I just bought the L6 kit and I love it. However, I am trying to get the gripper to pick up cds, but it always drops it. Everytime the finger closes with the cd the finger “jitters” back and forth shaking the cd loose. I adjusted servo limits to stop the jittering, but it still doesn’t hold the cd tight enough to move around with.
Ideally, I would like the gripper to firmly hold the cd so I can have the base rotate and the elbow move up and down with out the cd sliding or dropping. Any ideas?
Perhaps re-clock the servo horn and adjust the servo positions to give a tighter grip? If the servo is near the end of it’s travel and the gripper is not fully closed, my guess is to re-position the servo horn as well as the servo’s end position. This should give you more room to close the gripper without puting the servo at the end of it’s travel. This is the only thing I can think of off hand.
Modify the gripper to have more surface area in contact with the CD. The round rubber end caps are good as a general purpose “finger” but you need to make a custom one with flat “fingers”. Check out the weatherproofing section of your local home improvement store for adhesive backed insulating strips for example. Good luck!
How are you gripping the CDs?
Are you grabbing them flat?
From the edges?
From the hub?
If you’re using an unmodified Lynx-6, I assume you’re picking them up flat, across their narrowest dimension.
Looking at photos and video clips of CD handling robots from various sources (manufacturing process, duplicating, etc.), it seems that they often have specialized grippers to handle the discs by their edges, or their hubs. Some lightweight metal or hard wire might work for that approach, or plastic, if you’re worried about scratching in “almost had it” situations. Manufacturing robots seem to handle them with vacuum pickup assemblies quite often.
Now that I think of it, I do recall having seen a photo of an older 5 axis arm with a U-shaped “paddle” on the end for CD handling, rather than a claw (though for the life of me, I can no longer locate the link).
I agree with Jim.
Get something that’s flat, squishy, and rubbery.
The squishyness should take care of the “jitteryness” as it’ll allow some give and take without actually dropping the CD.
The flatness and rubberyness will aid in the gripping.
I noticed All Electronics Corp has a micro air pump. I don’t know much about the terminology, but it is rated for: minimum vacuum @ dead head, 9.1" HG (307 mbar). It has two 1/8" ports, a 6vdc, 80mA no load. Cat# PMP-6 for $14.75 each.
You will need a rubber suction cup thingy to attach the vacuum pump to. I’m not sure where to get something like that.
You will also need to control the motor. You can rip the guts from a cheap servo as the voltage and current are in the right range. This will allow you to create and release the vacuum as you can control the speed and direction of the motor. If you’re using RIOS you can connect it as one of the spare servo channels.
I’ve been wanting to do something like this for a long time. Not necessarily for CD manipulation, but just the vacuum gripper part.
This thread has evolved into a CD manipulation topic, so I renamed it. 
Vacuum picking surface mount parts is pretty standard. Perhaps you can buy a SMT rework vacuum pen with several tips to see if one or more work for you. Also if you use a small 3-way or 4-way valve to switch the vacuum on/off you will likely have a lot better performance, speed in particular, than turning the vacuum pump on/off because you don’t have to wait for the suction to build up.
Thats a fantastic idea, A vacuum SMT pen does have remoavable nozzles of different sizes. I was even thinking about SMT machine nozzles but they are more expensive than a vacuum pen nozzle. They even sell battery powered vacuum pens that are attached via a flexible coil of tubing attached to a hand held unit containing the vacuum motor and batteries, these units can pick up some pretty heavy QFP’s.
The pen thingy is a real good idea. Any links to where they can be purchased? Are they expensive? The vacuum pump and servo guts would be pretty inexpensive. Like $30.00 ish… I don’t think it would take a long time (over a second or two) to develop enough vacuum to pick something up though. The cheapest air valve I know about is $25.00, and two would be required. Anyway this looks pretty doable.
There is no reason to buy the whole pen, yes? What you need are the tips and probes. This may be a good place to try.
howardelectronics.com/virtual/vacuumcups.html
The valves, I’d go for surplus or ebay maybe. Look for small Clippard, Dynamco Dash-1, or Mac might even have some small ones. $18 to $20 ranges stuff. Why do you need 2 valves? Isn’t this just a 3-way app where the pick cup is on the common and then you switch between the vacuum and atmosphere?
I seem to remember seeing someplace that was selling small motorized air pumps a while back. I don’t have any specs on them, but perhaps they’ll draw a vacuum if run in reverse…?
Edit to add: Many years ago, I saw a column in an electronics magazine that was talking about hacking together a pneumatic system from commonly available parts. I think he was using some sort of automotive valve (TCS, maybe?) to shunt the air around. His project required on-off switching, and the valve switched between pressure and atmosphere, but he sealed up the vent with PC-7, and it supposedly worked well enough for him.
Yes, tips and probes are all I would need.
The valves I was using are just open / closed. So you need to open one and close the other…
I don’t think they draw a vacuum in reverse. I think I tried, but it’s been awhile…
Generating a vacuum from positive air pressure isn’t difficult as they do that for desoldering equipment all the time using a venturi. However, is the goal of the project to put this stuff on a mobile robot or something sitting on a table? It seems like there is a lot of hardware accumulating.
Edit: Anver makes small venturi type blocks for making vacuum from pressure and supplys suction cups, hose, and fittings. I picked a few parts and asked them for a quote. When(if) I get the info I’ll post it here.
Just to throw this out there…
What about ducted fans?
You can get those from Tower Hobbies, and the like.
I suppose if you reversed one…
