Calibration of your RepRap

Calibration of a RepRap is the single most important part of assembly.  Once you have the Cartesian bot is completed the next step is calibration.  Calibration is a several step process to insure that all axis of your Cartesian bot are working nominally, and the Cartesian bot is properly described to the firmware.  Follow these steps and your prints should look great from day one.

writing a calibration guide, would you agree the proper order of calibration is confirm free motion of all 4 axis, stepper motors able to strongly move all 4 axis over 100mm without overheating, calibrate step/mm, confirm belt tension with vibration test, confirm acceleration with a high speed movment test (X-100Y100 to X100Y-100), then level bed, tune PID, confirm extrusion temp

Confirm free moment and levelness of all Axis

All Axis of your machine should be able to move along their full travel length with almost no resistance.  Meaning if you where to lean your machine to 1 side the trolley should glide along to follow the lean.  If your Axis does not move this smoothly you likely have one of Several issues:
  • Your bearings are not Properly aligned with the rods:  This is the the most common issue issue with RepRap machines.  a slight warping of parts can lead to rods and bearings  not lining up perfectly.  Higher end linear motion like Igus bushings or Self Centering brass will bind if there if they are even 0.1-0.5mm of out of parallel.  LM*UU style bearings are more tolerant of slightly out of parallel rods, but it will lead to thier them failing quicker.  The easiest way I have found to fix this issue is to 1st clean out what ever is holding your rods with a drill bit, if that does not work use a hot air gun to soften the plastic enoug that you can move the rod the less than 1mm it takes usually to make the rods true.

  • The Bushing is too tight/broken: Igus and Self centering can be a really tight fit.  Before installing your bushings on your machine be sure to slide them up and down your uninstalled rods.  There should be almost no reistance to motion when they move.  If you can't make them fall down the rods with no effort, the bushing is not ready to be installed.  If this is a Igus or brass bushing sometimes you need to place one of your rods in a drill and "burn in" the rod

  • Confirm Stepper motors have the ability to move all axis the correct direction and power

    Q: My motor steps in the wrong direction - + moves it toward the endstop, and -moves it away.
    A: Reverse the motor wires - ABCD to DCBA.

    Q: My motor only steps in one direction - away from the endstop.
    A: Your firmware thinks the endstop is blocked.
        1) Block the endstop, and see if you can move toward it.
            Yes: Adjust the endstop inversion constant in your firmware.
            No: Insure that the endstop is connected to the proper connecter.  You want to connect your endstops to the "Minimum endstop" connectors on your hardware.
    Q: My motor doesn't step in either direction.
    A: There are several possibilities:
        1) The firmware isn't configured properly, and is trying to use different pins to control the motor than are required for your hardware.
            Double-check your firmware's configuration.h and pins.h files to insure that they're set up properly.
        2) The step signal isn't making its way from the processor to the stepper driver.
            Resolder all of the pins between the processor and the stepper card.
        3) The motor current is way too low.
            Turn the motor current adjustment pot clockwise a bit at a time, until the motor is stepping properly.
        4) The magic smoke leaked out of the stepper driver.
            First, figure out what it was you did that smoked the driver, so you don't repeat it.  Then replace the stepper driver.

    Q. I can't get my motor into the sweet spot between enough current and too much.  If I turn it down enough to stop from overheating, I get skipped steps.
    A. Add a fan, heat-sink or both to the motor and/or driver (depending on which one is overheating).

