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synchronize flow rates and motor speed
« on: June 19, 2008, 02:20:13 PM »
Hi!
Is that possible to synchronize flow rates of a motor driven pump and XY axis travel speed.
The viscotec claims that.

http://www.viscotec.de/pdf-dateien/Englisch/brochure-adhesives-and-sealants.pdf   (page 6) (see also page 5)

"The ViscoTec dispenser is the obvious choice when precise, fully
automatic and reliable dosing is required. This is not just because
it is suitable for all types of adhesives and sealants, but also because
quantity and speed are so simple to programme ? a feature
greatly appreciated by many users. It is so easy to adjust the
dosing quantity to the travel speed of the robot. If, for example,
the robot travels more slowly in a curve than on the straight
line, the speed of the dispenser is slowed down accordingly. Spot
dosing that can vary in quantity from spot to spot presents no
problem either."


is that possible to set-up a 4th stepper motor to do that?
thanx!!!!
George!
 ???

Offline Chaoticone

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Re: synchronize flow rates and motor speed
« Reply #1 on: June 19, 2008, 09:24:24 PM »
George, let me think on this. I'm sure it is but need to think about it. Got to head in so please bump this thread in a day or 2 if your still not sorted. I would think you could look at the blended feed rate DRO and do it pretty easy.

Brett
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Re: synchronize flow rates and motor speed
« Reply #2 on: June 19, 2008, 09:47:55 PM »
George,

I'm not I totally understand you- a 4th Stepper motor?  You mean to drive the pump?

We did something very similar to this a while ago but it was all done with VFD's on the 2 seperate Pump Motors (not Steppers).  Steppers need pulses to keep runing and that didn't work for us since our pumps, when not dispensing, were recirculating.  In other words our pumps needed to stay on all day so steppers were not the answer. 

If it were me... I would try and rob some kind of analog output signal from Mach (like Brett suggested Blended Velocity DRO = 813) output that via Modbus and use that analog signal to drive a VFD.

HTH,
Sid

Offline jimpinder

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Re: synchronize flow rates and motor speed
« Reply #3 on: June 19, 2008, 11:52:25 PM »
Are you contolling one of these Viso Tec Dispensers, or making a similar type of thing.

What is the scale of this thing. Are we talking perhaps of a garden robot that runs round the lawn spraying fertilizer, or maybe some automated spraying system.

I didn't know there was a blended feedrate DRO - but if information from that can be fed into an "A" axis to run a stepper, then that would seem to give you a perfect link for the speed.

As Sid said, it would stop when the machine stops - but if the stepper was providing the power to the pump, it wouldn't matter - the pump would stop.
Not me driving the engine - I'm better looking.
Re: synchronize flow rates and motor speed
« Reply #4 on: June 20, 2008, 11:34:20 AM »
"Are you controlling one of these Viso Tec Dispensers, or making a similar type of thing."
I have those pumps (Viso Tec Dispensers).

What is the scale of this thing. Are we talking perhaps of a garden robot that runs round the lawn spraying fertilizer, or maybe some automated spraying system.
I have built a xyz table. Its size is   x:15 inches   y:32 inches  and  z:10 inches.

In my case there are motions of two kinds.
The first one is dispensing dots.
So the move is something like this
x0  y0  z0
x0  y10
z-5 (dispense)
z0 (stop dispense)
x0  y20
z-5 (dispense)
z0 (stop dispense)
It is like drilling a series of holes.
I have solved this problem by using a valve made especially for dispensing dots

The second one is dispensing lines and arcs or along a path.
And this is the difficult part.
If I use a common on-off valve, the flow rate (of polyurethane in my case) would be steady.
If the head moves more slowly in a curve than on the straight
line (while dispensing along a path), the line of the dispensed material will not be even (in some places will be thin and in other places will be thick)
Therefore, the desired move in this case is:
when z axis goes down (z-5) the motor that drives the viscotec pump has to start and its speed has to be relevant to the head's speed along the path.
And when z axis rises (z0) the motor must stop.

So this is my question.
Is this thing possible??

ps. I would really like to thank you for your help.

George.
Re: synchronize flow rates and motor speed
« Reply #5 on: June 20, 2008, 12:32:15 PM »

So this is my question.
Is this thing possible??

Sure!  Given enough time & money virtually anything is possible but, let's be practical....

1.  Are you using a plural component Urethane Formula?
2.  What do you mean by "I have those pumps"?  The .pdf that you reference is a general brochure and lists MANY different models/systems-which one do you currently have and What kind of motor is currently turning your pumps now (i.e. Inverter duty? Variable speed? Voltage?  HP?)
3. IMO-I don't think that it is practical to use a stepper to turn a pump.  As mentioned previously a stepper needs pulses to move- those pulses need to be generated by something but from where?  There are a couple of possibilities but, again, I question their practicality (admitadly due to my inexperience with these methods....
       A.  I suppose you could use a 'Brain' to use the Blended Vel DRO signal to somehow generate pulses (I think that Scott/Poppabear would
            be the specialist in this area)
       B. Slaved Axis won't work because X & Y move in + & - and you want your pump motor to only move in the +
       C.  You could use some database software (like access or excel) to modify your G-code file and add lines to your existing G-code that create     
            additional commands to generate pulses for another axis.

4.  Like I said before- you need to 'tie-in' to the Blended Vel DRO and use that signal to drive something  (or generate pulses).  I really think that best way is to use Modbus to use this signal to drive the analog input on a VFD

HTH,
Sid

Offline da21

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Re: synchronize flow rates and motor speed
« Reply #6 on: June 20, 2008, 02:11:16 PM »
yes it's possible , but you need a proportional valve to regulate the flow , on off valves etc won't do , you need to drive a pump with constant pressure  and a relief valve before the proportional valve to feed back into the feed tank or a holding tank etc for when the pressure of the pump is greater than the flow rate etc , so it can just feed excess back around the system , set the relief valve just a small amount above the pressure of the flow , so it easily trips ,

Dave
Re: synchronize flow rates and motor speed
« Reply #7 on: June 20, 2008, 02:34:15 PM »
If he's running a plural component urethane system I don't think a PV will work as it will throw mix ratio off.

Sid
« Last Edit: June 20, 2008, 02:36:25 PM by sshneider »

Offline Chip

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Re: synchronize flow rates and motor speed
« Reply #8 on: June 20, 2008, 08:56:30 PM »
Hi, George

From what I see in the link you posted, This pump is driven by a stepper motor.

A little rambling hear:

Setup Mach in CV mode and set a feed-rate that will allow the blended speed to be constant.

Set up your stepper pump control to turn on and off with M3, M5 (spindle ON, OFF), Or Coolant ON, OFF.

Stepper Pump Control, It appears that if the pump is driven at a constant speed it delivers a constant flow.

May need an ON OFF valve also depending on the viscosity of your fluid (cont with same ON OFF.

Use a 555 timer to set an Adjustable pulse rate to Calibrate your Stepper Pump Control, Pulses to "step input" (direction needs to be held to Hi or Low for proper pump direction). There are many ways to set pulse rate.

I think trying to integrate the pump as an Axis has allot of issues, The biggest being that all axises are Blended and fed to the printer port for execution.

Maybe using the Step/Dir Spindle feature could work, Haven't fooled with it hear much.

Hope this Helps, Chip

Offline Chaoticone

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Re: synchronize flow rates and motor speed
« Reply #9 on: June 20, 2008, 09:52:48 PM »
Could he not set the pump up as a step direction spindle and set it to surface speed?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!