HSM vs HSS

I've done lots of 2.5D work with solidcam but I'm starting to foray into 3D. As far as I can understand so far, HSR is basically just a single operation that would basically be the same as multiple pocket operations at different z-levels to clear the majority of material away. Then, as I understand it, you would use hsm or hss to do your actually 3D milling. So, then, what is the actual difference between hsm and hss and when would you use one over the other?

Is HSM basically 3D milling the entire part in one operation whereas HSS is just for localized faces? Is there other major differences?

The basic difference between HSS and HSM is one is surface based (HSS) and the other is model based. I use both depending on what I need to do, though I would say that I use HSM about 80% of the time. For example, for general finishing where the direction of the cutter path isn't important I use HSM but for a feature where I want the cutter path to follow a particular contour of a face (or faces) and gradually change to a different contour as the cutter progresses across the face then I use HSS.

This only a quick example. Someone working in mould & die machining would be able to explain the usefulness of HSS a lot better than I.

So is it fair to say then, that if you had a model that was mainly flat surfaces, but had a couple radiused faces on it you'd be best using traditional pocket & profile strategies and then use HSS on the 3D surfaces. As opposed to using hsm (consant Z, etc.) which would machine everything, including the flats and would probably be less efficient and leave not as nice of a finish on the areas which could have been pocketed/profiled?

Also, would it be fair to say that HSM and HSS are basically doing the same work it's just a matter of how the toolpaths are designed and laid out? Lastly, could HSS technically accomplish everything HSM could, but it would be a whole lot more work defining paths for every surface?

From what I'm understanding so far, it sounds like HSM is more for models that are comprised mainly of 3D surfaces (such as a mold for an xbox controller) whereas HSS would be used for traditional models comprised mainly of floors and walls but that may contain a couple 3D surfaces (such as a large fillet or a morphed surface)

All sound right?

Mike,

You are spot on with your first point. If you can use 2½D strategies, do so. It might take longer to program or be a little more involved, but the machining will be far more efficient.

In your second point, yes, HSS & HSM are designed to do the same work but HSM is more efficient in terms of programming input. However HSS will more than likely produce a more aesthetically pleasing part (presuming the programmer knows what he is doing ;).

As I said in my earlier post, I use both but far more HSM and HSR than HSS. I look on HSS as the 3 axis version of SolidCAM's 5 axis machining module - in fact except for the tool axis control element the way geometry is defined is almost identical. Sometimes using HSM gives you a tool path that will result in excessive chatter or aggressive plunging or some other undesirable condition - that is when I use HSS.

I think I've got a good handle on the differences now.

Next question. HSR and HSM seem to be always referenced as a duo. However, is HSR always strictly the precursor to HSM? In other words, if you had a 2.5D part with pockets at a bunch of various depths, would HSR be your best bet to get the majority of the roughing accomplished and the move in with some 2.5D strategies to finish the walls and floors (with HSM not being used at all in this example)

I assume that HSR is nothing more than an automated way of defining several 2.5D pockets. So on a strictly 2.5D model, it would save defining several pocket roughing operations. Obviously HSR also has the benefit of being able to automatically create pockets in places that would normally be impossible or take creating some extra sketch geometries (such as at various z levels down a sloping 3D wall)

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Originally Posted by mikemaat

Next question. HSR and HSM seem to be always referenced as a duo. However, is HSR always strictly the precursor to HSM? In other words, if you had a 2.5D part with pockets at a bunch of various depths, would HSR be your best bet to get the majority of the roughing accomplished and the move in with some 2.5D strategies to finish the walls and floors (with HSM not being used at all in this example)

I assume that HSR is nothing more than an automated way of defining several 2.5D pockets. So on a strictly 2.5D model, it would save defining several pocket roughing operations. Obviously HSR also has the benefit of being able to automatically create pockets in places that would normally be impossible or take creating some extra sketch geometries (such as at various z levels down a sloping 3D wall)

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Mike,

If you have a lot of pockets at different depths with flat floors, vertical walls and the need to maintain a tolerance then I don't think using HSR will gain you much, Consider it, If you go 2½D First you use a Pocket job to rough them out (and if the corners are big enough, rough & finish in one job), then you use a Profile job to finish them. Both those jobs use the same geometry and if you rough out with HSR you would still have to define the geometry for the finishing profile jobs, so what has HSR saved you? the time spent creating the Pocket jobs - if you use the 'Save & Copy' option then the only work would be selecting the different depths. I use HSR a lot for roughing out parts but I also use 2½D Pocketing a lot too, usually when I need to finish a profile with tool radius compensation.
Your assumption that HSR is merely a way of roughing out 2½D pockets in one go is not strictly true -HSR's great strength lies in its ability to do 'Rest Machining' whereby the software 'knows' what metal has been removed in earlier operations and produces tool paths that only take way metal that is still present, thus saving a lot of air cutting.

Very good point. So If you can do it easily using 2.5D strategies, you're usually better off using them. And HSR is really geared towards machining where later operations need to know what has already been removed in order to be efficient and avoid air cutting. In essence, HSR is best used for roughing of 3D surfaces. Technically you could rough 3D surfaces using 2.5D pockets, but you'd be creating a lot of extra geometry and sketches, whereas HSR takes care of that for you.

Sound about right?

So if I have a mainly 2.5D model, but it has a couple 3D surfaces that id like to do with HSS, could I use HSR on a localized surface or is it "full model" like HSM? If not, what would be my best bet at roughing the surfaces, just gradually reducing tool offset?

(Let's say we have a cube with large radius fillets on its edges. I can face and profile the flats and walls, but what would be the best way to rough the fillets before hitting with a ballmill using HSS?)

By and large, your summary is spot on. You can control HSR using constrain boundaries just the same as in HSM and you can use a 2½D profile as a constrain if you wish.

With a 2½D part only needing some localised 3D machining I would use HSS and set up some check faces to make sure the cutter didn't gouge the faces produced using a 2½D strategy. In HSM, I wouldn't have to do this as HSM is a 'whole model' technology whereas HSS is, as the name implies, a surface based technology.

In your example of the cube with corner rads, I would use HSS and control the roughing with the 'Roughing and more' page of the HSS dialog. Alternatively, finish all the faces 2½D and then use HSR with large diameter ball or bull nose end mill and rest machining strategy to finish. Just because it says HSR it doesn't mean to say that you can't use it for roughing and finishing in one go.

I have a rough rule of thumb which is the more time I spend programming, the shorter the cycle time on the machine will be or the neater the part will look. So then programming a complex part becomes a series of compromises between how much time I have to program, the likelihood that the part will become a runner (a lot of what I do is prototype work) and how important the aesthetic appearance is. It is on this basis that I make the choices between 2½D, HSR, HSM, HSS or 5 axis (that is if I have the luxury of making a choice - sometimes the design of the part will force me down a certain road). Roughly speaking, I find that 2½D is the fastest to program, then HSR /HSM (if you use automatic constraint boundaries) then HSS with 5 axis taking the longest of all. If you start using user defined constraint boundaries, then there isn't much in it between HSR, HSM, HSS or 5 axis - they all take time to do properly.