Using a cross section curve to drive threading passes - how many CAM supports this?

**gregormarwick** · 01-12-2021, 03:31 AM

Inspired to ask by a recent thread in the CNC sub.

I use FeatureCAM, and I use this function reasonably frequently to generate large threads or other spiral forms (rope drums etc.)

It seems that this feature isn't all that common in CAM software, so I'm curious, which CAM softwares do have explicit support for doing this?

I ask because this is functionality that I would be reluctant to lose if I were to switch in the future.

**Mtndew** · 01-12-2021, 08:26 AM

Mastercam 2021 can do Rope, Buttress, Square and Trapezoidal threads.

**hanermo** · 01-12-2021, 10:41 AM

Very interesting thread.
Grin.

I never thought the cam would do threads on its own.
How do you program it in cad ?

**gregormarwick** · 01-13-2021, 06:35 AM

Originally Posted by Mtndew

Mastercam 2021 can do Rope, Buttress, Square and Trapezoidal threads.

So just to clarify, it's limited to those threadforms specifically, or you can define an arbitrary cross section/threadform with a curve?

Originally Posted by hanermo

I never thought the cam would do threads on its own.
How do you program it in cad ?

Not sure exactly what you mean, but my typical workflow for such a part is to model it including the fully modelled thread. Then import that model into cam, extract a curve from the cross section of the threadform, then create a thread feature and select that curve as the profile of the thread. Then I can select any tool, usually I use a basic grooving tool if the threadform has a flat floor, otherwise a full radius tool, and it will post progressive screwcutting passes to generate the threadform. You can use this feature to cut huge threads that would be impossible with a full form tool, or to cut threads with any weird arbitrary thread form, or even to cut augers and suchlike.

**Mtndew** · 01-13-2021, 11:11 AM

Originally Posted by gregormarwick

So just to clarify, it's limited to those threadforms specifically, or you can define an arbitrary cross section/threadform with a curve?

Well, technically you are unable to define your thread profile with wireframe entities.
It has those forms that you can choose from and obviously enter in your own values for them.
I believe they are working on custom profiles for threading as we speak, although it's not even in the 2022 beta version so it could be further down the road.

EDIT:
goooose proves me wrong.(see post below)

**goooose** · 01-13-2021, 11:50 AM

You can draw your thread shape/profile/cross section/thread form (whatever you want to call it) and chain it to cut in Mastercams Custom Thread toolpath.
There is also a chook called Thread C, it has some more customized threading options for the path of the thread.

**Mtndew** · 01-13-2021, 12:25 PM

Originally Posted by goooose

You can draw your thread shape/profile/cross section/thread form (whatever you want to call it) and chain it to cut in Mastercams Custom Thread toolpath.
There is also a chook called Thread C, it has some more customized threading options for the path of the thread.

I thought you could do that! But I tried it a couple of months ago and couldn't get it to work. Maybe because it was a multi-start thread?

**hanermo** · 01-13-2021, 01:15 PM

Em ..

so to clarify, in principle one can draw a ballscrew ogive arch, and use a suitable rounded toolbit, and the lathe will cut the ogive arch within given machine limitations.
In Mastercam, yes ?

Any idea form someone how many passes a 32 mm / 5 mm rise thread would take with a suitable toolbit ?
On 32 mm OD stock.

And what toolbit one might use to do such ?

**gregormarwick** · 01-13-2021, 01:31 PM

Originally Posted by hanermo

Em ..

so to clarify, in principle one can draw a ballscrew ogive arch, and use a suitable rounded toolbit, and the lathe will cut the ogive arch within given machine limitations.
In Mastercam, yes ?

Any idea form someone how many passes a 32 mm / 5 mm rise thread would take with a suitable toolbit ?
On 32 mm OD stock.

And what toolbit one might use to do such ?

Number of passes simply depends on tool radius and acceptable cusp height, same as milling a surface with a ballnose.

**Mtndew** · 01-13-2021, 02:32 PM

Originally Posted by hanermo

Em ..

so to clarify, in principle one can draw a ballscrew ogive arch, and use a suitable rounded toolbit, and the lathe will cut the ogive arch within given machine limitations.
In Mastercam, yes ?

Any idea form someone how many passes a 32 mm / 5 mm rise thread would take with a suitable toolbit ?
On 32 mm OD stock.

And what toolbit one might use to do such ?

It depends, on larger rope drum threads, the radius and lead is just too large to do with 1 single rounded tool.
On smaller ones, it's certainly doable, but you're gonna have to fight chatter and vibration.

**gregormarwick** · 01-14-2021, 04:56 AM

So we've established that besides FC, MC also can do this.

Any others?

Am I wrong that it's an uncommon feature - maybe just a seldom used one that users are not always aware of?

**EmanuelGoldstein** · 01-14-2021, 05:31 AM

Originally Posted by gregormarwick

It seems that this feature isn't all that common in CAM software, so I'm curious, which CAM software does have explicit support for doing this?

APT

I ask because this is functionality that I would be reluctant to lose if I were to switch in the future.

Somehow, I don't think my choice will be a problem for you

btw, G&L had a feature built into the control that would do the kind of thread that goes most of the way around in a circle, then skitches over one pitch, then goes around in a circle again. This is supposed to wind better, twist the cable less, and get more wire rope onto a drum.

