Dangerous Prototypes

In development => Project logs => Topic started by: hak8or on December 18, 2011, 06:23:23 pm

Title: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 18, 2011, 06:23:23 pm
I found a good acronym for my projects! Yet  Another  Unfinished  Project
Mostly because I never finish the projects I start, heh. :P

Anyways, I found two printers in the garbage, one is a HP that does not seem bad while the other is a dell. I checked the reviews of both printers online on amazon and I found the dell to be apparently the worst printer in the universe, so I decided to take it apart since using it as a printer will probably bring endless frustration, not to mention the cartridges were empty. Oh yeah, the person throwing it out did not leave the power supply for the printer in anywhere close by.

So I took apart the printer and here is a simple write up to a lot of pictures!
This is the printer I will be taking apart. Main thing about this printer that interests me is the DPI:  4800 x 1200
More information about the printer: http://http://www.staples.com/sbd/img/rebates/pdfs/718342.pdf

A close up of the printer to show what model it is. Even the screen itself is not worth salvaging! :P

The scanner ontop. A huge amount of room in there between the glass and bottom plastic, far more than needed for the scanner heard to move, I wonder why there is so much room in there. Maybe to just have the dell logo at the perfect angle or something? :P

Closeup of the rod and scanner head connection. You can see the little "pulley" (I do not know what the string with teeth on it is called) too! My guess is that the scanner head is moved along by being pulled by the pulley and using the rod as a stationary point to prevent it from wobbling around too much.

Taking the scanner off was incredibly easy! There were three screws in the back of the printer near what you can see what the hinges that held the scanner on. After unscrewing those I was able to, with lots of wiggling, get the scanner head off. There were about four connectors attached to the scanner portion of the printer, two of which are FPC (Flat Pin Connectors), and the other two being normal molex connectors.

The two FPC's and molex connectors. I presume the inductor (black tube holding 2 wires together, bottom left connector) is for power filtering, but I am not sure.

The PCB connectors for the above cables. What is interesting for me is the holes in the plastic cover of the PCB. I presume the holes are for air movement from the motor drivers and not just aesthetic because the printer is not processor intensive and has the power supply separate from the printer.

As this is an inkjet printer, the tiny holes for the cartridge sometimes clog, so inside most if not all inkjet printers there is a "sponge". What you see hear is the sponge that cleans the cartridge head of gunk that might get stuck on it. The cartridge goes over this sponge and it pushes against the print head to take off dried ink and anything else that might get stuck on it after use. In some printers there is actually a puddle of ink in the container, you can search for yourself on youtube or just googling to see just how much ink goes in some of these areas.

I used a flat head to push the cover off the printing part of the printer, much how you use a credit card to open other plastic electronic cases. Of course, there were a few screws I had to unscrew to open it, but if anyone is trying to open something plastic and you are sure that all the screws are unscrewed, just stick a flat head along the edges and separate the plastic walls. Sometimes you can slide the plastic walls apart by pushing the walls in parallel directions (left or right), though I had that happen to me only once.

Here is the left side of the printer that has a pretty nifty printer head cleaning system going on. The orange walls you see brush against the print head getting rid of ink that is stuck. Then the rectangles you see seem to push against the print head, so I guess when the printer is turned off this is where the cartridges go, and the little rectangles form an air tight seal around the cartridge head to prevent ink from drying and clogging up the heads. The left rectangle is for the black cartridge, and the right rectangle is for the color cartridge. Either way, it is a very cool little contraption, especially because when the print head slides to the left it causes the entire assembly to lift up against the print head. Also, a bit blurry but still able to make out, you can see a little optical sensor in the bottom middle of the picture (clear plastic), I assume its function is detecting if the cartridge is actually present in the printer.

Some ink splattered on the wall of the printer, I presume the print head maintenance is a rather messy process. :P

This is the motor that controls the linear motion of the cartridge. I was hoping for it to be a stepper motor but it turned out that it is only a DC motor, which are not precise at all. Luckily, this printer has optical encoders so it isn't as bad as I feared. But, what is that thin strand there !? And that paper thing under the motor?

