5th axis help

[bet338]

Hi all,

I'm trying to get a 1/4" ballnose to cut the surface shaded in yellow following the 1/4" rad at the bottom with no luck. I've tried 5axis swarf using drive chains and that has gotten me the closest to following the bottom, but the tool gouges in the 'z' along the back wall and lays off the 'z' as comes to the front. I created curves on one edge using the intersect of the 1/4" rad around the part to the side wall then did a project to flatten it for the bottom chain and using a chain around the opening for the top chain. this is to be machine on a haas vf-5 trunnion.

Any ideas what I'm doing wrong?

 

[Nick Eaton]

I like 5ax Curve myself as it gives me more control.....I only do 4 ax continuous tho'.

Swarf is going to pose problems trying to project you drivelines properly around the surface. I have had more success with this toolpath on "open" surfaces.

HTH

Cheers

Nick

[bet338]

Thanks Nick,

Would I use a chain at the bottom for the 3D curve? And I'm guessing I would have to construct some geo for tool axis control.

[Jimmy Wakeford from Barefoot CNC]

Try using comp to surface in your 5ax settings to keep from gouging the other surfs.

[bet338]

Jimmy,

Is that using 5Axis Swarf or Curve?

Thanks

Brian

[Nick Eaton]

You can construct your control vectors using create line perpendicular.

I usually use the bottom edge curve.

Create point segment gives me something to attach the vectors to. I like to keep everythiog on separate levels cos' it can get kind of crowded.

You can use comp to surface or curve in Curve 5ax.....not sure about Swarf. If you can it will be on the geometry tab.

You can also manipulate your vectors and add lean/lag....I like the amount/choices of control in this toolpath. It takes longer to set up but I usually find the effort pays off in "fine tuning" the toolpath

Cheers

Nick

[Jimmy Wakeford from Barefoot CNC]

Should work with either one, but I prefer using curve5ax on tuesdays

[bet338]

Nick,

The problem I'm having with this part, aside from not doing alot of 5x surface work, is the bottom at the back corners is wider than the top. It's hard to see in the pic. My bottom geo is made of curves but the top boundry is a spline that won't simplify. I'm going to try to draw geo on top of the spline to match and then maybe I can connect the two with lines to use.

 

Thanks,

Brian

[Nick Eaton]

The nice thing about Curve 5ax is that you can manipulate your tool control vectors to compensate; rotate around the point you create them from, project them onto the surface etc....In this case you might want to manipulte the "fanning" effect in the corners.

If your vector lines change to splines during this process I create another point at the top of the spline and then redraw a line between this point and the base point. This is a bit of a cheat but if the results exceed the tolerance of the part it will have to be stitched anyway.....

Cheers

Nick

[Nick Eaton]

Just another thought.....you might find it easier to create 2 toolpaths, one for the "straight" section and another for the rest.

You could then use lead in/out to help with the corner blends.

cheers

Nick

[bet338]

Nick,

Do vector lines have to be straight to use 5ax curve? If you look at the end of the yellow shaded area the wall has a curve blending on the sides to the corner rads. I have some toolpath verified

with 5ax curve and it looks like it's a powerful tool, but can it be used here?

 

Thanks

Brian

 

[bet338]

Nevermind I answered my own question.

No you can't. Looks like I have to try something else.

[Nick Eaton]

You can project your vector line onto the yellow surface, you might need to untrim your surface. Then check to see if its a line or a spline. If its a spline create a point at each end and delete the spline. Then join the 2 points with a line.

It can be a fair bit of work. But if it wasn't we wouldn't have Starbucks and 7-11s on every corner, we would have 5ax machine shops a thriving manufacturing export industry and a much lower deficit....!!

Cheers

Nick

[bet338]

Ahh.. but that's the problem. The inside wall isn't flat and a line between two points would be.

mmmm... more coffee......

 

Thanks

[Nick Eaton]

If the inside surface is "domed" you can run a high pass and a low pass with different amounts of "lean". This would allow you to use the same geometry.

Alternatly you could do two line/vectors to control each level individually.

If its a dished surface its more problematic as the bottom cut will undercut your initial cut.

How much is the loft? If its only a couple of thou. and you are not using 50% of your tolerance you can cheat it.

Technical term is 5 axis mismatch. We see that call all the time on our paperwork in our business (aerospace).

Cheers

Nick

[Trevor Bailey]

check email.

[Trevor Bailey]

used Advanced Multiaxis:

- parallel to curve (red you see on the bottom)

- drive surfaces are the side walls and the fillets

- Linking - gaps along set to "blend"

- clearance are set to sphere

- tool axis control is used by closed boundary at top with rounded corners to help tool pivot in the actual corners of the part.

 

[bet338]

Big thanks to Trevor and all who had advice for me.

 

[Nick Eaton]

Sweet.....Haven't used advanced 5ax as I only use 4ax.

 

Will keep that one in mind when its time for me to step up to the 5ax plate

Cheers

Nick