Reliability

The computer industry needs some indication of the reliability and robustness of things. Product build can vary, and IT products cover a range from toys to industrial necessity. Printers are a special problem because they have so many moving parts and might do any job from printing student essays to continuous production of price lists, catalogs and mass-mailing lists.

In the average computer there are just two moving parts - the fan and the hard disk (OK that disregards the keyboard).

Other than those parts everything in a typical computer can run 24 hours per day for years with no ill effect. An electrical surge might damage the power supply. Static damage, and hairline fractures are all possible but not particularly related to use. Indeed being left on can be good for electronics. Thermal stress from being turned on and off is more of an issue. (Off when not in use is better for fuel economy).

Printer electronics can run continually. Mechanical parts can't necessarily do that. Manufacturers sometimes give figures for expected use - anything from a few hundred to a few hundred thousand pages per month.

Duty-Cycle

One of the ways to suggest an expected usage pattern of machines is to declare a duty-cycle.

Things like motors and pumps use duty cycle in a straight forward way. Motors and solenoids are often expected to give a strong magnetic field. A voltage is used that causes the coils to heat up noticeably. Figures might be given saying a motor can run for 25% of the time or 15 minutes per hour at 220 volts - so that is a duty cycle. If the motor were to run continually the coils would overheat, the insulation might melt and a short-circuit would damage the device.

Printers can have limits on how long they can work before they overheat but they commonly cope with this by measuring the temperature of critical parts and slowing down or stopping to cool off if they are pushed too hard. So when we read that a printer can do 40 pages per minutethat's a speed, not a duty cycle.

Printer Duty Cycle

Duty cycle figures for a printer are often given in pages per month.

HP and several other manufacturers often give some indication of how robust they think a printer is by citing a “ duty cycle ”. People are sometimes rather dismissive about the idea of a duty cycle as applied to printers. As a single measure of how robust a machine is, and how it is to be treated it has some merit.   Other possibilities are Recommended Monthly Volume and Mean Time Before Failure (MTBF).   Print Speed is also an indicator of quality, if a machine is fast it is usually well built.

‘Duty-cycle’ as applied to printers is a bit of a misnomer. Nothing very dramatic is likely to happen if the printer is used beyond it's duty cycle.

The most likely problem is erosion of bank-balance;   small printers with low duty-cycle figures almost always have small cartridges and a high price per page. So if you do expect to exceed the duty-cycle, a larger more expensive printer with a much larger cartridge would be better economically.

A cartridge   changes more than half of the parts that wear out in most printers.   This is one of the benefits of cartridges, they make maintenance simpler. The maximum monthly duty cycle for a lot of printers is something like 10 cartridges worth of print. Not everything in a printer is easy to change however, particularly in smaller printers.

Rollers   for paper-pickup and feed do wear out.  A lot of larger printers make these easy to change, but that isn't always so for smaller machines. When the pickup rollers are worn the printer will misfeed more often.

Fusers   are a critical part in laser printers. The fuser puts a substantial amount of heat and pressure into a printed page using a heated roller. The roller wears out and the heater ultimately fails. Fusers wear out a bit more quickly if used with high page cover (photographs for instance) but they mainly vary with model. Small fusers may have a short life of 50,000 pages, big fusers might last 500,000 pages.

Fusers also differ in how easy they are to change. Heavy duty printers often have fusers that just unplug - (Laserjet 4200, 4300, 8000, 9000, CLJ 3600, 4600, 5500 etc). Light duty printers (like the LJ1000, 1012, 1160 1320 and CLJ 2600) need partial dismantling of the machine.

Spares   are more likely to be available for bigger printers. A rough rule of thumb is that if the printer sells for less than $300 in the US then spares won't be available because it wouldn't be worth a technicians time repairing it. In Britain we're a bit more inclined to fix things (caring about the environment, or mean with money) - but spares policies tend to be global.

Some of the parts of a printer that wear wont be easy to replace. The LaserJet 4200/4300 is a great printer in most respects but has a notorious problem with the swing-plate assembly. However the great thing is that there are spares.

