What are your most used mass property items?

scott_harris

In the context great forum discussions, several people have mentioned using mass properties. Since mass properties is a category of calculations I am interested in the results that you use the most and what workflow suits you best with respect to volumes, mass points, axis of inertia, moments of inertia, etc.

Thanks,

/Scott

caradon

One of my most frequent uses for mass properties is 'enclosed volume'. (as a side note: I would really like the ability to quickly visualize internal volumes.)
I mean like in this example:
*Take a pump housing (consisting of multiple parts/bodies, including a rotor).
*Shut off (planar cap) all intake/exhaust openings.
*Calculate volume of internal 'flow body' (internal volume, minus rotor, in this example).

I would really like a workflow that automates:
*Capping of intakes and exhausts.
*Boolean operations to generate flow body.
*Volume and mass calculation of flow body.
*Parametric relation: if model updates, then flow body and calculations update as well.

Dries

mark_biasotti

Hi Scott,
expanding on what I send you by email:

For me, the big 4 that I use most often for Mass Properties are:

Volume
weight
Surface area
CG

- In the normal coarse of my work I'm finding that I use surface area frequently for calculating size of PCBA's that EE's give me in sq. inch area.
- For Volume and Weight, I've been designing a 2-person submersible and you can imagine how I'm using MP to calculate negative Ballast and neutral buoyancy.
- I've also been designing charging docks for consumer products where we incorporate zinc die cast parts to weight the dock as well as calculate the amount of weight to overcome the pogo pin contact force.
- Recently designed a table top scanner for the TSA that has a 120.lbs magnet in it and I needed to insure that it did not tip over with a 15 degree angle of movement (CG.)

these are just a few examples that make having MP essential.

Mark

kevin_quigley

For us it is:

1. Weight of assemblies and parts ( for shipping, foundation sizes, shot weighttc)
2. volume and weight of fluid( in bathroom product design, packaging, medical etc)
3. Surface area of selected faces ( not mass but essential)

pete_yodis

1. Weight of the assembly/parts and an ability to select which components get calculated. (volume must be an inherent calculation for this, so I'll take volume too if it can be output)
2. The Center of Mass locations for the entities being calculated. Along with this the moments of inertia
3. Surface area of surfaces selected
4. Section modulus of an area (useful for quick structural deflection calculations).


This is a separate thought, but it would be helpful if we could have a tool to create material definitions that can then be applied to parts. A material library. This would play into the calculation arena, but also would be very important for FEA downstream. It seems if the material library were thought out, it could be done in a way that is not a bolt on library, but one that is integral to Onshape and could have implications for helping users with BOMs - identifying what raw material a part is made from, possibly what part number that raw material is. This would be important on the PLM/ERP facing side of things. If Onshape is going to support BOMs and if it is a database system, then why not extend it to the most granular state that users would ultimately want in order to capture product structure. The material database/definitions would also be important for regulatory compliance with users, as well.

michael_leslie

We need to provide the weight in water a lot . It'd be nice to have in as a native property.

traveler_hauptman

Mass, center of mass, moments of inertia with respect to a user specified origin for use in kinematics and dynamics studies. It's important to me to be able to fake the mass properties for parts that are placeholders or representative volumes from someone else that I'm integrating into my design. (eg I should be able to set the mass and inertial properties directly if needed)

bergdesign

I need part volumes and weights. I use wood and plywood for my products, so I usually have to enter custom material properties for the weight calculations since woods are not typically included in libraries (due to the vast differences between various species). I also use perimeters calculated from planar parts so while it's not a mass property, it is a geometric property that I need to extract from sketches or cross-sections for CNC run-time calculations.

rajendra_bhat

Part/ assembly weight, volume of enclosed parts( for air, oil, water etc), surface area, CG

gal_raz

Hi @ScottHarris‌ , For me , Minimum boundary volume ( not depend on part orientation) and part weight. Option to calculate the Mass properties with coating and color is most welcome (internal, external and both).

brucebartlett

*Volume. When doing tanks and bins quite often have to model the internal shape to get the volume, it would be nice to cap the external holes and get the internal volume without an independent part.

*Weight. This is a must have but needs to be couple with material properties, you need to know the exact materials the weight is calculated on. It could be good in an assembly to itemise material weights, then you know if you have not got the properties mixed up. e.g. you should know if your assy is meant to be all steel, or a split between aluminium, plastic and steel.

*C of G. This is a must have. Ideally coupled with the weight command but also the ability to save to part for reference to calculations. It would be nice if when the C of G is saved to the part you could hover and also see the weight as normally I would be using the C of G and weight to calculate a lifting ram or spring capacity.

*Surface area. Has to be also on the section tool as I regular compare section surface area during design. I would also use Surface area this to give an estimate of paint volume, it would be nice to have an external faces only switch.

The external dimensions e.g. box size would be a nice feature.

kevin_quigley

Yes. Bounding box feature and scale by Bounding box would be AWESOME. 

mark_biasotti

Good start on Mass Properties this past week but... for MP to be of any use to my product design I need to have materials assignment to get some useful feedback. Hope this is next on the list?

Mark

pete_yodis

@mbiasotti I second the material assignment. I hope it could be as I explained above.

Jim_Anders

Weight and CG

lougallo

@mbiasotti Yes we are planning on that.  

brucebartlett

I went looking for materials in the properites section, I assume this is where materials will be added. I like the way it nests the properties when looking from an assy

Steve Hoffer

We also sometimes have a product, and want to assign the weight to a part that is being designed, which can then be used to calculate the material density. This may well be a not-to-normal way of doing things, though.

traveler_hauptman

Steve Hoffer said:

We also sometimes have a product, and want to assign the weight to a part that is being designed, which can then be used to calculate the material density. This may well be a not-to-normal way of doing things, though.

It's normal for me... and I also requested it above...