    Q: In which direction should the Axis move? 
    A: Z goes up when going positive, down when going negative
        X goes left when going negative and right when going positive
        Y goes forward when going positive and back on the negative
       You can reverse stepper direction by flipping the stepper plug, or changing settings in firmware.  ALWAYS REMOVE POWER BEFORE UNPLUGGING A STEPPER

    Calibrate the step/mm on all 4 axis

    Confirm belt tension on X and Y axis

    Calibrate Acceleration Value (recheck belt tension)

    Level Bed, Set Z endstop

    Tune PID on Hot end

    Perform Temp check with bridging object

    Q. In some places on my prints, the infill doesn't connect to the perimeter shells.
    A. You have backlash in one or both axis.
        1) Check to make sure your belts are tight.  You should be able to pluck them like a bass guitar string.
            Adjust your belt tension.
        2) Check to make sure that your belts actually match your pulleys.  Kit manufacturers are notorius for providing XL belts and T5 pulleys.  As much as people in forums claim that you can use T5 pulleys with XL belts, it's just asking for backlash.
            Replace the pulleys with ones that match the belts.
        3) "I have T5 Belts, and aluminum T5 pulleys I bought on ebay"
            Replace the machined pulleys with printed ones. Unless you bought ones that were specifically designed for use on a printer, the teeth on them were designed for a single direction of rotation, and make no attempt to reduce backlash. 
        4) Check to make sure that your belts aren't binding against the guide washers.
            One way to fix this is to double up the belt guide bearing, and leave off the fender washer.  Then carefully adjust your belt's position and angle on the carriage so that it doesn't drift off of the bearing.
            An easier fix (that works for me) is to lubricate the belt guides with Teflon/Silicone lubricant.  The disadvantage to this method is that the lube will eventually make its way to the pulleys, amplifying any backlash potential that is there.

    Q. My print suddenly gets shifted over by Xmm, partway through the print.
    A. This could be caused by a number of problems. The most likley is you need to adjust the current for your stepper motor - find the adjustment pot for the motor, and carefully turn it up (clockwise) a tiny bit.  If you still lose steps, turn it up a bit more. It could also be due to your belt tension being too low (and too high of tension can lead to current probelms as above). Belt or bearing binding is another common cause of these problems. Make sure your axes all move smoothly, if you feel any sticky spots that could be the cause. 

    Q. One of my motors just stops turning partway through an otherwise perfect print.
    A. Most likely, the motor is overheating, and losing torque.  You need to turn down (counter-clockwise) the adjustment pot for the motor.

    Print calibration piece and upload image in #RepRap channel to have community help you find final issues. 

    Troubleshooting your axis motion:
    First off - If you're using Pololu motor drivers, make sure they're installed facing the right direction.  They're not keyed, and installing them backwards can damage all kinds of things.
    Second - if you haven't adjusted your motor current, then turn the printer off, find the trim pots on the motor drivers, turn them all the way counter-clockwise, and then turn them about 1/4 turn clockwise.  This will be a good starting point for adjusting them.  Failing to adjust motor current can damage either the motor drivers, or the motors themselves.


    Q. Which type of plastic should I print with?
    A. PLA and ABS are the two main types.  They both have advantages and disadvantages.
      PLA warps less and can be printed on an unheated surface (3M Blue Tape 2090 works well. 2090 only, 2080EL and Edgelock/Advanced types do not stick as well.). It is also a harder plastic, it has less flexibility than ABS and when it breaks it tends to shatter.  PLA prints at about 180 degrees C and has a sweet smell (like burned sugar/waffles). PLA also prints wonderfully to either plain glass or Kapton heated to 60c. 
      ABS prints best on a heated surface, kapton over aluminum or glass are popular choices.  Without heat abs will curl up and ruin the print.  ABS has a bit more flexibility than PLA which makes it better suited to parts like the prusa bar clamps.  It prints between 200 and 230 degrees C and the smell bothers some people.