I never had a big G&L but thought it was interesting at the time. There's a name for that thread, maybe an oil patch guy will chime in ?

**gregormarwick** · 01-14-2021, 05:48 AM

Originally Posted by EmanuelGoldstein

APT

You again!

I'm beginning to think that I need to learn apt just to shut you up

**EmanuelGoldstein** · 01-14-2021, 06:11 AM

Originally Posted by gregormarwick

You again!

Well, you asked

I'm beginning to think that I need to learn apt just to shut you up

But those are the kinds of things that APT is very good at. Mathematically defined curves and that kind of thing. All that point-and-clicky programs are is a layer on top of a mathematical solution ... nice for general use but not that great for the case where you want tight control.

It's actually more capable than the point-and-click but not as easy to use.

Anyway, I'm happy to send you a manual ...

**gregormarwick** · 01-15-2021, 05:29 AM

Originally Posted by EmanuelGoldstein

Well, you asked

But those are the kinds of things that APT is very good at. Mathematically defined curves and that kind of thing. All that point-and-clicky programs are is a layer on top of a mathematical solution ... nice for general use but not that great for the case where you want tight control.

It's actually more capable than the point-and-click but not as easy to use.

Anyway, I'm happy to send you a manual ...

You have probably picked up on my interest in old computer technologies, but it's a fools errand to pursue obsolete technologies in the workplace and I am careful to keep my work and my hobbies separate!

Everything APT can do is possible in all but the lowest end of the modern CAM systems, and if I really need to do something programmatically I can leverage the API in any language I want, if macros are not sufficient. That's not to say APT isn't capable, but it has been fully superceded, and not recently...

Back on topic, nobody else going to chime in? I was hoping to hear about Esprit, NX CAM etc.

**CAMasochism** · 01-15-2021, 08:49 AM

Originally Posted by gregormarwick

You have probably picked up on my interest in old computer technologies, but it's a fools errand to pursue obsolete technologies in the workplace and I am careful to keep my work and my hobbies separate!

Everything APT can do is possible in all but the lowest end of the modern CAM systems, and if I really need to do something programmatically I can leverage the API in any language I want, if macros are not sufficient. That's not to say APT isn't capable, but it has been fully superceded, and not recently...

Back on topic, nobody else going to chime in? I was hoping to hear about Esprit, NX CAM etc.

No such feature that I am aware of for NX, though I don't have the most extensive training in it yet. You just select your crest line, tell it the depth, pitch, and number of starts for basic threads. It would be a really good feature to have because right now we are manually programming the threads you are talking about and it is tedious.

**SD&M** · 01-15-2021, 04:12 PM

Hi Gregor:

"Back on topic, nobody else going to chime in? I was hoping to hear about Esprit, NX CAM etc."

This is not quite what you're after, but maybe it's a useful data point anyway(?): TopSolid has got a module that does screw milling. I don't have this module and therefore can't offer any first-hand feedback. I have no idea if this can be used in a turning scenario or not....

TopSolid 7 - machining a timing screw: TopSolid 7 - machining a timing screw - YouTube

TopSolid 7 - How to design a timing screw: TopSolid 7 - How to design a timing screw - YouTube

Cheers, Brian

**gregormarwick** · 01-17-2021, 08:37 AM

Originally Posted by SD&M

Hi Gregor:

"Back on topic, nobody else going to chime in? I was hoping to hear about Esprit, NX CAM etc."

This is not quite what you're after, but maybe it's a useful data point anyway(?): TopSolid has got a module that does screw milling. I don't have this module and therefore can't offer any first-hand feedback. I have no idea if this can be used in a turning scenario or not....

TopSolid 7 - machining a timing screw: TopSolid 7 - machining a timing screw - YouTube

TopSolid 7 - How to design a timing screw: TopSolid 7 - How to design a timing screw - YouTube

Cheers, Brian

Not what I am asking about, but definitely interesting! I could probably replicate that in FC, but it would take a fair amount of work to get such a clean toolpath, considering the irregular geometry. Not sold on the modelling in the second video though, seems excessively convoluted.

**EmanuelGoldstein** · 01-17-2021, 08:54 AM

Originally Posted by gregormarwick

Everything APT can do is possible in all but the lowest end of the modern CAM systems, ....

Really ? Because the major users of APT were doing five axis work. Last I looked, Fusion and the rest were not capable of that.

And your own question here would seem to refute that statement, because this task is simple in APT. I guess no one piped up to say they could do it in Fusion because they couldn't find the correct icon ?

I don't expect you to use it but please, no more incorrect statements about capabilities. There's nothing the most advanced modern CAM system can do that APT cannot. Nothing.

**gregormarwick** · 01-17-2021, 09:55 AM

Originally Posted by EmanuelGoldstein

Really ? Because the major users of APT were doing five axis work. Last I looked, Fusion and the rest were not capable of that.

And your own question here would seem to refute that statement, because this task is simple in APT. I guess no one piped up to say they could do it in Fusion because they couldn't find the correct icon ?

I don't expect you to use it but please, no more incorrect statements about capabilities. There's nothing the most advanced modern CAM system can do that APT cannot. Nothing.

Indulge me then, and write a program in apt to generate, for example, a TR100x36P12 (12mm pitch / 36mm lead, three start) external thread using a 4mm grooving tool. I'm genuinely interested to see how it compares to doing the same in Macro B.