PRO_MP_MASS VS MASS:FID_MASS_PROP , best practice?

[CD_10645700]

hello,

in the idea of standardising, we are in the process to recreate our start parts (prt template).

The question of the mass properties calculation comes in. If I check the legacy data, some are using the mass property retrieved throught PRO_MP_MASS and some have a mass property feature in the footer and retrieved through MASS:FID_MASS_PROP (relation in post regeneration)

I can't come out with a real pro or con from one or another solution...

We use the mass in windchill, on the drawing and with family tables (even huge ones). Does anyone has an opinion on that?

how are you doing in your compagny and why did you choose this solution?

[Chris3]

I would strongly advise against using a mass property feature in the footer in your start parts. Doing this adds a lot of overhead processing especially when you get into large assemblies.

If you are starting over, I would recommend using the config.pro option 

mass_property_calculate report_outdateness_only

This will throw an error when PRO_MP_MASS is incorrect.

You likely have lots of models in which PRO_MP_MASS has not been updated correctly. There is a config option for automatically updating PRO_MP_MASS (mass_property_calculate automatic) but again you need to be careful with this for large assembly management. We do not have that config turned on because of performance but also because we have lots of legacy parts in PDMLink that have outdated mass properties and they get marked as modified with this config option checked.

[GEAB]

Having MASS_PROPERTY_CALCULATE to AUTOMATIC will generate problems since PRO_MP_MASS is on EVERY CAD-object OOTB. This means that if you have one part that is reused in several assemblies all the assemblies will go out-of-date as soon as the part is modified. Also, standing on a top-level and regenerating mass properties will affect all sub-models - so it hits both up and down.

For as automatic management as possible, I would go for the feature-parameter (set to automatic) and a relation (WEIGHT=MASS:FID_MASS_PROP or something) that converts the feature-parameter to a model parameter that can be designated into windchill. And I would only set this feature-parameter on parts and weld-assemblies. On the start-part the feature should be placed in the footer. The difficulty is when one part in a weld assembly has an assigned weight. The feature-parameter needs to change from "calculated" to "assigned". 

Crazy how stupid Creo is when it comes to weight management - or perhaps lack of best-practice communicated. 

[BenLoosli]

We do the weight = pro_mp_mass in our start part template relations. Simple and gets the information where we need it. We have mapkeys to recalculate the mass properties for parts and assemblies. Our default material is defined as 99 pounds/cubic in, so everything is very heavy and the users MUST assign a material from our material library and then run the mapkey to get things updated.

The only time I do something different is with family table parts where I do set a saved mass property calculation and put it in post-generation relation instead of initial. This is documented in a CS article to get the weights to update on family tables.

[Chris3]

We use pro_mp_mass in our formats ... what does adding a relation add? Seems like you are just adding another regeneration step.

We also have our start parts with density set to black hole.

[BenLoosli]

It just allows us to have it called WEIGHT when we upload the value to Windchill. Carry over from the original system setup of Windchill 8. I suppose I could redefine the Weight Windchill attribute to reference the Creo parameter pro_mp_mass instead of Weight.

It works and there are always other things that have a higher priority to deal with in Creo and Windchill. I do have a test system at the moment so I could play with it while doing other Creo 9/Windchill 12 upgrade changes.

[CD_10645700]

It comes from legacy, the attibute was call weight and is mapped implicitely if I remember well, in addition we have explicitely mapped other attributes on "weight" (wibdchill) coming from legacy (creo) like  "gewischt", I don't see the benefit to change it now, it would just be adding another case to manage... in fact using a relation gives you the possibility/flexibility to change the relatation an use an alternate mass property if needed

[Chris3]

If you have a large assembly with thousands of components then you pay the performance tax for that relation in Creo.

[Patriot_1776]

Regardless, mass props may not regenerate unless you have certain settings in the config.pro.  If I remember, one of the options for this setting is "on demand", which means you must specifically run a mass prop calc.  Then another option is "automatic", which does it every regeneration if I remember, BUT it's a HUGE performance hit for large assemblies.  So, using mass props is a mixed bag.  We stopped using it in our dwg notes for this reason.  If we wanted the volume (not weight) of an IM plastic part (to help calculate cost), we ran the mass props manually, specifically for whoever asked.  IMO, at least for things I've done over the years, there is amost no reason to include the weight of a part on the dwg.  The ONLY time we did it, was for large weldments that needed to be lifted with a crane, and then we also needed the CG so we could make sure any lifting hook/loop was placed properly based on the location of the cg.