    Q. What order do the wires in my stepper motors get connected to my Stepper Driver?
    A. Ramps and Sanguinololu Electronics both have motors attached in an AABB pattern meaning the 2 wires from one coil are attached to the first two pins and the 2 wires from the second coil are connected to the second 2 pins. The order of the coils is not critical. You can determine which wires go to the same coil because you will be able to measure the resistance of the coil across the wires. Wires from separate coils will read as open-circuit. The color coding of the stepper motor wires is different for each manufacturer.
    Q. My print suddenly gets shifted over by Xmm, partway through the print.
    A. This could be caused by a number of problems. The most likley is you need to adjust the current for your stepper motor - find the adjustment pot for the motor, and carefully turn it up (clockwise) a tiny bit.  If you still lose steps, turn it up a bit more. It could also be due to your belt tension being too low (and too high of tension can lead to current problems as above). Belt or bearing binding is another common cause of these problems. Make sure your axes all move smoothly, if you feel any sticky spots that could be the cause. Also maybe due to firmware (such as Marlin).
    -It also could mean that your motors are getting too hot. Try putting a small PC fan on the axis that is having the shift. (Example: Print shifts in Y-direction, put a fan on the Y motor.)
    Q. One of my motors just stops turning partway through an otherwise perfect print.
    A. Most likely, the motor is overheating, and losing torque.  You need to turn down (counter-clockwise) the adjustment pot for the motor.
    Q. I can't get my motor into the sweet spot between enough current and too much.  If I turn it down enough to stop from overheating, I get skipped steps.
    A. Add a fan, heat-sink or both to the motor and/or driver (depending on which one is overheating).
    Q. My prints will not stick to the HBP (Heated Build Plate).
    A. Many things can cause a print not to stick, check these things:
    -Is your HBP hot enough?  70C for PLA 110-120C for ABS
    -Have you got skin oil or lube from the axises on the plate?  It will cause prints not to stick (you can clean them with alcohol, acetone, or ammonia (Windex, tested on glass) )
    -Are you pressing the 1st layer into the HBP enough? The extrusion should take on a slightly flat appearance without actually squishing it (you should not see the nozzle dragging thought he middle of the print. Starting height differences of only 0.05mm can make a big difference.
    -Are you printing the 1st layer slow enough?  All materials like the travel speed to be 15-20mm/s for the 1st layer.
    Q: My printer is doing things not covered in this FAQ, how should I ask my question in #reprap (the irc room)?
    A: 1-  Collect the basic facts about your machine:
    Printer Model:
    Electronics Type:
    Software Toolchain+OS:
    2- Try to include as much detail as possible in your question, every little bit helps.  
    3- Just ask the question, don't worry about asking permission first
    4- Have some patience, there are a lot of people in the room, someone will answer you but you may have to wait a few minutes.
    Q: At the Start of a Print. The Motors begin to print in the top right corner of the HBP Bed. How do I center the motors so they print in the center?  Thanks -
    A: This has to be done in two parts. The first part is setting the maximum bed size to be accurate to your actual bed in the configuration.h file of your firmware. The second part is telling your slicer how big the bed is, and where the print should start.
    Q: My motor will only move towards the endstop, when I press + and also when I press -. I already checked my endstops, and they're fine.
    Q: In the middle of my print, my laptop shut down completely, and reboots. I've already tried it with a different laptop, and the same thing happens. Also checked the temperature of my laptop, and it's barely luke-warm, so that's not the problem either. Anyone has any idea what else to try?
    Q: How inadequate would a 1 cm thick solid pine board be to build some printers envelope? I'm scared about the warp wood has when humidity changes.

    General Questions Below
    Q. How do I get the parts to Build a RepRap?
    A. Big Question, it has it's own Pad at More information on vendors is here
    Q. Where can I buy a completely assembled 3d printer?
    A. Big Question, it has it's own Pad at
    Q. What software should I use to run my printer?
    A. Currently, the easiest software to work with is:
        PrintRun (Host software) -, precompiled for windows (with sfact) at
        sfact (Slicing software) - https:/​/​​ahmetcemturan/​SFACT/, or sfact daily -
        or alternative Slicing software slic3r
        or Repsnapper (all-in-one, fast and 3D)
        Sprinter (Printer Firmware) -

