Re: Please help me with this part modification!

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Re: Please help me with this part modification!

MichaelAtOz
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This missed the mailing-list.

> -----Original Message-----
> From: johneron [mailto:[hidden email]]
> Sent: Tue, 10 Apr 2018 09:29
> To: [hidden email]
> Subject: Please help me with this part modification!
>
> http://forum.openscad.org/file/t2217/image832.png 
> http://forum.openscad.org/file/t2217/Screenshot_%281%29.png 
>
>
> Hello everyone,
>
> I am a materials engineering student working in a research lab. We are
> building a syringepump which has 3d printed components. These components
> hold the syringes. The current design allows for only one size of syringes
> to be used. We want to make it so that we can use different size syringes on
> it; i.e. 5, 10, 20, 60 mL.
>
> My simple solution to do this is the modification I've shown in the picture.
> The screenshotted image is the original design and the handrawn one is what
> I want to achive
>
> I just don't know how to design this on openscad as I've never used it
> before. Can someone help me out wit this problem?
>
>
>
>
>
> --
> Sent from: http://forum.openscad.org/



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Re: Please help me with this part modification!

MichaelAtOz
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I presume the syringe is strapped down somehow?
Would a V shape be suitable, any radius (with parallel sides) will be held
in a V.



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Re: Please help me with this part modification!

johneron
In traditional syringe pumps they are but in this design we may not need to.




this is the design. 

On ‎Monday‎, ‎April‎ ‎9‎, ‎2018‎ ‎08‎:‎41‎:‎54‎ ‎PM‎ ‎EDT, MichaelAtOz <[hidden email]> wrote:


I presume the syringe is strapped down somehow?
Would a V shape be suitable, any radius (with parallel sides) will be held
in a V.



-----
Admin - PM me if you need anything, or if I've done something stupid...

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.

The TPP is no simple “trade agreement.”  Fight it! http://www.ourfairdeal.org/   time is running out!
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Re: Please help me with this part modification!

fred_dot_u
At this point, I'm lacking the concentration to follow through on my
"discovery," but a preliminary drawing shows that the process of creating
the part can be made parametric. If it doesn't need to be parametric, it's
easier to make the drawing and pull the numbers off via the appropriate tool
for the drawing software.

I'm "building" this model by creating cylinders to be subtracted from the
monolithic base. For practical purposes, the cylinders can be considered
circles in this exercise.

Picture the smallest diameter for the collection of syringes. You want the
most support, but you don't want the C-shape of the cross section to impede
insertion. That makes the end result limited to the diameter of that
syringe. Any cross-section cut higher than the diameter becomes a "gripper"
of sorts and may be beneficial, but impedes this calculation. It can be
added later as a parameter sum of an arbitrary distance of percentage.

<http://forum.openscad.org/file/t824/syringelayout.png>

The centers of the circles are the parametric aspect that currently escapes
me. I know it's simple, but the pounding headache I have is preventing me
from proceeding.

What I have been able to determine is that the spacing of the center of the
second circle from the first circle is the diameter of the second circle
minus the distance of the chord of the second circle from its center, with
the chord of the second circle being the diameter of the first circle.

I've done math of this sort before and have found an abundance of formulae
to solve for this result. Because each circle references the preceding
circle, the primary formula should be iterative, allowing for as many circle
stacks as desired.

In the image above, I used syringe diameters based on arbitrarily taking the
capacity and making those numbers diameters, only to manage a relatively
proportional image.

I found a  web page containing the formula
<https://www.ck12.org/trigonometry/Length-of-a-Chord/lesson/Length-of-a-Chord-TRIG/>  
I'd likely use to pursue this as an OpenSCAD project.

The "welded" version of the above diagram:

<http://forum.openscad.org/file/t824/syringelayout2.png>



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Re: Please help me with this part modification!

NateTG
> ...  spacing of the center of the second circle from the first circle is
the diameter of the second circle
minus the distance of the chord of the second circle from its center, with
the chord of the second circle being the diameter of the first circle. ...

Unless you want to get fancy, if you have circles with radius r_0 and r_1,
then the z-distance between centers is
simply sqrt(r_1*r_1 - r_0*r_0) since there's a right triangle.

A (probably managable) issue with this design is that the position of the
center line of the syringe then depends on the syringe size, so the other
parts need to accommodate that as well.



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Re: Please help me with this part modification!

fred_dot_u
It's not the distance between centers, it's the distance between the center
of circle 1 and the center of circle 2 minus the distance from the chord on
circle 2 that has the diameter of circle 1, if the other aspects of the
design are valid.

I had not considered that the center line of the syringe has to be
maintained, and the information from the OP doesn't give that indication.

If it's necessary to maintain a common center, it would be easier to create
a series of inserts/sleeves to secure each smaller syringe in the larger
mounting hole.



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Re: Please help me with this part modification!

NateTG
Here's code to show what I'm thinking of:

cutout.scad <http://forum.openscad.org/file/t2140/cutout.scad>  



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Re: Please help me with this part modification!

NateTG
FWIW: I ran down the project that this appears to be based on:

https://github.com/naroom/OpenSyringePump





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