clarification formulas screw recirculation of spheres

[cacciatorino]

f: indica "guide surface resistance without load".

probable that f is friction due to:

1) preload of the spheres
2) friction of the front and side seals.

What values are we talking about?

p.s.:
next time you don't have a problem opening a new discussion, you get the readability of the forum.
I fixed the discussion so as to make clarity but I can't move your answer as a result of the request.
I point out that the hunter's response refers to post #2.
mod

 

[disteso]

Bye to all,
I am a new entry of this interesting community. I have just begun to collaborate with a design studio and I am defining a telescopic panel opening system (m=40kg) enlivened precisely by a screw recirculation of spheres and guided by rollon guides shaped with skates and blinds. It's the first time I use this system and I have a question to ask you about the formulas of the thk catalog for the calculation of the force necessary to win friction in uniform motion conditions. a catalog is indicated the formula:
fa=μ•mg + f
where:
μ=0.003 frictional coefficient of the guide surface
m: mass of moving panels
f: indicates "guide surface resistance without load".
"f" is therefore the friction force relative to the only skates without the mass to be moved?
My doubt is that the case presented in this debate (http://www.cad3d.it/forum1/showthread.php?p=118104&mode=linear#post118104):
force necessary to win the friction of skates = 0.003*700*9,81+4*4,4 = 38.2n then f=4*4,4=17,6 n
and from examples to thk catalog:
- fa = μ• (m1 + m2) g + f = 0.003*(60+20)*9.8 + 15 = 17 n
it is immediately seen that the weight of the term f is definitely preponderant compared to μ•mg.
I thought that f was the friction force of the used driving system downloaded (without load) from the moving mass : in my case I have 6 swivel pin skates and therefore I thought to use m=0.1*6 g=9.81 and still μ=0.003 for a total of f=0.02n. the order of magnitude is definitely not comparable with the previous examples. the fact is that thk not from any indication of how f has been obtained. alone the description I have reported but I think it must be a priori data of the precarious or held because it is listed as an initial data for calculations and the choice of the recirculation screw together with the moving mass, the race, speed, acceleration...etc
Is my interpretation so loud?
I'm sorry if maybe the question is trivial, but I'm at the first job with this firm and I don't want to make any sense.
greetings and thanks
Faithful

 

[gerod]

"f" is therefore the friction force relative to the only skates without the mass to be moved?

It would seem so.
I would say yes to the budget.

 

[disteso]

thanks to the answers and excuses for the mess...is the first time I participate in a forum