    Pronterface is and precompiled for windows (with sfact) at
    Q. How do you print multiple stl's at the same time using pronterface?
    A. First open, you'll find it in the same directory as  Next right click the grided area and open your first stl file.  Drag the stl around the grid space (your print bed) and use the scroll-wheel to rotate around the z axis.  Right click again to add another file. Export the stl and run it through your slicer.
    If you want to print several of the same stl use the Multiple plugin in skeinforge. 
    Q. How do you move things on the print area?
    Use included with Pronterface, or use the centering part of the skeinforge multiply plugin.
    center is in skeinforge or sfact, activate mGultiply, set rows and columns to 1 each, set x and y center to 100 each. This will center the object on your bed

    Sfact FAQ
    Below answers are based on default SFACT settings.  If you have messed them up you can revert to the defaults by closing SFACT and deleting the sfact_profilesClick directory afterwards.
    This will delete all profiles and SFACt will recreate one with defaults on restart.
    Plugin Names are Printed CAPS
    Q:        How do you open SFACT? Also, how do you load a .STL file in order to create the .GCode file?
    • 3Open the file inside the SFACT directory.  Click the "skeinforge" button to get an open dialog for the stl you want to skein.
    Q:    Why do my Prints come out crappy.  Is something wrong with SFACT?
    • First of all please consider that SFACT was created/is maintained by someone who has no Programming background.  He sled into this while wanting to write documentation for setting up Skeinforge, found that it would be easier to make a spreadsheet for calculating the many Skeinforge settings and finally found that it would be wisest to enter thformulas directly into Skeinforge. 
    •  That resulted in SF by ACTion68 (ACT being his Initials) >> SFACT.  So it is possible that there are faults and we welcome it if you inform us about them.  BUT if you have never had a successful print before and are printing with the default settings of SFACT, you can be sure (about 99%...   yeah I measured..:P) that it is some other problem than SFACT.
    • Too many people had slam-dunk success with their first prints.  Just forget  everything you know about Skeinforge settings. (feed=flow and things like that).
    • Make your first print with default settings of SFACT.   They will be created when you first run SFACT.  Only change Filament diameter to the exact diameter of your filament (3mm filament does NOT equal 3mm, usually it is more like 2.8).
    • The default settings assume you are printing with a 0.5 nozzle. See the calibration section below if you are not running a .5 nozzle.
    • Possible faults for just inconsistent prints are under: Where do I look for possible hardware problems?
    • Look here for some hints on common print problems: 

