motor driven dispensing cartridge

[hugh111111]

Hi, I have no background/knowledge in electronics but I'd like to start a project as a learning exercise but also to fill a genuine need at work. I'd appreciate any advice that will point me in the right direction. I'm a total newbie.

I'd like to dispense a two component epoxy into a mould. At the moment I use a two component cartridge but this will only allow a fixed mixing ratio because the dispensing gun I use drives the plungers into the cartridge barrels at the same rate - the mixing ratio is determined by the volume of the barrels relative to each other (See attached image).

I'd like to be able to vary the mixing ratio and I believe the best way to achieve this is to control the rate at which each plunger is fed into its cartridge barrel. If i had two threaded bolts attached to motors then the speed of the motor will determine the rate at which the bolt pushes on the plunger as it feeds through the cartridge barrell.

So the way I see it, I need two variable speed motors and also an interface/control dial/software from which I can set the motor speeds for each motor. I'd welcome any ideas to get me started. What type of motor do I need how do I interface the motor with a control device? Thanks for your help.

 

[ClydeCrashKop]

I would use a linear stepper motor like this one. https://www.mpja.com/Stepper-Motor-Linear-NEMA-17-15A/productinfo/31564 MS

You can find them cheaper.

They turn incrementally. Maybe 200 steps per revolution.

You could get a 2:1 ratio by sending 2 steps to one motor for every 1 step to the other.

BUT... You need a driver board (small & cheap) and / or a computer or micro-controller to send the desired number of pulses.

 

[hugh111111]

Thanks for your reply ClydeCrashKop, this is exactly what I had in mind. I hope you can help me with a few more questions please...

Is there a reason to choose a stepper motor over a DC variable speed motor? Is one better than the other or is there little difference? My application requires a relatively high torque as the epoxy resin is quite viscous. Also ideally I require accuracy to within +/- 1%.

Is it simply a case of connecting the motor to the driver board then plugging the driver board into the USB port on my PC? Or do I manually adjust something on the driver board? I guess there will be some trial and error to correlate motor speed with quantity of liquid dispensed. Also, is the motor you suggest compatible with any driver board?

That's a lot of questions but I did say I was a beginner. Thanks for any further advice you can offer.

 

[ClydeCrashKop]

This would be extremely accurate and could control the total volume also.

I bought this driver to run that motor: https://www.mpja.com/Stepmotor-Driver-3A-Max-TB6560/productinfo/31306 MS Those are all gone but you can find similar on line.

You hook the motor directly to the board. You put power to the board, 12 or 24 volts.

The board wants 2 more inputs. The direction input wants 5 volts to turn the motor one way and 0 volts (ground) to turn the other way. The step input wants a 0 volts to 5 volts pulse. On the above motor, one step will turn the screw 1/200th of a revolution. 200 steps for a full revolution.

I started playing with these long ago by writing Basic programs that sent the outputs to the parallel printer cable.

If you are not a programmer, I think you could use this interface.

**broken link removed**

And the free version of the MACH3 CNC controller program.

If you set it up that one motor is the X axis and the other motor is the Y axis, you can enter a “G-Code” command that will run both motors a precise amount.

I’m not very familiar with it yet but I think “G0 X400 Y100” would step one motor 400 times and the other 100 times.

You will find an overwhelming amount of info on this subject at https://www.cnczone.com/forums/index.php

 

[ClydeCrashKop]

The more I think about MACH3, the better it sounds. With the “G0 X4 Y1” instruction, the MACH3mill program thinks it is moving a milling machine table in a strait diagonal line to that coordinate. The first thing you do is to set up the program. If you find out that your device takes 275 steps to squirt out one CC of resin. Set up the X axis with 275 steps per centimeter. Do the same for the Y axis. Then with the “G0 X4 Y1” instruction, it will dispense 4 CCs of resin and 1 CC of hardener. The program doesn’t have to know that you are getting volume instead of linear movement.

 

[hugh111111]

Thanks for taking the time to explain this, the links you provided are also very useful. I'm an OK Java and .NET programmer (mostly desktop applications) and could learn enough C++ for this project. However, the MACH3 software you suggest seems a nice simple option and will do what I need it to do. I certainly feel you have told me enough to get started so thank you again for your help.

 

[ClydeCrashKop]

Info is sparse on that Chinese Mach3 interface board. You will want this.

You will want a jumper wire from P10 to the ground on that same terminal block to turn off the emergency stop.
Good luck.