Promax Imaging Ltd

Vacuum Filling – Does it help us?

Basically YES.  Now that’s grabbed your attention, let’s take a look at vacuum filling and it’s place in our industry.  No matter whether you are a retail shop or a volume remanufacturer you have either heard of, or experienced vacuum filling first hand.

There are many people remanufacturing inkjet cartridges who swear that you cannot successfully remanufacture any inkjet cartridge with a sponge if it is not filled under vacuum.  Conversely there are an equal number who claim that it is not required to refill under vacuum, and that a syringe and needle suffices.

Well, I fall into the first category.  In my mind there is no doubt whatsoever.

Vacuum filling is absolutely paramount to the process of remanufacturing an inkjet cartridge.  Years of experience lead me to this point of view.  You might even call my opinions on vacuum filling an obsession.  Well maybe, but it’s not, it is an absolute conviction.  But let me tell you why.

Back in the mid nineties I invested in the state of the art desktop publishing system.  Part of the system was a Canon LBP-II laser printer.  By now you may have guessed, I played with this new toy until the cartridge ran out.  Very quickly too, even then a starter cartridge only was bundled with a new printer.  Before you ask, I still have it, and I regard the SX printer as one of the best ever made.

The cost of a new replacement SX cartridge was £115.99 plus VAT, a staggering total of £136.29.  Bet you would like to get that for one now.

Having a yield of 3000 pages @ 5% density, (which did not mean much then, but that’s what Canon & HP claimed.) meant that an A4 page cost me 4.6p every time I pressed the print button.  A lot of money back then, about 12p now.  Add to that the stress factor at the rate of about one cigarette per page, and the cost mounted considerably.

I monitored this costing over the next two cartridges.  I could never get more than 2100 copies out of my cartridges.  I also learnt what the 5% density meant, and I can tell you by my calculations my pages averaged 4.6% density.  I am very, very good at maths.

So from there it did not take me very long to feel that these cartridges could be refilled with toner, just like a photocopier.  So I spoke with my photocopier engineer.  Fortunately, he was an independent, or at least he was out of office hours.  He tested the residual toner in one of the cartridges and identified it for me.

From thereon in I never bought another OEM cartridge. I refilled them.  I very quickly learnt that refilling alone was not enough. When my prints started to go black, I found out that it was necessary to clean out the debris chamber of spent toner.  At that point I was truly remanufacturing my own cartridges.

This has nothing to do with inkjets or vacuum filling does it, well bear with me, there is a point here.

Sitting in the pub a few days later, I was having a pint with my accountant. Robbie is not only my accountant, but has been a close friend for over thirty years now.  He told me that his practice had got an HP-II laser a few days previously, and had blanched when they had to buy a new toner cartridge the very next day.

So, never looking a gift-horse in the mouth, I told him I could do him a new remanufactured cartridge for £60.00 plus VAT   I also said I wanted his empties and that was part of the price.  Well he went for it.  He had one to start with, and when he tried it, he was hooked.

From there on in he was buying three cartridges a week.  What’s more, he put a couple of other accountants on to me, and within two weeks of having his first cartridge from me, I was selling ten SX cartridges a week.  With a margin of £50.00 each….well you do the maths.

I had become a remanufacturer.

After three or fours months I gained a major client taking twenty cartridges a week.  Great, however there was a draw back.  They had some Thinkjet printers, and some pre DJ 500 printers.  The deal was I had to supply remanufactured cartridges for those too.  HELP!

I tracked down ink, and the inevitable syringes and needles.  Then I set to refilling my first inkjet cartridges.  Like most of us in the fledgling industry then, I had no test printer, who needed one.  The cartridge had been refilled.

In hindsight, I had a very lucky escape.  My customer was local, so I collected their empties every three or four days.  I always refilled them on the same day as I collected them.  It all worked well apart from a couple of failures.  They accepted that, they got credit for those, and it did not happen often.

In fact they were so pleased that they recommended me to another logistics company locally.  That’s when it hit the fan.

They had the then new HP colour DJ 500C.  This was 51625a with the black base plate.  Yep, not clear as it is now.  This became new territory overnight and a nightmare too.

