Introduction: How to Make a Heat Sealer

Picture of How to Make a Heat Sealer

Well, finally, as promised, here's my how-to.

Q. What's a heat sealer?

A. Also known as an impulse sealer, a heat sealer uses a resistive heating element to seal and/or cut thin plastic bags or sheets. Rather than using continous heat, which would turn the bag into a gooey-edged mess, it uses a timed impulse of heat - hence "impulse" sealer.

This instructable reveals to you many secrets that certain people do not want you to know! I have already received several death threats from one of the major recloseable bag companies. Please enjoy this instructable, which might be my last....

Step 1: Why Would I Want a HEAT SEALER, Anyway?

Picture of Why Would I Want a HEAT SEALER, Anyway?

Using a proper heat sealer, you can do a much more than making toothpaste packets!

Click on the pics below to find your reason. If you do not see it, then perhaps playing with Dremel tools and electricity is reason enough.

And dare I say, you can even store your beads with it?!

Step 2: So HOW Do You MAKE THIS THING?

Picture of So HOW Do You MAKE THIS THING?

The parts:
Some of the things you will need are:

Structual Pieces:
1. Some plexiglass or wood, approx 1/4" thick and about a foot in length. I always have some plexiglass around, so that's what I used, but hardwood would probably be better.
2. Four nails
3. A Dremel tool or router, and preferably a routing table.
4. Routing bit and side-cutting bit (or perhaps a thick cutting disk would suffice).
5. A drill and drill bit the same size as your nails
6. Coarse sandpaper
7. For plexiglass: some acetone and a dropper bottle, or some epoxy.
For wood: wood glue? I dunno much about wood-working.

Electrical Part:
There are literally an infinite number of ways to skin this cat. I can't describe them all, so I'll tell you exactly how I made it, using a laptop power supply, 19.5V and 3.16 amps.

If you have the power supply and the tools/supplies to make the structural parts, and you can solder smd parts and read a schematic, I can provide you with the exact circuit components I used. The kit would include all of the following items.

1. Nichrome wire (this comes in a plethora of specs and sizes. After much experimentation and for several reasons, I have settled on Kanthal A1, 27 gauge.) 2 yards of it. More than enough for a couple of screwups.
2. A power mosfet that can handle 9amps!
3. A PIC microcontroller, custom programmed to provide the pulse and to be user-programmable on the fly so that it can be instantly adjusted for a myriad of wire length, power supply, and bag thickness combinations, using only a single button!
4. A bicolor LED, red/green.
5. A 78L05 voltage regulator to power the PIC
6. A couple of caps and a few resistors
7. Some SIP headers, male and female
8. Some protoboard
9. 30AWG kynar wire, about 3 feet.

Step 3: The Science

Picture of The Science

So, what's going on here? Well, ohm's law is a good place to start. I began by taking a look at my available power source... a 19.5v, 3.16A powerbrick for a laptop. My particular nichrome wire has a resistance of 4.4 ohms per foot. So in making a 12" heat sealer, I use just over a foot length of nichrome wire.

19.5V/4.4 ohms is... 4.4 amps! This draws too much current! Well, yes, and no. The rating on a laptop psu is the constant current rating. A peak rating is typically 2-3 times as high. Because the pulse is going to last under 1 second, it's all good. So let's get started.

Click on each pic below and read the highlighted captions.



Step 4: Ok, Now What?

Picture of Ok, Now What?

Ok, so take the blade and sand the cutting edge flat as you can. Use coarse sandpaper. Take your time. This part is important.

Then you can make the base. Basically, I just used some scrap pieces of plexiglass and bonded them to the four corners of the base. The ones at the base are the hinge. The pair up front are guides, to keep the blade squared up.

Also, notice I put all the electronics right onto the blade. The base is just a base. This way, I can take the blade out and use it alone. This allows partial cuts, by using just the tip, or you can combine two cuts for a larger bag.

You might think "why not just leave off the guide rails." Don't do that. The guide rails are necessary, and I can't bother to explain why, at this time.

