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Apple iPhone 4S Screen is Black but Sound is still heard

Recently troubleshot and repaired a iPhone 4S. I will share this information with you, perhaps it will help you get your iPhone up and running again saving you lots of $$$. At times the digitizer screen will have to be replaced if the following solutions do not work for you since it might truly have failed.
There are a few things that can cause an iPhone 4S to display a black screen. If the sound is still working you can rule out the possibility of a dead battery. This iPhone 4S I will working on had the black screen but sound could be hear and also it would ring when its number was called, everything was functional just no video on the screen.
Most causes can usually be solved by restarting, resetting or restoring the iPhone to its factory settings (the last resort). If none of these solutions work for you it most likely is a hardware problem, i.e screen needs swapping out or the connector is loose and needs to be re-inserted. They can become dislodged from impacts or drops. The nice point about these phones is that removing the 2 bottom screws near the charging connector lets you slide the back off the phone giving you access to the internal the upper top left part of the phone under a small metal plate are many of the connector plugs that you can check.

Apple suggests a restart as a first troubleshooting step. A restart is done by pressing and holding the “Sleep/Wake” button for five seconds. Normally, a red slider appears on the screen, but you probably won’t see it since your screen is black!. Place your finger a half inch from the top of the screen on the left side and then drag your finger to the right edge. The slider doesn’t require much precision in where you place your finger so, assuming the touch controls are still working, this should work. After a half-minute or so, turn the iPhone back on by pressing and holding the “Sleep/Wake” button.

If restarting your iPhone doesn’t solve the dark-screen problem, reset the device. Do this by holding down the “Sleep/Wake” button and the “Home” button at the same time for at least 10 seconds. Hopefully, you will see the Apple logo appear before you release the buttons. If you don’t, release the buttons anyway and then wait a minute or so for the iPhone to power down and turn back on again. If resetting the iPhone doesn’t work the first time, try it once again.

Restore to Factory Settings
Restoring an iPhone to its factory settings is generally the last hope you have to resolve a black-screen problem yourself. To do this, connect the iPhone to your computer and launch iTunes. After selecting the iPhone in the right corner of the screen or in the left sidebar, if you activated the sidebar option, click the “Summary” tab and then click the “Restore iPhone” button. When the restore process is finished, the iPhone should display a gray screen with the word “iPhone” on it. Drag the slider at the bottom of the screen and follow the prompts to set up your iPhone again. This process restores your iPhone to its original factory condition. During the process, you are prompted to restore a previous backup to return your files and data to the phone.

Recurring Black Screen
After your iPhone is working properly again, update to the latest iOS and update your apps. For example, some iPhone 4S owners reported black-screen problems after upgrading to iOS 6.0, but these issues were resolved with the release of iOS 6.1. If the iPhone goes black again after updating and applying a backup, you may need to repeat the restore process, this time without the backup. Bugs between an app and the iOS may also be the cause of a black screen.

Hope this helps you, Good Luck!

What are winding analyzers ?

Surge/HiPot/Resistance Tester
The Static Motor Analyzer – is a predictive maintenance solution which offers flexibility in providing fault recognition in a single portable instrument. They integrate a wide range of electrical tests, including surge comparison, DC hipot, step voltage, continuous ramp, mega-ohm and winding resistance tests.
Some manufacturers are Baker-SKF, Electrom Instruments and Samatic.

What is Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF) ?

Fused Deposition Modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications.

FDM works on an “additive” principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part.

The technology was developed by S. Scott Crump in the late 1980s and was commercialized in 1990.[1]

The term fused deposition modeling and its abbreviation to FDM are trademarked by Stratasys Inc. The exactly equivalent term, fused filament fabrication (FFF), was coined by the members of the RepRap project to give a phrase that would be legally unconstrained in its use.


FDM begins with a software process which processes an STL file (stereolithography file format), mathematically slicing and orienting the model for the build process. If required, support structures may be generated. The machine may dispense multiple materials to achieve different goals: For example, one material may build up the model and another may be used as a soluble support structure.[2] For another example, multiple colors of the same type of thermoplastic may be laid down on the same model.

The thermoplastics are heated past their glass transition temperature and are then deposited by an extrusion head, which follows a tool-path defined by CAM software, and the part is built from the bottom up, one layer at a time. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle which can turn the flow on and off. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, directly controlled by a computer-aided manufacturing (CAM) software package. The model or part is produced by extruding small beads of thermoplastic material to form layers as the material hardens immediately after extrusion from the nozzle. Stepper motors or servo motors are typically employed to move the extrusion head.

Although as a printing technology FDM is very flexible, and it is capable of dealing with small overhangs by the support from lower layers, FDM generally has some restrictions on the slope of the overhang.

Myriad materials are available, such as ABSPLA, polycarbonate, polyamides, polystyrene, lignin, among many others, with different trade-offs between strength and temperature properties.

Commercial applications

FDM, a prominent form of rapid prototyping, is used for prototyping and rapid manufacturing. Rapid prototyping facilitates iterative testing, and for very short runs, rapid manufacturing can be a relatively inexpensive alternative.[3]

FDM uses the thermoplastics ABS, ABSi, polyphenylsulfone (PPSF), polycarbonate (PC), and Ultem 9085, among others. These materials are used for their heat resistance properties. Ultem 9085 also exhibits fire retardancy making it suitable for aerospace and aviation applications.