My god! It is hard to make out in this picture but there was a hairpin in there with some hair (the strand above the motor was a piece of hair), a gum wrapper, and some tiny specs of what I guess is food or seeds. I have no idea how that even got in there, the printer was rather well sealed.

This is the optical encoder for the paper feed of the printer. As you can see, it says 150 Lpi and 892 CPR. Now, here is some short simple math to find the precision of the paper feed.

150 LPI = 150 Lines Per Inch
1 inch / 150 = 6.66666667 mil

892 CPR = 892 Counts Per Inch
6.66666667 mil X 892 CPR = 5946.66666964 mil

5946.66666964 mil = 5.94666666964 inch

Circumference of optical encoding disk  = 5.94666666964 inch
Circumference / Pi = Diameter of disk
5.94666666964 inch / Pi = 1.89288279 inch

The shaft that pulls/pushes the paper is 0.5 inch diameter
0.5 X Pi = 1.57079633 inch
6.66666667 mil / 5.94666666964 inch = X / 1.57079633 inch
1.76098243 mil = X

So I can feed paper in steps of 1.76098243 mil.

Here is the encoder tape for the linear motion of the print heads. I did not find anywhere the specs of this line, but I will find out later easily by just moving the print head a set distance and seeing what the optical encoder spits out.

Surprisingly, just unscrewing 3 or 2 screws I was able to get the entire printer assembly out of the plastic case.

Awesomeness! Now, to continue with the printer and seeing what I could put where. I need to be able to make a makeshift attachment in the printer cartridge holder to hold a thin needle or a small marker, and get rid of the angled paper feed. Unfortunately the paper feed is very thick plastic so I have to find out what to do with that.

Close up of the black printer head. I left the color printer head somewhere and can't find it, heh, it will show up eventually!
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 19, 2011, 05:48:37 am
And here are some more updates!
http://archive.hak8or.com/pictures/HP_Printer_Teardown/ (http://archive.hak8or.com/pictures/HP_Printer_Teardown/)

So first thing was to get rid of the angled paper feed. Problem was that the paper feed was part of one large plastic component that included the entire bottom of the printer and pretty much held everything together. I was unable to cut through it with any of the tools I had, so I decided to make a little makeshift hot knife to cut through plastic, and it worked well! I have since taking these pictures hammered the knife part so it would be thinner and longer, which means hopefully easier cuts.

The remnants of the paper feed.

What I used to make the hot knife was just getting a soldering tip that was meant to be thrown out and crushing the tip with a vice to get a mostly flat "knife", and then hammering it down some more to get it even more flat.

Very sharp!

The general look of the printer out of the case and rid of the back angled paper feed.

And here is the linear encoding tape with the measurements, I have yet to mirror the image to get those numbers, heh.

A much better view of the plastic covering the circuit board inside the printer, with a close up on the cutting. First time I ever used a hot knife, so please excuse the horrific "cuts"! :P The three FPC's on the right are from the cartridge, and I presume one for each cartridge (black and color) and the third would be for the encoder on the cartridge holder.

And offcourse I wanted to take apart the cartridge to see what was in it, out of curiosity.

I just pushed a flat head between the edges and it popped open without too much problems. The inside of the cartridge can be seen, and the gaps in the left of the cartridge is where the printer head is.

The cover of the cartridge.

The inside face of the cover.

The sponge that held the ink. I tried to rinse the sponge out but the ink splotch stayed inside, which led me to a suspicion. Do they even fill the cartridge all the way? If I couldn't wash the ink splotch out then I presume no ink ever touched the other parts of the sponge. Could it be true, or am I hopefully wrong in my deduction?

The paper feed shaft that actually touches and pulls the paper. I put my finger there for comparison, and it seems that my guessing of the shaft size is correct, it is about a half of an inch in diameter. Also, you can see my fingerprint! :O I wonder if it is possible for someone to replicate my fingerprint like this, heh. Anyways, you can also see the "sponge" I mentioned in the first post, and I am not so sure about its function anymore. Maybe it is to collect gunk that flys off or is stuck on the plastic gear? The gunk to the right on the shaft is lubricant I guess. The spring holds the toothed strand that pulls on the cartridges to give the line constant tension.

