orienting conical flower pots

[jlnsol]

For orienting plastic conical flower pots (7 inch top outer diameter) as soon as they are ejected from the mould of a plastic injection machine, I am thinking of using two transport screws with a blade pitch large enough to catch a falling pot in the cavities between the two screws. Preferrably the screws would be located horizontal under the mould of the plastic machine to transport the pots sideways for stacking and packing. Internet search sofar did not show any useful result. Important is that the released pots can have any 3d orientation as they fall onto/into the srews. Any help in finding or designing such type of orienting device (or an alternative) is very much appreciated.

 

[Pud]

I would have thought a pick and place robot with suitable end-of-arm tooling (onto conveyor/ into box) might be cheaper - at least it could be used for other stuff when required.

www.tynevalleyplastics.co.uk

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[jlnsol]

@Pud, thanks. It is more a matter of cycletime than money. Pots fall much quicker blown out of a mould than that they can be taken out by a robot.

 

[AWloo]

Perhaps using a thin walled chute that leads down the line? Very economical, and it would get the part out of the machine reliably without any moving parts.

 

[jlnsol]

@AWloo, thanks. We tried this and built several chutes to test. The objective is that the falling pots will we be oriented in some known position and location so that a robot hand can pick it from there and stack it on a pile. In principle the conical pots have three possible orientations: standing upright, standing top down and laying on a side. The first two are OK, but the problem is the third one. Because of the fixed location we needed to add side walls to the chute and made it tapered. That created a lot more possible orientations to the original three: pots can lay on a side but against the wall. Second problem with the chute was the loss in height: starting below the mould the floor is not far down!

 

[MikeHalloran]

The robot would make more sense in the case of a multicavity mold, where it could grab the tree, and carry all the pots to a degating station, where the same robot could clip the gates for all the pots, then discard the tree, and pick/place the pots from the degating station in a stack where you like, or in shipping boxes or whatever.



Mike Halloran
Pembroke Pines, FL, USA

 

[JohnRBaker]

I've never seen 'flower pots' being molded, but I once visited a plant where they were making styrofoam drinking cups. Each machine had a 4-cavity mold which when opened, the cops were upside-down and the tooling was designed such that the cups were retained in the lower fixed male-half of the mold which allowed them to then blown with compressed air up into waiting plastic tubes in which air was being sucked into thus providing a vacuum, carrying the cups to the packaging stations. When running full out, the cycle time for each 4-cup molding operation was only a few seconds and with a dozen or so machines running basically around the clock, you can imagine how many cups could be produced every 8-hour shift

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[ornerynorsk]

Assuming this is a horizontal machine. Study the tuning and orienting techniques of a vibratory bowl feeder, and I think you could apply much the same principal. The pot falls into an inclined orienting ramp/channel, where a robot then retrieves and stacks it while the machine continues to cycle. No loss of cycle time.

Just a thought.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[jlnsol]

@Mike, your right about the multicavity moulds in combination with a robot. But in our case it is single cavity mould and the pot is oriented with its rotation axis horizontally.

@John, nice system and it sure makes sense for multicavity moulds to do this in combination with a stacker.

In our case we are looking to gain just a few seconds per cycle. This business is all about cents per product!
So hopefully someone can guide me in finding a source for some active orienting device!

 

[jlnsol]

@ ornery: interesting idea! a question which comes up is: how would the pot be able to 'climb' up an inclined channel? The 'no loss of cycle time' is what we are looking for though!

 

[ornerynorsk]

The inclined channel would be oriented downward from the opening under the press platens, so gravity would do the work to carry it to the point where the robot would pick up.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[MikeHalloran]

Okay, vibratory hopper builders have lots of tricks for orienting a part, but I think letting go of the part in the first place is a mistake.

Even with a single cavity mold, you could mold a spud on the tree that would let the ejected product be caught and picked up by something like a toolchanger arm that would swing it out of the molding machine, where the part could be degated and stuffed into a static tube with one stroke of a cross cylinder.

The static horizontal tube could be lined with plastic to produce a wrapped stack of pots right at the machine (like a Christmas tree wrapper or a sausage stuffer), or it could just lead to a packing station where the pots are manually handled.





Mike Halloran
Pembroke Pines, FL, USA

 

[dhengr]

Jlnsol:
The parts all come out of the mold in the same orientation, and the place to catch it, grab it, whatever, is right then and there. Before it has any chance or movement during which it can change orientation. You have to figure this out, because you haven’t bothered to tell us how it comes out of the molding machine, only you know that.

 

[jlnsol]

@ornery: OK understood. I have to look into this though. In vibratory bowl feeders products climb up the wall over a spiral and when then hit an aligning tool in the wrong orientation they tumble down in the bowl and the complete process starts again. Isn't it? I am afraid it asks some kind of hopper to gather the tumbling pots. Which hopper we have no space for available... Maybe the aligning tools can do their job without the 'wrong pots' falling down?

@Mike and dhengr: indeed creating chaos (with respect to pot orientation) seems a mistake. I understand what you say. The existing production cell right now has a robot with a hand with suction cups. As soon as the mould is opened (horizontal movement) the robothand enters into the mould to the machine centerline (horizontal stroke in), the machine blows out the pot into the hand, suctions cups build up vacuum, the hand moves a short stroke to move the pot from the male mould part and than the hand with cup moves out of the opened mould (horizontal stroke out) before teh mould closes again. This whole emptying process takes about 2,2 seconds (this mould open time is added to the total machine cycle time as you will understand)
We have calculated that when the pot is blown out of the mould (downwards), the mould open time can be reduced to about 0.6 sec. So a 1,6 sec gain each machine cycle!
This number is so huge that we cannot ignore it anymore, so therefore we are looking for some active orienting system to quickly reorder the chaos we created when blowing the pot out of the mould quickly.

 

[ornerynorsk]

No, I think an accumulating hopper would be counterproductive. If you imagine 2 parallel rails or rods in which the small end of the pot will naturally fall, preventing the larger rim from falling through. You may need some guides to "funnel" the pot into the rail in the event the drop pattern varies widely when it is blown off the B half of the mold. Is this a hot runner or is there a sprue on the bottom of the pot. Large diameter of the pot is B half, correct?

Also, do you use any mechanical ejection or does compressed air do all of the work?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[jlnsol]

@ornery, yes, it is a hot runner system and there are small mechanical release pins. Addtionally we can switch on blow-off. Plus we plan on adding blow-off nozzles above the mould to accelerate the falling down motion as soon as the pot is released from the mould have. The large diameter of the pot is B half.
I think I understand your rail approach but am a bit worried about efficiëncy. We need 100% uptime, since the machine runs unmanned overnight. Do you have any experiences with the falling pattern variation you mention?
(am worried about the pot entering the rail properly/constantly)...

 

[ornerynorsk]

I do have some experience with press takeaway systems. The only way to ensure 100% reliability is live-run testing. Do you have an electric eye or other sensor to prevent the mold from closing on a hung up part and/or a mold sweep?

The rail idea is only the most simplistic approach. Depending on the amount of automation you wish to incorporate, you can run an orientation program with the robot, as well. Your gains in cycle time as described should justify an adequate budget. IM's live or die by seconds of cycle time.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[jlnsol]

@ornery, thanks. We can install a sensor to prevent the mold from closing on an hung up part.