FDM is also used in prototyping scaffolds for medical tissue engineering applications.[4]

Maker Faire Rome, Big Numbers and Big News from Rome

Big Numbers and Big News from Rome


Maker Faire The European Edition Rome

Corrado Doggi is Managing Director of Irish based start-up Creo 3D Printers and he attended the Maker Faire Rome event this past weekend. His dispatch from the heart of Italy, is here for 3DPI’s readers …

Rome has possibly never looked as beautiful as it did last week when I landed, since the glorious days of the Roman Empire, thanks to all the work done in recent years. The size of the Colosseum, the Pantheon and  Vittoriano are intimidating — as were the numbers relating  to “Maker Faire – The European Edition”, which the mother of all cities hosted from the 3rd to the 6th of October at the “Palazzo dei Congressi” 

Maker Faire The European Edition Rome Hall

Quin Etnyre QTechKnowAcross 8000 square metres of exhibition space, which provided a temporary home to more than 200 exhibitors, who were demonstrating many different “make” activities to 20,000 visitors, Maker Faire Rome exceeded all expectations. Individuals and companies were present, with company CEOs as young as 12 years old — I kid you not — personified by Quin Etnyre who founded his company QTechKnow last year at the age of 11 to promote his ArduSensors. He’s also a regular on the hackerspace tutorial circuit. 

Thursday, at the opening conference, the big news that had previously been hinted at by Massimo Banzi, the father of Arduino, at the World Maker Faire in New York last month was revealed in full. After an outstanding introduction by Dale Dougherty, the founder of Maker Faire, Massimo together with Brian Krzanich, CEO of Intel,  announced the collaboration between the two organizations on the development on the new Galileo board. A huge step from a “Big Player” toward the Makers community.

In terms of 3D printing activity — I heard a lot of talk about the acquisition of Makerbot by Stratasys, again a big player spending unbelievable money by any economists calculations…. 450 million! The reactions to the deal tended to be mixed, with some keen to see where MakerBot would go with major backers while others felt betrayed by the corporate sell out.

Ultimaker was present at the faire and it was great to see their  newborn “Ultimaker  2“ featuring a neater look with upgraded solutions that includes much faster but quieter printing. Not that it was easy to tell with the noisy crowds.

CRP, the Italian-based 3D printing materials  and service company was there and presented its electric 3D printed racing bike — this attracted lot of attention from the crowd. Me included.

electric 3D printed racing bike

The Rome event was also the launch pad for the FilaMaker device for easy recycling of 3D printing filament material. Designed by Marek Senický, who had a fully working prototype on show at the event, the FilaMaker produces 3 mm filament which has been tested, and successfully proven, on an Ultimaker 3D printer. Marek is hoping to have a first batch production ready by the end of the year, if all goes well, and sell the Filamaker for around €500.

Robots were also prominent at Maker Faire Rome, as you can see from these pictures I took:

The sheer number of  visitors was unbelievable, considering everyone  had to queue  under the rainy Saturday sky to get into the Faire, you could really feel the excitement in the air when people were seeing and touching 3D printers or 3D printed objects for the first time ever.

The event gave the overall feeling of huge things to come in the 3D printing world, with untold development over the next few years. Everyday people are starting to notice what’s going on and taking an interest. No doubt… this really is the future.

As an entrepreneur in this field, being there for the announcement by Massimo Banzi and Intel was a serious “wow” moment for me. It felt like the beginning of the snowball effect for a movement that’s beginning to gather real momentum.

3D Printing in the Classroom

Interview with Dana Foster: 3D Printing In Education

3D Printing in education is going to be one of the key catalysts to renewing manufacturing in The West. It is literally that important. Something that even politicians are beginning to realise. With this in mind, upon hearing that Dana Foster, Marketer for rp+m and 3D printing evangelist had recent experiences with 3D printing in the classroom, an interview seemed like an opportunity for an educational experience in itself.

3DPI: Hi Dana. As a 3D Printing Marketer you also have experience with children and 3D printing in the classroom. What age group were you talking to?

As a volunteer of Junior Achievement, I was selected to teach a 3rd grade classroom once a week for five consecutive weeks. I had the opportunity to not only teach 3rd grade students about business concepts, but I also introduced my company to them so they could learn about manufacturing and 3D printing.  I have also had several opportunities to attend high school and middle school classes with one of rp+m’s engineers to help introduce 3D printing and how the information they are learning in the classroom can be applied.

3D Prining in Education

3DPI: Children in industrialised countries gain lucidity with technology very quickly in this digitally saturated days: was there a thirst for the technology?

Students were absolutely engaged in our discussions.  The 3rd graders wanted to know if different objects in the classroom were made using our technology (injection moulding and 3D printing).  As for the high school and middle school students, they wanted to use their design software more, so they could print their own parts.  According to the teachers, students were coming into school early, staying late and asking to come into the classroom during their study halls.  The teachers said this never happens! 

3DPI: How did you communicate the way additive processes work?

For the 3rd graders, I described the process as you can create your own 3D model on a computer, such as an iPhone cover (Yes- 3rd graders know everything about iPhones, iPads, etc), send the file to the magnificent 3D printers and the 3D Printer will read the file and start printing your part.  There were a lot of questions if it’s similar to a computer printer and I would answer “Yes, very similar, however instead of 2D, the part comes out as an iPhone cover, so you can touch and feel it. 

3DPI: Was there an onus upon particular types of 3D printing such as FDM or SLS?

I would not say there was an onus, however, when we brought in parts to show or the actual 3D printers themselves (middle school and high school classes), they were FDM and Objet.  At the time, those were the two 3D printing processes we had in-house. Although, now we have also expanded into metal machines — but these are not so easily transportable. 

