My fisrt PLC based project ( need help on some stuff ).

[BGAmodz]

Hello every body .

Am currently working on a project with some friends , i just need some opinions .

So the idea is to create a machine that have on top a roll of side-sealed plastic witch will be pulled down by a rotating mechanism , and next sealed and cut .

I have already installed the mechanism that will pull the plastic , and also got a small mechanism from a HP inkjet printer .

Now what am trying to do is use the printer mechanism for cutting and sealing at the same time , any ideas on how to do that ??


Here is two pictures of the parts am using right now ( attached bellow ):

 

[cowboybob]

I suppose the inkjet device can be modified to both seal and cut the plastic.

What you don't have is sufficient equipment to manage the plastic sheet.

For instance, once cut, how would you be able to feed the next plastic section into the sealer/cutter device?

 

[4pyros]

You could use a hot wire on the carriage holder.
If you put the print head assy under your rollers you could hope gravity takes the plastic into and thru the print head.
Static electricity is going to kill you thoe.
The static is going to build up as the sheet is unrolled. You are really going to have a hard time with this.
You really need something in the bag.
So if you can get the plastic sheet thru the print head.
The hot wire on the carriage will cut and seal the plastic sheet at the same time.
Then the cut piece will drop to the floor.

 

[BGAmodz]

I suppose the inkjet device can be modified to both seal and cut the plastic.

What you don't have is sufficient equipment to manage the plastic sheet.

For instance, once cut, how would you be able to feed the next plastic section into the sealer/cutter device?

Hi cowboybob , thanks for the input.
I think this will be achieved with a guidance rails , so when one bag is cut , the pulled plastic should be already on the guidance rail and then moved to be sealed and cut , its all about timing and positioning .

You could use a hot wire on the carriage holder.
If you put the print head assy under your rollers you could hope gravity takes the plastic into and thru the print head.
Static electricity is going to kill you thoe.
The static is going to build up as the sheet is unrolled. You are really going to have a hard time with this.
You really need something in the bag.
So if you can get the plastic sheet thru the print head.
The hot wire on the carriage will cut and seal the plastic sheet at the same time.
Then the cut piece will drop to the floor.

Hi pyros ,

I agree with you this part of the project will be hard to make , and i have said this to the guy who announced the idea , but i don't have a choice now unfortunately .

So the idea i had initially is installing a blade for the cut and a rolling element bearing on the print head .
The roller should carry a heating element enrolled on it ; But before cutting , it must be preheated , but it should move freely(while still hot) with the cutter , this way the print head will do the heating and the cutting at the same time on one move or two moves .

What do you think ?

 

[cowboybob]

... I think this will be achieved with a guidance rails , so when one bag is cut , the pulled plastic should be already on the guidance rail and then moved to be sealed and cut , its all about timing and positioning . ...

If pulling the plastic, how will you do that once it's cut?

And if pushing the plastic, how can that be done such that it doesn't wrinkle and jam?

And, of course, the seal/cut head will, necessarily, have to contact the plastic which, if not restarined in some fashion, will tend to bunch up as the head passes across the plastic.

Or is your plastic much stiffer than that I am envisioning?

Not trying to be negative here, just not seeing how the plastic handling, as you've described, can work.

 

[4pyros]

Hi cowboybob , thanks for the input.
I think this will be achieved with a guidance rails , so when one bag is cut , the pulled plastic should be already on the guidance rail and then moved to be sealed and cut , its all about timing and positioning .


Hi pyros ,

I agree with you this part of the project will be hard to make , and i have said this to the guy who announced the idea , but i don't have a choice now unfortunately .

So the idea i had initially is installing a blade for the cut and a rolling element bearing on the print head .
The roller should carry a heating element enrolled on it ; But before cutting , it must be preheated , but it should move freely(while still hot) with the cutter , this way the print head will do the heating and the cutting at the same time on one move or two moves .

What do you think ?

The molten plastic will stick to your roller and build up. thats why I am suggesting using a hot wire like a knife. Any plastic build up should fall off.

 

[BGAmodz]

The molten plastic will stick to your roller and build up. thats why I am suggesting using a hot wire like a knife. Any plastic build up should fall off.