I tried to get a good picture of the way the cartridges move, but this was the best angle I could get. It looks awesome regardless! The reflecting strip you see is the linear encoding strip, the toothed string is what pulls on the cartridges to move them, and the metal rod is what holds the cartridge in place, limiting its movement so it moves in only one dimension, left and right across paper.

And lastly, another close up of the rotary encoder disc! The numbers are not gaps of inches, I presume they are "O clock" style indicators, but I am not absolutely sure.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 20, 2011, 09:30:19 pm
Here are some more pictures/progress! :D

Also, apologies for the bag quality pictures, I put my camera somewhere and couldn't find it later, so I used my phone. Turns out I left the camera in my room and a piece of paper fell on it so I did not see it. :P

I used my "hot knife" to cut through the plastic some more so there will be room for the needle. I got rid of the rotary encoder and I will use only the linear encoder. Comparing the linear encoder to the lines on the rotary encoder, it seems they are equal, so the lines on the linear encoder are 150 lines per inch, meaning 6.66666667 mil.

Side view to get a better idea of the size. I am going to leave it on the plastic chassis so I can get a better attachment to the rest of the unit.

From the back of the chassis. The three FPC's you see are from the printer carriage. Two of them are for the actual cartridges, and the third is the optical encoder and the two side metal pieces on the carriage to detect collision. The cutting looks much worse in this picture than it actually does. Or maybe I am just fooling myself with my hot knife cutting skills. :(

This is what I will be using as the "table". I am not sure how accurate it will be, but it seems good enough. It is driven using "pulleys" instead of any screws, but it seems very precise. It can wobble left to right though, so I will attach some piece of plastic to the riding component preventing wobbling. This was taken from a I think laser copier, and it had no digital encoding of the image, it copied using the mirrors you see, lenses, and a very bright light! It seems rather precise, and it has a stepper motor (7.2 degree steps unfortunately) in it which will hopefully give me some good accuracy. The reason I did not use the scanner that the Dell printer came with was because the printer overall was rated as garbage, so I presume the scanner did not function well, causing me to not want to even bother with it. Plus, it looks like it could be useful for a UV light box or something. :P

Here is the PCB and its cover when I took it out of the printer. I was really curious as to what was under the black plastic that required such air holes, so I took it off.

And here is what was under it. It really surprised me, I never saw a BGA in a printer before, especially with D/Sram! There was a metal cover over the bga and sram, I presume to meet emission requirements and keep it RF shielded. I will hopefully add in some better scans/pictures of the pcb for all those interested. I am VERY curious about the bga ic. It costs them a lot more money to have such a bga ic in their pcb, due to much higher accuracy from the pick and place machines and higher layer count on the pcb to accommodate the bga footprint.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: blarson on December 21, 2011, 03:07:26 am
Some printers come with partially filled ink cartriges, just enogh to show you the printer works before you buy real ink cartriges.  (where they make their profit)
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 21, 2011, 03:47:23 am
Oh, good point, I forgot about that. I do not know if the cartridges that I found in the printer were with the printer when bought or if the owners bought their own cartridges. And yeah, they usually make a loss on printers too, which is why some of them are so cheaply built, hence me being so surprised at the PCB on this printer being so "advanced" compared to other printers I gutted.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 21, 2011, 04:31:31 am
As was said in my power supply thread, a member made the fantastic idea on what to use as a printing head for making the etch resist on a pcb, which was a needle. So I presumed that the only option then would be something low temperature that melts but is a "strong" solid when at room temperature, which would be wax.