3DPI: Did you have props such as 3D printed items, or a 3D printer itself?

Yes.  For the 3rd graders, I brought in various parts they would recognize, such as a toilet, that we 3D printed. For the middle school and high school classes, we (Patrick Gannon and myself) brought in a Stratasys uPrint 3D printer and would leave it in the classrooms for a week or two. Specifically for the high school class, we had an iPod case design contest between all of the students and the winners were able to print their design on the uPrint.

All of the designs were very creative, so we decided to leave the uPrint in the classroom for a couple of weeks to print all of the designs.  This is when the students would come into school early to see their design being printed, stay late, or ask to come into the classroom to see the printer working instead of going to Study Hall. 

3DPI: What sort of questions were the students asking?

As stated above, the 3rd graders started asking questions if we made certain parts, such as trashcans, tables, chairs, and more items located in the classroom.  My favorite question was, “Do you make the plastic bags that my mom puts my peanut butter and jelly sandwich in for lunch?”  I tried to hide my laughter, however, thought it was a great question!  You could see the engagement in the students and they were only 8 or 9 years old!  When I was growing up, we never talked about how things were made, such as trashcans, tables, chairs, etc.  In my opinion, these kids will look at manufacturing as an attractive career choice if we include manufacturing education and software into the curriculums.

3DPI: What recommendations would you make to teachers and others in explaining 3D printing to kids?

My recommendation I would make to teachers and others in explaining 3D printing to kids is to first fully understand why 3D printing is so amazing.  Once this is complete, you should explain it in a way the kids will be able to understand.  Relate it to their lives.  Show examples of parts they will understand that can be made on 3D printers.  Videos help tremendously too!  If you do not have access to a 3D printer, do not hesitate to contact me or others around you to figure out a way to see it live in action.  My final recommendation is when explaining the process show your passion while doing it.  Kids pick up on those kinds of things, so if they see you are passionate and excited about 3D printing and manufacturing they will be that bit more interested in the process!

3D Printer Calibration, General procedures

by: RepRapWiki

Calibration is the collection of mechanical “tweaking” processes needed to get exact, quality prints. While your reprap machine may be working as far as the electronics are concerned, calibration is necessary to have well printed parts.

Without calibration, prints may not be the correct dimensions, they may not stick to the build surface, and a variety of other not-so-wanted effects can occur. A Reprap can be calibrated to be as accurate as the mechanics allow.

Once you have finished the physical build of your reprap printer Calibration is the next big hurdle. Trying to print before calibration will likely result in a messy “blob” smeared over the printer bed.

The following set of objects and notes are taken (and edited) from Coasterman who posted them to Thingiverse. They have been moved to the RepRap wiki so that they could more easily be edited and contributed to by the broader community.

The specific recommendation made in this article are based on Skeinforge (or sfact). This information should be nearly equivalent for many other softwares. Regardless of the software used, the set of calibration objects is invaluable.

Note that calibration is an ongoing process that needs to be performed throughout the life of the printer. There are almost always adjustments and tweaks that can be done to improve print quality.



Whilst calibration is a somewhat iterative process; the order of calibration laid out below is quite important.

It is PARTICULARLY IMPORTANT that the calibration of the motors is done first as poorly calibrated motors can destroy a Pololus and potentially the motors!


Before attempting calibration, a few things are necessary:

  • A stable build process should be established. Your machine should be completely built and all of the nuts and bolts tightened down.
  • The machine should be on a steady, flat, level surface.
  • Calipers, a level, and any necessary wrenches/screwdrivers to adjust the machine should be handy.


Calibration processes

Motor Calibration

Objective: set the current for the stepper motors to the correct level.

Your motors should be quiet when running and can occasionally make musical sounds, particularly when making circles. If they are making a fair amount of noise then you have a problem.

Calibration Object: None

NOTE: incorrect current settings can damage your pololus and/or your motors.


Motors make significant noise.

This generally means you have too much current.

Motor vibrates without turning.

This generally means that you don’t have sufficient current to the motors. You could also have a problem with a part sticking which stops the motor from being able to drive the axis. It might also be possible to be way off in your steps/mm (eg typo), when steps/mm is double the correct value your motor might vibrate on the spot.

Axis movement pauses momentarily and then resumes.

You may have too much current going to the motor which is causing the pololu to over-heat. Reduce the current. This can also be caused by firmware but check your motors first. Another possible cause is the set screw on the gear is not tight enough.


Each Pololu has a trimpot located next to the heatsink. The trimpot controls the current that is sent to each motor. Turning the trimpot counter-clockwise reduces the current to the motor, turning it clockwise increases the current to the motor.

Start by adjusting the trimpot down until your motor vibrates on the spot rather than turning cleanly. Now turn the trimpot in a clockwise direction in small increments (1 eighth of a turn) until the motors just start running. Then give the trim port a final turn of about 1 eighth of a turn and your should be good to go.


Bed Leveling

Objective: To level the print bed so that your objects will adhere to the surface. The result of this step should make the extruder nozzle the exact same height above the bed across the entire bed surface.

Signs of having an unlevel bed: Plastic will adhere to part of the bed but not others. The extruder nozzle might “dig” into parts of the bed, pulling up or deforming the bed surface.

Importance: The first layer of the print is the foundation of all subsequent layers. Having bad first layers could mean the part might peel off of the print bed during the print, “blobs” of plastic may form, causing problems in following layers, and a variety of other things.