    Q:    Where do I look for possible hardware problems?
    • Sloppiness of anything. the belts, bolts, smooth-rods, gears, motors.... anything will unavoidably worsen you print quality.  And they dont add up but they multiply....
    • Bad hotend: You might have self sourced most of the parts but stay with the experienced folks for the hot end.  For recommendations visit IRC channel or look up in
    • Bad filament feed system.. I could also have said hobbed bolt but You could also have some other system.  Inconsistent feeding will give you very very bad prints.  You will not be able to calibrate.  Quick way to test this is when you extrude a long piece say 50mm of filament  mark the filament with stripes and then let it slip through your fingers.  It should have one continuous move...  Other methods are to do the calibration of 100mm several times.  The filament should be pulled in the same distance every time. While doing this calibration extrude at no more than 100mm/min, anything faster and your hotend might not be able to hold a high enough temperature.  It is not too bad if its say 98mm, as long as it is 98mm every time.  You can correct for that during SFACT calibration later.
    • A quick check for the   health of the filament feeding system is to make a reference mark on the filament, extrude a certain distance (not too much as you dont want to come the filament loose from the extruder later)  then retract the same amount and see whether the mark arrives at the same point.  20-30mm should be a safe distance for most extruders.  It is no use trying to calibrate/get good prints if your feed is not consistent.
    • Filament that has soaked up humidity.  Most plastics love to soak up the environments humidity.   So does your filament.  But H20 becomes a gas at 100oC.  So the humidity/water in your filament becomes a gas that pushes your filament out 
    • in  bursts or less severe case you have a very runny nozzle..   No way You  will be able to stop that ooze and still get a decent print.   You need  to dry that filament.  For PLA it is recommended to dry in an oven at  60C.  You need to have some fan circulation during the drying process.   PLA will start to soften at that temperature so keep that in mind when  you put it in the oven.  It will get soft and take the shape of the  material it sits on.  Best is to try small amounts first to make sure  the oven shows tha right temperature.    About 2-4hrs the drying will  take.  And reseal the filament after use.  It will soak humidity  again...
    Q:    How do I calibrate Sfact?
    • DIMENSION: Measure your filament and enter it (measure across multiple places using digital calipers and enter the average to 2 sig figs (3.1 or 1.7 respectfully)
    • Inset: Enter your nozzle diameter (no need to measure, just enter the number you bought it as. Nozzle diameter only affects bridging.
    • Set your Filament Packing Density ratio to 1 before beginning this process
    • Print the _40x10.STL file included with Sfact. The default extrusion width in SFACT is 0.6
    • Using Calipers measure the wall thickness of all 4 sides of the thin wall cube.  Throw out the largest value, and average the other 3. (Be sure you measure from the top of the box, not the bottom, the bottom might be flared out because of the 1st layer not being perfectly level.  Also if you have big variations it is a good idea to measure the side that is extruded last as the extrusion will have mostly stabilised by then (after the Z-move).  Try to measure the smallest number of layers possible from top as the slightest vertical misalignment of your layers will increase the measured value.  Ideally a single layer would be best but very difficult with regular calipers. (Make sure the measuring device is not biting into the filament during measurement.)
    • Go Back in Sfact to DIMENSION and click the "Calibrating" radio dial and enter the measurement into "Measured Width of Extrusion".  Reskein the _40x10.STL file.
    • At the end of the skeining process you will see (on the command window) a new packing density ratio, it should be somewhere between 1.2 and .8 .  Enter it into the filament packing density ratio box(called "E-steps Corrector" in later versions of SFACT). (If it's more off than that you very likely have a badly calibrated Estep on 1 of your axis’s.  This is not too much of a problem when you want to get to printing rightaway but be aware that bad precision does not add up but multiplies...  So go back later and fix it by re-calibrating E-steps)
    • Do not print the G-code that is output with the "Are You Calibrating" checkbox on.   Untick the checkbox and skein again.
    • Print the created Gcode.
    • Remeasure.  
    • If the measured wall width is now equal to your extrusion width set in the "Carve" tab, you're done.
    • If not, just enter the newly measured value into the measured width in DIMENSION.  repeat until you are happy with the result. (remember to tick the checkbox "Are You Calibrating" to calculate new values based on the new "Measured With Of Extrusion" value)
    • Note:  You can interrupt and measure the print as soon as you feel the extrusion has stabilised.
    • Tip:  To avoid extruder related inconsistencies it might be a good idea to turn heat up, to a level that really reduces backpressure.  I have calibrated with 250c for PLA as my bolt was bad and slipping.  BUT BE CAREFUL!!!  TOO HIGH EXTRUSION TEMPERATURES CAN DAMAGE YOUR EXTRUDER/PRINTER.
    Q:    The Thin walled print comes out dead on, but my top and bottom layers are overfilled, how do I correct this?
