Printrbot Hot End Tip Clog

Unfortunately, it is just a matter of time before your 3D printer’s hot end tip (or sometimes referred to as the nozzle) will clog. Actually, there are some 3D printers that require proprietary filament spools that provide a new tip with every filament spool. These printers are meant to be maintenance and hassle free, but have the restriction of not being able to use any filament available in the marketplace. All Printrbot 3D printers that use a Ubis ceramic hot end use the same hot end tips. I use the same .4mm hot end tips on my Printrbot Plus Metal, Printrbot Simple Metal and Printrbot Plus v2 (Model 1306).

The hot end tip screws onto the bottom of the Ubis Ceramic hot end. Below is a pictures of a Ubis Ceramic hot end. The shiny gold colored tip on the far right side is the hot end tip. Most of the tip is covered by the red insulating material:



The following pictures show a used, clogged tip (left) and a new tip (right) from Printrbot:


The behavior of your 3D printer makes it obvious when your hot end tip is clogged. If your printer has been printing properly and you start to see one of the following symptoms, you need to unclog or replace your hot end tip:

  1. Nothing is coming out of the hot end tip and you you may hear a clicking as your extruder motor tries to push the filament into the hot end and it is slipping (and probably chewing through the filament)
  2. The melted filament is coming out inconsistently from the hot end tip and instead of seeing a nice bead of melted filament, you see small blobs of filament with gaps between the blobs. It seems like the filament is sputtering out of the hot end tip.
  3. Filament exits the hot end tip at an angle and is not falling straight down, and instead is pushed at an angle. In severe cases, the filament will get balled up on the hot end tip because the angle is so extreme. This symptom might only be able to be seen by raising the z axis up 50mm or so from the bed and extruding 10+mm of filament.

If you are experiencing symptom #1 or #2, you need to remove your hot end tip and either clean it or put a new tip on your printer. If you are experiencing symptom #3, be on the lookout for the clog getting worse and escalating to symptom #1 or #2.

Removing the hot end tip: On a Printrbot, you need to change your hot end tip with the machine at operating temperature (I set mine to 210 degrees Celsius for PLA and 240 for ABS). You have to be careful to not damage your thermistor that is located on your hot end underneath the red insulating material. I use an 11mm open-ended wrench to loosen and mostly unscrew my hot end tip, and use needle nose pliers to finish unscrewing the nozzle as it is VERY hot and I don’t want to drop it on the printer bed or anywhere else where something could be burned.

Cleaning the tip: You can search online and read about different ways to clean a tip. I have had mixed luck and like to have new tips available because you will undoubtedly encounter a clogged tip while you are printing something. You don’t want to have to wait for a tip to arrive in the mail to finish a print, so buy some extra tips and have them around.

Although it has not worked for me, some are able to unclog their tip by turning their printer’s hot end to a very hot temperature, say 250 Celsius, and leave it at this temperature for an hour or so. The idea is that the stuck filament will get hot enough to melt and ooze out of the tip.

For tips clogged with only ABS filament, try removing, cooling and soaking your tip in acetone and attempt to open the nozzle (hole) with a sewing needle that has a fine point (or consider small bits that can fit inside printer hot end tips). For tips clogged with only PLA, you can try heating the tip over an open flame to heat the filament and scrape it out with a needle. I print most with PLA and have had very limited success cleaning hot end tips.

Reinstalling the hot end tip: To reinstall the nozzle, make sure your printer’s hot end is at an operating temperature and start screwing the nozzle on with your fingers. Once your tip is grabbing the threads, use a 11mm open-ended wrench to finish tightening. The hot end tip will get hot VERY quickly. I tighten the hot end nozzle so it is snug (maybe a 1/8 turn after i start to feel resistance) and leave it for 10 minutes with the hot end still at operating temperature. Once the tip has come up to temperature, the tip will expand a bit, and then I use the 11mm open-ended wrench to again snug the tip tight. You do not want to crank down on the tip too much! If you skip the final step of heating your tip and doing the final tightening, you will likely have filament leak from the top of your hot end tip (not good).

When you change your tip, it is very possible that the new tip may not be the exact same height or the threads may cause the new tip to sit at a different distance from the printer’s bed. Once you install your new hot end tip, you should make sure you don’t have to manually adjust your z azis end stop (for manual z height machines) or adjust your z offset using M212/M500 for Printrbot machines with auto leveling. Below is a pictures of my original and replacement tip in digital calipers showing a .21mm difference, which is significant enough to require adjustment of my z height.


That’s it. Please leave comments if you have found better ways to clean or change your tip…

3D Printed Plywood Clips

I realize that this pretty specialized, but I needed a way to connect two pieces of 5-ply 6mm birch plywood together in a perpendicular manner. Specifically, I have a Printrbot wood 3D printer and I needed a way to secure the stack of a wooden filament spool coaster/holder on top of my power tower (see pictures). Only one of the filament spools I have purchased over the last year fits into the filament coaster/holder built into the top of the power tower. So, I wanted to find a way to attach a different, adjustable wood spool coaster/holder on top of the power tower.


The concept behind my design is pretty straightforward and started with this drawing.


I just need two U channels set perpendicular to hold the plywood. The plywood measure about 5.8mm using my digital calipers and I believe from this measurement and from listening to an early Printrbot video that this is 5-ply 6mm birch plywood.

I planned to print my final parts using PLA, which does not flex as much as ABS, so I created the clips to be approximately .2mm greater than the actual thickness of the plywood. I designed the clips to use 3mm walls and a pocket 6mm deep for the plywood. I made the length of the clip 20mm as I thought it would be long enough to provide stability.

