Help With High Speed Counter on sewing machines

The new project calls for a left and right sewing machine to be controlled by a touch screen using a micrologix 1200 or 1500 plc. The Inverters will be toshiba vsf-11s with 1/2 hp motors turning a 40:1 gear box which is directly hook to a screw bar.

The max machine rpm is 3400.
--The left and right machine will have a encoder mounted to the shaft going into the motor.
--The machines will have to be within a set deviantion in rpm to allow consistancy between the stitch rates
-- Is there anyway to gather position at the same time as rpm to not let the machines start without the needdles in the up postion(save broken needles)

kevin fleming

I know nothing about industrial sewing machines, however I would presume if the motor is somehow mechanically coupled to the needle, then you should be able to tell the needle position & speed from the encoder on the motor. However...I would guess that you would need an encoder that would provide a count in direct relationship to the needle position. For example lets say the motor turns exactly 4 times for every needle stroke then you would place the encoder on the shaft so that the "Z" output would be on when the needle was at the top of the stroke. In that case on every 4th revolution of the encoder, you know that the needle is up...

This is all presuming that the PLC will be reading the encoder, and not the drive...

As much as I can tell by the description of operation, my choice would be to use servos instead of VFDs. Two servodrives can be linked together in "master-slave" mode to be completely synchronized (so-called "electronic shaft"). An encoder is a necessary part of each motor and the position and speed can be detected in fast and reliable manner.

P.S. 3400 rpm on the output shaft with 40:1 gear ratio? 136000 motor rpm?

Sounds a bit too much to my taste.

i made a mistake ladder logic The 40:1 gear box is going to be hooked to the screwbar which is directly coupled to the machine foot plate. the 40:1 gear box will allow me to run around 30 hz so i can stop quickly. The guideing system has to be able to track according to the speed so it doesn't cause wavy edges. The sewing machine is hooked to the motor with a belt. i planned on putting the encoder on the input shaft of the machine to get a accurate reading. As for waiting 4 time to find the needle up postion would not work becuase i need to be able to stop with the needle up for repair and color changing.


thanks
kevin fleming

waiting 4 rev. was only an example. I would think somehow you could place a small sensor to detect the crankshaft position, that's driving the needle. The problem is that on a power cycle you will have to reset the count on the encoder, relative to the needle position. If the encoder Z fires when the needle is at the same position on each rev then it's easy, if not, then that's another story....In otherwords, on startup you will have to know the needle position, and the encoder position. The other two alternitaves would be to use an absolute encoder, or a prox switch on the needle drive.

We made a sewing machine controller once.

It controlled 3 stepper motors. X and Y for the button holes and a Z for the stitches.

At 1800 rpm it would be pretty hard to stop the needle in a certain position (all the way up position, I guess) by latching a sensor signal via high-speed counter PLC input and then commanding the VFDs to stop. One full needle stroke (360 deg) is 33.3 ms... if you want to achieve at least 20 deg accurate stopping position, you need to be able to evaluate encoder data every 2 milliseconds or so... Then there is inherent latency and the smallest possible decel time...

Not a task for Micrologix, I reckon, need a motion controller for that. This requirement makes it a positionng application, not just constant-velocity one.

Thanks ahead of time. I think that it will be best to just use a separate prox swith to indicate the needle up position and use the encoder to track the sewing machine rpm. What type of sensor would be good for edge detection. The machine now is using a paddle setup with to proxs on the arms from the paddle. This have been known to cause alot of unnessessary off quality by hanging up . Is there different type of eyes that would work with no machanical parts (paddles)

kevin fleming

We plan on using a micrologix 1200r(2 comm ports) with a eztouch 8" screen. The goal to the project is to allow the operator to press one recipe on the screen depending on the rug size. The recipe will control the pull roller speed and the stitch rate on 2 sewing machines. We are going to use the touch screen for fine tuning and downtime monitoring. With the new arc flash 70-e regulation we are wanting to control everything from the screen so we have limited reasons to ever be in the panel besides blown fuses and etc. I am needing some advice as to how to display rpm of 2 sewing machine simutaniously to make sure each side of the rug is getting the same stitchs. The thought was to use a prox and the bolt on the pulley due to the need to change machine due to breakdowns quickly. The machine only run in the forward direction. and have a max machine rpm of 3000. The 1200r micrologix have 4 high speed inputs 25us-2ms. Any help or same code would be extremely appreciated,

kevin fleming

I have read this a couple of times and the specific details are not clear too me.
1. Its 2 separate sewing machines providing stitching on each side of a rug...correct?
2. Are the drives going to be controlled via digiatl or analog outputs or is a fieldbus option available?
3. Are the motors "mechanically" coupled in any manner besides the connection to the rug?

