Calibration processes
Calibration processesMotor CalibrationObjective: 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.
SymptomsMotors 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.
InstructionsEach 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 LevelingObjective: To level the print bed so that your
objects will adhere to the surface. The result of this step should
make the extruder nozzle extruder nozzle might "dig" into parts of
the bed, pulling 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 up or
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.stlInstructionsStep 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 theBed Leveling Calibration test
objectand ensure that each square is even, smooth and
consistent.
Other methods do exist. ReferenceLeveling the Print Bedfor 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 preparationObjective: correct preparation of the bed
to ensure that objects adhere to it.
InstructionsAn 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:
GlassClean the glass with a common household window cleaner and
a lint free cloth. Spare no effort in ensuring that the glass is
spotless.
TapesWhen 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 tapehas 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.
Other MaterialsTODO: need details on other materials.
ExtrusionObjective: to ensure the hot end temperature is set
correctly so that material is extruded cleanly
Calibration Object: None
PLALayer heightObjective: to correct the layer height settings
to reflect your printer's actual layer height.
Calibration Object:0.5mm-thin-wall.stlInstructionsPrint 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.
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.
InfillObjective: to correct the infill setting.
Calibration Object:20mm-box.stlInstructionsSet infill solidity
to 1.0 for this.
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.
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 controlObjective: 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.stlInstructionsSet the 'Infill
solidity' to 1.0.
If the plastic comes out as a drip instead of a cylindrical
filament, the temperature is too high.
--http://wiki.ultimaker.com/Troubleshooting#Plastic_comes_out_of_extruder_head_in_a_flowing_stateStart
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.
RecommendationsPLAHotend: 185C Bed: 60C
ABSHotend: 230C
Bed: 110C
Perimeter WidthObjective: correct the perimeter width over
thickness. In newer versions Edge Width over Height.
Calibration Object:perimeter-wt.stlInstructionsThis 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.
If you CANNOT get it in AT ALL, and you are sure there are no
whiskers blocking it, INCREASE perimeter width over thickness. The
latter is more likely.
BridgingObjective: to maximize your printers ability to bridge
gaps (i.e. print in thin air).
Calibration Object:20mm-hollow-box.stlInstructionsPrint 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 PrecisionObjective: improve print precision
Calibration Object:precision-block.stlInstructionsThen 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.
OverhangObjective: fix overhang problems
Calibration Object:overhang-test.stlInstructionsThen 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.
OozebaneObjective: 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.stlThe 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.
Symptoms
InstructionsThis 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.
References:http://reprap.org/wiki/Sfact#Q:____What_happened_to_the_old_retraction_settings.3F__What_the_hell_is_oozerate.3FOverhangsObjective:
eliminate droop from overhangs.
Calibration Object:BridgeTestPart.stlInstructionsIf 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 calculationsThe 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.).
tl;drThe 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:
E. g:
(41.8*100)/94.94=~44.02780703602275121129
Then repeat:
(44.0278*100)/99.95=~44.04982491245622811406
Until you get your desired steps per mm.
Useful G-code-commands to use withPronterface/Repetier-Hostor
whatever eases your RepRap replication.
(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 OffsetOK, 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] 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] 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] 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] 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] To be honest, I never used Skeinforge, this adjustable
track offset is an assumption.
[14:38] Traumflug: it would be a good setting, i agree.
[14:38] Traumflug: I think the only way to achieve a track
offset is to adjust the perimiter w/t ratio.
[14:38] So, Skeinforge doesn't compensate for track width?
[14:38] Traumflug: it does. but it uses the perimiter witdth/t
and infill w.t settings
[14:39] Traumflug: then it uses the layer height
[14:39] Traumflug: and useing those it works out the track
offset.
[14:39] ok, good to know.
[14:39] Traumflug: but the kicker is, changing perimeter w/t
also adjusts the flow rate
[14:40] Traumflug: so theoretically when you choose a new w/t,
it puts out enuf plastic to fill the width.
[14:40] Yes, theoretically
[14:41] 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] but the one setting that allows you to compensate for
that adjusts the flow on all other lines (both infill and
permiiters)
[14:42] IMHO, changing the plastic flow to compensate for size
errors isn't a good way.
[14:43] Traumflug: I agree completely.
[14:43] Each time you change the flow, a lot of minor parameters
change as well, so a prediction is very difficult.
[14:43] I want to change the track offset.
Theory and MathsByMarkus "Traumflug" Hitter.
X and Y AxisBoth 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:
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 ObjectOpenSCAD// X-Y Calibration object
// See http://reprap.org/wiki/Calibration#Theory_and_Maths
difference() {
cube([100,100,3], true);
cube([80,80,3.1], true);
}
STL fileFile:XYCalibration.stlBasic EquationWith that knowledge,
we can sum up what the extruder moves to get the size T = 10mm
exactly 10mm wide:
This holds true for measurements of any size, i.e. also for the
100mm size of our calibration frame:
You see? Two unknowns and two equations, so the set is
solvable.
Extending to Erroneous MovementsNow, 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:
Again, this holds true for both our measurements:
... to be continued ... about a formula to get scaling and track
offset from measuring these 10 mm and 100 mm ...Z AxisOn the Z
axis, there is no track offset compensation, so calibration is
reduced to scaling of part height. Build any part of 50mm 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 should match reality pretty close. However,
there's also material shrink as the plastics is printed at a higher
temperature than room temperature.
