Are really deformed or is it just the shading (toggle smooth shading on/off to find out)?
Voxel remeshing can’t really be used to retain sharp edges in Nomad.
Trim tool will produce sharp edges though (but since it doesn’t have regular topology on the cut it will only appear nicely with smooth shading off)
Sometimes I use the “trim” tool or sometimes “voxel merge” to cut pieces …
In this case I use trim to make the holes in the helmet visor and “trim for the” ridge "above and the result is almost the same. … “soft shading” is disabled.
In this object it is easier for me to cut the opening of the helmet with “trim”> “polygon” … And the result is not clean … I don’t know why this happens on the right side and on the left it is perfect …
Yes the Trim doesn’t cut perfectly, I only meant the “edges” of the cut only, not the filled part.
It’s not really proper boolean, so it can break sometimes.
Line mode should work correctly however.
I find myself with the problem that the designs I make are almost impossible to manage on the pc when joining solids etc …
The reason for the millions of polygons that my works have … What to do about it? 
You can experiment with decimation in the topology menu to get your poly numbers down - but you have to play around with the numbers as it’s a fine line between just enough polys and not enough polys. You don’t have to go too hard on the number of polys, just depends on what software you’re trying to work with on the pc.
I have been testing decimation … But it deforms the figures (perhaps it is this to play with the numbers, as you advise me). I am using meshmixer or 3dbuilder, I just want to join all the pieces of the design in one to better manage the 3D printing, they are very slow or freeze … I have a fairly powerful pc My pc is an Asus, with an AMD Ryzen 5 3550H processor , 16gb of Gtx 1650 graphics ram and 2 ssd of 500gb each …
I guess you‘re having simply wrong expectation from a voxel based sculpting app. Also 3D coat shows those artefacts. The artists know that, and taking it into account for the benefit of quick concepting. After, retopo is used. Mostly manual. Or probably in case of your simple ( seeing it from low poly modelling point of view) helmet, they are completely new done in an low poly app.
The target of an sculpting app was in early days to use an existing, pipeline ready mesh for detailing.
Soon concept work free came along, free of any polygon concerns, but with the knowledge that topology have to be completely redone from scratch later again.
Topogun was and is one tool people use, but blender offers a bunch of tools for this as well, as all big packages.
ZRemesher in zBrush and retopo in 3D coat made Auto retopo an option for some objects, even though animation deformation in faces etc. still requests hand made topology or at least refined.
Good artists take all this in account.
If they go crazy with topology, they are aware that retopo will be a big part of work later.
Today, high end sculpting apps are offering low poly tools, and high end low poly tools are offering sculpting tools.
Nomad is on a fantastic way. Once, there are real Boolean operations, not via voxel remeshing, all your props are gone.
Till then, import parts into your pc for retopo, if it’s to weak. Or start on low poly app and use Nomad for refining……
The options are endless, but everyone must find the pipeline fitting for him and his working environment.
Thank you very much for your responses! 
. I really have a lot to learn about the concepts of voxel, overlock and much more … I increase the polygons when I work so that when cutting pieces they do not look like teeth of a saw … But then that is inconvenient because each piece is too heavy and the whole is impossible to deal with … I still have to learn a lot …
Maybe 7.22 million polygons is too much … And more for a “simple” helmet …
Does anyone know of an external program where I can join all the scenes without losing much quality?
I was trying around a bit. To take your initial helmet problem you can try trim instead of voxel remeshing two objects. Trim only add polygons on cutting edges. It needs a bit of tryouts but could do the trick with only a few polygons.
Else, as much as possible, try to use project. It’s function is limited but gives cleanest topology result. Split should by tried as well.
Be aware that in 1.55 are some bugs around this functions that can cause issues though
I have returned from vacation and have managed to print the helmets without loss of quality. The biggest problem I found when trying to handle the files in different programs (meshmixer, 3dbuilder) being very heavy files and with many millions of polygons. A friend was able to downsize with an external (and very expensive) program, “materialise magic” that’s the only drawback I have now. to be able to deduce the size of the works …
Why don’t you use the “Decimation” feature in Nomad?
You can drastically reduce the polycount by keeping a good quality.
I had never paid attention to this tool. I’m going to try to use it and tell you what the result is. once again thank you very much for your attention Stephomi! 
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It has worked! Got down the design of a lightsaber from 10 million to 637k …polygons! Of course, the tool is not very intuitive, it would be nice to be able to lower the size by percentage that would help a little. But very happy with the discovery …
Hahaha, you are funny. Not very intuitive? Easy to understand and to use is intuitive. If you took longer than 5 minutes to understand decimation, I would say it’s not the tool’s fault.
The target triangles count is exactly what one needs to know for printing etc. Percentage? You can look at status and at decimation target count and guess the rest in percentage if you want to.
I can’t imagine a situation where one needs 53,567% of actual.
I don’t say percentage is nonsense, but not that much needed.
It was not my intention to offend anyone. I simply wanted to say that for me it would be more intuitive to put a percentage and what that is the number of polygons to reduce.
For example, if you have 1 million polygons and you put 50% in the bar the result would be 500k polygons. As simple as that.
I do not speak the English language, and perhaps it is difficult for me to understand a little more than you.
There are also many concepts of 3D modeling that I learn as I go along. Still I think this application is the best application I have used in my life and I am very happy with it. My intention is to give my opinion without offending anyone.
Thanks for answering and teaching your wisdom 
I agree, the decimation feature is quite intuitive. However, I feel a percentage would be easier as well. It’s what I’m use to. Yes, one can simply look at the poly count in Nomad and do some calculations but there’s an extra step to it than selecting a percentage. And for those that don’t keep the poly count displayed? There’s more steps involved. I use a couple programs that have the option to reduce poly count but either a percentage or by a number of polys which is nice.