This piece requires support to print properly, so the support must be carefully removed after printing. In my case, I had to use an exacto knife and 220 grit sandpaper to remove all the support material, although it was quick and only took about 3 minutes per piece.

I started with a design in SketchUp that offset the two sides of the clip, but after printing, I decided a centered design would hold better as all the weight would sit squarely on the bottom of the bracket if it were centered. Here is the first design from SketchUp.


Then I moved on to a centered design, and prior to printing, noticed that support would be required to hold up the overhang and thought a more elegant design would include the support in the design. I was inspired by Clifford T Smyth’s book Functional Design for 3D Printing: Designing 3D printed things for everyday use – an engineering handbook to create better designs to make better 3D print models.


Here is the default support that was required for this centered design. The colors indicates the speed of the extrusion, but some of the green (green == fast) is support as indicated by the arrows. The green support on the lower left-hand side of the image below is specific support for the overhang.


Below is the improved design (STL Download of final design) that eliminates some of the support required and, IMO, looks better with the support under the overhang.



As you can see in the below image, the support for this new design is minimized, which is ideal and minimizes post print cleanup/finishing. The only support material is centered in the image below.


This is how the print looked on the print bed of the Printrbot.


In Marcus Ritland’s book 3D Printing with SketchUp, he recommends making copies of the model every time prior to make any large modifications, that way, you can always grab the model partially through its transformation to redo an operation or generally do something different. If you don’t keep a copy of the model along the way, sometimes it can be impossible (or seem that way) to adjust your model without starting over. Here is a screenshot that shows how I created copies and therefore managed my model throughout its evolution.


Below is a pictures of the stack of power tower and filament spool coaster/holder with the clips in place.


And a closer look at the black clips in place:



Occu-Pi-ed Sensor Part 1/2

I’m starting a project to sense motion in our conference rooms at my office at SPR Consulting. We recently build a mobile web app that shows availability of conference rooms at our office. Currently, the web app shows availability based on the scheduling of the room resources in Microsoft Office 365. But we have a policy that rooms can be claimed if they are empty, so knowing whether a room is physical occupied is also important.

For this project, I’m creating a motion detection device that sits in each conference room and senses motion in the room. The device checks for motion and reports whether there is motion (conference room is occupied) or no motion (conference room is not occupied) and then sleeps for a configured number of seconds. Because the sensor checks whether a room is occupied and it uses a Raspberry Pi computer, the name “Occu-Pi-ed” seemed obviously appropriate.

The device reports the occupied status to a custom web service. Our conference room web app checks this occupied status and includes the status in the web app UI.


This blog will cover the first half of the project by covering the electronics and wiring of the project. The second half (not yet written) will cover the programming on the Raspberry Pi and physical packaging into a custom enclosure.

The project wiring is very simple, you only need the following parts:

I was not able to find any data sheet on this exact board, so I’d like to share my findings to make it easier for others. The PIR motion detector board has 3 pins and they are labeled:

  • VCC – is connect to the 5v pin 4 on the Raspberry Pi
  • OUT – is the pulse out pin that is set to high if motion is detected and set to low if no motion is detected, which connects to pin 11 on the Raspberry Pi
  • GND – is connected to the ground pin 6 on the Raspberry Pi


The PIR motion sensor has two potentiometers that allows adjusting the sensitivity of the motion sensitivity and time lapse (or stickiness of sensing motion). The potentiometers can be adjusted with a small screw driver. Be gentle and be aware the potentiometers only turns about 270 degrees. While holding the board with the potentiometers at the top and the sensor dome facing away, the left potentiometer (labeled Tx) adjusts the time lapse of the sensor. Turning the potentiometer clockwise causes the sensor to continue reporting motion even after the motion stops. Turning the potentiometer all the way counterclockwise causes the sensor to report whether motion is being sensed real-time. The rightmost potentiometer (labeled Sx) adjusts the sensitivity of the motion sensor. Turning the the potentiometer clockwise causes the sensor to be more sensitive to movement (especially farther away). Turning the potentiometer counterclockwise causes the sensor to be less sensitive to motion.




Why the adjustments?

  • Time lapse – Most PIR sensors will be connected to a microcontroller (or circuit) that will be “listening” to the PIR board for the pulse pin to be raised high, to indicate movement. Depending on the implementation, the connected microcontroller may poll the pulse pin periodically. Time lapse allows the identification of motion to be propagated through the pulse pin after the motion is sensed, for a configurable amount of time. This is very useful if your microcontroller, is for example, checking for motion every 30 seconds and then sleeping. You could miss the motion if you are just checking at a given microsecond every 30 seconds, so the board can propagate the sensing of movement for a longer period of time to increase the chance that your board catches the movement. As you turn up the time lapse, the board increases the amount of time the pulse pin is high after sensing movement. From some playing around, it seems the potentiometer for time lapse is exponential and not linear, meaning that the time lapse gets dramatically longer as you turn the screw little by little. In my experimentation, if I turned the time lapse sensitivity to high, I waited over 15 minutes and the sensor was still sticky. Because I am impatient, I turned the sensitivity back down and unplugged the 5V jumper and plugged it back in to get back to a reasonable time lapse potentiometer setting.
  • Motion sensitivity – From my experimentation, I found the sensitivity effected the distance more than any other aspect of its sensitivity. With the sensitivity set at its highest, it seems there may be some false positives, meaning the sensor every long once and a while pulses the output pin even though I was not aware of any movement in the room.

For my final configuration, I have the sensitivity turned all the way up (turned to High location on image above) and time lapse set to 1/3 of the way between Low and High. I have found this creates the pulse out that is high for about 1.5 minutes whenever motion is sensed.

Stay tuned, the next blog in this series will include the python programming on the Raspberry Pi as well as the physical packaging into a custom enclosure.