I found a good idea and write up on it from here: http://wiki.makerbot.com/frostruder-mk2 (http://wiki.makerbot.com/frostruder-mk2)
It did not even come to my mind about using a "relief valve" to get rid of pressure in the tube preventing more paste than wanted from exiting the tube. MUCH better than a linear piston pushing the paste out. Now, to find some material for the tube that won't melt at the same melting point of wax! :P

Also, I found some of the design ideas I had a while back when thinking about the printer. I was mainly interested in finding if I could design the entire thing from scratch, and have the necessary parts done using ponoko or other services. Turns out that some of the parts I want would cost $45 EACH, and I need at least two of them, which to me sounded far too high considering my budget, so I put the idea of making it from scratch on hold. Maybe when I get more money some day I will be able to have it made, but for now it is out of my reach. :P

This is not even the most recent design, just found these files when looking for something else, so I decided to post them up in here. Once I get my laptop I will put the most recent design in this post.


IF anyone is interested, I can upload the original design files from Autodesk inventor. You can get it for free if you are a student and have a student email. It is SUPERB, and it has awesome built in physics simulation and tutorials are on youtube which are very easy to follow and high quality (720p, good audio, and well done over all)
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on December 23, 2011, 07:53:34 pm
After looking around for some information on the BGA chip, here is what I got:

Manufacturer: Zoran
Quatro 4201S
ARM logo

Seems Zoran merged with CSR a bit ago, hence me not being able to find the actual zoran website but instead getting redirected to CSR.
"On 21 February 2011, Zoran announced it was merging with CSR (Cambridge Silicon Radio)"

I shot them an email yesterday asking about access to the datasheets for this SOC, no answer yet, but it was worth a shot. :P
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 02, 2012, 04:07:35 am
Here are some more updates! Granted, it is from a while ago, but I now have to time to finally post it up. :P

This is what I will use for the Z axis, a floppy drive. My aim for this is not to do 3d printing, just to make tracks on a PCB, and the floppy drive has the head which moves maybe an inch or two, which is very sufficient for me.

A floppy drive as you hopefully know reads a floppy disk. The floppy disc has an actual disc inside which is read using a head, this is one side of the head.

The other side of the head, the small rectangle is what actually reads the magnetic bits on the floppy disc.

Anyone has any idea why there is such a pattern for the read head? My guess it has to do something with RF, as I see such "unusual" designs in RF circuits, but I am not sure, maybe to allow movement of the head?

Blurry picture of the closeup of the screw that moves the head. The screw seems to resemble a ACME screw, but I may be wrong. You can see the metal rod acting as a linear motion guide for the head in the middle of the picture. The rod is held in place with screws, which I never thought could be possible in a large scale production.


The multi phase motor in a floppy drive which makes the disc in the floppy disc spin around. There are some angled tracks from the highest ic to the actual motor, whic is strange, and I see quite a few right angles, to the left of the top most ic.

The part of the floppy drive that interfaces with the computer. The black is the Floppy IDE connector, and on the right is the power connector.

Other side of the PCB from above picture. Also quite a few angled traces, specifically above the IDE connector and next to the logic ic (74HC00A).

And here is the actual printer so far. I got rid of a majority of the plastic of the old printer, and managed to attach it securely to the metal scanner chassis using screws.

Here is the stepper motor I will be using. I should go for a more accurate stepper, but for free it is good enough (7.2 degrees per step I think).

The part with holes in it was what used to hold optics for the laser copier, but I will use it as the part which holds the PCB, so I drilled some holes into it. Off course, me being the person I am drilled the holes in a straight line, but the straight line is not parallel to the edge, and I drilled a hole in the wrong place, drilled another hole too close, causing it to just look ... ridiculous! :P
At this point I am realizing that this will probably not work, but oh well, I want to finish it for the sake of having something CNC ish so I can learn how to use EMC2.

Close up of my horrid mistake. :P

The PCB holder, this will be the top of the PCB holder so it will give me better grip on the board than the flat plastic on the other side.

Other side of the PCB holder, it used to be the cover of the Dell printer I found in the garbage a while ago. :P

I had no idea that the pictures will make it so hard to see the printer in its entirety, so I will offer a few pictures. I am still working on the supports for the PCB holder so it does not tip over.


