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Temp problems with gen 3 electronics

Posted by PimpKittah 
Temp problems with gen 3 electronics
October 12, 2010 12:41PM
Hi

Ive got a little problem with my extruder, i cant seem to get the temperature to be stable or "correct" im currently using a B57560G104F thermistor using the values r1 = 0, r2 = 4700 and beta = 4085 according to datasheet.

Ive also stumbled across a post about some design error in the Extruder Board V2.2 pcb i dont know if this is related or not. due to my lack of german knowledge and googles crappy translations i didnt make any sence of it. Apparently the Point left of the Crystal is Grounded by design ? dont know if it should be ?

i know that the heat block should be able to muster power to melt pla and abs (as i managed to melt some of my parts due to an accident when testing.)

Im currently using an M7 threaded brassrod with a 0,3 mm hole on the end. and an alu block with dual 6,8 Ohms Resistors in parallel. (can attach pictures if needed, actually made it using a drillpress and no lathe tongue sticking out smiley)

Trouble is the PLA / ABS Melts but never seem to get hot enough to get "glue like" and according to temp monitor ive tried running up to 250C (cant even get it to get brown) i also get erradic readings once i try temps close to 250 as it jumps and says that the temp i closer to 300+ (as i understood this is due too some calc problems in the MPU therefore the reference table?)

Both firmwares are updated with correct ref table for thermistor.
Both compiled under 0017
Firmware version unknown as there dont seem to be any version info anywhere in the source files.. (not the newest and not that old somewhere from august?)

any help would be appreciated as my only trouble seem to be the melting itself

Currently my machine works as an exepensive ornament for my kitchen table sad smiley
Re: Temp problems with gen 3 electronics
October 12, 2010 02:33PM
Pictures would help. How are the resistors making contact inside the block? What is the temp reading before turning the heater on? Can you attach your temperature config?
Re: Temp problems with gen 3 electronics
October 12, 2010 02:54PM
Thermistor config

short temptable[NUMTEMPS][2] = {
{1, 827},
{54, 253},
{107, 207},
{160, 182},
{213, 165},
{266, 152},
{319, 141},
{372, 132},
{425, 123},
{478, 115},
{531, 107},
{584, 100},
{637, 93},
{690, 86},
{743, 78},
{796, 70},
{849, 61},
{902, 49},
{955, 34},
{1008, 3}
};

Temp before usage is 23 C (room temp) 0 if i disconnect the sensor and it changes if i touch it by hand.

The resistors dont make any electrical contact to the block itself, they are glued into place using thermal glue for PC heatsinks. also the thermistor.

For extruder pics check attached files, pardon the bad quality as im using my iphone 3gs for pics. also pardon my paint skills..

also good to know im using PLA from ulitmachines PLA4043D somewhat higher melting temperature

Edited 1 time(s). Last edit at 10/12/2010 03:00PM by PimpKittah.
Attachments:
open | download - IMG_0903.JPG (554 KB)
open | download - IMG_0902.JPG (415.1 KB)
open | download - heater.png (11.1 KB)
Re: Temp problems with gen 3 electronics
October 13, 2010 07:15AM
Ive updated to the latest version of the firmware works better but still not quite as it should be

Readings till erradic.
Re: Temp problems with gen 3 electronics
October 13, 2010 09:39AM
Could this be a problem related to PID vs bang-bang temperature control?

Some insulation might help to stabilize the temperature.


--
-Nudel
Blog with RepRap Comic
Re: Temp problems with gen 3 electronics
October 13, 2010 09:50AM
im gonna try using some fiberglas insulation, report back on how it works.

ideas for good insulation except for fiberglas thats easy obtainable in local hardware stores ?

about the PID / bang bang i dont really know what you mean tongue sticking out smiley
Re: Temp problems with gen 3 electronics
October 13, 2010 02:54PM
Temp is still fluctuation even with golden fiberglas insulation improvements are "small" but still need to push extruder close to well above 250 to get some sort of liquid state of the PLA instead of string like constistency. (and i know i im only guessing how high since it doesnt get liquid like)
Re: Temp problems with gen 3 electronics
October 13, 2010 04:02PM
You don't want it liquid like to extrude, you want it to still be a filament.


[www.hydraraptor.blogspot.com]
Re: Temp problems with gen 3 electronics
October 13, 2010 04:57PM
Allright nophead.

well i dont want it to be liquid but i want the PLA to be hot enough to stick to the build table without a heated platform and i seem to have trouble manageing this

ive tried using Kapton and also Scotch but still i dont get it to stick good
what the rekommended spacing for extruder / build plate ?

any other things i should think about when it comes to using a 0,3 mm end piece ?

also managed to solve the extruder issues under linux seems that linux doesnt like when its running on 19200 but works great once it runs on 38400 smiling smiley

Also noticed some odd behavior my soldering iron is connected on the same power line in the kitchen where my machine is if i turn it off during operation the power fluxes and causes the software to crash or the micro's software to crash. can this be "fixed" easy with some components ?
im currently using an standalone powersup that ive modded for use with the reprap (not PC PSU)
Re: Temp problems with gen 3 electronics
October 13, 2010 05:10PM
The distance to the bed is critical!