    • In the FILL plugin in Sfact you can change the distance between the parallel lines as well as the concentric rings (extra perimeters).  They are controlled by Extrusion lines extra spacing variable.  The default value is 1.  It adjusts itself automatically according to your other settings and this varibale is just for tuning.  Increasing it will make the spaces between these lines bigger.  (with "these" I mean all the layers that have parallel lines as well as the lines in the line fill.  If you reduce the number .95 they will move closer and you will have a more "packed layer".  So if you need to have say a watertight bottom you might need to decrease the spacing (0.95).
    • Another way to reduce the full layers density is to turn down the main flow rate.  This has the unfortunate drawback of also reducing the density of your infill.  Always remember that reducing the flowrate means (as the height is given by the space between the already printed piece and the nozzle) that you are changing the extrusion width. This can fix the issue, but should NOT be a 1st choice. 
    Q:    What Do I need to change to make SFACT work on my specific printer?
    • In SFACT Settings need to be customized only according to your nozzle size (under INSET set nozzle diameter - 0.5mm by default)  and filament diameter (under  DIMENSION set filament diameter - 2.8mm by default).
    • The nozzle diameter dictates also your setings in CARVE: it would be very wrong to expect an orifice of 0.5mm diameter to put out extrusion of 0.5x1mm.  That would be more than twice the amount it is capable to extrude. 
    • A good rule of thumb is to set layer height slightly lower than the nozzle diameter and extrusion width a bit above the nozzle diameter. ( LayerHeight + ExtrusionWidth = slight bit more than 2xNozzleDiameter)
    • Limitations on speed are only set by the capability of your extruders heater, slippage of the filament, mechanical friction/binding etc., and weight of moving parts (acceleration needs to be set slower resulting in lower topspeeds..)
    Q:    What does COOL do?
    • Cool will slow down your speed to allow the layer to cool before you move to the next layer.  
    • In cool you define a minimum layer duration and a minimum feedrate.. (It wont go slower than that as otherwise it will also spoil your print.)
    Q:    Why do I need to calibrate in SFACT.  Doesnt calibrating E-steps in FW do that already?
    • In theory yes.  If you are 100% sure that you have set the E-steps right you could skip SFACT Calibration.  
    • On the other hand, calibrating the E-steps in Firmware is only one step beyond calculating your E-steps based on Motor step angle, microstepping ratio and gearing. Whereas the SFACT calibration allows you to calibrate based on actual extruded material, compensating for all possible errors inbetween.
    Q:    What the heck is SKIN?
    • When SKIN is enabled SFACT will slice your model regularly with a layer thickness as is set in CARVE.  
    • Then it will split your perimeter extrusion into 4. (e.g, a 0.4x0.6 extrusion will become 2x0.2x0.3 extrusions stacked onto each oher.  
    • This will NOT improve resolution but it will effect your finish as instead of having 0.4mm (half layer height) ridges you will have 0.2mm  (quarter layer height) ridges.
    • Possible problems:
    •  If your layer height and extrusion width is already low, trying to extrude 1/4th of the previous cross-section will probably result in very inconsistent flow.
    • Another problem is the decimals.  You might find that the output code does not increase as the increment is so little that it gets lost during rounding.
    • The situation is even worse with relative E-steps.
    Q:    Why are the width setting in SFACT absolute and not a ratio as in SF?
    • The reason the width settings in SF are ratios to the layer height is to decrease the amount of settings that you need to adjust when you change layer height,  In SFACT these settings are already interconnected (in the background).  So you can set height and width of extrusion freely.
    Q:    Can I set width and height of extrusion at will or are there any guidelines?
    • Regarding the calculation and the generated G-code the answer is yes. BUT the real world has limitations:
    • Your hot-end has a limit.  It is imposed by the nozzle diameter, shape and internal details, as well as the capacity of your heater/heating system and how good it can transfer the heat to the filament.  An upper as well as a lower limit.  
    • If you go below the lower limit, you will have inconsistent extrusion. (Just imagine a water hose that fows only little water. The flow will wander and be inconsistent.)  This effect becomes worse when your filament has soaked up humidity as it will create steam pockets that will cause small jets of filament during print.
    • If you go higher than the limit you will have lots of pressure in the nozzle.
    • This can cause excessive stringing as plastic will still flow when the extruder motor stops, as it will try to get the pressure down.  Retraction helps here a bit but it will never release the pressure instantly.  This is the best case...
    • If all parts of your Extruder are sound and the extruder just cant handle that much flow, you will strip filament.  Stripped filament can cause less grip, and therefore even more stripping.  It also could cause inconsistent flow if the teeth are partly jammed with plastic as it will alter the "hob diameter".  
    • Worst case You could have leaks in your hotend.  In such a case try to d isassemble the hot-end before letting it cool,  otherwise it might become impossible to seperate the parts.
    • UTMOST CARE IS NEEDED AS YOU WILL BURN YOURSELF. (Not otherwise but be prepared to have burns..) I am using Latex covered textile working gloves when working with the hot parts of my printer.
    • Plastic parts might have become soft,  try to reinstate their original shape/state before they cool down.
    • Filament gets to a rubbery state at some temperature (PLA about 120-130c)  Thats the best time to clean it off.  (with some experience you can take off the whole contents of the nozzle in one piece)
