? OK I understand that part if its right. OK I want to cut out a corostang fusalog. for that all I would net to do is make a flat drawing of it. would the CAM program still have to put in the coro thickness? I guess it would because the router has to be lowered to cut, correct? ok now Im understanding it better. Thank you and look forward to reading the next chapter
THend
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Post by THend »

Draftman, if you can draw it in AutoCad it will be fine. A flat part is a flat part, and when you to the CAM portion of the deal, you specify the depth of the material.

What really happens is, you set out the design in 2d for a flat part. Then, you select whether you are cutting inside or outside of the lines you have drawn.

The drawing can have all kinds of stuf on it. The CAM will make you select what line you are working on at any particular moment. This it what Visual Cam calls "Regions", and honestly at first it was causing me GREAT GRIEF, but once I settled down and kept hacking away at it, I figured it out.

Now here is another funny issue... You would think that drilling holes would be a very EASY process.... well with Visual Mill, it seems to screw it up. So, I go into the G-code and clean it up.

THAT, is another lesson...

Draw it in CAD, and be precise!

Generate the toolpath for your machine by using CAM.
Learn to read the G-code, which is like making your brain follow the tool as it goes through the code.

The G-code is read by another software package that will convert the G-code into step and direction signals that will eventually drive the machine.

Placing the material on the machine, setting "Work Offsets" and finally cutting IS another topic.

There is quite a bit to this, but as I get better at it, it does become so much more fun.

The fire wall in this tutorial was cut and completed in maybe an hour of real time. It is not super easy at first, but man, it is cool and gets better each and every time I make something.

Dr. Evil has had one of these for a few years now, and I am sure he can attest to the effort required and the joy of finally cutting good part.

I'll get back to this. I need to do a contest, and then some holiday stuff, but I will walk through this process.

th
Hat Trick
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Post by Hat Trick »

There was a lot of head scratching cursing and frustration for a while! Once you figure it out is now seems obvious and it's easy and fast to get a part done!

I'm semi-retired now and have time on my hands especially in winter if anyone wants some custom routing done. I work pretty cheap! I only do 2d work though!
draftman1
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Post by draftman1 »

Thanks guys. Im a slow learner with this kind of stuff so a littla at a time would be great. maybe I will start working with those programs an get a couple of small things really, send the file to you and see how it worked. in the mean time I can start building a CNC settup. Terry, you said you might have some parts for sale???
THend
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Post by THend »

I've got some stuff I could probably seperate myself from..[:p]

Doc, I thought you had control over your Z axis?? I wondered why you weren't doing 3D???

Head scratching and cursing...that describes it nicely... but you are correct in that now I can sit down and in a short amount of time have the G-code in hand and ready for the machine.

The motor mount, in this example, took longer to measure (the Dave Brown mount) and get it accurate than it took to draw it, process the drawing in CAM, and then cut it. And, BTW this motor mount fits perfectly into that Ki, and the Dave Brown measurements are dead on and went together in minutes. I have those numbers if anyone needs them, might ge a good item to add to the workshop.
crash_out
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Post by crash_out »

G code is what I used when I did CNC programming, but alas it was so long ago I've only a faint memory of how to do it.
Hat Trick
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Post by Hat Trick »

I do have control of the Z axis. My software doesn't do 3d stuff like your doing with the fuse plugs etc. At least I don't think it does! I'm happy cutting out flat things like motor mounts and tail feathers! I don't think I'll be doing any fuse plugs or things like that. What software do you use to draw and cut with?
draftman1
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Post by draftman1 »

wouldnt the 3d part of autocad be the same as a CAM program?
THend
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Post by THend »

I use Rhino for the CAD, which is the drawing. AutoCad can do 3D too I think, but I never could get the hang of AutoCad. My understanding is that CAD refers to the drawing and the process of designing. Some of the high end CAD programs can also process the CAM portion of the production cycle in parallel while the drawing is being made. There is a Rhino plug-in piece of software from Visual Mill that does this. I don't own that plug-in, however I do use Visual Mill to process the drawing and convert the geometry into G-code.

If you want to start out, you can download free CAD programs that will do 2D type stuff all day and work just fine with most CAM software. You can download Rhino for a free 30 day trial.

I think you can download Visual Mill too, and play with it on a limited time basis.

I am going to get access to my webspace for posting pics, and then if you guys want, you can download the freestuff and play along. Let me get a bunch of stuff started and uploaded, and then we can do a walk through.

Here is what I would do. Get Rhino, Get Visual Mill or any other CAM you can for free trial, and get Mach3 as well. You draw it in Rhino (CAD), process it in Visual Mill (CAM), and then load and run the G-code in Mach3 (machine controller)

There is quite a bit to it, but once you got it figured out in your noggin it gets pretty easy, and then you start really thinking out of the box to create stuff and then it is challenging again as you come up with new ideas etc... and then...and then....and then...

[:p][:D][8D][:o)]
draftman1
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Post by draftman1 »

Cool thanks Terry, Im home sick today and I am cruising cnc zone to try to find the router table plans that I like. what one were going to build before you bought one?
BTW did you get the new spit in the air for the event?
THend
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Post by THend »

New Spit did not make the event. I have all the plans for the HobbyCNC router which is pretty nice and looks easy enough to make.

th
draftman1
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Post by draftman1 »

Ok Terry. did you want to sell the plans? let me know. I can build it. I have a cabinet shop. (I dont build cabinets anymore,I havnt built any for 4 years, burned out bad) the shop is now "Mid Cal Spads"

Any Ideas on when your next event is down there? we have ours on the board and Gary is getting his ready. CA will be a great combat mecca next year!
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