Duty cycle figures given are typically high, beyond any likely use of the printer. High figures may represent an old specification-war where manufacturers tried to outdo one another on speed and resolution. Duty-cycle was a figure that could be inflated without too much risk of a practical challenge .

Build Quality

The idea of “duty-cycle” indicates build quality but is also part of a maintenance policy.

Bearings   Components in a machine are often not ideal designs but cost-effective compromises. Low cost printers often just have ABS shafts running through bearings of similar plastic. A rather better design will have a nylon collar as a bearing. Better still is steel shaft in bronze bearing and best of all a roller bearing. Duty-cycle is an indication of this build quality.

Lubrication   in printers is usually ‘ for life’;   that is, the cogs are given a light coat of non-volatile grease that should last a long time. Overuse of the machine is likely to exhaust the lubrication. It is possible to re-lubricate the cogs, but if the old lubricant is dirty the cogs need cleaning and that means a strip-down of the machine.

Warranty and Maintenance Policy   is a potential issue if a printer's duty cycle is exceeded.   Printers keep count of the number of pages they have produced. If the printer develops a fault and the service technician finds it has been used more than envisaged in a maintenance policy then repair is likely to be outside the warranty terms.

Practical Examples

HP, Lexmark and some others give a figure for duty cycle that it typically between 5,000 pages per month for little printers like the HP LJ 1020. And 275,000 pages per month for their larger office printers like the HP LJ P4515.

Duty cycle figures are often way beyond what most people would practically attempt. For instance the LaserJet 9050 has a quoted duty cycle of 300,000 pages. Printing that many would use 10 of the largest cartridges at around £200 each (US $299 from HP) and a £340 maintenance kit shortly afterwards. However people don't buy printers this size to have them standing idle and the rated duty cycle is less than a quarter of what the printer could do running 24 hours per day 20 days per month.  The purpose the duty cycle mainly serves is as a warning - if you are going to use the printer beyond the duty cycle vendors are likely to quibble about warranty and maintenance contracts.

Duty cycle figures are often increased where a manufacturer has a lot of experience of an engine. The HP CLJ 4600 had a rating of 85,000 pages per month. The later CLJ 4700had a rating of 100,000 pages per month. There were minor improvements in the hardware but the main factor might have been confidence in the design (It remains a good machine).

Comparison

Manufacturers figures for duty cycle have some grounding in reality, they shouldn't renege on a warranty if the printer is inside it's maximum use. The figures aren't a great deal of use beyond that;  it isn't necessarily reasonable to take the Lexmark T644 figure of Up to 250,000 pages per month and say it's more reliable than the HP LJ 4300 with 200,000 ppm and P4015 Up to 225,000 pages per month. They are all robust office printers.

Recommended Monthly Volume

“Recommended Monthly Volume” is a term printer makers are introducing into their specification sheets. The recommended figure is often substantially lower than than duty-cycle, and more in line with consuming a cartridge perhaps every month or so.

For instance for the HP CLJ CM3530.

• Up to 75,000 pages per month maximum duty cycle.
• Recommended monthly volume 2,00 to 6,000 pages per month

We rather wonder whether the recommended monthly volumes might be tuned to toner, fuser and ETB use and pitched to giving favourable per-page prices by not factoring those costs in. But surely not everything manufacturers do is a conspiracy to hide true costs

Notice the implied minimum recommended volume as well. Usually this is set at the point where the toner cartridge would exceed two years life. Modern killer-chip cartridges are usually set to last about two years from manufacture. Very low toner consumption would lead to inconvenient out-of-date messages. Straight forward black toners don't decay much - it's common to take a printer off the shelf after several years and have it work. Recent high-resolution toners may be less stable - they are a wax-resin mix made in solution and may be hygroscopic. Yellow seems to give most problems.

It can be difficult to estimate how much printing actually gets done. A small office processing 20 orders per day and printing out ledger copies of two documents for each will use 1000 pages per month by the time a few pages have been printed for emails, Internet baking and so on. That's well within the Duty-cycle rating for any printer but implies a new cartridge every couple of months with some small printers.