Step 5: Now Make the Circuit

Picture of Now Make the Circuit

Here's the schemmy. If you want to really DIY, you can forego the PIC and power it with a 555 timer and potentiometer setup.



Step 6: Ok, Now String Up the Wire

So you put a single nail in the front. Wrap one end of the wire around this nail and then twist it a few times. Then put the nail in. Then, holding the other end in a crescent wrench, or wrapped around a stick a few times, pull it taught across the edge of the blade and then wrap it around the other two nails in a figure eight. Make sure you don't pull towards your eye, in case the wire breaks while you are doing this!

There are two reasons I prefer 27AWG for this (whereas 26AWg or larger is typical). 1. It heats up very fast, even with a laptop supply. 2. It cools down very fast. 3. It is easier to get decent tension on the wire even using this crude method. Tension is important, because the wire stretches when heated. If there's not enough tension, the wire will "walk" during the impulse. 4. It's big enough to do the job. Mine will seal 4 mil bags. I use 2 mil for everything in the pics.

Step 7: Now Set Up the PIC for Use

Picture of Now Set Up the PIC for Use

Click the video link to see a demo. For my particular setup, it takes about a half second impulse for get a good seal on up to 4 mil bags.
http://s18.photobucket.com/albums/b103/klee27x/?action=view&current=bfd9110a.pbr

Now here's a video of it in action. Mind you, in this vid, I am still experimenting with 26AWG KA1, so the impulse is much, much longer than it is, now, and it doesn't work quite as good.
http://s18.photobucket.com/albums/b103/klee27x/?action=view&current=83ed7b18.pbr

Step 8: Now for Some Tips and Tricks

Picture of Now for Some Tips and Tricks

The best bags for heatsealing are polyethylene or polypropylene bags. The more they stretch when pulled, the better. The bags can make a big difference in how strong a seal you get. The bags I use are polyethylene, 2 mil thick, 9x12" bags made by Uline. They work alot better than a seemingly similar polyethylene bag I was using before!

Here is a pic of 4 different ways to use your heat sealer.

But how good can these seals hold? See on.

Step 9: Water Tight Resealable Closure With PACKING TAPE? Are You Serious?!?!

Picture of Water Tight Resealable Closure With PACKING TAPE? Are You Serious?!?!

Here's how to make a recloseable seal that is OJ-tight. Click on the pics below to see the step-by-step.

Step 10: I Want One!

Picture of I Want One!

Well, the longest part by a long shot was to obtain the wire and to program the pic. The rest was relative child's play. I always buy in bulk, because I never know what I might want to make next, but in this case, I have way more nichrome and mosfets than I'll ever know what to do with. The minimum order from the specialty shop I found for wire was 2000 feet! So I have the parts to make several of the control circuits for this project, and will be putting together some kits for my fellow enthusiasts.

I'll be giving away kits on my favorite electronics forum, http://dutchforce.com/. Check the Trade Forum under the "Want its," section. They should be avail in the next few days. If there's any demand, I might try selling some on ebay!

Comments

Brandonoutdoors (author)2016-10-26

I need a device similar to this one but hand-held for welding long runs of 8 mil pond liners. Industrial welder a are very expensive so I need a DIY solution

Brandonoutdoors (author)2016-10-26

Could this be made to weld 8mil poly

razordu30 (author)2016-09-28

If anyone is trying to find wire in smaller bulk, I'd suggest vaping supplies. Nichrome wire is usually pretty cheap there, and in many different sizes and lengths.

amiir (author)2016-07-12

acetone is not good for welding plaxiglass! you should use Chloroform (CHCI3) its the only liquid that could weld plaxiglass in best way!

