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Horizontal VS Flat toolpath. Are you still using Horizontal and why ?

Message 1 of 26
3101 Views, 25 Replies

Horizontal VS Flat toolpath. Are you still using Horizontal and why ?


For those of you that are using the Horizontal Strategy, can you share why you are still using it?
We introduced the Flat Strategy a while ago now, so I would be interested to hear if you are still using the Horizontal Strategy and for what reason. All feedback welcome

Kieran Gill
Technical Consultant
Message 2 of 26
in reply to: kieran.gill

I don't like to use either. The new flat toolpath takes way too long to generate, misses parts of flat areas when finishing passes are specified, and doesn't have enough options to make it useful for me.


Options that would be nice:

- Repeat [wall] finish pass

- Multiple [wall] finishing passes

- Different feedrate for [wall] finishing passes

- Ability to take multiple depths of cut for finishing passes only

- Ability to take multiple depths of cut on the first finish pass but then 1 single (or a different amount) finishing pass on the second pass

- Ability to specify a minimum cutting radius

- Finish pass overlap/tangential fragment distance

- Outer corner mode (roll around/keep sharp)

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Message 3 of 26
in reply to: FrodoLoggins

@FrodoLoggins , great feedback so far, so thank-you.

Since your clearly seeing a disparity on missed areas of the flat regions, would be able to DM me the part F3D in question ? If not, would you be willing to have a quick zoom call to go over some of your issues to better understand them. Ultimately i want to capture them with sufficient reproducible data . 


Let me know whichever is easiest for you ?



Kieran Gill
Technical Consultant
Message 4 of 26
in reply to: kieran.gill

Hi @kieran.gill,  I also agree with @FrodoLoggins.


Flat always takes too long to generate / regenerate a toolpath and in my case, it always leaves stock on selected features (see image below highlighted in red) even when I have machine over holes tab selected or when I create patches/ surfaces over the holes and select them for areas to machine. most of the time resulting in a secondary toolpath (2d contour) to clean up the missed areas.  


I do find that horizontal does produce a better toolpath in regard to fully machining flat faces, but I also find horizontal a lot harder to limit the faces it machines due to the toolpath not having a touch/avoid surfaces tab

missed areas flat.png


Message 5 of 26
in reply to: j.mitch97

@j.mitch97 , Thanks for this feedback. Great example btw. Are you able to share the F3D with me so i can discuss with the development teams ? PM me is the best way to share it or or via another private means is also ok.

Kieran Gill
Technical Consultant
Message 6 of 26

Flat consistently seems like the longest time to generate of any toolpath I use, even when I constrain it down to only what I want, both height constrained and boundary constrained will take minutes to do what I feel is a simple generation


Have not used Horizontal since Flat came out, just wish it was much faster, like why is this 2+ minutes to calculate, when I set the top reference .01" above surface, and bottom at surface, contained by the slight boss of the hole




Message 7 of 26
in reply to: kieran.gill

One big problem with both strategies is, that no matter what I change, sometimes it plunges straight in the material, even if there is plenty of room to start from the outside. Is there any way to make this work? I can´t force it to allways start from the outside.

Message 8 of 26
in reply to: kieran.gill

@kieran.gill  - One thing thing that I'd like to see flat do better is how it generates linking moves when using "finishing pass". I find that flat will do a decent job most of the time in generating the passes but it tends to want to retract before the finish pass then plunge down into material.

I find myself regularly keeping flat off the wall then using 2d contours to have a smoother lead-in and avoid these minor collisions. I've included a photo below of a simple example but can generate a file if that would be more helpful.

Screen Shot 2022-11-06 at 8.23.41 PM.jpg

Message 9 of 26
in reply to: Koch612

@Koch612 , Thanks for the feedback. Feedback like yours becomes is even more valuable when we have tangible examples like model data sets. 


You say you are having an issue getting the toolpath to start from the outside, Flat certainly was designed to do this for open pockets. Do you have data set you can share, so we can test this? If you could save model with the toolpaths already calculated then export it that would be great and then send the model set to me via PM please!