Figures for home printing are even more difficult to guess. A US Court case regarding ink prices suggested that the average home user prints about 2 pages per day, probably 60 per month. But home users go in for flurries of activity, printing Birthday invitations and suchlike. The average figure hides all sorts of life choices. If you decide to print the scores for an opera or the draft of your novel that suddenly goes way beyond normal home print.

Mean Time Between Failures

A lot of capital equipment has some sort of Mean Time Between Failure (MTBF) or Mean Time To Failure (MTTF) figure associated with it.

Brother don't tend to give a duty cycle figure in their brochures. The service manuals often give more enlightening figures, for instance for the HL 5200 we get under   "Service information"

These are key service information to maintain the product. Machine life: 200,000 pages / 5 years MTBF (Meantime between failure): Up to 4000 hours MTTR (Meantime to repair): Average 30 minutes Monthly volume: 20,000 pages Periodical replacement parts: Parts; Approximate Life Fuser Unit; 100,000 pages Separator pad holder assembly; 100,000 pages Pick up roller assembly; 100,000 pages Laser Unit; 100,000 pages

Experienced engineers won't be surprised by most of this; its not a heavily built printer so 100,000 pages is about right for the fuser and pickup rollers to need replacing. The 4000 hours will be (8*250*2) 2 years - they would want to be clear of warranty call-outs.

Like many manufacturers Brother seem to have a bee in their bonnet on some point. With Lexmark its overly precise measuring of the fuser lamp current (surely its the temperature that matters ?). Brother are always suggesting changing the laser unit. Laser's do decay with use but no other manufacturer seems to think the unit will need replacing after a mere 100,000 pages. To our knowledge engineers are just ignoring the service manual on this point.

A problem with MTBF for IT equipment is how anyone can know. With vehicles or power generation equipment there are statistics for similar designs stretching back years that give some idea. A lot of printers are based on ‘ engines ’ but the design life of a whole series might only be ten years. There are few statistics available. With a relatively simple component like an OPC drum or scraper blade (or indeed a semiconductor laser) a fairly linear process is at work leading to it's ultimate failure, so the MTTF of a cartridge or fuser can often be foreseen. However some Brother Multifunction printers have a weak hinge on the ADF cover - that presumably wasn't foreseen, just as the problem with the HP LJ-4200 swing plate was not.

Hardware manufacturers don't do a prolonged beta-test where they put several thousand machines out to users and wait to see what goes wrong. That is only affordable with software where the testing carries few costs.

Reliability testing for printers happens live.

The figures we really want are practical outcomes:

the percentage failure rates over time by printer and by component. These figures clearly exist - manufacturers will get them as part of their warranty cover and extended maintenance contracts, and in even greater detail via their Managed Print Services (MPS) contracts.

The field service outcomes are commercially sensitive and presumably there are just a couple of printer companies who wouldn't have a problem with users knowing the figures.

Usage Patterns

Whatever measure of build quality we choose: Duty Cycle, Recommended Monthly Volume or MTBF, has its defects. One problem is that real world use patterns vary. A mono laser printer might be used for 100 pieces of correspondence each day. A colour printer might be used for 200 10 page catalogs once each month - its the same level of use but a different pattern.

Printers tend to have a speed rating in pages per minute and then a duty cycle rating in pages per month. Pages per month takes the same form as other duty cycles expressed in actions per hour. However if we look at it more closely its a pretty meaningless figure.   For instance if a printer has a maximum "duty cycle" of 100,000 pages per month and can print 60 pages per minute it COULD print the entire monthly rating in under 30 hours. However we might bear in mind that one day on and 29 off is not likely to be the expected usage pattern. The manufacturers are more likely to mean that the printer CAN print several thousand pages per day - but not the whole 100,000.

Ordinary cars tend to be serviced after a certain mileage; that wouldn't be good enough for racing cars. With printers the milestones are usually pages and the duty cycle is a guide. If you have an unusual usage pattern it isn't necessarily much help.

