4th Axis Question?

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Jeff Chandler
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4th Axis Question?

Post by Jeff Chandler » Tue 05 May , 2009 11:14 am

I have been working my way through the 4th Axis Machining manual and machined the 'Methead' and the 'Jurrasic' machine codes. The Methead has the Z level set to the billet and the Jurrasic has the Z set to the centre.
My Questions are why set to the billet and when?
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Post by Steve » Tue 05 May , 2009 16:00 pm

The setting is a personal preference.

If you have a billet it is easy just to set the offset on the top surface and if you are programming a part it is simple to enter the program and the offset from the outside.

If you wanted to make the part again out of a larger billet the same program could be cut by just touching on the outside and setting the offset to zero.

When the offset is set to centre the tool knows where the centre of the billet is and possitions relative to this. The part will always be cut at the correct size so if you had a larger billet then the program would have to be recreated.

Really it is a personal preference. If you set the datum to centre then you only ever have to set it once but you must always ensure the program has the correct billet size.

When set to the outside the offset is set by touching on the outside of the billet. This can be less accurate but will let you cut a part in a billet that is not to size without exceeding the cut depths.

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Post by Denford Admin » Wed 06 May , 2009 8:57 am

My preference would be to set the datum to the centre of the billet.
That way you only ever have to get it right once and then all your models should come out accurately every time.
It means that you could use billets that vary in size. eg, You created a 4th axis program that used a 50mm diameter billet, but you later found they were actually 2" (50.8mm) then the program would still cut correctly if its datum was the centre line.

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Re: 4th Axis Question?

Post by Bernie_of_CPE » Fri 23 Sep , 2016 23:27 pm

I have been making prototype cars for the F1 in schools challenge and had to come to grips with the 4th axis. Having tried both methods of setting the datum I have to say that I would set from the centre when I do this again. I had several issues that for a total novice are not predictable when choosing a machining approach. I tried a circular tool path initially thinking that the part would be made in one operation. This didn't work because the cutter I was using didn't have the flute length to cut through the block to the surface of the model without the plain shaft above the flutes pushing against the excess material of the block. I had cut a blue foam block to the maximum dimension I could fit in the 4th axis jig, this was wasteful of material and time.

I am still learning but having a good time despite the frustrations and drawbacks, what I have read here is gold and I am prepared to learn.
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