Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

jw0752 — Fri, 06 Jan 2017 16:02:38 GMT

Hi Rachael,

In one of my previous posts I used electronics as an analogy for the vacuum system. I thought it might be helpful to complete that analogy a little further. If we consider a given electrical battery system as an analogy for vacuum pumps we can see that just as we can get no more than 2 volts from a lead acid battery we can get no more than one bar of pressure from a vacuum system. With a vacuum pump, no matter the size or the quality we are limited to a potential energy difference of one bar. All batteries of a similar chemical system regardless of size are limited to one voltage. So what do we get from a vacuum pump by making it bigger or by spinning it faster? We get the electronic equivalent of lower internal resistance. The hoses of our vacuum system or any constriction of the air flow can be considered as resistors. We already mentioned that the reservoirs are capacitors , the solenoids are relays, check valves are diodes, and the whole system operates as a circuit if we consider that for it to work we must draw air from the environment and return it to the environment on the other side of the pump. You can think of what you are trying to do as driving a 1.5 volt LED (the hole in the end of the pic) with a 2.volt battery (the vacuum pump). Your pressure drops in this system will be across the points of highest resistance. While carrying any analogy too far has its pitfalls I have always found this analogy useful when visualizing what is going on.

John

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

balearicdynamics — Fri, 06 Jan 2017 10:02:55 GMT

Rachel, I love this project. If you will publish something more I think I can replicate it for my lab... Just a question about the micro piston pump; does it is not too loud?

Enrico

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

mcb1 — Fri, 06 Jan 2017 07:22:07 GMT

Nice post [mention:7d5ee4caf55f4ccaa8b711eb508ecedd:e9ed411860ed4f2ba0265705b8793d05]

This design series (you and [mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05]) has been quite interesting, and certainly has perculated an interest ... once you two perfect the design.

I'll try to take some pictures of the mechanical mounting arrangements for the vaccum pump in my Duratool Desoldering station (thanks [mention:6f7924a04a1349b2ac17b4cde35daef5:e9ed411860ed4f2ba0265705b8793d05]).

DURATOOL - D00672 - Desoldering Station, 80W | CPC UK

It's very lucky that we have [mention:f80b53cee57c44bc9d7c577d07d7c791:e9ed411860ed4f2ba0265705b8793d05] to pass on his knowledge of things that suck ... [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-a167ade1-a6f2-4db4-b31a-2683adf14251/8741.contentimage_5F00_1.png:16:16]

Mark

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

jw0752 — Fri, 06 Jan 2017 03:16:48 GMT

Hi Rachael

The bladder might work if you had perfect placement of the part on the tip. If there was not a good seal the vacuum would very quickly be lost. The re-compression of the bladder would have to have check valves to prevent a blast of air coming out the tip and potentially blowing the parts away. It would be easier to get a high static vacuum with a small bladder. As the bladder gets larger the increased surface area makes the generation of a high vacuum more and more difficult with this method. Pumps are usually just repeating bladders with the valve systems necessary to keep flow in one direction. I doubt that you will be happy with a static vacuum level that is below 250 mm of Hg. My system with the external pump operates between 400 mm of Hg dynamic and 600 mm of Hg static.

Reservoirs are very nice but you are correct they take up too much space in integral desk or hand held units. The only substitute for lack of a reservoir is a higher power pump. It takes power to maintain a dynamic vacuum level against a system with even a small open port.

John

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

jc2048 — Thu, 05 Jan 2017 12:57:57 GMT

"Please excuse the rough hand sketches..."

I like seeing things drawn by hand. If you can't draw, you can't design (in my, admittedly biassed, opinion). The rest is good too, though it's a bit passive voice ("The rear panel will have..."). You know that though. I shouldn't fret over it - just keep going and you'll naturally fall into a more chatty, lighter, more personal way of presenting things.

How does your power supply manage the 6A at low output voltages? Does it select transformer taps [can you hear relays clicking?] or is it a switcher front-end tracking a linear output stage? (Or does it merely sit there and pretend to be a fan heater? I'm sure TTi are better than that, though.)