JessicaC151 (author)2016-04-22

I would like to make one these but it would be in a design. I am about to try to look into how to attach the wires. I know a few people in electronics and i am going to show the to them to help explain. I do not know if my idea is possible but i will find out. Thanks for this information. You broke it down very well.

asdfa2 (author)2015-10-13

If you have a kitchen food vacuum sealer try using that first, it has a heating element built in for sealing the bags after the air is vacuumed out

Mikechristeson (author)2015-06-28

I want to make a 36" weld on 6 mil Visqueen and it needs to be 5 mil or greater. Can your impulse sealer be adapted for this?

bgroicahn (author)2009-12-29

 An incandescent light dimmer though a GFI breaker would be just a useable and a lot easier to make.

klee27x (author)bgroicahn2009-12-29

That would miss the point. This isn't a foam cutter. The PIC doesn't do PWM power control. It is just a fancy way to provide a user-adjustable full-power timed pulse with a single button. (Actually 2 timers... there's an adjustable delay BEFORE the pulse starts, too, in case you want it. For instance, you might want a half second or so to readjust your hands after pushing the button, if you're sealing a bag in a way that you can't use one hand.)

You have to melt the plastic. The idea is to get the wire up to temp AS FAST AS POSSIBLE, then immediately cut power. So you could use an on/off switch, if you have good timing. But a light dimmer would do nothing to help for a heat sealer. Sure, you could set the power to the point where it would only just be able to reach the melting temp of the bag, but then it'd just take LONGER to actually reach that temp, and you'd still have to turn it off and wait for it to cool down before opening the heat sealer.

neffk (author)klee27x2015-05-04

Thanks, klee27x. That's all I needed---full power on for a certain time. Could not find that anywhere. Theory of operation should be covered in the intro, especially for something so simple.

bhushan1572 (author)klee27x2011-10-04

Dear klee27x,
please let me know if the current to be passed through is AC or DC.

I have tried for both AC and DC in one of my designs where i have a grid system to pass the current through. Please answer my few quries :

10 Ni wires in series total resistance 25 Ohms with : (each piece : width 1mm, 18inch long, 2.5 Ohms )
1. Do we have information regarding plastic bag thickness and temperature needed to seal it and corresponding current required?

2. I am able to seal it with naked wire but when put behind a teflon tape(standard one used in impulse sealers), then it does not seal at all. to solve this problem, should I pass more current or should I heat it for longer duration.

I have a very simple circuit designed for the pulse.
I am not using any transformer as AC supply is 240 V, current being passed is around 10 Amp for this 25 Ohm series strip. if any one is interested.. i will post the full design details.

Francisco.G (author)bhushan15722012-04-24

Hi bhushan1572, I´m interested in see the details of you circuit for the pulse, seem quite more simple. I´ll would be very grateful. I´m making an automatic bag sealer and once if finish it i will post my instructable. My e-mail is francisco.g.h@live.com.mx

bhushan1572 (author)Francisco.G2012-04-24

Hello, thanks for your interest. I have actually completed and successfully implemented the circuit.
As mentioned earlier, I took 10 Ni wires of 2.5ohms/18inch in a grid based structure. We have 230 V AC supply at home. I prepared a timer - RC circuit through a relay where in i used a switch.
Once the switch is turned ON, the capacitor starts charging, within 3 seconds the capacitor is charged and the relay is cut-off (reverse action through a NOT gate to a transistor).
So actually I am passing around 9.2 A AC current through the NI grid for 3 secs. This heats up suffieciently to seal up the bags.
The said design as attached is used for packaging 25 bags in 6 seconds.
This is faster than an automated machine.
Please find attached images for the actual design

klee27x (author)bhushan15722014-01-20

That's awesome. But I wouldn't call that my circuit at all. This looks to be 100% bhushan! I'm glad you found my instructable helpful.

hi bhushan,
I came across this instructable when trying to concept some thing you seem to have done. I'm actually trying to build a batch packing machine. I think ill use your plans. Just a couple of things though. How have you been using this and any problems yet?

klee27x (author)satwikUnderhill2014-01-20

I'm still using it. I had to rebuild it after a couple years, though. The wire had melted into the plastic enough to cause trouble. When I refurbished it, I put teflon tape UNDER where the wire sits. (On commercial sealers, the tape goes over the wire; mine is not powerful enough for that). My GF and her roommate also have been using a copy of the improved version for almost 3 years, now.

