What is the most cheap and efficient PLC for MOTION CONTROL?

[Anthony80]

You guys seems to be pretty good with PLC!

Here is my current project

I have a linear actuator(Ball screw) that i need to control the position with a PLC and an AC inverter. My stroke is 24-30in, speed 10in/sec and my cycle time is 3-6sec.

I know that usualy AB are more expensive but does it worth it?. Is expantion module from Siemens S7-200 are good for motion control? And does anyone have ever heard about AROMAT?(now it's Panasonic i think)

 

[mordred]

The S7 do work good for motion control as well as the Omron line, I haven't tried Aromat

 

[OkiePC]

Some questions
1.What is the required position accuracy of the screw?
2.Are there multiple positions that are frequently changed?
3.What type of feedback device will be used?
If the position accuracy is not too critical, the PLC may be able to "close the loop" and do the posiioning you need. I have done positioning with a PLC5 and cheap AC drives where I had good analog position feedback. It has worked well and acheived a position accuracy of plus or minus 2 counts on a scale of 0-1024, but the speed of the axis was slower than yours (3 in/sec).
If there are a limited number of positions, but extreme accuracy is important, you may want to look at a servo drive with selectable preset positions. You can select positions with the PLC and let the drive do the positioning. Some drives porvide a means of sending a position command so you don't require a full blown motion controller, and can still have infinitely adjustable positions. That arrangement can be complicated depending on the hardware. If you need high precision, speed, and numerous positions, it may be best to use a motion controller/servo drive instead of PLC/AC drive.

 

[Peter Nachtwey]

Easy answer.

None, unless they already have a motion controller built in.
Think about it.

 

[TConnolly]

I just finished a project using a CompactLogix and two indexing drives. The indexing drive is configured with several preset positions, in this case there were ten positions. The PLC did not handle the motion control - it sent the preset position command to the indexing drive and the drive controller took care of the rest. If your application involves repetitive motions that are not changed then this will probably be the most economical way

 

[Anthony80]

Motion control

- My accuracy needed is about 0.015"
- I need to cut aluminum extrusion(5lbs) to preset lenght depending on the production schedule.
- My feedback will be done using rotation encoder(Analog plus/minus 5V)
- I've got 5-6 position that will always come back all day long
- My AC motor is 1/3Hp

Thank you for your time

i'm seriously starting tinking using Siemens S7 technologies.

Anthony

Some questions
1.What is the required position accuracy of the screw?
2.Are there multiple positions that are frequently changed?
3.What type of feedback device will be used?
If the position accuracy is not too critical, the PLC may be able to "close the loop" and do the posiioning you need. I have done positioning with a PLC5 and cheap AC drives where I had good analog position feedback. It has worked well and acheived a position accuracy of plus or minus 2 counts on a scale of 0-1024, but the speed of the axis was slower than yours (3 in/sec).
If there are a limited number of positions, but extreme accuracy is important, you may want to look at a servo drive with selectable preset positions. You can select positions with the PLC and let the drive do the positioning. Some drives porvide a means of sending a position command so you don't require a full blown motion controller, and can still have infinitely adjustable positions. That arrangement can be complicated depending on the hardware. If you need high precision, speed, and numerous positions, it may be best to use a motion controller/servo drive instead of PLC/AC drive.

 

[OkiePC]

With a required position accuracy of 0.015", you're probably gonna need a servo. I would get an indexing drive/motor and implement a solution similar to what Alaric described. If you will be indexing to an infinitely adjustable length, make sure you get a drive that allows you to write a command position to it. That means the addition of an HMI (Human Machine Interface). The HMI may connect directly to the drive, or to a PLC and then let the PLC command the drive.

 

[Anthony80]

Is your CompactLogix with indexing drives, is a Servo with a standalone drive without the need for the PLC? I've heard about that kind of equipments, do you know a furbisher for that kind of stuff?

thanks, Anthony

 

[Unregistered]

easy

Before you spend a lot of money call these people.
http://www.deltacompsys.com/company/dist.shtml
They can save you a lot of time and money.
Tom

:site:

 

[jimtech67]

I used Control Techniques (Emerson) on a cut to length machine. The Ei-200 drive Epsilon Series.

They have Maple System operator interfaces that communicate directly to the drive. The interface writes and reads directly to and from the drives parameters, makes things very easy. I used a small 2 line display to enter length and number of cuts.



[font=&quot]I used a MicroLogix 1000 to handle stop and start and other logic the servo needed through its digital ins and outs aboard the drive

The price was not that bad either

GO JETS
[/font]

 

[TConnolly]

Anthony, I used Allen Bradley Ultra-3000I drives. This is an indexing drive in which you can configure several preset positions (up to 64 positions) with acceleration and velocity profiles using Ultraware software. Ultraware is only about $85.00 (Gasp! cheap rockwell software!). The configuration is done entirely in the drive unit. I connected to the drives using Device Net, but DN is not necessary, the drive has digital inputs that you can hardwire to the drives from a PLC output card to select which preconfigured position you want the servo to move to. The indexing drives are ideal for applications such as indexing tables, pick and place, assembly machines, sorters, and the like which always follow the same motion profile or a set of limited profiles. The PLC only controls the rest of the sequencing on the assembly machine and tells the drives when to move and to which position to move to. Homing and setup operations are included, but I used absolute encoders on my motors so the shouldnt need to homed unless mechanically disturbed.

There are many different brands of indexing drives out there. I used AB because we have an excellent distributor right down the road and we have been very happy with them - but they come at a premium price.

We built this entire machine for less than 20K, that includes all the pick, place, alignment, part feeders, and press, acutators, the servos, drives, and the PLC. Putting the motion control in the PLC would have escalated us to a full control logix system and drastically increased the cost.

 

[elevmike]

Anthony,

If you just moving a ball screw back and forth, and the encoder will be mouned on the drive screw, you might be able to get by with a PLC. Using a PLC & encoder might save material costs, but consulting with an expert, such as Peter, will likely save you a lot in development costs, and get your machine into production much quicker.

Also I would reccomend reading this thread from begining to end. Theres a lot here that's simmiler to Paula's machine:

http://www.plctalk.net/qanda/showthread.php?t=11015