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Help with helix/ramp non milling

sandrewb

Plastic
Joined
Apr 8, 2016
Hey

Does any one know a different method to make the helical ramp pictured? We currently make a similar feature in house by milling it. This part has no rad at the end of the pocket, extends 3.5" above the bottom of the ramp and is only .439" wide. That overhang in our machines would likely chatter and break the endmills. hoping someone knows of a shave tool or something that may do the job.

Thanks in advance!
HELIX RAMP.png
 
Assuming from the image that the top of the ramp and the bottom of the ramp result in a step?
The pocket at the bottom of the ramp not only has sharp floor corners but also the 2 wall corners are sharp as well?
If this is the case you could only EDM this feature.
 
Assuming from the image that the top of the ramp and the bottom of the ramp result in a step?
The pocket at the bottom of the ramp not only has sharp floor corners but also the 2 wall corners are sharp as well?
If this is the case you could only EDM this feature.
Well that doesn't sound very fast at all ;P Management is going to ask the customer if we can revise it so that an endmill can be used. I still dont like the process of using an endmill with how far it will be sticking out.
 
Here are some questions marked up on your drawing:
ramp.png

I can't tell what shape the ramp is. This?
helix ramp.png

Maybe this?
blend ramp.png

We currently make a similar feature in house by milling it.
Genuine question: how do you do that? If the ramp is made by sweeping a line around a helix and it's between ID and OD walls I don't see how to make that with the round bottom face of an endmill. Or on the similar part that you make now are there no walls?
 
Here are some questions marked up on your drawing:
View attachment 443299

I can't tell what shape the ramp is. This?
View attachment 443300

Maybe this?
View attachment 443301


Genuine question: how do you do that? If the ramp is made by sweeping a line around a helix and it's between ID and OD walls I don't see how to make that with the round bottom face of an endmill. Or on the similar part that you make now are there no walls?
No! Like this.1718307194771.png
 
Here are some questions marked up on your drawing:
View attachment 443299

I can't tell what shape the ramp is. This?
View attachment 443300

Maybe this?
View attachment 443301


Genuine question: how do you do that? If the ramp is made by sweeping a line around a helix and it's between ID and OD walls I don't see how to make that with the round bottom face of an endmill. Or on the similar part that you make now are there no walls?
It is more like the first drawing but negative (Like if you did a face groove but the bottom of the groove ramps down.)
 
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Ask the engineer who designed the part.

I find that is typically the fastest/easiest way.

One way or another, you'll learn what you need to know.
 
It is more like the first drawing but negative (Like if you did a face groove but the bottom of the groove ramps down.)
Not sure if you saw, but I asked other questions in red.

It looks like the part is actually 2 pieces welded together. You wouldn't have to tangle with the shaft if you cut the ramp prior to welding. Still no idea how you'd do it with an endmill though since you didn't answer how you've done it before.

Anyway, you could probably make a helical ramp with a step on a lathe using a face grooving tool by synchronizing C and Z axes like for threading. Operation would be like a shaper wrapped into a circle: 1 stroke at a time, so it will be slow. Probably rough out with an endmill first.

Grooving tool will need relief greater than helix angle of ramp and there will need to be an undercut (made with endmill) at the step so that the grooving tool isn't trying to slam the chip into the step.



ramp.png
 
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Not sure if you saw, but I asked other questions in red.

It looks like the part is actually 2 pieces welded together. You wouldn't have to tangle with the shaft if you cut the ramp prior to welding. Still no idea how you'd do it with an endmill though since you didn't answer how you've done it before.

Anyway, you could probably make a helical ramp with a step on a lathe with C-axis using a face grooving tool by synchronizing C and Z. Operation would be like a shaper wrapped into a circle: 1 stroke at a time, so it will be slow. Probably rough out with an endmill first.

Grooving tool will need relief greater than helix angle of ramp and there will need to be an undercut (made with endmill) at the step so that the grooving tool isn't trying to slam the chip into the step.



View attachment 443303
Good eye, but it looks like there would still need to be an inside wall on the ramp? I suppose you could change the design to accommodate accordingly?

I'm not sure what to make of where you have noted tangent lines.
 
Good eye, but it looks like there would still need to be an inside wall on the ramp? I suppose you could change the design to accommodate accordingly?
I think this is the shape:
ramp groove.png

When you say inside wall do you mean the red one?
inside wall.png

Please clue me in on how that wall is a problem for the lathe approach. Or did you mean for milling? For milling I'd much rather ditch the outside wall and then swarf mill it.

I'm not sure what to make of where you have noted tangent lines.
Yeah that's why I asked the OP and those lines are what got me thinking that the ramp might be this kind of shape (though they are angled the wrong way for this):
blend ramp.png
 
I guess if you had orbit machining in your mill or C axis on your lathe you could use a face grove tool to letter rip.
 
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I have attached some pictures to help explain what is going on in the prints. There is a step and it ramps down to the lines shown in the print. From those lines to the end it is flat and stops ramping down. The part in my hand is what we currently make by using a end mill sticking out 7xD. This part is much shorter and smaller then the print I am questioning about. The new part would require a stick out of 8xD and a larger diameter end mill. I do not think our machines would be rigid enough for this.(Nakamura WT150)
 

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Not sure if you saw, but I asked other questions in red.

It looks like the part is actually 2 pieces welded together. You wouldn't have to tangle with the shaft if you cut the ramp prior to welding. Still no idea how you'd do it with an endmill though since you didn't answer how you've done it before.

Anyway, you could probably make a helical ramp with a step on a lathe using a face grooving tool by synchronizing C and Z axes like for threading. Operation would be like a shaper wrapped into a circle: 1 stroke at a time, so it will be slow. Probably rough out with an endmill first.

Grooving tool will need relief greater than helix angle of ramp and there will need to be an undercut (made with endmill) at the step so that the grooving tool isn't trying to slam the chip into the step.



View attachment 443303
The spot where you have Weld? is a groove in the back face of the part. The part is to be made as 1 piece.
 
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The new part would require a stick out of 8xD and a larger diameter end mill. I do not think our machines would be rigid enough for this.(Nakamura WT150)

The 2 approaches that I see are:

Using a face grooving tool and C-axis like I mentioned above.

Supporting the 8xD endmill with a drill bushing just above the flutes. The bushing would be held in an arm mounted rigidly to the lathe's turret. Maybe coolant (or oil) could be pressure-fed to the bushing to keep it happy.
 
I would find something from Harvey Tool and use their speeds and feeds to start with. They seem to be pretty conservative, the only time they steer me wrong is when I misread the chart and use the finishing feeds for slotting.

If it is a lot of parts I would talk to Harvey Tool and tell them what you want to do and have them design a tool for you.

 
The 2 approaches that I see are:

Using a face grooving tool and C-axis like I mentioned above.

Supporting the 8xD endmill with a drill bushing just above the flutes. The bushing would be held in an arm mounted rigidly to the lathe's turret. Maybe coolant (or oil) could be pressure-fed to the bushing to keep it happy.
I do like the face grooving tool and C axis idea. I dont think there would be clearance enough around the end mill for a busing. It would be approx 150,000pcs a year so finding a off the shelf tool would be best. having to custom tooling would be a headache and likely inconsistent.
 
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