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Translucent Syringes

02/06/2009 9:44 AM

At our facility, we deal with medical syringes; pliable,translucent and hard clear. One of the inspections involved with these is checking inside diameters. The only major piece of inspection equipment we have is an optical comparator ( no vidoe option). There is always an issue of focusing in on an edge. We have tried "coloring" the inside black and trying to find the edge from that, but this method is not viable.

Bore gages are good, but there is always the chance of deformation from the gage, plus some of the syringes we deal with are fairly pliable not hard plastic..

Any suggestions?

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Guru
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#1

Re: Translucent Syringes

02/07/2009 12:47 AM

Hello need_to-Know:

I am thinking off the top of my head so bear with me please......................

You want to know the length and or bore of the syringe? Can this be a destructive test or are you looking to design an 'in-line' test to read the internal size and any deformations as they are made? And do you deal with all sizes from the tiny up?

I have in mind to use a colourometer, which would 'view' through the side of the syringe body to a blue or ultraviolet light. Any extra thickness or deflection would be picked up as a different figure on the meter.

This colourometer would include or have a pulsed laser to measure the internal size, with the appropriate light source if different types and or colours are necessary for the tranluscent syringes.

Can you tell me if you want to measure the product as it is manufactured please?

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#2

Re: Translucent Syringes

02/07/2009 4:12 AM

You should be able to infer the diameter, by delivering a fixed volume of water (weigh the water (cc) and use the density of water (=1.00 gms/cc) to infer the volume in cc as numerically equal to the weight (gms). Strictly the water should be a 4 degrees C

Now calculate the diameter of the cylinder from rearranging the formula of a cylinder

Vol =Pi x D2 x L /4 where L= length of stroke to deliver the measured amount of

viz

D= SQRT (4 x Vol / (L x Pi)

This method checks the syringe in exactly the way it is to be used in Medicine

Good Luck

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#3

Re: Translucent Syringes

02/07/2009 5:45 AM

Why don't you use a simple plug gauge system, ie one gauge will fit the correct diameter the other gauge will not fit and can be made as close a tolerance oversize as you wish.

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#4

Re: Translucent Syringes

02/07/2009 6:54 AM

Thanks everyone.

Cannot use destructive testing due to the deformation that occurs to the walls.Samples include new from the vender as well as syringes that have been used for injections.

Part of the study is to see how the walls have expanded when subjected to injections.We are wanting to see what part of the cylinder has been deformed and taking those measuements, from inside. Bore gages are a contact type of tool which makes each test measuement subjective.

The pin gages ( a go/no go type of measurement) would not work for this purpose if you can see my point.

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#5

Re: Translucent Syringes

02/07/2009 7:56 AM

It is a tough call, Have you checked out internal bore laser scanners, this is a specialised field and very expensive. But tied to a computer program would do fast job for you.

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#6

Re: Translucent Syringes

02/07/2009 9:26 AM

Why not use one of the oldest measuring methods around - air gauging?

The plug fits in the syringe tube and has jets of air sideways to measure the diameter, using two jets will show ovality as the plug is rotated giving you a more accurate measurement, or if you just want a quick check use a three jet plug gauge, this will give an average diameter.

resolution is better than 1 micron and there is no contact with the syringe tube.... plus the air jets will clean the tube if there is any residue inside the syringe.

I've been involved with air gauging techniques and design for over 25 years!!!

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#7
In reply to #6

Re: Translucent Syringes

02/07/2009 11:16 AM

I was reading on down to see if anyone had yet mentioned this method. You did, and get a GA from me. It PRECISELY (yeah, pun intended!) fits the OP's needs.

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Guru
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#8
In reply to #6

Re: Translucent Syringes

02/07/2009 2:16 PM

That is an excellent idea I had forgot that method. Much simpler than the method I suggested and more robust.

A GA from me

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#9
In reply to #6

Re: Translucent Syringes

02/07/2009 2:25 PM

Why thankyou Garth and Ron....

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#10

Re: Translucent Syringes

02/09/2009 12:02 PM

What is the diameter you are trying to measure?

I agree with one of the members comments that an air gauge is good, it is however expensive, and with small diameters, often having to make contact with a device can add other errors, I am not about to argue with someone with 25 yr experience with air gauges. - What would be the cost of this system, I wonder?

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#11
In reply to #10

Re: Translucent Syringes

02/09/2009 2:15 PM

Depending on the specifications a simple system could be as cheap as a few hundred quid (£), more likely £500 and with all the 'bells and whistles' etc... £2500

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#12
In reply to #6

Re: Translucent Syringes

02/10/2009 7:15 AM

What types of gages are there for this?

Also, cost. What is the cost for a system like the one you speak of?

Tell me more.

thanks!

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#13
In reply to #12

Re: Translucent Syringes

02/10/2009 10:36 AM

I designed a range of air gauging instruments for Quality Gauging Systems back in the 1980's they are based on the Solex gauges.

Have a look at their 'Flex air' range, they won't be cheap, maybe £2000 As I used to design and manufacture all their instruments, I am sure you will understand that they put a heavy mark up on the prices, as all sales and marketing companies do!!

Some other names may not be around still.... such as Federal gauging in the USA?

Still have a look at this pdf

http://www.qgs.co.uk/automotive/documents/FlexAir-Linear%20Leaflet.pdf

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#14

Re: Translucent Syringes

02/11/2009 4:28 PM

What about a simple system consisting of the appropriately sized plug, a source of precisely regulated air pressure, an orifice and a precision differential pressure gauge? Measure the D/P across the orifice to get a flow measurement? In effect make one's own air gauging system. It could be calibrated using appropriately sized metal or glass tubing samples and the size interpolated from the differential pressure (air flow) measurement. It would probably be closer than an inside mike on a thin plastic tube. Care would have to be taken to avoid pressure expansion of the syringe barrel but that could be handled by adjusting the pressure so that it is not a problem.

What difference does it make if the syringe barrel expands upon use? As long as the measurement scale is correct and the syringe is not reused, it only has to be good for one measurement.

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