#3 is the main part that is not clear to me, are both sewing machines also doing the "pulling" of the rug?

If both sewing machines are doing the pulling then it will be difficult to match speeds using digital outputs. I have not seen any details stating how speed would be controlled if necessary.

I am not familiar with the S11 drives but have used the G7's for several applications, I am not overly fond of Toshiba drives but they do work.

An encoder is basically a device that offers accuracy when speed and/or position is necessary, if the sewing machines are doing the pulling then each would probably need an encoder that is more accurate than a proximity switch and a bolt. The same applies to speed control for the machines, digital ouputs probably wouldnt not be efficient.

I am also a tad confused on the gear box thing and your reference to 3000 max rpm, is that the max of the machine or the max for the motor? I am use to thinking of gearboxes doing reduction...ie if its 40:1 then using a 1750 rpm motor the output shaft will rotate 44 rpm.

Sorry bout all the confusion.
1 the machines are stitching each side of the rug.
2 the speed is going to being controlled by analog inputs (1 for each of the 3 motors)
3 the machine are not machanically coupled
4 the machine will be intially contolled from a recipe in the touch screen but will have a fine tune cabability.
5 the toshiba drive are commonly used in out plant WE are going to use digital start inputs with analog speed references
6 the sewing machine use feed dogs to push the rug rhrough. the pull roller has to be faster to keep the rug from wading up.

If the inoput shaft speed on the sewing machine what would be a good ppr encoder to use. I was thinking about the prox and bolt (which is common on a cmc tufting machine to display rpm)only because of the amount of machines that are changed throughout the day. I understand a encoder will be more accurate but was wanting a cheaper alternative. All the motor will have to have some sort of rpm pick-ups

AS far as the gearbox thing that was completely wrong and need to be ommited. I should have started a new thread.
thanks for your patiences
kevin fleming

Automationdirect has several low cost encoders at different ppr, the idea is to match the ppr to the desired resolution.
http://web1.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Encoders

The last post explains alot, let me verify I (we) fully understand the operation. The rug moves at X feet per minute based on the type of rug (material, thickness etc) and the sewing machines need to run X rpm (as closely matched as possible) based on the rug type. The eztouch is to allow you to use a recipe to tell which type rug is being sewn and display what the rpm should be and what it actually is? Is this a fairly accurate description?

This is a Getting Started document for using the HSC with an ML1200 or 1500 that has an example using an encoder.
http://domino.automation.rockwell.com/applications/kb/RAKB.nsf/0/78ac8a1e76a34fc585256afb00672a49/$FILE/QuickStart_uLogix_HSC.doc

This is another technote showing how to use inputs to control outputs: http://domino.automation.rockwell.com/applications/kb/RAKB.nsf/0/B549C5C514C6C34685256B17004F7FB2?OpenDocument

I offered those as a reference to get you started. I am sure once the operation is better understood more people will offer more help.

Rsdoren
I think u have a excellent grasp as to what i am trying to accomplish. The mircologix 1200r has 1 on board high speed counter function file and 4 high speed digital inputs. I plan on using the on board hsc for the pull roller but need help with some code for the two sewing machines. As for the encoder i am not sure what ppr would give me the best resolution. the max speed on the sewing machines is 3000 rpm. the max speed on the pull roller is like 50 ft per minute.

thanks for your input
kevin fleming

I keep asking questions. Where will the encoder be mounted for the "puller"?...ie how many revolutions equal say one inch? I dont think you will need a high ppr encoder so go for one that will make the math easy to follow.

More than likely by the time I get all the details sorted out someone will have already provided you with some kind of example, just be patient.

I have ideas though just want to verify all the details.

Another thaught.. why not try a Resolver..No need to worry about power ups and a hell of a lot more robust that an encoder..The last one i set up could go as high as 7000 counts per revoultion..

D