Calibration Object: bedleveling.stl


Step 1 – Establish a corner height:

  • Move the nozzle to a corner of the bed and measure its height at this point.
  • Move the nozzle down close to the bed.
  • Use a thick piece of paper or plastic as a shim and slide it under the nozzle. You should feel a slight drag from the extruder on the paper as you pull the paper through. If not, move your nozzle up or down slightly until it does.

Step 2 – Getting the second corner:

  • Move the Y axis (the bed should move) to the second corner.
  • Using the same shim, determine if the bed is too close or too far away from the nozzle at that point.
  • Adjust the screws that hold up the bed along that edge so that the height at the corner matches your shim.
  • Move back to the first corner and check the height with the shim again. It should match, if not, repeat step 1 and step 2 until it does.

Step 3 – Getting the third and fourth corners:

  • There are two ways to adjust this – tweaking the jack screws that hold up your X axis rails and adjusting the bed itself.
    • Jack screw method:
      • Move the Y axis to the third corner and check it with the shim. If it is too high or too low, turn off the motors and slightly rotate one of the jack screws until the nozzle height matches the shim.
      • If this method is used, you MUST return to the second corner and move the nozzle up/down to the shim, and then repeat this method until both sides line up with the shim.
    • Nut and bolt method:
      • Move the Y axis to the third corner and check it with the shim. If it is too high or too low, adjust the bed screws along that edge until they line up.
      • Check the height with the second corner and repeat this method until the corners line up

Once the bed is level print the Bed Leveling Calibration test object and ensure that each square is even, smooth and consistent.

Other methods do exist. Reference Leveling the Print Bed for more information. You may want to download the original scad file so that you can change the dimensions to match your print bed.

Bed surface preparation

Objective: correct preparation of the bed to ensure that objects adhere to it.


An incorrectly prepared bed can result in poor adherence of the plastic to the base as well as a ‘bubbling’ effect.

Even a little bit of finger print grease on some surfaces is enough to ruin a print.

Bed preparation will depend on what material your bed is made out of, what you intend on covering it with, as well as what material you expect to be printing:


Clean the glass with a non-abrasive common household window cleaner (or some would recommend acetone/cheap nail polish) and a lint free cloth. Spare no effort in ensuring that the glass is spotless. With a heated bed and ABS you will probably want something to help the print stick to the bed. Options include: 1. Sugar water (Sugar dissolved in Water approx 1:10 by weight) -> bed temp approx 95 2. ABS juice (ABS dissolved in acetone, eg 10mm length of 3mm filament (0.07g) dissolved in 10ml acetone) -> bed temp approx 90 3. Kapton tape (as below)


When applying any type of tape to print on, it is important to make sure the print surface is still smooth when you are done. Attempt to lay down tape edge-to-edge, with no overlap. If applying multiple layers, it can be benificial for the layers to alternate directions, so that direction-specific defects do not build up as you add layers.

Blue Tape

For those printing PLA, blue tape has been found to adhere well to 3M’s ‘Scotch-Blue Painters Tape for Multi-Surfaces #2090’. This tape may be found in two inch rolls, or three inch rolls. The PLA will adhere to multiple layers, so it is advised to place down at least three layers of tape, before printing on a surface, to prevent damage to the print bed.

Kapton Tape

Kapton tape is a heat resistant tape which is commonly used to cover a variety of material types used in beds. The kapton tape provides good adherence for a variety of plastics. It is important to avoid bubbles while applying the tape. The “wet method” is particularly helpful as explained in this video.

Other Materials

TODO: need details on other materials.


Objective: to ensure the hot end temperature is set correctly so that material is extruded cleanly

Calibration Object: None

Extruder steps

Objective: to adjust the extruder steps per unit

Calibration Object:

Printer: Prusa i3

PLA, Bad result at 530 steps:

PLA, Good result at 670 steps:

Maybe others can add there results here


Layer height

Objective: to correct the layer height settings to reflect your printer’s actual layer height.

Calibration Object: 0.5mm-thin-wall.stl


Print the 0.5mm thin wall cube and make sure that the layers adhere well but the nozzle does NOT drag through while printing.

Adjust softwares layer height in .01 increments until you get a nice print. In Pronterface/Skeinforge settings, this can be found under Craft > Carve.

Depending on other factors you may find it hard to get all four walls to print nicely. For the first pass if you can get just one wall looking good then move on to the next test.


Objective: to correct the infill setting.

Calibration Object: 20mm-box.stl


Set infill solidity to 1.0 for this. In Pronterface/Skeinforge settings, this can be found under Craft > Fill.

QUESTION: Now that Slic3r is recommended/integrated,

Which is the correct infill option between:

Rectilinear, Line, HoneyComb, Hibertcurves(slow), Archimedeanchords (slow), Octagramspiral (slow)
Print the cube and analyze the top. If there is NOT ENOUGH plastic (a concave top), reduce the Infill Width over Thickness by .05 increments. If there is TOO MUCH plastic (convex top), turn that parameter up by .05 increments. In Pronterface/Skeinforge settings, this can be found either in Craft > Inset in some versions, or Craft > Fill in other versions.

Once you’re feeling close, start bumping it around in smaller increments.

You may also need to adjust your feed rate.

Adjust the feed rate by increments of 2 or so until you feel close. If it looks really disgusting and blobby, go by increments of 0.5mm. Then go by smaller and smaller increments until you’ve nailed it. Although you probably just want to decrease Infill Width over Thickness instead of decreasing Feedrate because lowering feedrate will degrade the resolution.

