Plastruder MK5 Usage

Testing Your Extruder

Now that you have your extruder wired up, you'll want to test a few things. This will help you diagnose problems before they actually become problems.

Test 1: Measure heater resistance.


With the new heating system, everyone should have nearly identical heaters and heater profiles. The supplied power resistors are high precision (1%) 5 ohm resistors. Since they are wired in parallel, the resistance should be 2.5 ohms. Measure it with a multimeter. If it is any other value, make sure you wired them up correctly and that there are no shorts.

Test 2: Measure thermistor resistance.


With the Gen3 electronics, you'll be using a thermistor to measure temperature. At room temperature the resistance should be around 90k. (As the ambient temperature increases, resistance will go down.) If it is not in that vicinity, check that you have it wired up properly and that the leads are not shorted.

Wiring up your Extruder

Heater to Relay

1. Relay Board Power


Make sure you turn off your ATX power supply before attempting any of this. Better safe than sorry.

Find an free power socket and plug it into the board. Simple!

2. Extruder Controller Heater Output to Relay Input


Note: throughout this guide, we'll use RED wires for Positive and Black wires for Negative.

Connect these to one of the channels on your relay. Don't forget: polarity is extremely important, so don't get it wrong. If you do it will waste current and your relay board will not work.

3. Relay Input from Extruder Controller Heater Output


The extruder controller output will be powering the small control coil. The wires in this picture should be connected to the extruder controller mosfet output.

4. Relay Output to Heater Resistors


This step is pretty easy. Simply connect your load (heater) to the output channel that corresponds to your input channel (A or B). The polarity is clearly marked, but in this case it is not important.

Thermistor to Extruder Controller


The wires from the thermistor need to connect to the thermistor terminal on the extruder controller. The polarity is not important, so just wire them in.

Motor to Extruder Controller


The wires from the motor need to be wired into the H Bridge on the extruder controller. The red wire should be connected to the 1A terminal and the black wire should be connected to the 1B terminal.

Testing: Round 2

First, make sure your extruder controller is connected to your Motherboard, that the ATX power supply is on, and that your electronics are connected to you computer. Fire up ReplicatorG and open the control panel.

Test #3: Test motor


Enter 255 for motor PWM. Turn the motor on forwards. Turn the motor on backwards. Turn the motor off. It should do what you tell it. When it rotates forward, it should rotate clockwise. If it rotates backwards, stop the motor, and switch the motor wires.

Test #4: Test temperature


Check the temperature. Does it give you the room temperature more or less? If so, you should be okay.

Test #5: Test heater


Set the heater to something low like 50C. The relay should click on, and the temperature should start rising slowly. The MK5 heats up slower than the MK3/MK4 but it will be much more stable at higher temperatures. If the heater is working properly, then set the temperature to 220C.

Warning: The hot end will smoke for a couple minutes as the lubricating oil burns off. Try not to breathe this in and keep in mind that it is a temporary thing. Once it burns off, no more smoke should come off the plastruder.

Test #6: Test extrusion


While keeping the temperature at 220C, take some ABS filament and push it down into the extruder. Push it all the way down and you should see it extrude out the nozzle tip. If so, you're ready to try motorized extrusion.

Tighten the thumb screw down until the plunger bites down on the ABS. It takes a bit of getting used to, but the plunger system is very forgiving of different settings. Do not over-tighten the thumb screw. If you are really exerting yourself, you are setting it too tight. Tighten it until it gets nice and solid. If during the running of the extruder, you notice the ABS is getting flattened or white stress lines are forming, you have it set too tight. You can back it off during extrusion very easily. Likewise, if it is not tight enough, you can very simply tighten it more until the extrusion stops slipping. It is very forgiving of tightening mistakes.

Set the motor PWM to 255 and the motor direction to forward. You should notice the motor kick on, and the extruder should start extruding. Let it run for a few minutes and marvel at your awesome new extruder that you will come to love and cherish.

Daily Printing Operation

Replacing the filament

The basic process to replace the filament is:

  1. Heat up extruder to operating temperature
  2. Loosen the thumb screw tensioner
  3. Quickly pull out old filament by hand
  4. Insert new filament and push it all the way down.
  5. Tighten thumb screw
  6. Turn extruder motor on forward
  7. Wait for extrusion

This process is really simple. If you get good at it, you could even do it while the machine was printing and have an object that is made from multiple colors. Make sure you pull the filament out by hand and not by reversing the extruder. The melted plastic can jam up the drive gear and you'll have to disassemble the filament drive mechanism to fix it.

Keeping it Clean

It's important to keep your extruder clean for proper functioning. Always make sure you are using clean filament with no dust or debris. You may want to have the filament pass through a rag or something in order to remove the dust from it.

Also, during operation your extruder will probably pick up globs of plastic on the nozzle. These should only be removed when the nozzle is hot with a pair of tweezers. You can use needle nose pliers, but be very careful that you do not clamp the nozzle as you may destroy it accidentally.

Keeping Things Tight

As the extruder runs, the thumb screw tensioner may come loose, or things may settle into a looser configuration. Give it a twist to test how tight it is, and tighten it if necessary. You can also loosen it if necessary while the extruder is running.

