You've probably heard about 3 and 5-axis machining. You might already know the basics:
The cutting tool moves in the X, Y & Z axes (or any combination of them) as it mills the workpiece.
5-axis machining goes a couple of stages further, adding rotation (of the workpiece, or cutting tool) to two of these axes.
The workpiece or tool can be moved into a fixed position before machining (3+2 machining).
Alternatively, all axes can move at the same time (full, or simultaneous, 5-axis machining).
3 or 5-axis?
You may think that your tooling only requires 3-axis machining. This is a typical assumption if you have, say, a PU mould tool without undercuts to be made, or a foundry pattern, or a gravity die. The moulding process means that all features must, by definition, be accessible on a 3-axis CNC.
3-axis machining is great if the workpiece (your tooling) is relatively open and shallow, and all features can be accessed in a single set up with relatively short cutting tools. It’s a simpler machining process, and the machines themselves cost less, which probably suggests to you that it’s the way to go.
But your tooling might not be open and shallow. It might be tall, or complex, with small, hard-to-reach details. It could need machining front and back (like a rotational mould tool does). All features may be reachable, in theory, with 3-axis machining. But just because your tool can (probably) be machined 3-axis doesn’t mean that it should be.
A 5-axis CNC machine can do everything that a 3-axis can, plus so much more. And if your tool doesn’t tick the simple/shallow box, but you think it can be machined on a 3-axis CNC, then you really should consider a toolmaker that can offer you 5-axis machining, and here’s why:
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No multiple set ups
You may have:
A corebox that requires loose pieces
A composite pattern with compound angle dowel holes
A rotational mould tool that requires a uniform-thickness shell
All of these can be machined on a 3 axis CNC. But it does mean that the loose piece/ composite pattern/ mould tool will need to be set up multiple times to access all features.
It takes time, and time costs money and, where lead times are tight, too much time on setup can risk delivery deadlines being missed. 5-axis machining offers an alternative (better) way.
For a 5-axis CNC, the undercut geometry of a corebox loose piece, or the multiangles typical of composite patterns, or the front and rear face of a rotational mould tool, can all be accessed in one go, no problem at all.
One set up, one suite of cutter paths and the job is complete, and with an accuracy that multi-set up 3-axis machining can’t match (no danger of costly rework here).
The fewer the set ups, the less labour time required and (potentially) the lower the cost of your tool. 3 axis can do it. But 5 axis is better.
No multi-layer blocking up
Imagine you have a requirement for a tooling board tool. It could be an airset pattern, or a vac forming tool, for example.
If it's taller than the reach of the longest tool a 3-axis machinist can comfortably use (150mm is a good guide here), then the only way to machine it is in layers. So, layer one is machined, then a second layer of board is bonded to it before further machining. Maybe even third or fourth layers are added.
This layering process costs time and money. Each layer must be programmed by the machinist and has to be bonded by a toolmaker. Time is wasted waiting for the adhesive to cure before machining can restart. And surplus glue can run on to the machined geometry of the prior layer, which means someone (you) has to pay to have it removed.
(Yes, the workpiece can be turned upside down before bonding, so that the surplus runs away from the machined surface, but then you’re having to pay for the additional time involved in resetting the workpiece, and the potential for mismatch between layers increases.)
It can be done, but there is a better way...
With 5-axis machining, the complete tool can be fully blocked-up in one go.
The machinist can use the full capabilities of the CNC to tip and twist the workpiece, or machine head, to reach the deepest features that would be out of reach of a 3-axis machine.
Once underway, machining can continue uninterrupted. One machining cycle later, the workpiece is complete.
It’s faster and less labour intensive, and the quality of the machined result will be better (no mismatch/slip). In other words, you get far better value for money, and you’ll get your tool quicker.
Improved tooling quality
We’ve already covered some of the quality benefits for your tooling using 5-axis vs. 3-axis machining - but there’s more.
If your tool is machined on a 5-axis CNC, it is likely to be far better than if it is machined on a 3-axis CNC, and here’s why:
Shorter tools. The 5-axis CNC and workpiece will align for maximum machining access, whatever the feature, meaning much shorter cutting tools can be used. Shorter tools mean a better quality and more accurate surface finish, and less hand finishing. No thin, ultra-long, small-diameter (flexible) tools needed to access deep pockets or reach down steep, minimal taper walls - the possibility of gouging ‘cutter whip’, the scourge of the 3-axis machinist, is removed. All of which means less labour time is charged to you, and a quicker turnaround time for your tooling.
Improved accuracy. Having to manually set up a workpiece multiple times on a 3-axis CNC, to reach features not accessible in opp 1, inevitably means that relative accuracy between features is going to be lost. The corebox loose piece is bound to be slightly over (or under size), or not achieving the 0.05 positional tolerance on dowel holes across the multiple faces of a composite pattern is inevitable. This is not the case at all for parts produced on a 5-axis CNC. They will be bang on – fully to specification, and right first time. This is what you want as a paying customer: you don’t want to be paying a 3-axis-only machinist for additional fitting time or corrective work.
Time is money and reducing the manufacturing time of your tool is the best way to take cost out of it.
Using a toolmaker with 5-axis machining technology will do just that.
With 5-axis machining, more advanced cutting strategies and cutting tools can be used. Barrel/ lense cutters are a fantastic innovation. Properly usable on 5-axis CNCs only, they can reduce a machining cycle by hours, and are actually better suited to the sweeping geometries that your ‘simple’ tool may have, and which you thought qualified it for 3-axis machining only. Think again!
Not only will your tool cost less, but you’ll get it quicker. All that time spent by a 3-axis machinist on multiple setups and corrective work (probably) will be costing you at the front end (price) and at the back end (longer delivery). And the less-than-optimised machined result may continue the problem once you’ve taken delivery and put the tool into use – poor fit, pulling down, and so on (quality).
Just because your tooling CAN be machined on a 3-axis CNC machine doesn’t mean that it should be.
It really is worth your while considering what a 5-axis machinist can offer you for your 3 axis-machinable tooling – better tooling, faster. Who doesn’t want that?
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Did you find this article useful? If you did, then why not check out some of our other content like The Secrets to Successful Lights-out Machining?