Temperature control

Objective: to set the hot end temperature correct for your preferred plastic.

Note: you will find that different types of plastic have vastly different temperatures for both your hotend and your bed. What you might not expect is that different colours for the same material can also required different printing temperatures.

As the tower has quite a small ‘top’ surface area you may need to cool this object as you print. If your printer doesn’t have a built in fan you can use any room fan as a substitute.

Calibration Object: 50mm-tower.stl


Set the ‘Infill solidity’ to 1.0. In Pronterface/Skeinforge settings, this can be found under Craft > Fill.

If the plastic comes out as a drip instead of a cylindrical filament, the temperature is too high. —

Start by doing a simple extruder test to determine what the range of temperatures are that you can extrude at. Reduce the temperature in 5 degree increments until the extruder starts skipping when you do a manual extrude. Turn the extruder up 5 degrees and note this as your minimum extruder temperature.

Print this block.

If it looks like a blob, turn down all the temps by 5 degrees until you get something good. Chances are you won’t need to do this more than 5 degrees.

Note: Be careful as going too low can result in the plastic setting making it hard for the motors to drive the plastic, possibly causing wear or damage.

TODO: list temperature ranges for common plastics.



Hotend: 185 °C Bed: 60 °C

ABS Hotend: 230 °C

Bed: 110 °C

Perimeter Width

Objective: correct the perimeter width over thickness. In newer versions Edge Width over Height.

Calibration Object: perimeter-wt.stl


This test prints two objects which are designed to fit together.

Try to insert the smaller block into the larger block. Try inserting it differently a few times, and check your belt tensions.

TODO: Need notes on calibration of belt tensions
If you can get it in a few mm, good. If you can get it in all the way, awesome. The fit should be snug. If it is loose and can jitter around inside, decrease the perimeter width over thickness, also called Edge Width over Height. In Pronterface/Skeinforge, “Edge Width over Height” can be found in Craft > Carve in the Slicing Settings. If you CANNOT get it in AT ALL, and you are sure there are no whiskers blocking it, INCREASE perimeter width over thickness or Edge Width over Height. The latter is more likely.


Objective: to maximize your printers ability to bridge gaps (i.e. print in thin air).

Calibration Object: 20mm-hollow-box.stl


Print the calibration object and if the top droops in, increase the BRIDGE FEEDRATE MULTIPLIER in Speed by increments of .1 until the top stops drooping.

Print Precision

Objective: improve print precision

Calibration Object: precision-block.stl


Then there is the precision block. No real huge calibration parameter here. Just play with this and see how well it does on the overhangs and shapes.

TODO: We need to add some recommendations on how to improve this or find more direct methods of calibrating specific aspects of the print.


Objective: fix overhang problems

Calibration Object: overhang-test.stl



Then there is a simple overhang test. Print and observe the overhangs. This is up to you to figure how to improve the overhangs.

TODO: We need to add some recommendations on how to improve this or find more direct methods of calibrating specific aspects of the print.

gregor: i get better results when i add a fan to cool the overhang down

this was my test object: [1]


Objective: stop material oozing out of the noozle during ‘non-printing’ moves.

Many extruders will emit (ooze) plastic even when the extruder motor is not turning. To overcome this your slicing software needs to ‘retract’ the print medium during head movement when not printing. The retraction creates negative pressure within the hot end heating chamber which effectively sucks the print medium back up through the nozzle, stopping it from oozing.

Calibration Object: oozebane-test.stl

The calibration object prints two towers about 30 mm apart. The head must move between each of the towers at each layer. If your printer is not set correctly then you will see many fine filaments (or strings) between the two towers. You can eliminate these filaments by eliminating ooze.

Calibration Object 2 (Variable sized towers for testing ooze): variable_size_ooze_test_nobase.stl

This is a simple model to help tune reversal parameters for a stepper extruder (using much less filament before actually testing the ooziness). It consists of a number of towers with different thicknesses, with different spacing between each tower. A well-tuned bot should be able to produce even the smallest towers.


This is to try to control ooze and calibrate it to be useful.

Start by setting the Early Shutdown distance to 0 and Slowdown Startup Steps to 1.

Print the piece and measure the length of stringers where the extruder shut off and the line is thick before becoming a thin whisker. Take that length and put it into early shutdown distance.

Play with Early Startup Distance Constant until the place where the extruder arrives at the other tower is nice and smooth, so that there isn’t any empty space where plastic should be, but there isn’t excess plastic extruded.

Since Slic3r 0.9.10b there is a wipe before retract option (under Printer Settings => Extruder) which seems to make the most difference. Other options to consider: reduce temperature, increase travel speed, retracting more, retract slower, z-lift before travel or lowering extrusion ratios.


Objective: eliminate droop from overhangs.

Calibration Object: BridgeTestPart.stl


If the calibration object droops, you likely need to decrease “Bridge Flowrate over Operating Flowrate.” Or increase “Bridge Feedrate over Operating Feedrate.”

X & Y scaling and steps/mm calculations

The following information concerning steps/mm adjustments is outdated. It has since been agreed that steps/mm should be set to the exact calculated values since printing with non-ideal steps/mm results in an accurate test piece, but makes the dimensions on every other part even more inaccurate.

Scaling goes into the STEPS_PER_MM of the firmware, track offset goes into the G-code compiler (Skeinforge etc.).


The most simple way to get reasonably accurate parts is to simply ignore the track offset or to set it to some guessed value, then adjust scaling of the axes, only:

<math>\frac {\mbox {current steps per mm} \cdot \mbox {expected distance movement}} \mbox{actual measured distance}</math>

E. g:


Then repeat:


Until you get your desired steps per mm.

