Today we are going to talk about why CNC machining is just bloody awesome. Some of you may have realised already that I-
have an enormous amount of passion for CNC machining.
It was an amazing all-round machine for its time.
It had a blistering 2,000 RPM spindle speed, and a supersonic 1 metre per minute feed rate at cut. Well, I guess by today’s standard that’s like comparing a Model-T Ford to a Ferrari of today. Spindle speeds are rarely less than 10,000 RPM nowadays, and often as high as 30,000. You can also get speeders, which are little secondary spindles that you can tool-change into the main spindle, that go up to around 80,000 RPM. Typical feed rates nowadays are from around 20 metres per minute up to and above 60 metres.
So, what are the 7 things that make CNC machining totally bloody awesome and very useful from the perspective of the customer?
1: QUICK START
For very low quantities, it is very common that we CNC machine parts from solid rectangular or round billets. Most of these materials are available off the shelf within hours or days of an order being received. It usually takes hours or a few days to program a part on the CAD,CAM computer, in our case we use Autodesk PowerMill.
So, by the time we’ve planned, prepped the tools, programmed and verified the cutter paths, the material has arrived, and away we go.
2: MINIMAL FIXTURING
Most billets can go straight into a vice, on a mill, or a chuck, on a lathe, and again, away we go. We can even use soft jaws on vices and chucks to grip very complex shapes that are made during the first operation, so that we can turn the part over and hold the part for the second operation.
Again, this only takes a few hours, so it’s pretty quick to get underway. Very few parts need specialised fixturing, unless you want to do larger quantity production and put dozens of parts on a machine at the same time.
3: 14,000 CUTTERS
Now, this one is not necessarily applicable to all CNC shops, but it is for us. Because we have a specific supply chain problem, because we are based here in China. We have a computerised cutter vending system in house from the German cutter manufacturer Gühring with around 14,000 cutters available at a moment’s notice. We also have a Gühring storeman on site full time looking after that stock and providing us with advice on how best to use their tools.
We also have a small cutter grinding supplier down the road, and they have three 6-axis Walter cutter grinding machines, and we can get any kind of uncoated special cutter within 24 hours.So again, for us, it is really not that difficult to get going.
4: THICK SECTIONS
We also have metal 3D printing onsite, and it’s awesome. But the time it takes to make a part is somewhat proportional to the volume of material in the part. The heavier the part, the longer it takes. With CNC machining, it is almost the opposite.
The less material you want to take off, the lower the cost. So, although we can make parts where up to 95% of the material is removed, and we can have very thin sections, as a general rule, CNC machining is great for leaving the material where it is. So, thick chunky designs are no problem.
5: CHANGE YOUR MIND ON A DIME
Another fantastic thing about CNC machining, and for that matter 3D printing, is that you can change your design any time you like.We can stop and make changes to the CAD CAM program quite quickly and be back in production in a matter of a few minutes or hours.
That’s not so easy with die casting tools, or investment casting, or plastic injection mold tools
6: HIGH PRECISION
CNC machining has got faster and faster over the years. Cycle times have collapsed compared to when I started out. But they’ve also become more and more precise. 5 microns is now very achievable with CNC milling, when 30 years ago that was only in the realms of grinding.
Many companies now do hard milling and hard turning and hold the most breath-taking tolerances.Machines are so precise now, that many have to be kept in 20C temperature-controlled rooms, and the slides have thermal compensation, and secondary glass scales for high precision feedback. v
7: 5-AXIS WIZARDRY & VERIFICATION
The most amazing thing about CNC machining today is the degree to which 5-axis machining has developed. A few years ago, I saw a number of companies machining an aluminium version of a basketball hoop and net at the IMTS show in Chicago. I was mesmerised by how the tool and the tool-holder could machine all the way through one side of the net to the inside of the net. This can only be done by using 5-axis CNC machining, but more than that, you have to have the most amazing CAM system, the most amazing verification software, to ensure that you do not crash into the part or the machine.
In that case the programming was done on Open Mind’s HyperMill and the machining on a Grob horizontal, which you can see behind me now. If that doesn’t make the hairs on your neck stand up, I don’t know what will. Why do I mention this anyway? Well, it’s because these major steps forward in what is possible with CNC machining has unchained many designers and allowed them to think way outside the box. In a way, I personally think that CNC machining has advanced so much in parallel with metal 3D Printing.
It is no wonder that we are now starting to see so many amazing hybrid CNC & 3D printing machines.