CAM - 2D Contour Path Ignores Ramping Angle

[greeseFNJQF]

Steps to Reproduce:

1) Create a 2D Contour CAM operation

2) Under the 'linking' tab, enable 'Ramp' functionality and change the 'ramping angle' to something other than the default (2 degrees).

3) The resulting path will always have the default ramp value rather than the value you set.

[seth.madore]

You also need to change your maximum Ramp Stepdown. This area could be more intuitive, for sure.

[greeseFNJQF]

My stock is .75" thick. If I set the 'maximum ramp stepdown' to anything less than .85", it does not respect the ramping angle. However, at exactly .85" or above for the stepdown, it immediately uses the specified ramping angle.

Ramping angle 45 deg for both of the following:

Here is stepdown set to .84":

-and stepdown set to .85":

Is that, somehow, the intended behavior?

[seth.madore]

Could you share your file, or a sample file that reflects your selections and settings?

File > Export > Save to local folder, return to thread and attach the .f3d file in your reply

[oleg.tikhomirov]

@greeseFNJQF and @seth.madore 

Most likely it works as designed. As far as I remember it try to make BOTH "Maximum ramp stepdown" and "Ramping angle"(Maximum ramping angle is a better name) correct.

If distance between stock and you first z-level is bigger than "Maximum ramp stepdown" that ramp is spitted.

Sorry for the picture. I did quickly.

Just set "maximum ramp stepdown" to very big value that ramp must be controlled only by angle.

[greeseFNJQF]

Here is an example file I created to demonstrate the issue.

In this example, there is a 12"x12"x.75" plate that should be cut out of a piece of 24"x48"x.75" stock. The contour should be cut in a single pass with a ramp that respects the ramp angle (like all the other ramp-capable cuts).

So, the maximum ramp stepdown is equal to both the stock and the piece to be cut (.75") - which means that the contour should cut the piece in a single pass with a compression bit while diving into the stock at the specified angle (ramping angle).

However, with a ramping angle of 45 degrees, you can change the maximum ramp stepdown to any value between .75" and .84" and the generated path will be identical (ignoring the ramping angle). However, if you set the maximum stepdown to anything .85" or over, the ramping angle suddenly works as intended.

The workaround is simple now that you have pointed it out: set the maximum stepdown to something ridiculously high so that it respects the specified ramping angle, but it's still definitely a bug.

The ramping angle should be respected on any maximum stepdown value and should ramp the tool down at that angle until the maximum stepdown has been reached - cut the contour, and then repeat if there are additional stepdowns until the path is complete.

[greeseFNJQF]

Is this something that is going to be addressed in a future patch?

[engineguy]

@greeseFNJQF 

Looks to be working correctly here, in your file you have a Stock set in the Setup that has an offset of 0.0393701in and you have also a setting of 0.0984252in for a Ramp Clearance Height, so, Fusion is looking at where everything is and adds it all up so in your example you had to go to 0.89in in order to have the 45 degree angle go to the selected Contour whichis at the bottom of the material and is actually at a total distance of 0.8877953in so that is why you needed the 0.89in, in fact if I input the 0.8877953in value for the Max Ramp Stepdown the it does do the 45 degrees correctly, if I make it just the 0.88in then it doesn`t do a 45 degree because it has calculated that with those values added up it is not possible to do a 45 degree angle, pretty smart IMHO 🙂 🙂

Summary, check the values you have input for the Stock Top Offset and the Ramp Clearance height plus the distance to the selected contour, either do the Math or as @oleg.tikhomirov has advised just chuck a value in there that is easily greater than those values added together and you are good to go 🙂 🙂 🙂

[greeseFNJQF]

"

---

@engineguy wrote:

it doesn`t do a 45 degree because it has calculated that with those values added up it is not possible to do a 45 degree angle, pretty smart IMHO 🙂 🙂🙂

---

I don't know how much more clearly I can point this out; it is a bug. It is entirely possible to ramp down at a specific angle without proceeding entirely through the stock in a single pass (as evidenced by the attached example).

In the attached example, multiple passes are set at .25" each - however, only the first pass respects the desired ramp angle, then the rest revert back to the default ramping angle.

If it can ramp through a single step-down, that completely disproves what you stated. The fact that it doesn't ramp through the additional step-downs is a bug and is related to my original post.

So, no, it's not "pretty smart"; it's a bug - and it needs to be recognized as a bug so that it can be addressed.