(Do note that there is a setting in configuration.h that enable these EEPROM functions.)

 M501 (show current settings (steps per mm etc)
 M92 X44.04982491245622811406 (change steps per mm to your calculated value, useful for any axis; X,Y,Z and E for Extruder)
 M500 (save your new settings)
  • In Teacup firmware you multiply these values by 1000, to get steps per meter, and put the value left of the decimal into config.h’s STEPS_PER_M_X, STEPS_PER_M_Y, … . Then, re-upload the firmware.

Track Offset

OK, here we get a bit stuck. While the theory section below nicely shows how to calculate the optimum track offset, Skeinforge has no configuration option to adjust this value.

An excerpt from a chat between Greg Frost and Traumflug, on 2011/22/06:
[14:30] <GregFrost_> I calibrated the extruded length and then set feed=flow and pw/t and iw/t to 1.5 and immediately got nice looking prints. However, and here is the kicker, the objects are all slightly too big because my single wall box has an actual w/t of 2.1
[14:31] <GregFrost_> I can fix this with p flow but then i get thin preimeters and they dont alway bond well to each other (but objects are the right size).
[14:31] <GregFrost_> I would like normal flow on the perim but a wider w/t but if i do that it adjusts all of the flows up and I get far too much plastic.
[14:32] <GregFrost_> what I really need is a way to change the distance inside the objest that the perimeter is traced without changing the flow rates.
[14:37] <Traumflug> To be honest, I never used Skeinforge, this adjustable track offset is an assumption.
[14:38] <GregFrost_> Traumflug: it would be a good setting, i agree.
[14:38] <GregFrost_> Traumflug: I think the only way to achieve a track offset is to adjust the perimiter w/t ratio.
[14:38] <Traumflug> So, Skeinforge doesn’t compensate for track width?
[14:38] <GregFrost_> Traumflug: it does. but it uses the perimiter witdth/t and infill w.t settings
[14:39] <GregFrost_> Traumflug: then it uses the layer height
[14:39] <GregFrost_> Traumflug: and useing those it works out the track offset.
[14:39] <Traumflug> ok, good to know.
[14:39] <GregFrost_> Traumflug: but the kicker is, changing perimeter w/t also adjusts the flow rate
[14:40] <GregFrost_> Traumflug: so theoretically when you choose a new w/t, it puts out enuf plastic to fill the width.
[14:40] <Traumflug> Yes, theoretically
[14:41] <GregFrost_> Traumflug: but on the perimiter if you use the same volumetric flow as the infill, it bulges past the desired width because there is no containing line.
[14:42] <GregFrost_> but the one setting that allows you to compensate for that adjusts the flow on all other lines (both infill and permiiters)
[14:42] <Traumflug> IMHO, changing the plastic flow to compensate for size errors isn’t a good way.
[14:43] <GregFrost_> Traumflug: I agree completely.
[14:43] <Traumflug> Each time you change the flow, a lot of minor parameters change as well, so a prediction is very difficult.
[14:43] <GregFrost_> I want to change the track offset.

Theory and Maths

By Markus “Traumflug” Hitter.

X and Y Axis

Both horizontal axes can be calibrated with two values: track offset and overall scaling. To find out how this is done, let’s have a look at a part specially designed to find out those values:

RepRap Calibration Frame Drawing.png

It’s a frame, similar to the one you use to put pictures up onto the wall. The essential part here is, it has long and short distances to measure on the same part. We need to measure both, to distinguish between track offset and scaling.

To the right of the drawing, a few tracks laid down by the extruder are sketched in. It shows how the track offset lets the extruder move closer to the inside of the part, so the outer side of the track just ends where the part should end as well.

All the sizes are overlaid by scaling, which is sort of a “gear ratio” between measurement units and stepper motor steps.

Calibration Object


// X-Y Calibration object
// See

difference() {
	cube([100,100,3], true);
	cube([80,80,3.1], true);

STL file


Basic Equation

With that knowledge, we can sum up what the extruder moves to get the size T = 10 mm exactly 10 mm wide:


\mbox{movement} = ( \mbox{intended size} – 2 * \mbox{track offset} ) * \mbox{scaling} \\ \end{align}</math>

This holds true for measurements of any size, i.e. also for the 100 mm size of our calibration frame:


M_{10} & = ( 10\,\mbox{mm} – 2 * TF ) * S \\ M_{100} & = ( 100\,\mbox{mm} – 2 * TF ) * S \\ \end{align}</math>

You see? Two unknowns and two equations, so the set is solvable.

Extending to Erroneous Movements

Now, the whole point of this writing is, the extruder movement doesn’t match what we need to get accurately sized parts. So we have not only a movement, but also a movement error.

The reason for the movement error is, according to the basic equation, erroneous track offset and/or erroneous scaling.

Get these two into the basic equation, result to the left, reason to the right:


& \mbox{movement} * \mbox{movement error} = \\ & ( \mbox{intended size} – 2 * \mbox{track offset} * \mbox{track offset error} * \mbox{scaling} * \mbox{scaling error} \\ \end{align}</math>

Again, this holds true for both our measurements:


M_{10} * E_{M10} & = ( 10\,\mbox{mm} – 2 * TF * E_{TF} ) * S * E_S \\ M_{100} * E_{M100} & = ( 100\,\mbox{mm} – 2 * TF * E_{TF} ) * S * E_S \\ \end{align}</math>
… to be continued … about a formula to get scaling and track offset from measuring these 10 mm and 100 mm …

Z Axis

On the Z axis, there is no track offset compensation, so calibration is reduced to scaling of part height. Build any part of 50 mm height, let it cool down, measure it. Then adjust your STEPS_PER_MM in your firmware’s config.h to reduce the difference between intended and received part.

