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help filling containers with potting soil  RSS feed

 
gardener
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This is probably a far too specific problem, but it has been seriously nagging at me for a while.

For the better part of the past year, I've been filling 10cm x 5cm x 5cm plastic containers (yuck) with potting soil (actually cocco coir with some non-peat potting soil at about 20%)

Unfortunately, I'm sort of stuck with this non-standard container and I need to fill them "half way", which means anywhere from 77 to 85 grams. Any less or more means the final product is a little compromised. It's a little difficult because volume and weight don't always correspond and the difference of 5-10 grams might not be noticeable, but hitting 80 grams is like an obsession of mine.

For most of my time doing this, I laid out the containers on a table and eyeball filled them, getting more and more precise as things proceeded. Then I weighed them. Total time for filling, 15 minutes. Total time for weighing: 5 minutes. So the whole manual process takes 20 minutes. For 100 containers.

I recently felt the need to be able to do more in less time, so I'm currently at the end of a 3 week long quest for a prototype that would do just that.

After 3 different prototypes, the total time is still about 20 minutes. I compare it to a tandem bicycle, you just can't go any faster. There seems to be some physical limit to filling manually. One prototype seems to limit physical exertion, so I've been using that exclusively, even if the time is the same.

So, one option would be to video tape myself and try and eliminate all extra movement, or I could try and find a perfect machine that would do everything for me, or I could re-engineer everything from scratch.

Most nurseries fill to the brim and they're not as precise as I'm trying to get, so they can buy a huge machine that does things for them. Anything I do needs to fit on a desk, so space is an issue.

I've recently found that getting the soil to a fine grain without any chunks in it does help in noticing a difference in volume/weight. It does add work since I now need to sift the stuff (dreaming of a small, motorized trommel screen).

If anyone has any ideas, thanks. This is quite the pseudo-MIT project.
I can add pics of previous prototypes. Coming soon.

William




 
William James
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Currently thinking of the magic of plug-making technology. Maybe I could make a plug-transfer do-hicky that is the size of my containers...
-W
 
William James
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Found out that compressed cocco/potting soil mix maintains, more or less, the same grams when pressed into the same shape. Only problem is the process of pressing  and putting into containers probably takes more time than eyeballing it and weighing.
-W
 
pollinator
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I use my cement mixer for mixing soil FAR more then what I would ever use it for mixing concrete, and that is saying a lot. I have my own gravel pit and do mix the occasional cement pad.

In your case it seems buying one of those micro cement mixers would work well for you. They only hold a small amount of soil but you only have a small amount of area. As long as you have electricity, the small motor should mix and measure well for you. Here is one from Walmart.

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May I ask just why the fill has to be so precise?  I fill lots of containers myself with potting soil and when I am filling my smaller containers, 3" square+-. I sit them in a tub that is about 2X3 feet that is about 1 ft deep and just fill them to the top, settle the soil and level them off then move on to the next set of pots.  I typically do about 20 at a time and it takes all of a couple of minutes.  I would figure that 100 would take me about five or ten minutes, tops. When filling what we here in the states call "6 packs" I can fill 48 cells in about 30 seconds if I am in a hurry using the same process as my 3" pots.  I'm filling by volume though, not weight.
 
William James
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Thanks for the replies.

The reason for the obsession is mainly aesthetic, but it's sort of what our product has morphed into after about 5 different incarnations and 3 years, so I'm kinda stuck with half-filled containers whether I like it or not at the moment.
I'm currently wondering if liquefying beforehand might have some effect. Like some slurry that gets dosed out in Ounces/Centiliters. The containers have 4 holes in the bottom so hmmmmm, maybe it would leak out.

