I have a project in which I would like to dispense and mix over 20 dry ingredients.
The dry ingredients are of similar size, weight and texture. No more then 4 ingredients would be blended together at once, however all 20 ingredients would need to be accessible for mixing at request.
My initial plan was to house the dry ingredients in separate hoppers of identical size. Each hopper would be a volumetric screw feed type and arranged in a circle formation with the output of each hopper directly overhanging a central tumbler which would lightly blend the ingredients for several seconds before releasing them into a lower compartment for handling.
I planned to use stepper motors to precisely control the rotation of each screw and thus the quantity of dry ingredients dispensed.
Each hopper would house around 3-5kg of dry material and would release at any one time 2-10grams.
I don't have a particular question. However based on my admittedly vague description, I would be interested in knowing if my approach seems at all correct. If there is another approach which I have overlooked, I would be interested in knowing.
My budget for this build is around £1000.
Any additional information and diagrams can be supplied.
youngengineer:
I have a project in which I would like to dispense and mix over 20 dry ingredients.
The dry ingredients are of similar size, weight and texture. No more then 4 ingredients would be blended together at once, however all 20 ingredients would need to be accessible for mixing at request.
My initial plan was to house the dry ingredients in separate hoppers of identical size. Each hopper would be a volumetric screw feed type and arranged in a circle formation with the output of each hopper directly overhanging a central tumbler which would lightly blend the ingredients for several seconds before releasing them into a lower compartment for handling.
I planned to use stepper motors to precisely control the rotation of each screw and thus the quantity of dry ingredients dispensed.
Each hopper would house around 3-5kg of dry material and would release at any one time 2-10grams.
I don't have a particular question. However based on my admittedly vague description, I would be interested in knowing if my approach seems at all correct. If there is another approach which I have overlooked, I would be interested in knowing.
My budget for this build is around £1000.
Any additional information and diagrams can be supplied.
I am guessing you have not dealt much with dry material. You need a way to vibrate the walls of the bins while dispensing in order to avoid "voids". You use of screws will crush your dry material to some extent and leave dust.
IF that is all still ok with your project, then get the mechanical part working before trying to automate something.
IMO.. correctly dispensing the correct amount is the trick here (good point about the 'wall dust' too!)
If all materials react/behave the same.. then this may not be a big deal,... but if some of the material is more crumbley, than powdery.... or take up more space than a dry powered... you might need to think of another approach to accurately measure everything.. (perhaps a scale? or something)
If you can RELY on the 'screw' approach to dispense accurately, then the rest should be pretty straight forward from a mechanical standpoint..
In your approach, 20 ingredients, means 20 steppers! YIKES!
I don't see any need for stepper motors. A simple DC motor with a sensor to count screw revolutions will do a much better job.
Is your product dropping directly out of the screw? So, there are no residual pieces that can stick in the end of the screw? And that reminds me to have you set the pitch of the screw so that can't happen.
Paul_KD7HB:
I am guessing you have not dealt much with dry material. You need a way to vibrate the walls of the bins while dispensing in order to avoid "voids". You use of screws will crush your dry material to some extent and leave dust.
IF that is all still ok with your project, then get the mechanical part working before trying to automate something.
Paul
I have never worked with dry material before as you mentioned Paul. But you make a valid point on the material sticking to the insides of the bins. I thought about this and planned on combating that by mounting a small dc motor with an offset weight.
The dry ingredients are not sticky or dusty, however are very dry and would create dust if continuously agitated. I do realize that anything pushed through a screw will somewhat be broken down. Though I would hope it would not be pulverized..
I agree with your second point on building the mechanical part before anything else.
xl97:
IMO.. correctly dispensing the correct amount is the trick here (good point about the 'wall dust' too!)
If all materials react/behave the same.. then this may not be a big deal,... but if some of the material is more crumbley, than powdery.... or take up more space than a dry powered... you might need to think of another approach to accurately measure everything.. (perhaps a scale? or something)
If you can RELY on the 'screw' approach to dispense accurately, then the rest should be pretty straight forward from a mechanical standpoint..
In your approach, 20 ingredients, means 20 steppers! YIKES!
Obviously each hopper would have to be calibrated manually as the density and volume of the dry ingredient would vary. I planned on using digital scales to measure the output of each hopper. So for example, a quarter turn of the screw would result in X grams. Yes, I agree on the amount of motors. But with the output of a Mega, I don't think this would be a problem.
Paul_KD7HB:
I don't see any need for stepper motors. A simple DC motor with a sensor to count screw revolutions will do a much better job.
Is your product dropping directly out of the screw? So, there are no residual pieces that can stick in the end of the screw? And that reminds me to have you set the pitch of the screw so that can't happen.
Paul
Another good point Paul. I did give this some thought beforehand. That is, how the pitch of the screw would effect control. I would imagine that it would need to be quit fine to avoid pieces falling out un-accounted.
If anyone can think of another way to achieve this with a simpler method. I am all ears. I'm certainly not very excited about having to machine or print all of these screws.
You need to consider the construction materials to avoid a build up of static electricity.
This can be a problem with coffee grinders where the ground coffee becomes charged then flies off everywhere.
The materials being dispensed may also cause issues.
Cocoa power seems to have some odd properties when you try and mix it with things.
Cornflower is wierd stuff so I would not be surprised if it behaves strangely.
PaulS:
How about giving us a hint what the materials are?
2 to 10 grams, +/- 1 kilogram? Or +/- 0.0001 grams?
Materials used for hopper build or are you talking about the dry ingredients?
2 to 10 grams depending on the quantity required. If the machine is dispensing +/- 1KG then this would be completely pointless. I might as well have a trap door dumping the entire hoppers contents.
I'm not looking for accuracy down to 0.0001 grams either as this is just not realistic. Something like +/- 0.1 to 0.4 grams is acceptable.
youngengineer:
I've seen these before. Quite impressive! Though it only seems to ignite when either superheated, or in huge piles where friction and heat build up.
Room temperature and a small amount of dust are quite sufficient. All that is needed then is an ignition source. The chemistry teacher at my local high school used to demonstrate it with custard powder.
I'm no expert in this kind of machinery, but an alternative angle would be to use pressure (compressed air or co2 or nitrogen or...) to drive the power as a fluid.
Anyway as you say you've never worked with this materials before maybe you should try to do some small scale prototype to see how the system behaves, what issues appear etc.
wildbill:
Room temperature and a small amount of dust are quite sufficient. All that is needed then is an ignition source. The chemistry teacher at my local high school used to demonstrate it with custard powder.
Sounds scary. It's a good thing that no custard powder or flour would be used.
A serious suggestion. GO visit some plants that are doing what you are thinking about and see how they are solving problems. Doesn't have to be tea. You need some real world input.
All we can suggest are things we have seen/experienced in past lives. I worked 18 months at a composition roofing plant during college. All kings of dry material being moved. then running a grass seed cleaning mill one summer. Then living with a wood pellet stove for 11 years.
Each material and each way to move solids was different. Sometime gravity helped and sometimes it hindered.
And so does coffee according to that list. So coffee grinders and coffee makers all in one machines might be something to look at. How do those machienes dose the amount of coffee per cup? Might be an idea to look into.