Re: [CAD_CAM_EDM_DRO] Re: Hexapod ball joints, Moglice

Hi Graham:
I assumed the Moglice pour was going to be the final assembly step, and
that you'd never take the joint apart again.
I also, of course, assumed loading only in compression; Moglice will not
handle much in the way of tensile loads .
Have you considered a 2 piece Delrin cup as an alternative.
Don't even try to match the ball shape...just cut two big chamfers that the
ball can ride in, and bolt the works together.
If you need load capacity, you can encapsulate the works in a steel cup with
a lid that has the correct aperture in it.
Fitting a joint like that to have zero clearance is duck soup, but tedious.
If you want better load capacity, you'll have to go back to the Moglice pour
idea, but do it in two halves.
Suspend the ball inside the cup where you want it, and make a dam out of
sheet Delrin, that you can just force over the ball until one edge of the
sheet is at the equator.
Drill two holes in the cup; one for Moglice and the other for the vent.
Get some 10cc syringes, and syringe the Moglice in.
After hardening, pull the Delrin, spread on LOTS of release agent, bolt on
the upper collar, wax the aperture, and cast the upper half.
You can then unbolt the assembly and take it apart after hardening.
With large diameter balls and a steel shell, you'll have high load capacity
in all directions.
Cheers

Marcus

----- Original Message -----
From: "Graham Stabler" <eexgs@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, December 19, 2003 6:25 AM
Subject: [CAD_CAM_EDM_DRO] Re: Hexapod ball joints, Moglice


>
> > How are you going to get the ball out after pouring the Moglice in?
> >
> > Jon
>
> This is the problem really. I could make the joint as a one piece
> using and try and mould-in the aperture. Perhaps build up an area of
> wax on the ball where I don't want moglice before turning it on a
> lathe to make it nice and true. Then hold the ball at the correct
> height in the cup and pour in the moglice upto the level of the wax.
> Once hardened the wax can be melted leaving a perfect ball in a
> socket with the correct aperture built in. Then a metal ring might
> be added to reinforce this area as it will not have much cross-
> sectional area.
>
> A picture tells a thousand words so please see ball.jpg in the files
> section
>
> If it is made in two halfs then you could turn the molgice down until
> the ball was free. It would not matter if the ball was damaged a
> little as another could be used.
>
> I favour the one piece ball, tha accuracy of fit should be good
> enough.
>
> Graham
>
>
>
>
>
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