My efforts to refill these rated at about 50%.  Not good.  Bear in mind that as they had a black base, there was no way I could see if the ink had got to the head.
To ease my problems here I came across a remanufacturing company that no longer exists.  I purchased some cartridges from them.  Despite their claims of quality, their cartridges were even worse than mine, by a long way.  At this point I bought a printer so I could test my produce.  A good move, my customers then got 100% good product.  I got a box full of rejects that I could just not get working to a standard I could give my customers.  Guess what, the 49a did not improve the situation.

Then along came the 41a, closely followed by the 23a.  Things got worse with a vengeance, and the failure box became skip size.

By this time my research into inkjet cartridges was well under way.  Air was the problem, the enemy of the remanufacturer.  I had established that unless a solid link of ink was achieved between the sponge and the head, then print would not happen.  Or,at best it would be intermittent.  Also, some colours presented more problems than others.  Consistency was the problem, surely that was obvious.

With my background, I knew the answer.  To eliminate inconsistency use a machine.  So I spent many hours searching for suitable machinery to refill my cartridges.

I was amazed by the number of machines on offer, from well known names today to obscure and often bizarre offerings.  Frankly, if any of these machines were offered today along with the claims of success being made then, lawsuits would follow.   But hey, these were still pioneering days in our industry.  Hindsight is 20/20 vision after all.

More research followed and eventually I made the acquaintance of a guy called Steve Johnson.  He ran a company called R-JetTek in the States.  We had a long discussion lasting almost three hours.  Inkjets were something he was passionate about, and it became clear that he could think outside the box.  Some of his ideas initially sounded a bit wacky, but I could see where he was coming from.  Then he told me about his ideas for refilling under vacuum, which led to us discussing Boyles Law of Gases at length, also Henry’s Law and Raoult's Law in respect of the effects on ink.

This conversation was the first of many and developed into a long friendship lasting until the day he sadly died prematurely aged 39 earlier this year.  His passing is a tragic loss to our industry.  Steve was a truly great innovator when it came to inkjets.  He introduced us to the first cartridge transport clips and the first vacuum filling machine that inkjet remanufacturing had ever seen.

Shortly after our first conversation he told me that his prototypes worked well and that he had started building the machines.  I ordered one based purely on his word, I trusted this guy.

Shortly after Promax Imaging became the proud owner of the first vacuum filling machine made.  It was a revolution.  It worked, and worked superbly.

We were producing the most reliable cartridges there were to be had.  Word spread like wildfire, and pretty soon we could not keep up with demand.

At that point it dawned on me that if Promax did not tie up a distributorship deal with R-JetTek then someone else would.  I was convinced that when it became common knowledge how we were achieving such a high quality product, others would want this wonderful machine as well.  Better I sold it rather than a competitor.

To this date we have sold 47 of these machines in the UK alone, and they are still current product today.

Like the cartridge transport clip, once the value of the process became apparent, the vacuum filling machine Steve invented was copied by everybody around the world.  It is the most common type of inkjet filling machine there is now.

But what brought about the success of this machine and the process of vacuum filling?

Essentially because it works, so let’s look at the process.  It is the same principle for all vacuum filling machines.  Sadly a lot of the people making them don’t know what they are doing, or even remotely understand the process they are building the machine for.  In my experience only about 20% of the machines available in the marketplace are constructed along sound principles, and will work effectively.  Please do not ask me to tell which is which, not even privately, because I WILL NOT.

Boyle’s Law of gas is the most important part of the process.

Simply expressed, it states that a gas will expand to fill the available space.  This means that when you suck some away, the remainder expands to fill the gap left.

We all know that if you fill a 49a with a syringe and needle you can see the huge air bubbles in the passage in the clear base.  If you had sucked half the air out first, the bubbles would still be the same size.  That is until you bring the cartridge back to normal pressure.  When you do this you can see the bubbles shrink to half that size.

Easy, the more air you take out the better.  OK, in essence that is true…BUT.

It does not work like that.  It is not even that simple.  There are many other factors that contribute to being successful, several of which I am unwilling to disclose. This is not a good practice design lesson.

But eliminating as much of the air as possible creates a link of ink between the sponge and printhead.  That together with gravity will eliminate air from the pre-firing chamber.  That is essential to the reliability of the cartridge, and is what vacuum filling should do.
Remember I mentioned Henry’s Law and Raoult's Law.  These laws relate to properties of liquids, especially gasses within them.  Those divers amongst us know Henry’s Law only too well.  Those divers who didn’t are dead. 