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

jw0752 — Wed, 04 Jan 2017 19:52:11 GMT

Hi Rachael,

I like your blog very much. The organization and clarity make it easy and informative to read.

The dental industry uses quite a few hoses that incorporate wires and tubing. Here is a good example:

http://www.chapmanhuffman.com/index.php?main_page=product_info&cPath=10&products_id=166

If you have a dental equipment service company near you they may even have some used hoses that would be cheaper an still service your needs. The wires that get used in these hoses are fairly high current yet are very flexible having usually 100 plus strands of copper in a 22 Ga diameter.

With respect to the vacuum you will find that there is a static vacuum level that is present when there are no holes in the system. This is analogous to a voltge with no load. Once you start using the vacuum there is a hole created in the system and the vacuum level becomes dynamic. Depending on the size of the opening the pump may need to be bigger to maintain a desired vacuum level. The dynamic vacuum is analogous to a voltage with a load. Adding a reservoir to the vacuum system can serve to store and moderate rapid changes in a vacuum level caused by changes in the system such as valves opening holes in the system or adding additional volume to the system. Adding a reservoir to a vacuum system is analogous to adding a capacitor to an electronic system. If your pump is quite small you may have to struggle with the part you are trying to pick up so that it makes a good seal with the tip and then wait for the pressure differential to rise enough to secure the part against the tip. If you use a reservoir and are monitoring the vacuum level you can probably have the microprocessor shut off the pump when a desired vacuum level is achieved. The unit will go quite until you use it at which point the vacuum level will drop in the reservoir and the pump will restart to restore the vacuum level.

Keeping the hose inside diameter that goes from your pump or reservoir to the tip small can be a benefit as this allows you to equalize pressure more rapidly so that the part will release promptly when the vacuum is shut off. Having fine grooves in your vacuum tip can also be a benefit as this will not make a tight seal with the part and will also contribute to a more rapid equalization of pressure Your max lift weight is of course the pressure differential at the tip times the area of the opening in the tip.If you use a solenoid to control the vacuum to the tip make sure you get a 3 way solenoid so you can equlize the vacuum to the tip from the environment when you release the trigger.

I am really looking forward to seeing how your unit turns out.

John

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

DAB — Wed, 04 Jan 2017 18:46:35 GMT

Great post.

You have a good appreciation for keeping your descriptions simple and well focused.

Have you considered using a foot pedal for the vacuum control? Sometimes an extra free hand is very useful.

Well done.

DAB

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

dougw — Wed, 04 Jan 2017 17:01:36 GMT

Excellent write up. I like the LED idea.

It looks like you will have enough room for some sound insulation to reduce the noise.

Do these systems ever have a vacuum "reservoir" where the pump simply comes on whenever the pressure gets too high? This would allow the pump to operate at reduced flow rate as long as it can achieve the required vacuum.

RE: Lab Equipment Projects - Vacuum Pick and Place Assistant Part 2 - Prototype Design

shabaz — Wed, 04 Jan 2017 14:53:58 GMT

Hi Rachael,

This project looks awesome : ) and beautifully documented and easy-to-follow so far in Parts 1 and 2.

I will try to follow your code and also port to the FRDM board so that any PC software/scripts can be compatible.

I think it's a good idea to go for a 12V supply, since many low-cost pumps can operate at that voltage.

Regarding Mr. Sneeze, some implementations might not need it, and especially when components are placed in paste,

the tack may be sufficient to overcome component holding force from any low pressure in the tubing.

My pump and valve seemed to need it, because the low pressure didn't equalize so quickly. Possibly yours might not have that

behaviour. Also, it might not be needed for short lengths of tubing. I do intend to insert a pressure sensor to get more insight,

I need to drill another port in Mr. Sneeze.

As you say, all this stuff is perhaps best found out through experimentation and building the prototype, there doesn't seem to be

many resources, and I'm not knowledgeable on pneumatics to be honest so I could be doing things in a non-ideal ways.

Also, it seems a really good idea to fit the large display, since a lot of detailed information could be needed for a project such as this.

Thanks for taking the time to write up your project so well, it makes it a pleasure to read.