Picture from right in front. Lots more to do, and hopefully get better pictures!
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 06, 2012, 08:13:50 am
Today I got around to finding out how to drive the stepper motor with what I have on my hands now, so, here are a bunch of pictures! :D

To reiterate, here is the motor:
Five wires, no pin out online in the datasheet, and a quick look at the PCB that the motor was connected too also did not tell me much. This is the only stepper motor I have on hand suitable for this and it is already assembled with it and everything, so I decided to stick with it.

The motor is a unipolar stepper motor, so in this case that is two main coils with a wire in the middle of both. Five wires total to control the stepper, and you can see them on the PCB numbered one to six from down to up.

I took off the connector and IC so I can see the tracks under it to find the pin out of the stepper motor.

Bottom of the PCB

Here are my conclusions from using the datasheet of the stepper motor controller. Apologies for how bad it is, I drew it on my touchpad with my finger, so it isn't that accurate and readable, but hopefully it gives a good bit of information. :P I checked the resistance of each wire trying to find what the pin out was, but after I while I realized that checking by resistance won't work. Any combination of black, yellow, orange, or green will give me 12 Ohms, and red to and other wire will give me 12 ohms, so checking by resistance is futile. Instead, I de soldered the stepper motor driver and connector to get access to the tracks on the PCB. Visually finding what IC pin goes to what connector pin was too much of a pain, so instead I just did a continuity check, compared the number of the pin to the datasheet pin out, and found out that way what pin went where to the stepper motor! Still need to test it though, have to wire it all up. :P

I don't want to buy a stepper motor driver online and wait days for it to get to me, so I decided to use the stepper from the scanner. I was soldering wires to the IC so it will be able to fit into the breadboard , but I was not able to finish it today, so hopefully tomorrow if not later I will continue this.

Oh gosh this write up is horrid, at least there are some pictures and a drawing I did for you guys. :P Once I get this printer working correctly I will make a PCB with a proper stepper motor driver and then build up the PCB from plastic till I get the precision I want from it. When I was assembling my weird bus pirate with a DIP pic24, I bought two of the mcu's in case I accidentally destroy it when soldering, and I soldered it well, so I had one laying around for a while now, which means I will be using it for the printer instead of the now "ancient" PIC18f452 and PIC16f84.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: ian on January 06, 2012, 08:54:17 am
The encoder disk is really cool. Any what is with that hairpin, lol :)
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 06, 2012, 05:50:22 pm
Oh, the hair pin, yes, heh. :P

I always find the most unusual stuff in electronics, once when I was gutting a microwave I found bugs I never knew that existed before. D:

Kind of disgusting, so I won't put the images up in the forum and instead give you guys links:

I even used gloves for this, and I never use gloves for taking stuff apart! To date, the dirtiest find I ever had. I have no idea what these people did to their microwaves, but I know that it probably wasn't normal. :P
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: voidptr on January 06, 2012, 06:35:08 pm

i also trash apart stuff occasionally, u can get few good parts too.
encoder strip and disk are really nice in a printer ... but beware of button ink trash part,
they get really dirty inside no wonder why they are good for only few years ...

i reused my last 2 printer nice shafts in one of my friend projects...
i still have few of them for my future need !
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 07, 2012, 07:01:17 am
I also have an old printer under the bench waiting to become useful again (as piece parts, of course:)).  The older the better - engineers are getting better at cost reduction, which usually includes limiting the number of precision shafts and replacing them with sheet metal where possible.  I've read the old dot matrix printers were the best for sourcing parts because of how heavily they were built.