Reliability and Reputation

US magazine PC World does an annual survey by brand with tens of thousands of participants.

The survey asks questions on:

Reliability measures:

• Problem on arrival Any significant problem, Severe problem, Ease of Use, Overall satisfaction with reliability.

Service measures:

• Phone hold time, Average phone service rating, Problem was never resolved, Service experience.

In recent years there have been consistent

• top performers (best first)- Canon, Brother, Epson and Samsung.
• low performers (worst first)- HP, Lexmark, Kodak, Xerox and Dell.

PC-World's recent survey had 79,000 participants - that's one of the benefits of a big, coherent market like the US. They also have forum responses from people claiming bias in favour of Apple - but that bias wouldn't hold for printers.

It would be arguable that the biggest company will get the most complaints, but the survey method is based on averages and low ranking companies performed below average. In late 2010 PC-World even split the HP scores into HP for Business (LaserJet, Officejet) and HP for Home (Deskjet, PhotoSmart). HP's business offerings did a bit better on their own, rising above Kodak.

HP has 50% of the market and Canon 20% followed by Epson, Brother, Samsung and Lexmark.

We see quite a few brand and service surveys and might do a bit more research on the issue. HP sells more printers than anyone else but no longer has a great brand image.

PC-World's list of reliable performers is pretty much in order of worldwide sales with one notable exception. HP are bottom of the list for service, top of the list for sales (but falling). It seems that HP created brand awareness many years ago, perhaps as long ago as the 1980s when they coined the terms ‘DeskJet’ and ‘LaserJet’. HP made some creative decisions in the 1980s and have been losing momentum since.

Brand Name

What attracts people to brand-names in IT products? Why would an IT manager who has presumably risen through the ranks of analysts, programmers and support technicians buy products that score poorly in surveys. Perhaps its advertising - we all say we aren't influenced but know we really are. Perhaps its that the value-proposition at the point of purchase (accompanied by glossy picture) is different to that perceived in a survey.

Most of what can be researched on the web is anecdotal. Obviously there are more complaints about HP because they are the biggest.

Puzzlingly, HP's printers use Canon's engines. We might expect complaints to group by engine. Canon are at one end of the PC-World scale and HP at the other - but the machines are very similar. Likewise Dell are higher ranked than Lexmark. It looks like an interesting avenue of research.

If we were sure that some brands were always bottom of the league for reliability that might be useful. The real world isn't quite like that however.

There are about 10 well-known printer brands and 60 manufacturers altogether. There are several hundred different models on the market at any one time. Reliability is likely to go by model and engine type rather than by brand.

Individual experiences on websites and forums can make a trend clear but it will take time to unpick user mistakes and misunderstandings from help-desk attitudes and genuine hardware failures.

Real world information is always out of date. By the time it's clear that there are premature failures in the aliasing bar linkage or the swing-plate assembly that model is likely to be out of production. Most models have their quirks. For business IT brand name has an influence, but unless something spectacular goes wrong it reflects quite a long history.

Brands would also be affected by what technology they mainly use.

Canon and HP both make both reliable laser-printers and thermal inkjets using thermal printheads. Number 3 producer Epson is primarily known for their piezoelectric head inkjet printers, and we would expect those to be more reliable. OKI don't appear in the survey which is a pity because there ranking would be interesting. OKI make business printers; they don't make inkjets at all. They avoid those problems of unreliability but run the risk that some potential buyers have never heard of them.

Technology & Reliability

Print technologies themselves have quite different reputations and the choice of technology will ultimately reflect on manufacturers. Laser printers are noted for reliability, hence they are used in offices. Thermal inkjets are noted for being cheap to buy.

Print technology is not a recent invention; it reaches back a long way. A printing press with movable type appears in Europe around 1439. The process has been improved in all sorts of ways.

Printing tends to be a wet process - water or grease based ink dries on the page and ideally not in the print mechanism. The problem for inkjet printers (as for generations of machines before) is that ink dries in the printer and blocks the mechanism.