Here are couple pics:

https://www.instagram.com/p/BXDKAC4jtgk/?taken-by=piantanatura

https://www.instagram.com/p/BSWT3hFjkkh/?taken-by=piantanatura

https://www.instagram.com/p/BRjOHJSjoIr/?taken-by=piantanatura
 
Walt Chase
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OK, Makes sense to me now.  I would still think that filling by volume and not weight would be the way to go.  You need  a way to accurately scoop the volume to dump in the trays.
 
pollinator
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I don't get it . The picture shows ordinary brassica am I right? Why so much fuss about something kale or cabbage? Are these meant to be seedlings?
 
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So what if you used a measuring cup? That holds the exact volume of coir that you want in your pots?
 
Walt Chase
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Angelika Maier wrote:I don't get it . The picture shows ordinary brassica am I right? Why so much fuss about something kale or cabbage? Are these meant to be seedlings?



I think microgreens.
 
William James
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Microgreens, exactly.

@Joseph Lofthouse
You would think that a measuring cup would do it, but aside from being extremely slow (like half speed compared to other methods) the fluffed up nature of potting soil makes it so you don't actually get the same amount in the cup each time. It can vary by 10 grams from my most or least acceptable grams (85 and 77 grams)

Here's a prototype of a wooden thing I made. If you compress the potting soil into these, they come out almost exactly right. It's just slow.

W
IMG-0083.JPG
[Thumbnail for IMG-0083.JPG]
prototype for measuring
 
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Could you use cut-off versions of the plastic pots themselves as measures? Trim them down to the soil height you want, fill up with soil (compacted), then dump into the final sales pots. You might be able to rig them up to do six or nine at a a time, depending on size and how unwieldy that might be.
 
Joseph Lofthouse
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William James wrote:Here's a prototype of a wooden thing I made. If you compress the potting soil into these, they come out almost exactly right.



That looks exactly like a measuring cup to me... Just awkward and slow because there are a whole bunch of measuring cups hooked together.

Doesn't  the weight per volume vary a lot depending on moisture content?
 
William James
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Cynthia Quilici wrote:Could you use cut-off versions of the plastic pots themselves as measures? 



One idea I had is similar to this: use seeding trays with the exact size of the containers, and flip the greens out when done. The problem is nobody makes seeding trays that are this size/shape. Would have to be custom made and cost a lot of money and have minimium orders in the range of 20000 trays.

 
William James
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Joseph Lofthouse wrote:

That looks exactly like a measuring cup to me... Just awkward and slow because there are a whole bunch of measuring cups hooked together.



True, but like I said, there doesn't seem to be a way to get a similar weight when pulling out potting soil with a cup. Every time it's different. In the above case, when the soil is compressed, the weights are the same, within a few grams of each other. The quality is a lot better than cup-into-container-one-at-a-time. The difference in time when doing 100 is not that much different.

Joseph Lofthouse wrote:
Doesn't  the weight per volume vary a lot depending on moisture content?



Not very much. The coco coir stays in bags and pretty much maintains its moisture content pretty regularly. If you leave it out for a day on the table, absolutely.
 
Walt Chase
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William James wrote:

Cynthia Quilici wrote:Could you use cut-off versions of the plastic pots themselves as measures? 



One idea I had is similar to this: use seeding trays with the exact size of the containers, and flip the greens out when done. The problem is nobody makes seeding trays that are this size/shape. Would have to be custom made and cost a lot of money and have minimium orders in the range of 20000 trays.



Could you change your pot type/size/shape to match a commercially available one in order to be able to grow as mentioned in the above quote?
 
William James
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Walt Chase wrote:
Could you change your pot type/size/shape to match a commercially available one in order to be able to grow as mentioned in the above quote?



We've discussed that. It could be done, but we've sort of have everything based on this size. If we had a size that standardized seeding trays could work with, it'd be great. The problem is we would have to have to take it out of the tray and put it into something in order to sell it. Usually the seeding trays and the product containers aren't designed to match, so there's that.

But yeah, it's worth looking into further. It would definitely be a solution for 80 - 90% of our varieties.
-W
 
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