Machining Undercuts on Surfaces

[Metal_Eater]

Does anyone know how to machine undercuts on surfaces. As surface machinig does not allow to cut underneath a surface. Is there any way around???

 

[cadcam]

so you are saying that you want to cut the oppest side of the surface then the face that is faceing you.

one way would to change the normals and it will read the auther side.

but i beleave you mean like cutting a mold under cut like with a key way or what not.

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jay/ aka cadcam

Precision Programming

cnc programming &

Predator reseller

email: [email protected]

web: www.ppcad.net

[marcus]

Hi Metaleater:

Have you tried projecting profiles onto the surfaces and milling them as 2D or 3D contours?

Tedious as hell, but it gets the job done for me.

I get past the tendency to rapid up through the job by controlling the entry and exit parameters.

Marcus

[Christian Raebild]

Have you tried to give a negative finish allowance? That sometimes works.

If that does not work, I would suggest, that you offset the relevant surfaces. You may have to edit the surface normals first.

[JG]

I think you are going to have to use a flowline toolpath, that way you can shut off gouge checking.

Thanks,

J.G.

[Metal_Eater]

Thanks for all your Replies,

I think I should be little more specific about my problem. I am trying to cut some undercuts on bottle moulds. Theoretically I can reach those undercuts with lolipop end mill.

But when I try to machine them the tool won't go in undercuts. I tried flowline toolpath with gouge checking off, But it gives me error "surfacecs do not form a row"

I think surface normals is not a problem as the tool is cutting on right side, but does not follow undercuts.

Any advice would be appreciated.

[JG]

I think the error you received is due to the uv flow lines not matching, to get around this I either machine the surfaces individually or project new contours over the group of surfaces then make a new surface and machine it using flowline.

thanks,

J.G.

[Metal_Eater]

How do you project new countours over group of surfaces???????????

Can we machine those surfacecs using flowline???????

[JG]

You would need to create reference geometry to project, then "create, curves, project"

bear in mind you are creating a new surface to use a flowline toolpath on which will allow you to dis-able gouge checking, there are many variables to consider to get the results you are looking for.

If you want I could take a look at what you are trying to cut.

Thanks,

J.G.

[This message has been edited by JG (edited 10-09-2000).]

[CycleTimeCharles]

Set the Toolplane to Top and the Cplane to the left side (#6) and use Surface Finish Contour.

Email me if you want to see a sample.

This forum needs a FTP link for sample files.

[Webby]

Charlie - Working a getting an FTP drop zone for files.

[johns]

Tilt the block up at 15 or 30°, cut the areas you need. This would be less time consuming than projecting splines and cutting to contours. If you do this alot, make or setup a tilting vise with a known pivot point and use that point as your Z plane datum, then you won't have to reset your tools or reference point. If your blocks are steel, rough out on a vise, and finish on a magnetic sine chuck.

[Trevor Bailey]

To do undercut surfaces in V8, use toolpath-next menu-wireframe. You will see ruled, coons, revolved, etc... Expirement with these. There is nothing fancy you need to do, just choose the appropriate toolpath for the undercut. The key word here is expirement.

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Trevor Bailey

[email protected]

Dealer

[Toby]

I'm not sure how complex a surface your working with but something that has worked well with us is to use a keyway cutter with a precision radius (approx .02) ground on the top and bottom sides. Then we take the surface to undercut and offset it the full diameter and hight of the cutter. Now you can use conventional techniques on the offst surface asuming their is clearance. You would notice that the top rad of the cutter will follow the actual part undercut.

just a thought

TB

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[Webby]

I've heard that Metal_Eater's required undercut was satisfied with the Revolved toolpath. Would Metal_Eater please comment?

[Metal_Eater]

Have'nt logged on to forum for a while, I tried every method, but the method described by CYCLETIMECHARLES works best for me. I can make any toolpath (radial, scallop, countour etc.) using surfaces, No need to make any projected coutours. Saves lot of time & headache.

No need for tylonol anymore...:-)

 

Thanks Everybody

 

[kathy]

Hello All,

I read through this thread, and have 'seemed' to get what I want using a flowline finish surface Can’t wait for some real verification!!! (8.1) Right now, I am waiting to test out a sample cut in wood on our router to see if it is a good cut.

I may need to 'break-up' the cuts into different programs so the code will fit inside the controller. The 'prompt for tool center boundary' option is greyed out on my Mastercam. Is this option supposed to be available, or am I out of luck?? (If not, I will physically have to break up the surface into segments – arugggggggg……………….)

Thanks, Kathy

 

[Metal_Eater]

Hi kathy,

You can't use tool center boundary using flowline method, but I am sure you can use scallop or countour or radial tool path on your part., be sure to setup your construction plane to side or front so that your cutter can go into undercut, let the

toolplane set to off.

Still lost?

Send me your file to: [email protected]

I will be able to help you out. As I am machinig lots of undercuts on surfaces. You don't have to spend whole weekend scratching your head