Equipment for a pick and place robot manipulator

Hey everyone, I'd appreciate your opinion on this dilemma I'm having with choosing the appropriate equipment for automating a process. I just finished college and this is my first real world problem in automation.

The process in question is the assembly of window and mirror frames. The plant owner has this general idea on how the process should look like :

A block of wood arrives to the first workbench via a conveyor belt. It is then cut in two pieces of preset lengths, one longer and one shorter. A manipulator then picks up both pieces one by one and places them on a second workbench one perpendicular to the other. The pieces are then glued together. Another block of wood arrives and is being cut. The manipulator picks up another two pieces and places them so that they form a full frame with the previous two pieces. They are then glued together. The entire frame is then picked up by the manipulator and transferred to another conveyor belt.

The dilemma I'm having is with the manipulator itself. It has to be a 4-axis manipulator, possibly SCARA. The first two axis would be used to transport the pieces into appropriate x-y positions in the workspace. The third axis would be used for vertical movement of the gripper when picking up and releasing the pieces. The fourth axis would be used for rotating the gripper.

The motors for the first three axis which ensure the x-y-z movement should be servo motors while the fourth axis motor could be a stepper.

Since this is the first project I've come across after finishing college, I'm not familiar with the «commercial» side of things. My original idea was to use three servo drives Lexium05 ( since I've worked with Schneider's equipment throughout college so I'm accustomed with them)
with three BSH servo motors and a stepper motor. Everything would be controlled by a Modicon PLC.

After doing some research and reading alot of topics on this forum I started thinking more in terms of a 4-axis motion controller like PMAC because it seemed to me like this would be a more economical situation.

What would you guys recommend in this situation ? Are the Lexiums with the Modicon PLC an overkill for this process ? How much savings would be achieved with a motion controller card. The process is such that the trajectory of the tool is not an important factor, only the end positions. What I'm interested in is if the cost of the Lexiums and the PLC is justified for this process or a much more cheaper solution can be found.

I won't make this post any longer. If there are any more specific questions, ask ahead and I'll answer.

Thank you in advance, any insight will be extremely helpful !

I don't know much about eletronics, but we use robot for welding and I've seen so many doing pick and place and other things. If you can, have a look at ABB robots, you will find many videos on youtube. They are easy to program and if you have to change between sizes and shapes you just change the program.

If you want to perform all the operations with the same "manipulator" then a robot would be better.
My company have already installed some ABB robots for picking all source of things.

While you could build your own robot you are going to find it will probably be to you benifit to order something off the shelf. ABB, Fanuc, Move Master are just a few who offer robots that do exactly what you have described. Plus you are going to have to think of a few more details you have not listed.

How are you going to detect the parts?

How are you going to interface with the machine gluing the parts and sawing the parts?

How do you pick up the completed part with the same actuator you used to pick up the smaller parts?

You need a bit more detail up front and since this is your first project I would strongly suggest you work with someone and that someone can be the compnay you look to for the robot.

Your process is what you need to value.
The costing of drives and associated PLC will be at a cost.
The PLC - or rather the memory requirement will dictate that type.

Manufactured robots take all the risks out of the design.
they are also designed for your load requirements.
The Safety design required for your machine is also partially included in the robotic control.
Only the interface to the machine is needed to be designed.

I agree wholeheartedly with Clay and Iant here. Since this is your first project in the trenches, there are a bunch of things you don't know and a bunch more you don't know that you don't know.

My guess is that being successful is the most important piece of this for you. Sure you need to be economical in your decision, but as Iant suggests, the overall value of the machine is far more than the sum of the parts. A more expensive machine that is installed and operating profitably shortly after installation will pay for itself much faster than one that takes longer to get right and frequently needs attention.

My advise is to spend your time developing a scope of work focused on true requirements like speeds, heights, distances, and load capabilities. Then, once you feel you are in decent shape there, contact one vendor who sells turn-key systems similar to what you want. Bring him in and let him help flesh out all the details with you and get a quote. Then, once you have a 99% understanding of what he is offering, go get at least two or three competing quotes based on what you now know. By the time you are done, you will have a much better system in mind and it will likely come in to be less expensive than the one you would have developed yourself.

Good vendors can be your best allies. Don't be afraid to use them. In the end, nobody will remember whether the project cost $100K or $125K, but they will definitely remember whether it started making money right away or not. That's where your reputation is.

Steve