Is is necessary to merge (parting)surface

hi everyone, my quick concern is..Is that necessary to merge surfaces to form one single parting surface? Any beneficial or advantage of merging all different parting surfaces to form one parting surface? I splitted my mold from a number of parting surfaces including "copy" surface and it doesnt seem to have any issue...Please advise.

Hi TeQie


man it is not necessary to merge all parting surfaces if u r using more than one parting surface, but all surfaces are complete and separate. for example, u create a parting surface for outer area and another one or more than one surfaces for cover holes or slots in the part, then u can select multiple surfaces as parting surface when pro ask u for parting surfaces. but if u make two surfaces for one area (example outer area) then u must merge them . I will post an example shortly in pics.

here u can see


if ur condition like this u dont need to merge outer and inner ps for one, but u can see I had make four surfaces for outer area then merge them.


View attachment 2270


but in the following case I had merged all surfaces as one


View attachment 2271


View attachment 2272

thx for the prompt reply Zaki,

I do know some people merge surfaces to form one parting surface like
the second example you posted up here. but in my case, I do a lot of
"copy" surface from the ref model to form quilts. Those quilts/surfaces
never got merged by me and i simply select many parting surfaces
(around the ref part) and i simply part the model. It works fine and split
the workpiece but i do not know if there's gunna be a problem...

Correct me if im wrong, for your second example (third picture), I would
simply merge the planar parting surface (outer square one) with the
round surface (circumferent) but the rest i dont see any necessary to
merge them...you can simply copy surfaces from the ref part and select
them + the surface we have merged before (planar + round)...so in other
words the parting surface consists of at least 20
surfaces...It will split the mold but i dont know what is the consequence
of not merging it.
From my point of view, merging it is simply to cut the excessive section
of parting surface that we dont want.. kind of trimming. So if we have
surfaces that can represent the parting surface of the workpiece, I will
simply choose surfaces that I need (more than one) unmerged as long as
it is complete.


Please advise

Hi TeQie


The only thing that was I told u first that if u want to use multiple parting surfaces like example one, there is no need to merged all, but all parting surfaces must touch the part. but some times its making troubles, due to tolarence, due to some tiny surfaces at part or some other reasons. Then I copy parting surface from ref part then extend it to workpeice or make it by another way and merged it all. In all normal cases, first example works best.


Experiance is the main thing and it tell us more then any book or teacher.