3-axis servo application-how would you do it?

I would like to get some suggestions from people on this board more knowledgeable than me about servos. I currently build a line of pick-and-place machinery that is predominantly powered by air cylinders, a conveyor belt, and a small Micrologix PLC handling I/O.

I'm trying to expand the capabilities of the machine by powering it by servos, which will increase speed, setup time, and flexibility. The operator will select different jobs from an HMI screen which will cause the setpoints for axis 1 and 2 (described below) to change.

The axis I need to control are:
1)an indexing conveyor belt that moves trays through the machine and stops at programmed intervals. This axis requires a 400w motor.

2)a vertical pick and place axis that moves product from the top of the machine to the trays on the conveyor at the bottom of the machine. This axis requires a 750w motor.

3)a rotary axis that rotates the products 180 degrees as they travel from the top of the machine to the trays at the bottom. This axis requires a 750w motor.

Depending on the size of the product being moved, the vertical travel will need to change. Also, the increment distance of the trays will need to change based on product size changes. This will be setup using an HMI screen.

So far, I have spoken to my AB rep and he suggested using a Compactlogix plc and Kinetix 2000 drives/servos. However, this is too expensive. I am trying to keep my total cost for the control system below $8000.

I know I could use standalone drives and write parameters to the drives using ethernet or modbus. However, the ease of the Compactlogix programming approach is very appealing.

I'm looking for suggestions about what products to look at. I would prefer something that is easy to program, cost effective, and reliable. A motion controller that controls all drives would be ideal, but I'm not sure where else to look besides AB Compactlogix.

Thanks

As a Mitsubishi programmer, u can build it with mitsubishi servo using Q173H with MRJ3-B using SSCNET as an amplifier. The programming not too difficult if compare with AB (my opinion). I think using Mitsubishi PLC not too expensive compare with AB.

$8000 budget for a 3-axis servo system is a bit tight. A good guesstimate these days would be $2000 per servoaxis plus $2000 for the controller.

While AB is generally more expensive, there is an advantage of somewhat familiar software environment for you (although CompactLogix is quite different from Micrologix). Otherwise, you will have to look elsewhere. I, from my little perch, may suggest taking a look at Yaskawa servos and controllers.

Thanks for the suggestions so far.

A little more information that I forgot to include in the original post:

The indexing conveyor axis does not have to be servo. The required positioning accuracy only needs to be about +/- 1/16" and it moves pretty slow (about 3" per second) so this could be a motor/drive with an encoder mounted on the conveyor axle.

LadderLogic, how difficult is the Yaskawa programming?

Try Kinetix 300 Ethernet/IP servo's and compactlogix L23E, should come in under budget. Same drives can be used with micrologix 1100 or 1400 if you are more familiar with this family of processors

RH68 said:

LadderLogic, how difficult is the Yaskawa programming?

Click to expand...

Their controllers now come in two flavors: IEC61131 and traditional ladder. Although their marketing policy is to promote the first, the second is a bit more powerful, IMO.

There is a learning curve but nothing awful. If you never worked with servo motion before, you will have to get some crash training no matter which system you will pick, just to get the gist of it.

RH68 said:

I know I could use standalone drives and write parameters to the drives using ethernet or modbus.

Click to expand...

Another option would be to use a PLC with high-speed outputs and a servo drive that accepts step/direction inputs (most drives with basic position control have this capability). The Micrologix 1400, for example, can be had with 3 high-speed DC outputs. The RSLogix PTO instruction will send a pulse train to the servo with the exact distance you specify and with configurable velocity/accel/decel. You won't have encoder feedback back to the PLC, but the servo drive will know where it's at and will fault if there's an obstruction or overload situation. You could run an analog signal from the servo drive to the PLC if you really wanted a rudimentary position signal, however it's still the servo drive doing the high-speed control.

The advantage of this approach is that you can change motion parameters on-the-fly in the PLC without needing some fieldbus to the servo drive, or an integrated motion solution like the Compact/ControlLogix (and its added cost). It all depends on your requirements, but I get the impression that you don't need coordinated motion or particularly high-speed moves.