Note, my plans include a schematic using a PIC microcontroller. Without the firmware, it will not actually do anything. You might prefer to use a "monostable 555" circuit. Try google.

The hardest part is finding the exact right wire to work for your power supply and length of sealer.

I believe most commercial sealers use an SSR to trip mains current. So they can use thicker heating elements for a stronger seal. If you are need something robust, you might consider going that route. It's not much different, except you should be more careful if you are unfamiliar with working with mains AC.

klee27x (author)bhushan15722011-10-10

1. No.
2. Dunno what your timing circuit is, but it shouldn't be too hard to increase the pulse to see what happens? Or just trip it twice, quickly?

Be careful!

klee27x (author)klee27x2009-12-29

Well, to be fair, a light dimmer would be useful if you were running a very low resistance filament from AC power, and you had to reduce the current draw (to prevent overloading your outlet and/or circuit breaker). But timing the pulse would still need to be done with a separate method.

brian.david.73 (author)2015-03-27

Save yourself the time and expense of build your own heat sealer and visit: sorbentsystems.com. They carry a wide range of cost effective impulse sealers that all come with a 1 year warranty.

When ordering, reference PromoCode: BDK32715 to receive a 10% discount.

You can find nichrome wire in toasters and electric fires or can be salvaged from electric blankets. Take the wire out from the wife's side of the blanket and keep stum :)

Frankcw (author)2014-08-26

I realize this has been up a while but I've wanted to make one of these. I have finally found a schematic for the part of the circuit that would replace the custon PIC With a 555 chip and potentiometer. It took lots of searching, reading and learning.

It is step 3 in this instructible:

https://www.instructables.com/id/555-Timer/step3/55...

In the last paragraph he tells how to make it into a variable timer. I needed a variable timer because I plan on using various thickness plastics. He gives an excellent explanation of how the circuit works as well. When I build mine I will do an instructable including the final circuit diagram.

Frank

kemperburt (author)2014-07-09

I would like to know if you are still making these. My electrical expertise needs much improvement to say the least. can you direct me to the forum link you describe above thanks. Or your forum name so that I can find you.

Thanks

denewf (author)2013-11-30

I've read all the posts and comments on this instructable hoping to find if it could be made substantially wider. I have a requirement for a 4' (yep, 4 foot) sealer and not a clue as to how to go about it. A kit of some kind would be a blessing. If you are still responding to this instructable after 3 years any suggestions and/or sourcing info would be most appreciated. Thank you.

boing101 (author)denewf2014-04-05

It occurred to me your problem is not a problem, but a case for lateral
thinking!

Have a look-see at my solution for a multi-length sealer.

http://plusoneproducts.co.uk/imagesof/circuit_for_multi_length_heat_sealer.pdf

I was faced with a problem of requiring different lengths and not wanting
to buy a long 16 inch sealer to be sealing 2 inches most of the time.

The setup might seem labour intensive, but how hard is it to twist a knob
and press the same button four times.

This setup uses one length of wire, each section will burn for the same
amount of time using the same amount of power, rather than the obvious route of
four wires of different gauges with four different timer settings etc.

The two indicator LEDs are for ‘Element On’ and ‘Cooling’. Not shown is an
electromagnet circuit. The lock-down is released when the cooling period is
finished.

I could have used a PIC that had some more I/O pins, an AD pin for a
potentiometer, memory for modes, and a transistor and relay for each of the
sections, thereby getting rid of the need for a double-pole rotary switch and
adding in a bit of flexibility to suit the particular plastic thickness and
type, next time!

klee27x (author)denewf2014-01-20

I'm sorry, I am not much help, here. Sourcing the heating element is the hard part. Try googling "nichrome wire" or "resistance wire." Any steel wire actually has resistance, so you might find something around the house that might work. AT 4' you probably want to use mains current and an SCR. Please be careful when working with mains.