As most RepRaps use a threaded rod on the Z axis, the theoretical value, which can be generated from the online calculator, should match reality pretty close. However, there’s also material shrink as the plastics is printed at a higher temperature than room temperature.

ABS and PLA filament for 3D Printing


This entry was posted on January 27, 2013 by Luke Chilson.

You’ve got a 3D Printer, or you’re looking to buy a 3D Printer and each one seems to indicate it prints in either ABS, PLA, or both. So you find yourself wanting to know, what is the difference between ABS and PLA.


Some Common Ground

There are many materials that are being explored for 3D Printing, however you will find that the two dominant plastics are ABS and PLA. Both ABS and PLA are known as thermoplastics; that is they become soft and moldable when heated and return to a solid when cooled. This process can be repeated again and again. Their ability to melt and be processed again is what has made them so prevalent in society and is why most of the plastics you interact with on a daily basis are thermoplastics.

Now while there are many thermoplastics, very few of them are currently used for 3D Printing. For a material to prove viable for 3D Printing, it has to pass three different tests; initial extrusion into Plastic Filament, second extrusion and trace-binding during the 3D Printing process, then finally end use application.

To pass all three tests, a material’s properties must lend desirably to first, it’s formation into the raw 3D Printer feedstock called Plastic Filament; second, process well during 3D Printing giving visually pleasing and physically accurate parts; and lastly, it’s properties should match the intended application, whether that be strength, durability, gloss, you name it. Often, a material will pass one test so superbly, that it becomes worth the extra effort to battle with it during its other stages. Polycarbonate, a lesser known printing material is this way. For some applications, it’s strength and temperature resistance makes it worth the battle to print accurate and fully fused parts.

The first test, that of production from base plastic resin into top-notch Plastic Filament such as what we carry is a strict and carefully monitored process. It is a battle of wits and engineering that takes the plastic from a pile of pellets to a uniformly dense, bubble free, consistently sized, round rod. Here there is little difference between ABS and PLA; most thermoplastics can pass this test, it is mainly just a question of the time and costs required to do so while still producing Plastic Filament that runs smoothly and consistently during the next stage, 3D Printing.

Here is where the two plastics divide and will help to explain why different groups prefer one over the other.


Both ABS and PLA do best if, before use or when stored long term, they are sealed off from the atmosphere to prevent the absorption of moisture from the air. This does not mean your plastic will be ruined by a week of sitting on a bench in the shop, but long term exposure to a humid environment can have detrimental effects, both to the printing process and to the quality of finished parts.

ABS – Moisture laden ABS will tend to bubble and spurt from the tip of the nozzle when printing; reducing the visual quality of the part, part accuracy, strength and introducing the risk of a stripping or clogging in the nozzle. ABS can be easily dried using a source of hot (preferably dry) air such as a food dehydrator.

PLA – PLA responds somewhat differently to moisture, in addition to bubbles or spurting at the nozzle, you may see discoloration and a reduction in 3D printed part properties as PLA can react with water at high temperatures and undergo de-polymerization. While PLA can also be dried using something as simple as a food dehydrator, it is important to note that this can alter the crystallinity ratio in the PLA and will possibly lead to changes in extrusion temperature and other extrusion characteristics. For many 3D Printers, this need not be of much concern.


ABS –  While printing ABS, there is often a notable smell of hot plastic. While some complain of the smell, there are many who either do not notice it or do not find it to be particularly unbearable. Ensuring proper ventilation in small rooms, that the ABS used is pure and free of contaminants and heated to the proper temperature in a reliable extruder can go a long way in reducing the smell.

PLA – PLA on the other hand, being derived from sugar gives off a smell similar to a semi-sweet cooking oil. While it certainly won’t bring back fond memories of home-cooked meals, it is considered by many an improvement over hot plastic.

Part Accuracy

Both ABS and PLA are capable of creating dimensionally accurate parts. However, there are a few points worthy of mention regarding the two in this regard.

ABS – For most, the single greatest hurdle for accurate parts in ABS will be a curling upwards of the surface in direct contact with the 3D Printer’s print bed. A combination of heating the print surface and ensuring it is smooth, flat and clean goes a long way in eliminating this issue. Additionally, some find various solutions can be useful when applied beforehand to the print surface. For example, a mixture of ABS/Acetone, or a shot of hairspray.

For fine features on parts involving sharp corners, such as gears, there will often be a slight rounding of the corner. A fan to provide a small amount of active cooling around the nozzle can improve corners but one does also run the risk of introducing too much cooling and reducing adhesion between layers, eventually leading to cracks in the finished part.

PLA – Compared to ABS, PLA demonstrates much less part warping. For this reason it is possible to successfully print without a heated bed and use more commonly available “Blue” painters tape as a print surface. Ironically, totally removing the heated bed can still allow the plastic to curl up slightly on large parts, though not always.

PLA undergoes more of a phase-change when heated and becomes much more liquid. If actively cooled, much sharper details can be seen on printed corners without the risk of cracking or warp. The increased flow can also lead to stronger binding between layers, improving the strength of the printed part.

ABS and PLA General Material Properties

In addition to a part being accurately made, it must also perform in its intended purpose.