    • I found that it is a good value to have the layer height the same or slightly less than the nozzle diameter.
    • The width of extrusion should be chosen so that you stick to the formula:  Layer height + Extrusion Width  is slightly bigger (110-125%) than double the nozzle diameter 
    Q:    What exactly does the Infill Extra Spacing in FILL do?
    • The main indicator for wrong settings here is too sparse or too thick top layer.
    • If this happens you probably have wrong calibaration (as in your extrusion is not coming out the same as the setting in Carve.)
    • It is the setting that adjusts the spacing of the parallel or concentric extrusion lines (Top and bottom fill, regular line fill and extra perimeters).
    • A similar setting is also in Inset.  That one only will affect bridge layers.
    Q:    What are bridge/bridge layers? 
    • Bridge layers are layers that have areas that have no material underneath.
    • Bridges that span between two filled areas.
    • These can be extreme overhangs.
    • SFACT will try to print these areas with a 100%fill and in the direction of the shortest distance of the bridge.
    • Problem with bridge layers that you dont have a preceding layer to limit the layer height and adjust the extrusion width accordingly.  While with normal printing you can virtually achieve any w/h ratio that is not possible for bridges.
    • You can set the feed/flowrate for bridges under SPEED.  It is a relative setting that is calculated by multiplying the perimeter feed/flow values.  
    • Settings under INSET let you adjust the spacing of these 100% fill lines and also the nozzle diameter setting is needed here to be able to calculate a "natural flow" for the nozzle.
    • The default settings will result in an extrusion that has obviously same layer height as the rest of the print, the extrusion width will be set to a value that I call "natural flow" or "native flow".  That is the extrusion X-section is the same as the nozzle diameter X-section.
    • The bridge settings will only kick in if Infill in direction of bridges is checked.  This setting will cause for some fully filled layers if you are printing shapes with all-around overhangs (especially organic shapes or statue like things).  They might appear random to you but this is the reason for that.
    Q:    Why is TEMPERATURE disabled by default.  
    • The SFACT defaults are set the way that they provide failsafe defaults for beginners.  
    • SFACT is as tuneable as SF.
    • Setting the temperatures in SFACT would cause the G-code that is generated to include Temperature codes.
    • They would be issued every time the print type changes. (You dont notice it but it happens more often than you think..)
    • Temperature settings are very different for every configuration.  (plastic type, color, humidity, thermistor, thermistor placement, nozzle diameter, print speed, extrusion diameter)
    • A wrong setting is very difficult to correct during print as it will try to go back to the G-Code settings every time the print type changes.
    • Instead of that we advise to set the temperature in the host program and adjust if necessary..
    • If you are really sure that you are able to choose correct temperatures go ahead and enable it..
    • You can set a startup temperature seperately in Chamber.   This will issue a tempertaure command and wait until the nozzle heats up to that temperature before printing.  The command is issued only at the start so you can tune the temperature in the host software later/during print.
    Q:    My alterations and start.gmc, end.gmc files are not working.   What am I doing wrong?
    • You have to place them into the skeinforge_application\alterations folder.  Unfortunately there are other folders with the name alterations around but this would be the correct one!
    Q:    What is the penultimate gcode file I am getting?
    • It is the G-code file that SFACT uses to carry data from plugin to plugin.  It has lots of extra information inside.
    • At the start of the file there are most of your settings.
    • Each section is marked whether it is fill, loop, perimeter etc.
    • You can reopen a penultimate file with skeinforge to have a preview in SKEINLAYER or SKEINISO
    • It is a great source of information if you need help.
    Q:    Why are there now two dimension plugins (DIMENSION and OLDDIMENSION)?
    • DIMENSION Plugin has a new method to calculate Retraction.  It calculates the duration of the upcoming travel move and retracts accordingly. 
    • OLDDIMENSION is the OLD-DIMENSION Plugin.  It behaves the way You probably are used to.
    • Latest version has only one DIMENSION plugin.  It uses old type retraction.
    Q:    What happened to the old retraction settings?  What the hell is oozerate? (Not relevant from Dec'11 onwards)
    • XXXXOozerate is abandoned in recent versions of SFACT(Mid december 2011)XXXX
    • The old retraction is still available under the OLDDIMENSION tab.
    • The current DIMENSION calculates retraction differently.
    • It assumes that you are having either a drippy or very tight nozzle that oozes not at all... (Or anything inbetween).
    • The oozerate is what you are estimateing when you extrude filament and then stop, it is about the amount of filament that oozes from your nozzle in standby in one minute.(in mm)
    • SFACT will then calculate how long the travel move in retracted state will take and retract accordingly.  So if the next move is very short it will hardly retract (You can boost this with the minimum value..) or if it is a long move it will make a big retraction.(the max value is there to avoid any mishaps if somehow you have a very slow travel move or similar, otherwise the filament will pop out of the extruder..)