One way to do it with a low end PLC is to use AB Ultra3000 indexing servo drives. That way you don't need to do the motion control in the PLC. The drive does all the motion control. The PLC sends a position command to the drive via devicenet or enet. The indexing drive lets you have pre-configured motion profiles for repetitive motions. I've built small assembly stations that way using CompactLogix PLCs and connected the Ultra drives via devicenet.

You could reduce costs even more by using the Automation Direct line of servos. These are re-branded GE Versamotion drives and are good quality. They can be set up as indexing drives if desired and you can change parameters on the fly using modbus and the rslogix MSG commands.

Thanks for the suggestions so far. One aspect I didn't mention yet that may be important is that each axis does need to let the others know when it's at certain positions. For example, as axis 2 lowers the product a certain distance, it needs to tell axis 3 to rotate the product. Likewise, after axis 2 has deposited the product and raised a certain distance, it needs to tell axis 1 (the conveyor) that it can index to its next position and tell axis 3 to rotate back.

I know a lot of this can be done using proxies, but it would be cleaner and easier for me if the drives can be programmed to turn on outputs when certain positions are reached the would tell the plc to send motion commands to other drives.

Your AB rep is being way too careful. He is proposing a system the is capable of more than what you need.

kiwi sparky and Alaric are proposing basically the same system, although I would use kiwi sparky' parts. The Kinetix 300 is less expensive than an equivalent Ultra 3000 and has more capability (IMHO). Also, go with the CompactLogix L23. It is pretty reasonably priced and acts as an Ethernet/IP I/O master, which will make getting info to and from the indexers pretty easy.

Try and price that out using the AB online configurator and see where you end up. If you're in the ballpark go to your ep and see where the discount gets you.

Keith

I would do the obvious

I would use a Delta RMC, an Ethernet cappable HMI of your choice and simple drives. It could do this easily without the need of a PLC as long as there isn't a need for a lot of extra discrete I/O. If so then a small micro logix with ethernet could do the slow I/O portions.

The drives don't need to be anything special. It would be easier if the drives simply had a velocity loop and that is it. However, the drives could also run in current mode.

The RMC has Ethernet and supports Ethernet/IP and will appear on RSLinxs as a SLC500.

All the sequencing and coordination can be done on the RMC. The RMC is multitasking, synchronous and deterministic.
A video showing how the RMC works and is programmed
http://deltamotion.com/peter/Videos/FlyingShear/SimpleFlyingShear.zip

Hey, what did you expect me to say? This is how I would do it.

Peter,
It looks like the Delta RMC150 would be appropriate for my 3 axis servo application. Since it appears Delta is your company, can you give me the approximate cost of the 150 controller, assuming this is what I should use? Also, the cost of a discrete I/O module and 2 motion modules?
Thanks

RH68 said:

Peter,
It looks like the Delta RMC150 would be appropriate for my 3 axis servo application. Since it appears Delta is your company, can you give me the approximate cost of the 150 controller, assuming this is what I should use? Also, the cost of a discrete I/O module and 2 motion modules?
Thanks

Click to expand...

I didn't see this till 7 pm and everyone had gone home but me.
You need would be a RMC150E-Q2-DI/O
http://www.deltamotion.com/rmcquote/configure.php?product=RMC150
I can do that tomorrow when our sales guys are here. If you fill in the info you will probably get the quote faster as the east coast sales guys get in earlier than I do on the west coast. I get in trouble with them when I quote prices.

No disrespect to Peter, who I always read with interest. But to the OP... if you're going to skip the PLC entirely and replace it with a motion controller, give YOURSELF a LOT of time to do that first program.

Motion controllers are great... but they do not program at all like PLCs. You will get used to it, and you will eventually like it too, but the first couple programs are going to be a big paradigm shift.

However you do it, factor in some extra time and effort for the motion part on those first few systems.