ABS – ABS as a polymer can take many forms and can be engineered to have many properties. In general, it is a strong plastic with mild flexibility (compared to PLA). Natural ABS before colorants have been added is a soft milky biege. The flexibility of ABS makes creating interlocking pieces or pin connected pieces easier to work with. It is easily sanded and machined. Notably, ABS is soluble in Acetone allowing one to weld parts together with a drop or two, or smooth and create high gloss by brushing or dipping full pieces in Acetone.

It’s strength, flexibility, machinability, and higher temperature resistance make it often a preferred plastic by engineers and those with mechanical uses in mind.

PLA –  Created from processing any number of plant products including corn, potatoes or sugar-beets, PLA is considered a more ‘earth friendly’ plastic compared to petroleum based ABS. Used primarily in food packaging and containers, PLA can be composted at comercial compost facilities. It won’t bio-degrade in your backyard or home compost pile however. It is natural transparent and can be colored to various degrees of translucency and opacity. Also strong, and more rigid than ABS, it is occasionally more difficult to work with in complicated interlocking assemblies and pin-joints. Printed objects will generally have a glossier look and feel than ABS. With a little more work, PLA can also be sanded and machined. The lower melting temperature of PLA makes it unsuitable for many applications as even parts spending the day in a hot car can droop and deform.

In Summary

Simplifying the myriad factors that influence the use of one material over the other, broad strokes draw this comparison.

ABS – It’s strength, flexibility, machinability, and higher temperature resistance make it often a preferred plastic for engineers, and professional applications. The hot plastic smell deter some as does the plastics petroleum based origin. The additional requirement of a heated print bed means there are some printers simply incapable of printing ABS with any reliability.

PLA – The wide range of available colors and translucencies and glossy feel often attract those who print for display or small household uses. Many appreciate the plant based origins and prefer the semi-sweet smell over ABS. When properly cooled, PLA seems to have higher maximum printing speeds, lower layer heights, and sharper printed corners. Combining this with low warping on parts make it a popular plastic for home printers, hobbyists, and schools.

Industries and Companies ideal for 3D Printing

Industries and Companies ideal for 3D Printing                                         by: 3Sourceful

While mainstream adoption is still many years away, 3D printing is already common in certain niche applications.  The key success drivers to adoption of 3D printing for a particular application are:

Low Quantities – 3D printing technology is typically only economical for low production quantities.  As quantities increase, its higher production costs make it uncompetitive.

High Willingness-to-Pay – Since production and material costs are significantly higher with 3D printing; industries that are extremely cost sensitive are not good candidates for adoption.

High Complexity – Products demanding complex forms help justify the increased cost of 3D printing.  Traditionally, complexity can require multiple production technologies and assembly steps.  As described above, complexity is ‘free’ in 3D printing.

Supply Chain Impact – The unique tooling and setup costs of 3D printing mean that it can be quite disruptive in small niches of the supply chain.  Industries and applications that have high supply chain costs relative to products costs are good candidates for adoption.

Data Availability  – All 3D printers need computer data to operate.  Certain industries and applications have an advantage in having a wealth of data available so that they reduce the content creation barrier to adoption.

The following industries and applications can be broken down along these factors.  Note that most applications require that several factors be favorable for adoption.

Medical Devices –Medical devices have been using 3D printing technology for quite some time.  There are several factors for this.  All custom medical devices have production values of one.  Products are purchased on performance vs. cost.  Complexity is high for prosthetics, etc.  And, the recent advantages in scanning technologies mean that there is a wealth of digital data available.  An example application is Invisalign.  Invisalign 3D prints series of orthodontic correction devices for their customers from their dental scans.

Aerospace – As with many new technologies, aerospace is one of the first major industries to adopt.  Performance requirements are high and production volumes are much lower as compared with consumer devices.  There is also a high willingness-to-pay.  Finally, since programs can last decades, keeping the required spare parts on hand is very difficult and costly.  Examples of applications of 3D printing in aerospace include instrument panels made by RC Allen.  General Electric Aviation recently acquired one of the major metal 3D printing service providers, Morris Technologies.

Niche Markets  – Traditionally, when small companies have ideas for physical products they often cannot execute on their ideas because of the large fixed costs associated with having something produced.  These barriers are now removed.  Kappius components are a great example.  Kappius makes very racing bicycle components for a particular style of competition.  Due to volumes, high customer willingness to pay, and high product complexity, 3D printing was the best technology for production.

Spare Parts – While most businesses try to avoid inventory, inventory is the business in the spare parts industry.  A huge variety of parts have to be held for many years.  Rather than buying and holding, 3D printing could print spare parts on demand.  Volumes are low enough to remain cost competitive.  And customers typical have a very high willingness-to-pay since the parts may well be critical for larger equipment.  NASA has discussed using a 3D printer in space to produce parts when needed.  And newer companies, such as the Swedish music products business Teenage Engineering, are utilizing 3D printing to eliminate that portion of their supply chain.  Teenage Engineering now posts the CAD files for the spare parts for free and will tell users where to have them printed. (

Mass – Mass Customization – Shapeways is a New York based venture funded company that creates a market for consumer to consumer sales.  Individuals can upload their own designs for anyone to purchase.  Shapeways performs the 3D printing for all designs sorted through their site.  Additionally, Shapeways has solved the ‘CAD data issues’ as users provide the necessary CAD designs.  Shapeways has received $47MM in venture funding to date.  (Tech Crunch)

A summary of these factors applied across industries is below: