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Post by Deleted on Oct 29, 2016 18:12:31 GMT
Looks very interesting Roger....talking of CAD and 3D printing I had some pictures sent to me the other day which show just how far these building methods have become part of the film industry. Alas I can't share as I'm sworn to secrecy but I can say that it involves the building of a full size steam locomotive for an upcoming film. The pictures were very impressive but what really caught my attention is the speed in which this very large locomotive was built. We are talking of 6 weeks CAD work and 5 weeks build resulting in a locomotive nearly finished with only the motion left to go on, they had a week left to complete. This is for a very large european 4-8-2, I tell you until you look underneath were the axles are very small you wouldn't know it wasn't real. This loco will also be mounted on giant drop rigs for the shot in question..
I hate to think of the budget...big crew with big build equals very big bill.....
Pete
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Post by joanlluch on Oct 29, 2016 18:20:02 GMT
Looks very interesting Roger....talking of CAD and 3D printing I had some pictures sent to me the other day which show just how far these building methods have become part of the film industry. Alas I can't share as I'm sworn to secrecy but I can say that it involves the building of a full size steam locomotive for an upcoming film. The pictures were very impressive but what really caught my attention is the speed in which this very large locomotive was built. We are talking of 6 weeks CAD work and 5 weeks build resulting in a locomotive nearly finished with only the motion left to go on, they had a week left to complete. This is for a very large european 4-8-2, I tell you until you look underneath were the axles are very small you wouldn't know it wasn't real. This loco will also be mounted on giant drop rigs for the shot in question.. I hate to think of the budget...big crew with big build equals very big bill..... Pete Hi Pete, I assume this is a non-working locomotive, as there's possibly no point in making it work for a film. |
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Post by Deleted on Oct 29, 2016 18:34:28 GMT
Hi Joan
It will look like it's working, steam generator being fitted internally and it will roll ....I was amazed as to how much detail that they had gone too, even with what's normally hidden between the frames...the horns and bolts were all present, as were all of the stretchers, etc. As I said the only thing to shows that it was a lightweight mockup was the thin axles and the driving cogs fitted which I guess were for chains, I say lightweight but I bet this weighs a good few tons....This loco's massive, far bigger than 4472 and looked great in it's all black livery and polished tyre treads, ..the photo's showed the body separate from the chassis which showed thus just how much detail the crew had gone into...very convincing.
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 692
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Post by oldnorton on Oct 31, 2016 10:50:53 GMT
Hi Roger
I missed this thread when you first started it, and I have really enjoyed your description of how you move from the 3D drawing to the cutting. Clear words with all the necessary images.
It has interested me because I have toyed with the idea of converting my less-used Seig X3 to CNC. I have read about people doing this before. I can see the value of being able to turn out items with shaped faces or edges, and multiples. The technologies and learning curve would be absorbing. But I value your opening statement "this is a last resort for machining anything because the time it takes is prohibitively long". That view confirms what I sort of realised and has helped me say "park it for now!". I will stick to silver soldering lumps together, using the rotary table for curves and appreciating the old skill of filing!
I previously thought that one had to have an array of height-calibrated tool holders lined up with every needed cutting tool. But I see that you use the rotary table chuck as a reference height for each tool, with the X and Y pre-fixed for that chuck. I also appreciate now that the tool holder clearance from the chuck has to be one of those 'careful set-up steps' as you cannot allow for that during the CAD stage. I wonder how many people send the tool straight into the chuck - arrgh, does not bear thinking about.
How odd that the software will not start with round stock, only square. I presume your machine spends time cutting 'air' where the corners are not? When it then takes the second and the fine cuts it knows the rough stock shape and presumably does not cut all that 'air' again? You would think that you could input the shape of your starting material in the CAD software, or is this a more-money add-on?
Norm
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Post by Roger on Oct 31, 2016 13:49:41 GMT
Hi Norm,
I might have mislead you a little with that comment about 3D machining, because it's only used about 5% of the time. Most of what I do is 2D machining and that's as quick as any other milling operation. In other words, don't be put off converting a machine for that.
It's a common misconception that CNC is really only of benefit for making multiples of the same thing, or for complex shapes that are difficult to machine traditionally. Much of the value of CNC machining is in the fact that the machine has the backlash mostly removed mechanically, and the remainder compensated for in the controller.
If you look at machining a square on the end of a bar say, traditionally, that's a pain in the neck because you can't just drive round the shape. It's hard to do because of backlash, and also because you need to allow something on a roughing cut so you can end up with the right finished size. It's not really practical to do that unless you have linear scales, and even then, most people wouldn't do it because you have to compensate for the cutter radius.
Enter CNC and the picture is totally different. Backlash isn't an issue any more, and neither is the tool radius. You program to use a set size of cutter and ask for an allowance when you rough out the square. Once measured, you adjust the amount you asked it to leave to give the finished size. That alone completely changes the way you hold and machine jobs. It becomes much easier to arrange to machine multiple operations in one setup, with the improved accuracy that gives you.
You're absolutely right about the tool height setting. Industrial machines have the tool heights measured away from the machine and entered into a tool table. Another method is to touch a pad bolted to the table, and that's what I was going to do. The information would either be automatically entered into the tool table or be done manually.
In the end, I started off just touching the top of the work and calling that zero, and never found the need to do anything more sophisticate. I think it's a lot less error prone than the other methods which require a leap of faith and a very slow approach on the first cut! Of course, this isn't quite so convenient if your machine doesn't have a quill, but it can still be done. You can touch down on a piece of Perspex for example, if you know the thickness. I can touch a 0.5mm carbide cutter onto steel without chipping the edge so it's not a problem for me.
The situation where I touch the top of the rotary table is when I need to set the zero to the centre of the work and there isn't a convenient diameter to touch down on. Even so, I have to remind myself that the usual touch down isn't zero! I know the radius of the rotary table so I have to remember to enter that instead.
Doubtless more expensive software allows for the shape of the stock to be defined as a 3D model. I've only got the base version, so that's all it offers me. I could use a different strategy, using a horizontal Finishing operation instead, but I've not explored that as a roughing operation much yet. If the stock fairly closely matches the profile of the finished job, there's no reason why that can't be used. I might give it a go on this when I get round to machining it shortly. I will need to take a close look at what it's going to cut to make sure it won't take too big a cut. At least
if it knows there's stock there, it will try to machine it with the parameters that have been selected. It certainly can take a lot of time cutting air if you aren't careful. You can do a lot to keep this to a minimum once you've played with it a lot. Taking big cuts on s rigid setup means you waste a lot less time, even if it does machine some air.
Do drop by if you're ever over this way, I'm usually here since I work from home.
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