Rather than Hijack the "Whatch this Space" thread with further discussion of CNC machines casting kits I'll repost something I wrote on another forum a few months back:

I have mentioned it before a few times about being able to resurrect some of the older designs where patterns have been lost or if they are still knocking about and usable the owner can't find a foundry to cast them. With modern CNC it should be possible to reproduce these castings with the added bonus of none of the usual casting defects such as blow holes, undersize parts, hard spots, over fettling , etc and leaving the builder to do the final work such as finishing bores, drilling and tapping of holes etc. much as they would with a traditional casting

This video of E T Westbury's "Whippet" being machined would be the perfect example if the machining were stopped before the final holes were done, I'm sure they would sell

And what a set of "castings" may look like

I have enquired about costings but as the company can produce a fully working engine for $499 I should think that the castings would be quite favorably priced compared with what is available in this case from Hemmingway at about $200. If so it would be nice to see some of the "lost" engines from the likes of Wall, Westbury and the Motor Boys plans being made available to those who like to build them rather than just the collector of ready to run engines.

A couple more examples of my own making, a bedplate for a small long out of production steam engine

A flywheel again from a 1930s design long lost.

Crankcases never a commercial casting but taken from a 1936 magazine design

There seems to be a market for part machined barstock kits from the likes of Bengs so it would only be a small step further to have some more shapely parts. I think even Stuarts are supplying some of the smaller items CNC cut these days like the valves for the 10series so it may not be as far away as you think.

Discuss.

Leaving the more modern methods to one side there is also the fact that far more home workshops now have milling machines and access to relatively cheap tooling so a lot of parts that were at one time provided in a casting set can quite easily be made by the builder where they may once have struggled to cut the part from solid on a typical Myford or it would simply have taken a long time compared to on a mill.

As an example I'm in the early stages of making my version of a reasonably popular engine that is available as a set of castings c/w materials and fixings. Although I could make all the parts I have opted to buy (well Xmas present actually) the cylinder and flywheel castings as these are probably the two parts many would find the hardest to make themselves and be put off the whole idea. The rest will be from barstock but won't have that chunky polished up final look. Cost will be approx half of less of the kit and mine will have more detail and period features. But you will have to wait for another thread on that one or maybe I'll write it up for ME.

My main thought wa sof suppliers providing ready CNC machined "castings" the point about selling or providing G-code came up in the other thread as well as here, I don't think this is a very good option for a couple of reasons.

Firstly it would be a bit like putting your home movies on a VHS tape and then selling them to someone with a Betamax machine. There are many different machines and systems out there and each needs a slightly different code for example the Mach3 code that the post processor in Fusions CAM produces would not run straight off on a machine that was running LinuxCNC. There are probably a couple of 100 options for the different systems that F360 can generate the code for so not really practical to send out so many files.

Secondly even if two machines were running the same software just like in the manual home workshop you would not be taking the same cuts with a small hobby machine as you would with a Bridgeport so the g-code needs to be produced with that in mind. For this reason it is better that the individual enters the size of cutters they have as well as the size of cut they can take and at what rate.

If one was providing drawings and digital files for someone to do all the machining themselves then it would be better to use a common file type such as a STEP file either of individual parts or the whole assembly. As an example that photo of the two crankcase halves are from my Midget engine, I was contacted by someone who also wanted to make on and being the nice guy that I am I just sent him a step file exported from my assembly model. He was able to open this and then access the individual part sin his CAD, a couple of clicks and he had scaled it back up to the original engine size and then he ran the various parts through his CAM and produced the code to make the bits on his own machine. I did not even have to produce a set of 2D drawings, he just made them as he needed.

Pat, yes the CNC will produce a much better finish than the average sand casting even oil bonded ones so a lot less fettling to do to get a good surface for paint. I think those whippet ones have been bead blaste dto remove the visual machine marks though I expect it is almost impossible to actually feel what can be seen.

That bedplate for example was cut from poor quality salvaged grey iron and what you see is straight off the machine, there is a 3deg draft angle on the vertical sides made with a series of cuts as the CNC ramped the cutter down gently as it went round and round the contour. I just lightly deburred around the tops of the bosses with a bit of Emery and this is it straight after the first coat of primer, the few dark specs are small voids in the iron. You won;t get that straight out of the sand pit.

There is no real dividing line between metals, the bedplate and the flywheel were cut from solid iron, the crankcases from 6082. In much the same way as you would on a manual machine a slower speed and lighter cuts are used on iron and steel than you would with aluminium and non ferrious. This assumes a rigid enough machine, a lightweight router type machine may not cope so well with iron but it's much the same for the home foundry as not many can get upto iron casting temps but aluminium is not such an issue with a small furnace and burner.

For decent investment casting then it's better to print using a wax fillament and melt it out than a plastic that has to be burnt out as it's easier to join them onto trees and you don't risk leaving ash in the mould

Noel would that include the pattern making time? The way I see it for a one off the time spent making a pattern would be similar to the time spent just cutting it from solid metal so why do it twice. Buy just cutting it straight from the metal you totally do away with the pattern making time so it would be wrong to just compare the melt and pour time without including time spent making the pattern. Not forgetting that apart from the odd tool change if you don't have ATC then you can be doing something else while the machine is cutting so actual time spent will be further reduced.

And if making the pattern the traditional way you are waiting for glue to dry, waiting for filler and fillets to dry, waiting for paint to dry and then unless you have a well vented workshop waiting for a dry day to fire up the outside furnace. All the while I can be sat in the warm clicking a couple of buttons.

Want a handed pair of castings that would be a whole new pattern traditionally, one click of a mouse and regenerate the paths and you are ready to cut the other hand with CNC and CAD/CAM

CNC cutting the patterns will also be faster than making by traditional methods plus you have a lot more versatility for example take a simple name plate. Traditionally you would be limited to available fonts and sizes of pattern makers letters and then have to carefully space them out by hand. Doing it with CNC or 3D printing you have 100s of fonts available in any height you want and can easily arrange them in evenly spaced lines or to follow a curve

Edited By JasonB on 19/01/2022 10:17:21

Martin, as I mentioned earlier Stuarts are already providing things like the 10 series engine valves as CNC cut parts rather than lost wax castings so the answer is certainly not a flat NO. On another forum as Pat mentions where a few of the casting suppliers are members they were saying how hard it is to now find foundries that can do the work and may simply not be able to provide castings in the future so it's either give up or think of alternative methods, reducing the number of parts in a kit would certainly help in this respect.

Many suppliers already do laser and water jet cut parts as part of kits or along side their castings, I've also bought CNC machined parts from MJ Engineering for my traction engine so it's not much of a step to have the odd "casting" made by other means

Derek, I was having this conversation yesterday and my comment on the "watch this space" thread also applies as I too was put off by watching a demo where ages was spent manually writing a bit of code to do a simple machining operation, air cutting to test it then altering it. In the end I gave up waiting to see any swarf being produced.

However all is not lost as I can honestly say I have never written a single line of G-code and certainly have not had to learn it. Yes I have had to pick up how to use F360's CAM but it's a lot easier than having to type what would be tens of thousands of lines of G-code that are needed for some of the parts I make.

Yes I still like to twiddle the handwheels too and only use the CNC for things that it is best suited for and could quite happily operate a manual machine while the CNC is running in the background.