Ok i guess my method is not good , will try to get the sealing and cutting system from a home tool .

 

[4pyros]

They are all hot surfaces that need a lot of presser to hold them together tightly to work.
Still think you would be better off with a hot wire knife.
Look here to get an idea of how easy it is;

 

[BGAmodz]

They are all hot surfaces that need a lot of presser to hold them together tightly to work.
Still think you would be better off with a hot wire knife.
Look here to get an idea of how easy it is;

I see , this hot wire knife method seems the easiest thing to use ; So how do i avoid bad cuts with this ? i mean the plastic should be heated enough to be sealed and cut on the same time .
also what type of wire i should use , operating temperatures , current requirements ??

 

[4pyros]

Ideally you would hold the plastic web flat between two sets of pinch rollers and run the knife between them.
You would want the pinch roller sets (one on top and one on the bottom) as close together as you can get them and still be able to move the wire between them.
As for the wire you will have to play with that.
You can use guitar strings, stainless fishing leader or nichrome wire from a hair dryer.
So of the factors are;
The materal you are cutting.
Available power source, most people use a car battery charger.
The speed you are cutting at.
And the wire used.

Get your self a battery charger and a pack of guitar strings.
use about 4 inches and start trying to cut plastic.
You may have to play with some of the variables to get a good cut and seal.
Start off slow and see how fast you can go.

 

[BGAmodz]

Ideally you would hold the plastic web flat between two sets of pinch rollers and run the knife between them.
You would want the pinch roller sets (one on top and one on the bottom) as close together as you can get them and still be able to move the wire between them.
As for the wire you will have to play with that.
You can use guitar strings, stainless fishing leader or nichrome wire from a hair dryer.
So of the factors are;
The materal you are cutting.
Available power source, most people use a car battery charger.
The speed you are cutting at.
And the wire used.

Get your self a battery charger and a pack of guitar strings.
use about 4 inches and start trying to cut plastic.
You may have to play with some of the variables to get a good cut and seal.
Start off slow and see how fast you can go.

Thanks for the infos , i will try to get the wire and start cutting and see how things will go on .

 

[KeepItSimpleStupid]

So, you don't need a tension controller too? Without a tension controller, you may find problems when the roll is full vs near empty.

I tried to build one once, but we didn't need it and I could not do the lever arm thing. Brakes have residual magnetism and if you need low tensions, you have to be able to reverse the current "slightly".

 

[BGAmodz]

So, you don't need a tension controller too? Without a tension controller, you may find problems when the roll is full vs near empty.

I tried to build one once, but we didn't need it and I could not do the lever arm thing. Brakes have residual magnetism and if you need low tensions, you have to be able to reverse the current "slightly".

Hi KIS , at the moment am trying to figure out how to perform a stable cutting and sealing with the hot wire method ,i will figure out some solutions for problems that will get on the way later with some help here of course .

 

[KeepItSimpleStupid]

OK. The way I approach problems was once, "sort of", written up in Intech, The International Society of Automation's monthly magazine by the editor as being the "best way". I didn't contribute, but it was pretty close to what I do. The problem is, that "management" in general didn't/doesn't like it when you put everything you can, no matter how silly it is on the table to start.

It just allows you to anticipate as much as you can. I did programming the same way.

 

[BGAmodz]

Hi again dear members .

I have a few things to say about the cutting sealing mechanisms .

So since the machine is positioned vertically , i thought about moving the NICHROM wire horizontally through the pulled down plastic , for that i had the idea of using a roller rails based mechanism on the sides of the machine.

So what do you think about this , would i have a precise operation ?

Here is a picture ,

 

[4pyros]

Are you trying to cut the hole sheet at once?

 

[BGAmodz]

Are you trying to cut the hole sheet at once?

Sorry i don't understand your question , there is no hole sheet .

Each side of the wire is attached to a rolling mechanism , this Nichrome wire will be perpendicular to the plastic , and all the wire length will pass through it with the help of the rollers .

 

[4pyros]

Sorry I misunderstood your drawing and thought you were going to have the heat wire parallel with the plastic sheet and try and cut thru the hole width at once.
So you are going to use the rolling mechanism to replace the printhead assy.
You may need to adjust the speed of the cut, so plan on some adjustability.