The rest of the nuts and bolts should be kept tight, especially the ones holding the heater barrel assembly to the extruder housing. Don't tighten things too much so that the acrylic breaks. A good rule of thumb is 1/4 or 1/3 of a turn past hand-tight.


My Extruder does not report the right temperature.

Reality Check #1: Is your thermistor actually hooked up?

The thermistor should be wired to the two-pin screw terminal labeled 'Thermistor'.

Reality Check #2: Is it actually your thermistor?

Your thermistor should have a resistance of ~80K at room temperature. Measure the resistance with a multimeter. If it reads low, like say 6-12 ohms, then you have hooked up the heater to the thermistor port instead. Swap the heater and thermistor (double check the heater resistance to make sure!!!).

If the multimeter reads as a short or as 0 ohms, then your thermistor is shorted. Unfortunately, you're going to have to take apart the heater barrel, pull the thermistor leads apart to fix the short, and then re-assemble it.

If your multimeter reads infinite resistance, or no connection, then one of your connections is bad and you'll need to re-attach the lead wires to the thermistor somehow. This involves taking apart and re-assembling the heater barrel assembly.

My extruder does not heat up.

Reality Check #1: Is your heater hooked up?

The heater wires should be hooked up to the B+ and B- ports on the Relay board output port. The B+ and B- ports on the Extruder controller should be connected to the corresponding input ports on the Relay board. The polarity is important, so make sure you are using red for + and black for -. It is important that its hooked up and screwed down nice and snugly.

If that doesn't fix it, make sure that you have your heater hooked up. Measure the resistance between the two ends of the heater wire. It should be from 6-12 ohms, depending on the length of nichrome you used. If it is much higher, you have hooked up the thermistor to the heater and should switch them (double check the thermistor resistance to make sure!!!)

If they are shorted, then you have a short and need to fix it. Unfortunately, you need to take apart the heater barrel to fix it.

If that doesn't fix it, or there is infinite resistance (no connection) then one of the joints may be bad. You'll have to disassemble the heater barrel for this as well.

My extruder motor is not running.

Reality Check #1: Is your motor hooked up?

The motor should be hooked up to output 1 of the h-bridge outputs. The red wire should be hooked up to 1A, and the black wire should be hooked up to 1B.

My extruder motor is running backwards.

Easy! Simply swap the red and black wires. Remember to turn the power off first!

My extruder has stopped extruding.

This can be a bit tricky. There are a few tricks / techniques to make it work again. Just be patient and you'll have a working extruder in no time.

New Extruders

If you had your first extrusion, but it stopped shortly afterwards, you might have debris in your extruder nozzle. This happens when you do not properly clean your barrel/nozzle before using it.

The solution is to reverse the filament, cut off all the filament from where it got chewed up and below, and run new filament in. The old filament that you pull out will also pull out most of the junk that is in the extruder. Do this a couple times and it should be totally free of debris. You may even see tiny particles on the surface of the melted filament when you pull it out. If you see that, then that is definitely your problem.

Does pushing on the filament start up extrusion again?

If it starts extrusion again, then awesome. Chances are that the drive gear just chewed up the filament too much and lost traction. If you just had to push for a little bit to start extrusion and then the extruder continued to extrude then that was your problem.

If the extrusion starts, but stops as soon as you stop applying pressure, then most likely your plunger position is not tight enough. Tighten the thumb screw and it should fix it.

Does nothing work to start extrusion?

This could be bad. You may have a really bad blockage in the nozzle. If you're using ABS plastic, then your best bet is to take apart the entire heater barrel / nozzle assembly. You should then soak the nozzle and heater barrel in Acetone overnight. The acetone will dissolve the ABS and you can then thoroughly wash the nozzle / heater barrel to remove the blockage. It may be extreme, but it does work.

Does a test extrusion go okay, but then it stops extruding a few layers into the print?

Observe the temperature graph in ReplicatorG's control panel. When the MK5 heats up, the graph line of the temperature should level off and be flat when it gets to temperature. If you notice that your temperature graph has a sine-wave like rise and fall, going above and below the target temperature, you will need to adjust the PID settings in ReplicatorG -Machine -Extruder Onboard Preferences, drop down menu.

I like these settings for my MK5 with Relay Board: (Isaac)

  1. Set Proportional to 5.00
  2. Set Integral to 0.0078125
  3. Set Differential to 35.00

Here is a page for determining custom PID settings:

You might want to check this makerbot blog entry

My Mk5 Extruder runs non-stop (aka Mk5 Extruder Downgrade)

If you are using a Mk6 or newer Extruder with ReplicatorG 0026 or newer, and you decide to downgrade to a Mk5 extruder for any reason, you must rewrite your EEPROM. The controller for fans on Mk6 (or newer) is the same as the controller for the extruder on Mk5 or older, and that setting is stored in EEPROM on the Extruder Controller (aka Onboard the Toolhead). If not reset, the extruder motor will run continously when the nozzle is hot.

  1. Select 'Machine > Driver' with the correctMk5 configuration
  2. Connect to the machine.
  3. When connected, open 'Machine > Toolhead Onboard Preferences' and check that Channel Settings match your wiring. Uncheck Enable Regulated Cooling Fan
  4. Commit those changes, and power-cycle your power supply.

When you reconnect to your bot, the extruder should work properly.

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