Two-stage slider
Two-stage slider
(OP)
Hi,
I am designing a mechanical movement to drive two syringes that are parallel to each other. The issue is that one syringe is shorter than the other. I need to have one movement to push both syringes at the same time and when the shorter syringe is empty, the longer one needs to keep going until it is empty as well. Subsequently when I pull back the plungers, I need one movement to pull back the longer plunger when it reaches the same position as the shorter plunger then both plungers are pulled.
Thank you for your help.
I am designing a mechanical movement to drive two syringes that are parallel to each other. The issue is that one syringe is shorter than the other. I need to have one movement to push both syringes at the same time and when the shorter syringe is empty, the longer one needs to keep going until it is empty as well. Subsequently when I pull back the plungers, I need one movement to pull back the longer plunger when it reaches the same position as the shorter plunger then both plungers are pulled.
Thank you for your help.





RE: Two-stage slider
Is the order of the syringe pushing important - i.e. rather than both starting at the same time could they both end at the same time?
You might be able to come up with something using cams &/or levers if you want a mechanical solution. You'd probably be able to achieve similar with pneumatics/hydraulics.
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RE: Two-stage slider
Best,
RE: Two-stage slider
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Two-stage slider
This way when the plunger bottoms out, the spring compresses allowing the longer cylinder to finish emptying.
Then coming back, the spring will hold the shorter cylinder, until the longer cylinder is where you want it.
B.E.
You are judged not by what you know, but by what you can do.
RE: Two-stage slider
http://www.sealantequipment.com/pdf/See-Flo7.pdf
Just substitute syringes for the piston pumps.
RE: Two-stage slider
Cheers
Greg Locock
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RE: Two-stage slider
Compositepro beat me to it while I was figuring out how to get the URL.
RE: Two-stage slider
RE: Two-stage slider
RE: Two-stage slider
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RE: Two-stage slider
RE: Two-stage slider
Kenat had it in the first reply. A cam.
RE: Two-stage slider
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Two-stage slider
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RE: Two-stage slider
this problem was solved more or less in the 70's with resin metering equipment as Composite pro says.
Most of them used cylinders of the same size travelling different strokes. This was done by a sliding bar for each cylinder, altering the radius of a common lever.
Here is a link to a style of machine I used in 1972 that is still available today.
http://www.extec.com/mounting/equipment/labpro-1-p...
B.E.
You are judged not by what you know, but by what you can do.
RE: Two-stage slider
Two cam or screw drives run by a single microprocessor may be the most flexible solution.
In the applications where syringe drives are commonly used, the cams have to be pretty good, because the syringe amplifies irregularities in motion of the syringe plunger. Amplifies, as in being able to observe the passage of bearing balls within a ball bearing based 'roller' cam follower with a pressure transducer in the plumbing downstream of the syringe.
Mike Halloran
Pembroke Pines, FL, USA
RE: Two-stage slider
Mechanical cams are not flexible. It is possible to inject at any ratio you want with a hydraulic motion controller. Hydraulic motion controllers have electronic cams.
This application sounds like a reaction injection molding or RIM application.
[quote=MileHalloran]
Two cams with different rise on a common shaft may be the least awful solution.
[/quote]
What zzz2000 has described doesn't really require a cam based solution but that doesn't mean zzz2000 wouldn't use one if a cam capability was available.
Yes but if a microprocessor is used then why be limited by the mechanics? The hydraulic motion controller can do electronic camming or synchronizing easily.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Two-stage slider
My first thought was a stepper motor with integrated ballscrew-as-shaft. There are a number of those offered on the market today, but here is the first one I recognized on a G search.
http://motion.schneider-electric.com/products/mdri...
I love the Intelligent Motion System products from Schneider...integrated controller built into the motor. (maybe I should ask for endorsement payment?)
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com
RE: Two-stage slider
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RE: Two-stage slider
An electronic solution is the best but right now I am looking for a mechanical solution for cost consideration and the overall size consideration. I forgot to mention that the syringes are quite small, both are 1 ml and the shorter one was cut short.
I am going to try the cam approach KENAT suggested and the spring approach Berkshire suggested. If you have additional suggestions, I would love to hear them.
Thanks again for all the helps.
RE: Two-stage slider
Kyle
RE: Two-stage slider
http://deltamotion.com/peter/Videos/EM%200405-06%2...
I think it was for a painting platform.
I think the OP should tell us what his application is.
I can understand synchronizing two cylinders and one moving father than the other but what happens when the shorter cylinder gets to the end of its stroke. Does it hit the end and instantly stop or does it slow down to a stop at the end. During this time, what does the longer cylinder do? If the longer cylinder slows down like the shorter one then what? I see no other solution than to let the longer one keep moving.
Another option is to synchronize the motion so that both cylinders get to the end of stroke at the same time even though the actuators are moving different distances.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Two-stage slider
The OP’er. insists on resisting the simplest solution and that would be to buy one syringe off the shelf and make a second syringe of the proper dia. I.D., as a function of the two volumes being dispensed, so that both syringes would have the same travel, and could be pushed/pulled with one forcing device with a fixed head, with stops on it. On this thread we have already spent more in engineering time, someone else’s dollars though, than making the second syringe would have cost. But, that would be too simple, that ain’t real engineering is it. It can’t be gooder engineering if it ain’t more complicateder. One other improvement, with such small volumes as 1ml, you might consider smaller I.D. syringes so you have finer control over the injection rate.
RE: Two-stage slider
This would be a mandatory specification in a situation where, for instance, the smaller syringe is driving a sample, and the longer syringe is driving a carrier fluid or sheath or diluent, and both fluids flow through a lumen of substantial length after mixing or coming in contact and before reaching the core of the apparatus, so that when the sample has been fully introduced, additional carrier fluid is required to carry its tail through the apparatus core.
It happens that I faced a very similar situation 20 years ago, and used two cams driven by a stepper through a huge reduction. The instrument worked perfectly, except that it abruptly stopped the flow just as the last part of the fluid of interest reached the sensor, and left us wondering what might have been in the 'tail' that we couldn't see. The instrument program was scrapped for political reasons before we could re-engineer the cams or transition to a programmable screw drive or a servo, none of which was available off the shelf at the time.
Mike Halloran
Pembroke Pines, FL, USA