[greeseFNJQF]

So... did anyone actually look at this example and confirm the bug? I'd like to be able to do multi-depth 2d contour cuts without waiting for a 2 degree stepdown on every cut except the first. I'm cutting wood, so I can go quite aggressive and this bug is costing me quite a bit of extra cut time from the shallow ramps.

[engineguy]

@greeseFNJQF 

As far as I am aware this issue with the multiple depths has been reported, which is probably why no one Posted 🙂 🙂 @seth.madore  @oleg.tikhomirov   ????

If you are interested there is a "workaround" that has been around for a while, try using the 3D Contour instead of the 2D, it will plunge to the first -0.25in depth but it does it off the Stock so safe enough, then you can use a nice slow entry arc of say R0.25 at 10in/min, then it goes to your Cutting Feed Rate of say 40in/min, after the first pass it then does pretty much what you are asking for, it will do a 45 Deg Ramp down at the Cutting Feed Rate (eg 40in/min) at each susequent level, see image below. Example file attached, set your own feeds/speeds/angles/leads etc, etc, it is only for information, not a "hard and fast" rule 🙂 🙂 🙂 Have a "play" 🙂 🙂

[seth.madore]

Correct me if I'm wrong, but it appears that you are calling out two separate issues:
1) Max Ramping Stepdown needs to be greater than the thickness of your part in order to generate a proper ramp angle of 45 degrees, as shown in this photo:

 

2) Ramp angle is only being applied to the first pass, as shown here:

 

For the matter of #1; the reason that you need to input a larger value is due to two setting on the Linking Tab:

 Setting these both to zero will allow you to input the correct Max Stepdown value. Granted, it will now start right at the top of the part/stock, so you can either set them to zero, or create an expression that pulls in those two values.

For the second matter, yes, this does appear to be a bug, I will log this issue shortly.

[seth.madore]

Interestingly, if I set my Max Stepdown (in Ramp) to something absurd, such as 25 inches, it gives me what you're looking for:

 

[seth.madore]

I've opened up CAM-35544 to investigate this issue.

[greeseFNJQF]

Thank you for the information about the first issue and for logging the bug regarding the second.

[hendrikoRG4R6]

Thank you for sharing this workaround! I was very frustrated by this bug and happy to find this solution.

[info2ASY3]

4 years later and this is still happening. Whether or not its "doing what the code says it should do" this is a bug in that it does not do what us customers expect, and has a work-around that makes little sense. I had to ask the AI "Assistant" a few times before it told me this case number, as I hit the exact same problem: trying to do short ramp-downs while cutting plywood with a compression bit. If I don't ramp, the chips pack in during the plunge and the spindle never recovers. It has to ramp to the cut depth quickly to have as short a time as possible on the up-cut section of the endmill to prevent it from splintering the ply. Enabling ramp with a steep angle, it auto-corrected the 'max ramp stepdown' to the 'max stepdown' I had for multi-depth, but still does such a shallow full-perimeter ramp-down it tears up the surface of the wood while barely cutting anything, then does another full perimeter at depth, which only cuts full-depth for maybe 1/4 of the part , then another ramp, then another perimeter!! Big waste of time, not great for the bit, etc. If I tell it I can ramp down a certain distance, the first cut goes only that deep, it should be able to do that at the angle I specify. If its because the height at the top of the ramp-down is NOT being calculated from the same height as it measures cut dept (IE: It adds the ramp-clearance), that is definitely a bug. It should calculate that into what it already adjusts, and/or warn on this behavior. Current mouse-over help on these has no mention of any of this. It also does not seem to correctly do this "per ramp revolution" as my second dept cut it ramps at an extremely shallow angle again unless I set 'max ramp-down' to an absurd length. A full 1" for 0.75" stock was not enough, 300" was.

[andrew2085]

It's working how its supposed to.

Read this carefully. This means that if the maximum ramping stepdown is set to 1" that means that at most the tool can travel down 1" in Z in one full revolution around the contour (much less than 45deg). This is just another way of specifying the maximum ramping angle as a function of a Z distance and the length of the contour path. If whatever angle that would be is less then the ramping angle, then that angle is used. It uses whatever is the minimum of the two angles.

If you always want to use the ramping angle, then set a very large maximum ramping stepdown.

[Laurens-3DTechDraw]

I think for people who run mainly in wood, it might be good to change the default Maximum Ramp stepdown to the tool flute length, instead of the standard Maximum Stepdown value.
Which everyone can easily do themselves.