Again thanks for the feedback. Looking forward to investigating this one

Kieran Gill
Technical Consultant
Message 10 of 26
in reply to: Garrett_Wade

@Garrett_Wade , Good to chat again Sir.

Yeah this is great feedback. Are you able to share the model set which would be awesome ?




Kieran Gill
Technical Consultant
Message 11 of 26

@dwilliamsFM6K4 . This is great feedback. I wonder if if the Flat toolpath is still inadvertently still interrogating more of the model behind the scenes than is necessary. DO you still get the time-penalty when you model up the geometry for machining separately ?


Be useful to see your original data set if you don't see a time hit with the only-required geometry.


Look forward to hearing back from you on this one. Thanks for the feedback

Kieran Gill
Technical Consultant
Message 12 of 26
in reply to: kieran.gill

Flat completely superceded horiztonal. I've gotta be honest, I don't like the way smoothing is done. Running on old machines, on floor finishing where im not cutting any toleranced features, the only thing that's important to me is code size. I'm assuming this is because it's not a native fusion toolpath, but one brought in from another program?

Message 13 of 26
in reply to: wstoneandsons

Thanks for the feedback @wstoneandsons . Much appreciated. Glad your seeing improvements over Horizontal

As you have pointed out, Flat has a number of benefits over Horizontal but there is a couple of things you can do apart from loosing the tolerance of course which will have the largest impact.

You could also try lowering the smoothing deviation from 10%(default) to 0-5%. This will likely decrease code size by having less points around the inner cut areas.

Play with these two settings until your happy with the toolpath and the output code. 



Kieran Gill
Technical Consultant
Message 14 of 26

Flats don't detect tool length like horizontal will. You can pick it but it doesn't change tool length. It just trims the toolpath.

Message 15 of 26


Flats don't detect tool length like horizontal will. You can pick it but it doesn't change tool length. It just trims the toolpath.

Hmm? You mean this:


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 16 of 26

Yeah can turn it on but I get No tool length change just a  trimmed toolpath. 

Message 17 of 26
in reply to: kieran.gill

@CRANDALLPRECISION , yes your right. I believe this is a bug. I've opened up the required ticket to investigate this. Thanks for reporting it

Kieran Gill
Technical Consultant
Message 18 of 26
in reply to: kieran.gill

Flat toolpath cutting air! I've notice when facing from outside to in all material is removed before the end of the toolpath and you end up cutting air. I've noticed this with other toolpaths as well, the toolpath below works fine if you start in the centre and cut out but from outside in not so good.




I've attached the file.


Thanks Mark


Mark Hughes
Owner, Hughes Tooling
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Message 19 of 26
in reply to: HughesTooling

Thanks @HughesTooling .

This is an interesting one. There may be different results for other toolpaths, but when looking at FLAT specifically (for the benefit of others reading this post, the way you get FLAT to do Inside-Out is to not omit a machining boundary and use Touch surfaces) it would appear that Inside-Out appears to also appears to do a fair few air cutting moves (See image).

I'm probably of the opinion that I would go for the Outside-In as you have originally programmed.  My advice is regardless of whether your using Inside-out or Inside-out (with these sorts of whole part strategies) is that the toolpath will in most cases be 95% correct, which is why we allow users to apply toolpath modifications such as toolpath trimming and section deletes on toolpaths like FLAT so that you can get it as close to perfect as possible. Worth noting you will need the Machining Extension to take advantage of toolpath modifications.

Appreciate the feedback, unless I've missed something, and keeping us at Autodesk honest about our toolpath quality especially where they may not be working for you as intended.

Images below show Inside-Out with and without Optimized Open Pocket machining


Kieran Gill
Technical Consultant
Message 20 of 26
in reply to: kieran.gill

This has now been fixed and hopefully you should see the fix propagate through subsequent releases. 🙂

Kieran Gill
Technical Consultant

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