The older HP I have sitting around uses pretty much the same feedback mechanisms as the one hak8or posted.

good luck on the pcb printer!
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 07, 2012, 07:39:23 am
I have encountered the ink container thing being VERY dirty a few times, once causing ink to literally spill from the printer onto me when I was trying to take it apart and tilting the printer at a strong angle. And, yeah, the old printers that I used (such as the laser copier that my school had in the late 90's) are very well built full of nice parts here and there. Lately, agreeing with you, some of the electronics I gut are not as full of good parts as they used to. :(

Do you know if the optical encoders in your printers are also 150 LPI? I am starting to think that the optical encoders are reaching a maximum of 150 lines per inch for Printers/scanners/copiers.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 07, 2012, 08:15:58 am
[quote author="hak8or"]Do you know if the optical encoders in your printers are also 150 LPI? I am starting to think that the optical encoders are reaching a maximum of 150 lines per inch for Printers/scanners/copiers.[/quote]
I only looked at them briefly - but I would be surprised if they were much finer than that.  I'll dig it out an look within the next day or so since you're curious.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 13, 2012, 07:40:51 am
Still waiting on that look bearmos! :P

I did not do much lately, at least I am starting with the electronics. As you all know, I wanted to use the stepper motor driver that came with the scanner, so I soldered on wires to the chip package so I can put it into my breadboard. Turns out the cables that I used in the pictures above (Solid core wire, from ethernet cables) is too thick and I can't bend it, so getting it into the breadboard was a horrible pain. I de-soldererd those wires and used wires from a IDE cable (who uses IDE these days !?) and had a much easier time getting it to connect to the bread board.

So, it went from this:

to this:

Now, I put it into the breadboard and working on setting it up. After finally getting it all wired up, nothing happened. :( I rechecked my connections, checked power, checked if Vin_high (2v) was under the voltage I was using to toggle (2.8ish V), but still nothing. I quickly let go of the stepper driver because I wanted more control of the stepper, I was not interested in the other "features" of the stepper driver, and it was probably not working since I did not use a current sense resistor nor any Vref's.

So I tried to find some transistors or mosfets, and I quickly found a few mosfets I scavenged from other items a long time ago.
2x IRLI520G
1x IRLI530G
1x IRLI540G
All of them have a VGS(th) of 2 volts, and at 2.8ish volts I get 2 enough current flowing, but of course, at such a low VGS these suckers have a huge RDS(on), causing them to heat up very fast. But, you are probably wondering, where am I getting 2.8 volts from, and why is it "ish" too? I can't find any 3.3 voltage regulators anywhere for some reason, I guess I ran out of them a while back and ended up forgetting about them.  But, I had a LM317! And I have a large resistor assortment! So I wired it up, and the closest I can get with my resistors is 2.8 volts, and I don't want to bother to parallel/series them to get close to 3.3v, so that is why I have 2.8 volts. "Ish", because the multimeter I have is starting to go bad so it jumps a bit, but not really a big loss since it was a very cheap multimeter. I think the probes cost more than the multimeter itself, heh. :P Also, the PIC24FJ runs from 2 volts, so I should be fine.

Here is what the current setup looks like!

Turns out the pickit2 I have on hand is a dead on. :( Long story short, I bought a pickit2 many years ago and since I was so new to electronics I fried it. Software detects it fine, but it does not read any pic's, and visually there is no difference. I bought a new pickit2 after that, and ever since then I constantly get mixed up which is which. For some reason I never thought about marking it with a marker or something to tell them apart. :S

Checking out the stepper today made me extremely surprised! These steppers are INSANELY strong! I have never witnessed such a strong motor! Meaning, if one of the phases in the stepper is energized to just 12 volts (rated for 24), it has a very noticeable resistance to manually turning it.  I am inspired to make a few boards with a PIC32 that would be similar to the nedoCPU-32 but surface mount, and some additions just for me, like high voltage mosfets and a USB connector.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 13, 2012, 08:21:30 am
[quote author="hak8or"]Still waiting on that look bearmos! :P[/quote]
It's a good think you reminded me - I had completely forgotten.