One of the changes over time is the use of rollers rather than plates; the continual action of a roller tends to be fast and reliable. One of the reasons laser printers still have the edge over inkjets is that the mechanism is largely built around rollers.

Band-Printers

Early computer printers used wheels, drums and bands to achieve fairly high print speeds in excess of 2,000 lines per minute. The IBM 407 accounting machine was one of the first to use wheels and the ‘ Potter flying typewriter ’ used a drum. Successors are machines like the IBM 6252, Dataproducts FP 2000, and Fujitsu 3043. Band-Printer. Band printers are probably the most reliable print technology, but they are expensive to buy, bulky and produce rather ugly pages so they are now a rather specialist item.

Typewriters

Typewriters provide character-based printing from about 1866 and electrically controlled telegraphs were known in the 1850s and teleprinters around 1900.

Big brands in typewriters were Hermes, Olivetti, Remington, Smith-Corona, Triumph and Underwood. Several had a shot at making it into the computer age but are no longer with us. Technology was stronger than brand.

(IBM was also known for typewriters as well as computers and is still in the business - but is it the exception that proves the rule ? )

One survival from the typewriter age is the idea of a printhead in a carriage. Typewriters originally had characters attached to a flying key mechanism. Although the individual keys were light the type-basket was big and slow. By the 1960s a new generation of machines had emerged - the IBM Selectric with its golf-ball printhead (12 cps) and the Diablo Daisy-wheel (30 cps). Both were widely used as computer printers but had defects - they were still too slow for computer use and could only print one typeface. However they did introduce the idea that the typeface sits on a carriage that scans back and forth across the page. That idea is still used in most dot-matrix and inkjet printers. Incidentally the Diablo 630 was popular, Apple included an emulation of it on the first LaserWriter.

Inkjets

Inkjet designers aimed to replace dot-matrix printers, they have largely succeeded. Have a poor reputation for reliability. This might not be entirely fair. There are far more inkjets because they are often made cheaply and sold for home use. Inkjets do have weaknesses. Congealed liquid ink is likely to block the printheads. An inkjet with the heads installed needs to be used every couple of days or the ink is highly likely to dry out. It is generally unwise to put an inkjet away on a shelf and expect to be able to use it next year.

The nozzles in inkjet heads are very fine, less than 0.05 millimeters in old machines. In a thermal inkjet the temperature of the resistor creates superheated steam in the ink by raising to a high temperature momentarily. A pressure wave spreads through the ink but pressure rises rapidly at first, then surface tension on the meniscus of ink is overcome and a droplet flies to the page. Low pressure is left behind possibly leading to cavitation as new ink is sucked in to violently cool the resistor for the next shot. A significant problem is that boiling a liquid that contains a colourant leaves a build-up of solid particles called kogation. It has proved very difficult to make thermal inkjet heads reliable, so they were made exchangeable.

Piezoelectric inkjet heads use the distortion of a crystal to propel the ink. the piezoelectric effect is quite small so chambers need a relatively large surface area but on the other hand that does mean a less violent action - and there is no kogation. So piezoelectric inkjets can have heads built in. Heads are changeable in principle but the price for consumer heads is usually close to that of a printer - so it's often not worthwhile.

Otherwise the inkjet mechanism can be very similar to a dot matrix printer.

Thermal printers are scarcely known outside business and industry. The most common use of thermal printing used to be faxes but they have been replaced by inkjet and laser printers in that role - apparently people just don't like the "funny" fax paper. The most common application today is in point of sale terminals.

In the industrial sphere thermal printers are valued for doing unusual things such as metallic print and print on plastic cards and  for their robust reliability. Basically a  thermal-direct printer needs only one moving part - the paper. Usually there are a couple of feed rollers.

The failure of thermal printers in the consumer market is peculiar, they can produce material at low cost as they do in fax machines. A few consumer photo cameras use thermal transfer mechanisms.

Laser printers typically have the toner consumable and the other parts most subject to wear turned into cartridges.