Balancing Turning Fixtures.
Balancing Turning Fixtures.
(OP)
Hi everyone, working on a turning fixture which I need to balance. Now in basic terms I've done some calculations to the counter weights I need to put on the fixture. However my question is has anyone
A) Got any easy way to weigh a block in NX 7.5. At the moment I'm modelling a block weighing it, changing the size slightly weighing it again etc, is there any quicker way of achieving a known weight?
B) Balanced a fixture. Has anyone got any information to what accuracy I need to balance it too? By this I mean my calculations tell me the block needs to be 3.1776kgs. Now if I'm modelling a block and tweaking the sizes, I dare say I'll be at it forever to try and achieve that size. So how accurate can it be? Could it just be 3.1kgs? If so how would I know what affect the other .0776kgs would have on the fixture?
Hope this makes sense.
Thanks in advance
A) Got any easy way to weigh a block in NX 7.5. At the moment I'm modelling a block weighing it, changing the size slightly weighing it again etc, is there any quicker way of achieving a known weight?
B) Balanced a fixture. Has anyone got any information to what accuracy I need to balance it too? By this I mean my calculations tell me the block needs to be 3.1776kgs. Now if I'm modelling a block and tweaking the sizes, I dare say I'll be at it forever to try and achieve that size. So how accurate can it be? Could it just be 3.1kgs? If so how would I know what affect the other .0776kgs would have on the fixture?
Hope this makes sense.
Thanks in advance





RE: Balancing Turning Fixtures.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Balancing Turning Fixtures.
Cheers
RE: Balancing Turning Fixtures.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Balancing Turning Fixtures.
RE: Balancing Turning Fixtures.
That being said, if you're asking questions about something as basic as Expressions, it would seem that you could really benefit from taking a class in basic modeling. I say this because if you have not gotten any formal training, message boards are not the place to get it. You either need to take some real classes or find a mentor who can provide you some face-to-face help.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Balancing Turning Fixtures.
RE: Balancing Turning Fixtures.
My advice, get some personal help from someone who is familiar with NX or sign-up for a class somewhere. BTW, where are you located? And how long has your company been using NX? If they've been using it for awhile, perhaps you might someone in the office that could help you get started in the right direction.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Balancing Turning Fixtures.
If you look at my original post, it asks is there an easier way other than modelling it, weighing it then adjusting it. If using the expression (formula) to control the different sizes of a block is the way forward, then may be we should be discussing the sizes of the block length and width, and which formula to use to control the height.
For example the block is 40 x 40 x 20 and I increase the width by .1, and length by .2, this then adds x amount to the weight of the block? But on top of that, does this matter when balancing a fixture (my second point) how accurate do I need to be to balance a fixture. They both roll into each other, because depending on the second question, depends on how the formula looks for the first point........
This is what I'm asking. I'm not asking for a turtorial on how to use NX. Having said that isn't this forum here so people can ask questions on how to do things? I'm confused?!
RE: Balancing Turning Fixtures.
Mass = Volume * Density
Assuming the material has a uniform density and you are dealing with a rectangular block (no holes, pockets, bosses, etc), it is pretty easy to calculate mass. It is also possible to assert 2 dimensions of your block, choose the desired weight, then calculate the 3rd dimension of your block that will yield the desired weight.
Balancing a piece of rotating machinery is a non-trivial task. Beyond getting the center of mass on the axis of rotation, what you really want is to get the principle axis of the rotating mass to align with the axis of rotation. How accurate does your balance need to be? It depends on multiple factors such as speed of rotation, mass of rotation, desired life of the bearings, safety, etc etc.
Here is a pdf that gives some idea of how much balance you need (it appears to pull from ISO 1940). The table of interest is in section 3, balancing standards (pg 132).
Here are some other links you may find of interest:
http://en.wikipedia.org/wiki/Rotating_unbalance
http://www.balancetechnology.com/pdf/balancing_bas...
http://www.google.com/url?sa=t&rct=j&q=&am...
I used Google with the search terms: "single axis balancing vibration"; I would encourage you to look through the first few links then pick out some new search terms to hone in on what you need.
www.nxjournaling.com
RE: Balancing Turning Fixtures.
RE: Balancing Turning Fixtures.
RE: Balancing Turning Fixtures.
Scale Factor = (dw^(1/3))/(kw^(1/3))
where dw = desired weight
kw = known weight
RE: Balancing Turning Fixtures.
As Cowski noted Mass = volume * density
or if we use the provided example m = 40*40*20* 7.8
If we change 2 variables at the same time it's more or less impossible to solve(?) but if we only seek say the width for a given length and a given height it's simple.
Steel density ~7.8 kg/ liter
1 liter = 100mm^3
and if i assume that "40" is [mm] then 40mm > 0.4 decimeter ( 1 decimeter = 100 mm)
mass = 0.4*0.4*0.2*7.8 = 0.2496 Kg
Then if the original "20"[the width] is the value to modify and the desired weight = 0.5kg
0.5 [weight]
-------------------------------------- = [width] = 0.4006 decimeter = 40.06 mm
0.4[height]*0.4[depth]* 7.8[density]
regards,
Tomas
RE: Balancing Turning Fixtures.