Larzag (author)2012-08-31

how deep is the grove for the wire?
thks,
lz

klee27x (author)Larzag2014-01-20

There is no groove for the wire. The groove is only to hide the power wires. The heating element is stretched over flat plexi (with Teflon tape underneath to prevent it from melting).

mzminty (author)2013-02-15

hi any ideas on making a continous heat sealer to seal drinking straws in bulk.like a machine type which does not really involve manual labour

c-face (author)2012-08-12

Sweet! I was thinking about making one of these. I was wondering have you thought about using an industrial timer for this?

JanxAngel (author)2008-10-22

I've seen ribbon versions of the nichrome wire, which is better? I have yet to see 27ga but I have seen close to that, how hard is it for the electronic assembly n00b to substitute?

klee27x (author)JanxAngel2008-10-22

The ribbon is usually better for heavy duty sealing. The ribbon is typically laid out so it presses flat against the bag, producing a very wide seal. But you probably need a high amperage power power supply for that. It all depends on how much the resistance of the wire is, and also how much heat it would take to raise the temperature (thicker wire means more time or energy to heat up). So in other words, if you go just a little bit thicker, and you end up needing A LOT more power.

laurent coeuret (author)klee27x2012-06-11

Nice work, really looks like a pro one...
Just a thing, wire is usually used to cut the plastic bag meanwhile the ribbon is used to seal, the power needed depends of the ribbon width up to 9mm, the same with the wire gauge. Ribbon and wire are not used with the same kind of machine, your looks likes more at a thermo forming sealer means you make a bag around the product and you schrink your polietilenol with a hot air pistol to let him stick on your product, working with a wire( because of the low level between the work base and the sealer), meanwhile a sealing bag machine is higher, bags are generally full of product...)
If I can make a suggestion, if one day you look inside a professionnal sealer you will see very few components: a 110/24V transfo( for a 8'' sealer normally 200W), a 555 based monostable with a relay, a end of course switch (who is triggering the 555) and that's it. the simpliest the best. one thing more the pro model always got the hot stuff on the lowest jaws, helps you to have a better continuity on your sealing especially when you have more than 18'' to sew
Got some timer plan if interested, can send you a PDF
once again really a good job, sorry for the english but it's not my native language
Laurent

urbanwoodswalker (author)2012-02-16

I am wondering if I can heat seal an irregular line with something that will NOT gunk up the plastic mess. (Not a straight line).

I am enjoying your humor on this instructable ...

klee27x (author)urbanwoodswalker2012-06-11

Hmm. Not sure how you'd do that with a nichrome wire. They expand when heated. That would be tricky, for sure. You might need a thicker, formed piece of stainless steel for a heating element. But then you'd need a lot more power and it wouldn't cool off as fast. Yes, that would be tricky.

celiagp (author)2012-06-06

Wow I definitely have to try this. Do you think I'll be able to use it to seal polyethylene tubes like the ones used for lotions and such?
Thank you for sharing.

Francisco.G (author)2012-04-22

Hi, this intructable is awesome. I´m doing an automatic bag sealer as a project to collage, I have all the automatic mechanics done but I really having trouble with the actually sealer part. I already have all the components to make this instructable but I wanted to know what PIC and program environment do you use and if there is a chance you share you program?? My e-mail is francisco.g.h@live.com.mx I´m new at instructables and I´m enthusiastic about share my first instructable that will be this automatic bag sealer. Thanks a lot.

VadimS (author)2012-01-25

I'm thinking of building this, but using 12v and thin copper wire. I'll probably use a relay instead of a mosfet, they can handle much higher peek currents.

You can get 6 mil Polyethylene rolls for use in construction (vapor barrier). 16"X375' for about $32. Enough for a lifetime supply of bags :P
It's really good quality (I use larger rolls when insulating), should be perfect

Peraloca (author)2011-11-21

The Photobucket pictures are in a private album and can't be seen. Also, the link to the video, is missing. Can you help with that please? Thank you.

Peraloca (author)Peraloca2011-11-21

Ok, I will answer my own request. I already found your comment about this in another section of this page. Thank you anyway.

useful1 (author)2010-09-11

I made a 555 astable circuit using stainless steel wire as the wire sealer, with the claim on this instructable, saying you can make a heat sealer using a 555.

It's currently connected to a 12V power source. It doesn't work. The wire doesnt get hot enough to melt plastic. I believe that 200mA, which is the amperage, of a 555, does not make the stainless steel wire to get hot enough.

Perhaps, it is the wire im using. But as far as making a 555 heat sealer, I believe that myth is busted. Unless someone points to me a webpage which tells me how to make one correctly.

shinobitron (author)useful12011-08-08

using the 555 as a straightforward output source probably won't be enough power, what would be more effective, would be to route the output pin of the 555 to a transistor or mosfet. In this instance the 555 would only function as an adjustable signal generator (think pulse frequency modulator using a potentiometer) that triggers the mosfet which would be able to draw more power to your heating element/wire. you could either use separate power sources, or the same power source/battery, as long as the 555 signal generator part of the circuit was protected with a voltage limiter. the advantage of this over simply making an oscillator or astable multivibrator with only two transistors, is that you can control the frequency of the pulses easily and accurately with the 555.
hope that helps.

msw100 (author)useful12010-11-11

I think the author said nichrome wire was used not stainless steel,nichrome wire can be found in electric fire heating elements

klee27x (author)msw1002011-05-06

"Nichrome" is a trademark, I believe. But it's a commonly used term, sorta like calling any tissue a Kleenex. The wire I'm using isn't actually nichrome, FTR.

Stainless steel wire is generally pretty good for this kind of thing.

msw100 (author)klee27x2011-07-16

its resistance is different from stainless steel,whats so hard to ubderstand about that?

klee27x (author)useful12010-09-13

Hi. The 555 IC is suitable only to make the control circuit. To deliver the power, you just use the 555 output to control a power device such as a power relay or a power transistor.

Also, you must carefully choose the wire gauge, length, resistance, and power supply to work together. Using 12V, you would probably need at least 6+ amps and a suitable matched wire to make a decent sealer impulse. This is much more than 200mA!

ykikeg (author)2010-05-26

Hello
Is it possible to use an ac transformer 110 to 19v ac, or i can only use dc?

shinobitron (author)ykikeg2011-08-08

Like David said, technically you could rectify the ac first using a full wave (or even if desperate half wave) rectifier (diode bridge basically ,easy to find on google) and could then change the desired frequency of the DC by using a pulsed capacitor system on your output. You may ask, "frequency of DC??? but pulsed dc is fairly common depending on your rectification method. Anyway once you rectify the dc, you can control the power and speed of your pulses by using capacitors of varying sizes to determine charge/ discharge times. Variable capacitors are also an option. Additionally you would not necessarily need a separate DC source, as a voltage limiter such as LM78M05 could be used on the input of an IC to prevent any damage. However ykikeg's question i believe is if you can step AC voltage up and down, to which the answer is yes.
Step up and step down transformers do this all the time. using thicker/thinner wire, and varying combinations of turns on your primary and secondary windings of your transformer, you could change 110 vac to 19vac. hope that helps all.

DavidRobertson (author)ykikeg2010-07-06

You could just use a bridge-rectifier to convert it into DC. You would need to use a smoothing capacitor on the output of the bridge rectifier and then probably also regulate it using a simple voltage regulator IC.

klee27x (author)ykikeg2010-05-26

Well, if you want to control AC current, you can't use simple transistors. You would need to use TRIACS, relays, or SCRs. Also, you'd still need a separate source of DC to supply the uController or timer IC. Or you'd need to be much smarter than I am with electronics and design a timing circuit to run off AC.

jwu6 (author)2010-11-12

The video link is dead :(

Do you think you would be able to re-upload it?

Thanks in advance!

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