Food packaging machine problems

Dear brains trust - I know someone here has the answer but I am not sure if forum rules allow me to ask the questions. Moderators please advise.

A disclaimer: My day job is in 'development' in Africa working with small holder farmers trying to turn subsistence agriculture into a business. I am employed by an EU gov on a project working in a variety of regions. EU money often gets spent providing small groups with equipment to process, and thus improve shelf life and saleability, of agricultural products. The equipment is identified in broad terms and purchase done through a variety of local agents with varying effect. You guys actually offered some insight into a very peculiar design of food dryer previously. Needless to say your input facilitated a discussion that will hopefully ensure that design is never replicated . . . I don't get involved in the decision making on these things as I tend to highlight the pitfalls in the ambition of the twenty somethings with little life experience.

Sooo. A variety of food processing machines have also been sourced from China and delivered. No manuals, no training, no backup. Consequently these potentially useful bits of kit are lying idle in various farm groups because no one can sort out the problems associated with setting them up.

For the moderators - I have no commercial interest in these machines or the groups but as someone that fiddles with machinery as a hobby it is frustrating that these things are not earning their keep. The particular machine I'd like to ask questions on should create sealed foil pouches of tomato concentrate akin to crisp packets but on a much smaller scale. I think each pouch is around 12cm by 8cm and contains 100ml of sauce. As the strip passes vertically through the machine it should be crimped under vacuum to seal it leaving a bandolier type strip (where else could I get to use words like bandolier?) with perforations. The strip goes to market at people can then tear off the number of sachets they use.

The crimping/sealing isn't working and local mechanics cannot solve the problem. Consequently the pouches leak and the contents goes off. My gut says either compression pressure or temperature but there are lots of other variables. Mains supply voltage and local gen sets can be inconsistent.

Would it be okay to post some dodgy pics and videos I have been sent to see if the answer is obvious? N.B. They aren't great but I am mindful that the resources on here probably have the answer - but may not be able to share them.

To reiterate I have no commercial interest in these machines or the associated business. Ideally I will retire later this year and focus on improving my dismal skills. I just want to see them used.

Thanks in anticipation.

Andrew

Sounds like a Form, Fill, Seal device (FFS).

Yes temperature, pressure, also sealing time are key variables, and the jaws must be well aligned.

As well as the set up of of the machine, the quality of the packaging laminate used is critical. Needs to be uniform thickness (across the film and along it), and have an appropriate composition for the heat seal layer. Various different polymers or blends thereof might be used for the heat seal layer depending upon the contents. Lamination film is right at the high end of the packaging film market in terms of specification requirements.

Typical issues are lack of fusion at one extreme, 'burning' at the other - both of which will lead to leaks.

Is the issue with the end top/bottom seals or with the longitudinal seal?

Your bags are called DOYBAGS I believe. You could do worse by contacting a food company that uses them asking kindly for their help - they might even put you in touch with one of their retired engineers.

Wishfull thinking

Bob

Thanks David and Bob. I will see if I can get more details re source of packaging.

I'll push my luck now to see if video and photos invite any insights. My album has the photos I was sent earlier and the videos (if they work) demonstrate the poor sealing.

Edited By Andrew Smith 16 on 05/05/2023 12:32:41

Well the (usually PTFE based) jaw cover is missing from one jaw, and looks past its best on the other jaw. Beyond that can't see much.

That observation is interesting David. A local mechanic picks away at that bit of PTFE and flags it as a problem. Would you mind if I PM'd you a link to the videos which might shed more light?

In the interim can any member point me to an idiot proof guide to the set up and use of these machines? I assume the crimping plates heat up and meet at a certain temperature and pressure.

PM me if you wish.

The jaws will most likely be controlled to a specific temperature continuously (pulse heated jaws are sometimes seen). I doubt you'll find any idiots guide for setting up.

My knowledge of these things comes from working on the films, and measuring seal performance in the lab.

You would hope that EU money might source equipment from the EU. Lots of packaging systems are made in Italy for example - probably easier to get hold of instructions.

I have designed and made many "pouch" machines in the past. As well as doing repairs and maintenance on them. As a previous poster has described there are generally two different sealing operations. The plastic film is usually supplied as a single web on a roll. This is first formed into a tube by folding it over a hollow metal former and sealing the overlap, creating a continuous plastic tube. When the tube has been formed and before it leaves the former, the desired contents of the pouch are fed down the hollow former. As the film leaves the former it is first of all gripped by a pair of heated jaws and pulled down off the former. The action of these jaws is to make a seal in the tube and the distance the film is pulled will determine the length of the pouch.The jaws then release and return to the start position ready to pull the next pouch down off the former.

Now, both sealing operations are done using heat. There are a number of parameters to consider such as the temperature of the sealing head, the pressure applied and the time the heat is in contact with the film. The film itself will be extruded using different layers of various types of plastic. that is to say that the seemingly single layer of film will actually be composed of a number of different plastic types extruded and bonded together. The inside layer will be of an easily welded polymer and the outer layer will generally be a barrier film, typically a type of nylon. With probably, other layers as well to give the film strength or other properties.

The sealing heads can be either solid metal with an internal electric heating element. Or it can be a narrow flat band of ni-chrome heating tape heated by resistance to electric current. Sometimes the current is continuous and sometimes it is pulsed. Which ever type is used there will be a temperature control to keep it at the set temperature. This is generally in the region of 130 to 230 degrees C.Each method has advantages and dis-advantages and the type will be determined in the machine.design stage. All sealing heads need to be aligned properly so that contact is continuous and even, all along the contact point. The pressure applied should be equal at all points. The crucial thing is that the heated head MUST NOT come into direct contact with the film or the film will stick to the head and melt and burn. To prevent this a piece of PTFE coated glass fiber cloth (known as teflon in the trade) is placed over the heads. The grade of teflon and its quality will determine its life span.As always quality and cost are related!! When new, teflon looks like a shiny buff coloured ( it can come in other colours) fairly stiff material. If it gets too hot or burnt it will have a distinct line where the heat has been applied. Therefore it has to be monitored in use and changed regularly. If the teflon is damaged or burnt you will not get a seal. If the temperature is too low you will not get a seal. If the temperature is too high the film will stretch or burn through. If the head is damaged or mis-aligned you will have partial seals. If the pressure applied is too low you will have no seal. A perfect seal should be even, flat and have the imprint of the woven glass cloth visible when held up to a bright light.

The local mechanics should be able to maintain one of these machines when they understand how they work. However local supplies of the specialist materials Ni-chrome wire, teflon, silicone pads etcetera may not be available. If not, you will not be able to run the machines.

As ever I am amazed at not only the breadth of experience on here but the preparedness of you all to go the extra mile. The reply from Max Tolerance above is a case in point.

Gotta love this sight even if I do get drawn down too many rabbit holes. Never thought I'd end up reading papers about pendulums in such depth. . . .

Many thanks. Let's see if the local mechanics can sort the machine out.

Andrew

Nice one Max