    Q:    What is CLIP.  What does it do?
    • CLIP adjusts the gap between the start and the end of the perimeter (outermost) extrusion.  If there was no clip the halves of the extrusions would overlap, causing overfill at the join.  Too much clip will cause open perimeters.
    • Clip is to create a distance between the start and endpoint of a loop.  Be it a perimeter or inner loop..
    • The default of 1 in sfact will create a space (space is only there fort he extrusion path.) that is just enough apart to have a joined perimeter according to your extrusion settings.  It is calculated similarly to how top layer extrusion spacing is calculated..
    • When using Dwindle You can set this value to almost 0
    FAQ for general Extrusion issues
    RichRap has posted a great blog entry on troubleshooting bad prints with lots of photos, check it out and see if your problems match:
    Q.  Why does my extruder skips steps whenever I am trying to print?
    A.Issues to check
    • Is your stepper controller getting hot?  If it overheats you will get skips durring extrusion
    • If using a geared stepper, does the 2 gears mesh exactly the same across the full rotation of your larger gear?  If you have a part that has higher resistance your gear might not be perfectly round / have a defect.  Try to use a hand file to clean up the gear meshing, or move the stepper motor gear further from the driven gear to allow more room for the defects.
    • Is your thermal barrier getting hot?  If your thermal barrier gets to hot it can cause increased resistance to motion by your cold end.  You might need to put a fan on your thermal barrier.
    • Your nozzle might have trash in it.  If all else fails remove your hot end and clean out all the plastic.  Most hot ends this can be done with a blow torch, but some are too fragile for this and you must use a long acetone dip.
    • Did you overheat the nozzle when printin PLA? PLA decomposes into a crystaline solid when overheated. This cannot be dissolved in acetone so if you block your nozzle like this, the only option is to mechanically remove the blockage.
    • If you are using old wades extruder then check that you are using right small pully and not using smaller t5 pulley. I did that mistake in past and seen someone doing it.
    Q. With 1.7 filiment my plastic buckles inside the cold end of the Extruder, what is happening?
    A. If you experence buckling of your plastic the cold end might not be properly constrained to hold 1.7 filiment.  Try printing a cold end that only has a 2mm wide path for your filiment.  Plastic should strip durring a failure, not buckle.
    Print if your using a geared stepper or if your using a hobbed bolt/