Henry’s Law states that when atmospheric pressure is reduced, the liquid progressively loses its ability to retain the gasses dissolved in it, and they are expelled from the liquid relative to the loss of pressure.  So if you use too much vacuum you give the ink the bends.  Oh by the way, this effect is not immediate, it continues long after the pressure has been restored to normal. It continues for several days in fact. This means that after filling, the air bubbles inside the cartridge continue to grow in size.  You have just ensured that the air you wished to eliminate will be present, no if’s, no but’s, air will be there for sure.

So what is the optimum vacuum level?  Well that’s relative, Raoult's Law now comes into play.

What I will say is this.  Most of us have seen adverts for filling machines that claim they have the best and highest vacuum in the market at 28” Hg.  Total hogwash, machines we manufacture are capable of attaining 29.7” Hg, but they are regulated well below that.  Anyway, do not touch those machines with a barge pole, 28” Hg is way into the red zone.  Your ink will not just get the bends, IT WILL BOIL TOO.

Now for Raoult's Law.  Not too different from Henry’s Law, but in simple terms it focuses on compounds dissolved in the liquid, such as solvents and dyes, and their ability to release gas or sublimate when exposed to pressure reduction.  Also, as this is another form of the bends, this effect when induced lasts for days too.  Add this to the above and you have a double disaster.

As I said, this is relative.  First there has to be a vacuum trigger level before these phenomena raise their ugly heads. That’s fortunate for us.  But there are trigger levels and trigger levels.  At this stage the ink chemists amongst us might start to pay attention.

Because of the different types of dyes, solvents and additive compounds that can be used in thermal inkjet inks and pigment dispersions, all inks have different vacuum pressure points.  That is the level of vacuum at which Raoult's Law starts to take effect.  Other variables come into play here like the quantity levels of those compounds used in manufacturing the ink.  Higher concentrations of propanol, diethelyne and triethelyne glycol will lower the vacuum pressure point of the ink.  I have only named three compounds; there are dozens that are used to formulate ink.

Again, I cannot identify whose ink is best or whose is worst.  Yes, I know which they are, but this knowledge is either a trade secret or a matter of confidence, and even within my own company I have to maintain a “Chinese wall”.

I hope this article has given you an insight into why vacuum filling is a far the best process to use.  The factors I have described are by no means exhaustive, quite the contrary.  Vacuum filling alone will not give you good product; it is only part of a process. Cleaning is vitally important too, but that’s for another article.

If you are in the market for a vacuum filling machine, here is some advice.  Do not choose a machine just because it looks good and sexy.  You may well be disappointed with its performance later.  Whistles and bells might look good, but they only make a noise and are damn useless for anything else.

Ask the vacuum level the machine operates at and why at that level.  Do not rely on price as a guide, just because it is highly priced does not mean the machine is any good.  It is more likely to be over engineered, having more components to do the job than necessary.  That means more to go wrong, which it most certainly will.

Find out about warranty times and scope.  A lot of companies will promise the earth, but not deliver anything.  Once you’ve paid your money you are on your own.  Ask about how repairs are carried out and under what terms.  Where are the repairs carried out, and who is expected to pay the carriage if the machine has to go back for repair.

Do not buy the first or second machine you see.  Study several machines and be honest with yourself over what you actually need.  Ask others you know about their experiences with the machines they purchased, there are a lot who for several reasons, not just performance, wished they had purchased differently.  Especially the after-service support.  Very few companies will give a full technical support service covering processes not associated with your machine for free, if at all.

Most importantly, ask the machine manufacturer for references to other people who have that machine, and follow those referrals up.

If you are still unconvinced about vacuum filling, remember this, the OEM’s fill their cartridges under vacuum.

And that skip of failures?  It became a box again thanks to vacuum filling.  With the introduction of cartridge testers it ceased to exist.

Chris Brooks is the Managing Director of Promax Imaging Ltd.
Now devoting his time to research and development of new techniques for use in the industry, he is also a certified electrical safety inspector and a technical adviser to several companies in Europe and America.  Apart from writing technical manuals and articles for trade magazines, he is also the Chairman of the BSI committee for standardisation of test methods for printer cartridges, and the Technical Director of UKCRA.