Noob's Questions

Hi everyone,

I found this website couple of days ago, and decided to build a Mendel. I've read lot of wiki pages, but cannot find answers to some questions.

1. Fire Cement: I will build a geared extruder with "brass cube heater". What is fire cement? I will try to find some similar thing here in Hungary. Is it like "liquid metal glue"? Is it heat-insulating or heat-conductive thing? (For the Resistor in heater)

2. Heater wire-wound resistor: In the wiki page I read it is "vitreous", my dictionary tells it means: wounded on glass. Can you show me some pictures / types of resistors which are working good as heater.

3. Extruder stepper driving: I found some different solutions for connecting the extruder-stepper driver. Which one is the official? And where is it described/configured in the firmware? (Planed Config: MainBoard1.2, Stepper drivers3.0 also this for extruder motor driving, ExtruderControll2.2)

4. Thermistor temptable: I cannot get those type of thermistors, which are pre-configured in the firmware. How is the temptable calculated? (What is first, and second row)?

Thanks for your patience for a beginner, and for your answers

sytex

As my name suggests that i am probably the biggest noob around, i felt compelled to reply.

1. The fire cement is a cement that stands high temps.

2. Vitreous enamel wire wound resistor [hydraraptor.blogspot.com]
(and reading all other posts on Mr nophead blog would be highly recommended).

3. Best way would be to use an extra separate stepper driver board to run the extruder stepper (instead of using the EC2.2 h-bridges)

4. Thermistor temptable, if needed, can be made in several ways, one of which is a python script that comes in the firmware folder from mendel release. Possibly any thermistor can be used, if the operating range corresponds to the necessities.


Answers to all the above questions, and probably most of the next questions which would arise, can be found also on the reprap.org wiki and the forums (in Electronics, Firmware, etc). Its probably better to read the stuff there as the explanations are more detailed. Search -> read -> ask questions, the process works in the given order, doesnt make much sense in the other way around.

1. Fire Cement: talk to Laszlo you can find his info on Arcol.hu great guy in Budapest. He definitely knows what's up with fire cement there.

2. You can buy the correct resistor from Mendel-Parts.com , UltiMachine.com and others. They are very cheap, even through these vendors. I recommend talking to Laszlo on all the extruder stuff since he's local, hope he doesn't mind the reference.

3. What electronics are you planning on using? I recommend RAMPS for simplicity, it has everything needed including stuff for the extruder. If you are adventurous and want to build your own, you could try building your own RAMPS (instead of buying from ultimachine) or building a "gen 7" board.

4. If you get a thermistor from any of the vendors they are extremely cheap and they can tell you if they are 10k or 100k etc.

sytex

I guess you are looking for fire cement to fix your resistor in the heater block (personaly I would not follow the superceeded method of wrapping nichrome wire around the barrel and plastering it with fire cement.

Anyway, I have a resistor in a heater block. The resistor has one or two wrappings of tin foil around it before I inserted it in the hole and it is fixed very tightly. No need for fire cement.

Cheers

Thank you!

And how did you fasten your Thermistor in the block, if you didn't use cement?

Thermistor can be held in place on heating block with kapton tape

If you use kapton tape to hold the thermistor to the resistor block, beware that as the block expands, so does the kapton tape. I've had the thermistor actually lift itself from the surface of the resistor block (even if it's in a hole in the block) without something else holding it in place. As it's no longer in contact with the block, it assumes the temp is low, and turns the heater on (run-away effect).

Some people have reported success using a small piece of thin wire and tying the kapton down over the thermistor (so it cannot lift as the kapton expands).

I drilled a shallow 2.5 or 3mm hole and put some cheap thermal paste in the hole before inserting the thermistor into it and then a single wrap of kapton tape around it to keep it in place. Seems to be working fine.