Here's a quick tear-down of a HP deskjet 895Cse:

An overview of the printer, assembled (sort of):

Without the cover:

Closeup of the sled with the print heads:

the single linear bearing that the whole thing rides on.  The sled is belt driven with an encoder strip above the belt, there is a piece of formed sheet metal that loosely guides as well to keep things in place.

the brushed DC motor driving the sled:

the same brushed DC motor, the mount to the toothed belt can be seen here, as well as the linear bearing beneath it.  The formed sheet metal that the sled guides on is seen in the top center of this photo.  The spring is actually holding the linear encoder strip taunt:

there seems to be a six attachment limit? (TBC)
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 13, 2012, 08:31:35 am
a closeup of the encoder strip for the sled:

Now for a look at the roller encoder (I think that's why I'm posting all this after all).  It has 200 LPI (presumably lines per inch) and 1800CT written on it:

A look at the roller drive assembly - this is another DC motor - with a whole lotta gearing between it and the roller.

Finally, the ink cleaner/slop/drip well thing.  This actually has a bipolar stepper (with some gearing) driving it:

And a look at the whole tray:

As well as the PCBA responsible for taking care of business:
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 13, 2012, 05:06:56 pm
Woh, that is a huge amount of pictures! :D

The printer is very very similar to the printer I took apart, it has the same:
stepper motor (I think)
idea to hold the linear encoder
location of DC motor
Very similar paper hold down mechanism (The flaps in first post last picture)
and a bunch of other things

I think these printers are all manufactured pretty much the same, give or take a few non critical part locations. Can the cartridges wobble a bit, like, rotate on the linear rod? The metal at the top should have a small tab which prevents the cartridges from rotating further, it is weird that they didn't design it so they don't wobble at all.

I think 1800CT means 1,800 counts if you rotate the rotary encoder a full revolution. I am jealous yours is 200 LPI though, heh! :P So, these encoders can go above 150, I wonder if they put a lower LPI encoder strip to save money in the printer. >:( Also, your rotary encoder has numbers going all the way around, mine only goes maybe half way around.

Hp makes their own ASIC's !? I had no clue!

Thanks a huge bunch for the awesome pictures bearmos! :D
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 13, 2012, 06:21:57 pm
[quote author="hak8or"]The printer is very very similar to the printer I took apart, it has the same:[/quote]
Yeah, these seem like they haven't change much through the years

[quote author="hak8or"]
I think these printers are all manufactured pretty much the same, give or take a few non critical part locations. Can the cartridges wobble a bit, like, rotate on the linear rod? The metal at the top should have a small tab which prevents the cartridges from rotating further, it is weird that they didn't design it so they don't wobble at all.[/quote]
Yes, the cartridges wobble on this one as well.  The trouble with no wobble would be manufacturing to those tolerances (it gets pretty tricky (i.e. expensive) with less "slop").  Since these are made as inexpensively as possible, I'm thinking the design is simply relying on gravity to load down the print head assembly - after all, there is no "Y" movement to worry about here, just "X", which is quite solid.

[quote author="hak8or"]I think 1800CT means 1,800 counts if you rotate the rotary encoder a full revolution.[/quote]

I wonder if they put a lower LPI encoder strip to save money in the printer.
Don't forget, the resolution realized is dependent on the gearing between the encoder and paper roller, which can be different.

[quote author="hak8or"]So, these encoders can go above 150[/quote]
Yep, here's an example of one that's > 670 LPI:

[quote author="hak8or"]
Hp makes their own ASIC's !? I had no clue! [/quote]
It always surprises me too.

Hopefully the pictures are helpful!
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 15, 2012, 06:01:24 am
Bearmos, thanks for the pictures and information! :P A huge majority of help from you!
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: bearmos on January 15, 2012, 06:50:53 am
[quote author="hak8or"]Bearmos, thanks for the pictures and information![/quote]
Sure thing, glad to help.

Also, beware of my last comment on the LPI of the avago sensor - it was calculated based on the assumption that one count would equal one line.  After looking into the datasheet a bit, I'm not really sure what their sensor setup is, to the actual number of lines could be fewer, but still provide greater resolution, due to quadrature encoding.
Title: Re: YAUP: Dell Printer teardown for PCB making (56K warning)
Post by: hak8or on January 15, 2012, 07:55:35 am
Yeah,I am not exactly sure either on if a count is a line, I am seeing extra channels on the sensor. :(

Again, thanks :D