5 Axis Machining is it all it’s Cracked up to be?

5 Axis Machining

5 Axis Machining The latest Buzz Word

A few years back, probably more than I think. I was asked to speak at the Edgecam user group meetings.

If you have Edgecam you really should be going to these (they’re brilliant).

Anyway the buzzword was 5 Axis machining everything was bloody 5 axis machining. Anyway me being the agent provocateur, that I am, didn’t want to talk about 5 axis machining.

(Agent Provocateur: French meaning awkward old bastard)

Before you panic, 5 axis machining is not illegal but it may not be the panacea you think it is.

Armitage Shanks

Apart from being a great track by Greenday. Armitage Shanks is a company known for its toilets and its bathroom fittings.

At one time these were in every Shithouse in the UK.

Anyway the story I told was about when I worked for Armitage shanks making bidet taps.

A bidet is a sink that posh people wash their arses in.

They were making these bidet taps on a 5 axis machine. This meant that a completely machined tap could come off the machine in one hit.

I was asked to speed it up. After much deliberation I went back to the boss, who wanted a cycle time of about 3 minutes per tap, to explain that it was not possible.

I think the cycle time they were getting was about 10 minutes.

“Imagine” I said “if we only did tool changes and no machining”. He looked at me a bit strange (as they do in Wolverhampton).

“The cycle time would be 2.5 minutes. So there wouldn’t be much time left for machining”. I also asked him if he needed to be able to produce one complete tap at a time.

The five axis method would be perfect if they had needed to produce say five of one type then five of another type on a “just in time” basis.

Anyway it transpired that this was not the case.

There Lies The Problem

Because they were only making one tap per cycle the tool changes really added up. The solution was that we bought four three axis CNC Milling machines and each machine had a manual pallet changer.

The component was broken down into single operations presenting one or two operations per machine.

This meant each machine was working on 12 taps at once.

Just like a car track production line the time to produce one tap was the longest operation. The final time was about 2 minutes per tap.

Tool Change Time

So you pick up a tool and make 12 parts before you change to the next tool. If the tool change time was 12 seconds then that’s 1 second per part.

Are you with me on this one?

Can you see how all the tool change time is disappearing?

Happy Ending

The five axis machine got used for something else it wasn’t scrapped it’s ok no need to worry.

Five Axis Machining

A five axis machine will be a huge drain on your wallet and  can turn your brain to fudge.

So imagine I am a machine tool salesman and I am about to sell you five axis machine. Dead easy the machines would fly out the showroom like “shit off a stick”.

My Pitch (If I was flogging you a 5 axis Machine)

How often do you damage parts moving them from one machine to the next?

How often do you lose parts between operations?

Why set up a part for five operations when you can do it in one hit?

Yea and you get to do shit like this.

This is called a swarf cut Side Wall Axial Relief Feed. (Go on impress your mates with that one)

This is something you can only do on a 5 Axis Machine. And yes you need all five of em to do this.

Also unless your name is Alfred Einstein you will need a computer to calculate the code.

Now The Down Side of 5 Axis

It always makes me smile when people brag about being a 5 Axis CNC setter Operator. It’s actually more difficult trying to operate the self service checkout at Morrisons (an English supermarket)

I can certainly recommend the fish at Morrisons by the way, but go to one of the staffed checkouts otherwise you’ll meet me still trying scan my fuckin pizza.

The reason why I say this, before I get a terrade of hate mail from all the 5 axis machinists, is because it’s all programmed on a CAD/CAM system and downloaded to the machine.

The operator has the privilege of pressing the cycle start button.

Easy As X Y Z A C

So from an operating point of view once you get over the fancy footwork they are a pretty boring machine to run.

Disadvantages Of 5 Axis Machining

• Lots of tools to manage.
• Loads of features to check.
• High level of CAD CAM programming skill required.
• Machine initial cost.
• Software cost.
• Big investment in one machine, if it breaks down your haemorrhaging money.
• Set up time will be much longer.
• Difficult to multi load parts.

Three Plus Two 5 Axis Machining

You must have heard people say that?

Well what does it mean?

It means you have a three axis machine X Y and Z and then you stuffed on a rotary axis (4th axis) usually called A and then on top of that you mounted another rotary axis (5th axis) sometimes called C.

You can program the XYZ as usual and then add a position in A and C something like A60. C45.

Now the A and C axis don’t have a clue what the other axis are doing and frankly they don’t give a shit.

So you get to present a part at a compound angle and once it’s there you can do stuff.

You know stuff like milling a face, machining a pocket or drilling and tapping a hole.

So What’s The Difference

So to do simultaneous five axis machining your machine has got to have the software to produce simultaneous moves like SWARF cuts.

Three plus two could be done just by placing manual indexers on the table to create the compound angle you need.

Advantages of Thee Plus Two

• You can load a part and machine on different faces so you may only need to pick it up once.
• Cheaper to buy or can be retro fitted.
• It’s easier to control dimensions because once the datums are set each part will be the same.
• Reaches the parts other machines can’t reach.

Multi Loading With 5 Axis Machining

By the way you can multi load on a five axis CNC Machine but it does need to be quite a big machine.

This means you have a cube with several parts mounted on each face.

Thanks for reading my article.

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