There should be just enough room to fit a filament height underneath the nozzle, any more and it doesn't stick, any less and you squish the plastic too hard onto the bed.


Bob Morrison
W├Ârth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Temp problems with gen 3 electronics
October 13, 2010 07:22PM
so in my case around 0,3-0,4 mm ?
Re: Temp problems with gen 3 electronics
October 13, 2010 08:15PM
PimpKittah Wrote:
-------------------------------------------------------
> Also noticed some odd behavior my soldering iron
> is connected on the same power line in the kitchen
> where my machine is if i turn it off during
> operation the power fluxes and causes the software
> to crash or the micro's software to crash. can
> this be "fixed" easy with some components ?
> im currently using an standalone powersup that ive
> modded for use with the reprap (not PC PSU)

Is it a switch mode supply (eg: a Laptop-style adapter), or a wall-wart/plug-pack style PSU?

If it's a wall-wart/plug-pack style PSU, you may find that as soon as you have any disruption in the power (even sub-second amounts), the voltage will drop too low for the micro.

You could use a largish electrolytic capacitor across the output of the power supply to provide a bit more current in these cases. Anything from 1000uF to 4700uF is fairly common for use across most of these PSU's. Some of them have one inside, and some companies skimp a bit and put a lower value cap in to save space/money.

BTW: Electrolytic capacitors are polarised. If you do this, make sure you connect it the right way round (positive to positive, negative to negative - longer lead is the positive, and the negative is usually marked on the side of the capacitor). Also make sure you get one with a suitable voltage rating. If you're talking 12V, I'd recommend using at LEAST a 25V rated capacitor. A 16V one should be fine, but I always like to be on the safe side. The difference in cost is minimal if you're only buying one, and a few more cents is definitely better than having it fail.

If it's a switch mode supply, I'd recommend getting another one, probably that provides more current. A switch mode supply (whether a PC one or not) is the better option anyway, and worth investigating.
Re: Temp problems with gen 3 electronics
October 14, 2010 04:59AM
Well ive converted a "common purpose" switched power supply (or atleast i think so, most powercubes are switched nowdays) for the reprap using XLR connector of 12V the supply gives me around 3-5A at that voltage

if im not misstaken the psu should have those filter capacitors built in like all electronic supplys have.

And about the Cap polarisation i know thanks for the up, ive used to work as a repair technican for Hansol back in the days, also i run my own computer / electronics store smiling smiley

i not sure its a ground bounce interferance might be frequency interferance, i think im gonna try to encapsule the PCB's in some Tinfoil box to test if it stops. (should if its freqency related)
Re: Temp problems with gen 3 electronics
October 14, 2010 08:19AM
Perhaps your power supply isn't beefy enough? Isn't a stable 12V 5A supply the minimum requirement for mendel? [reprap.org]

Edited 1 time(s). Last edit at 10/14/2010 10:59AM by Nudel.


--
-Nudel
Blog with RepRap Comic
Re: Temp problems with gen 3 electronics
October 14, 2010 10:26AM
Not sure but this depends on the power consumption at the optimum moment, when the XYZ dont move they dont use much current. Much like any device thats graded for instance a router that has a default 500mA adaptor this is Optimum condition and even so like 2x safety margin cause the actual micros only draw probably around 60mA

Might be to weak im not sure havent run it long enought to see any problems. But just to be safe i think im gonna measure the current each axis uses + extruder.
Re: Temp problems with gen 3 electronics
October 14, 2010 11:11AM
Well, the wiki page I linked to states: "RepRap needs 5 amps, so don't use a supply rated lower than that." I doubt a 2x safety margin would be introduced to a DIY project without stating so.
Anyway, you need to run the x, y and extruder motor simultaneously with the heater when printing, so they aren't off much.


--
-Nudel
Blog with RepRap Comic
Re: Temp problems with gen 3 electronics
October 16, 2010 09:31AM
Hi Guys i gotta thank you all alot cause i actually managed to print something speciall thanks to nophead cause this machine is an offspring from one of his (the hydraraptor if im not misstaken?)

cant say its perfect but still proves that it actually works. i believe that some fine tuning is required tongue sticking out smiley

thanks again guys / girls (if any) smiling smiley
Attachments:
open | download - IMG_0907.JPG (511.1 KB)
Re: Temp problems with gen 3 electronics
October 16, 2010 10:52AM
Hi PimpKitta,
Your parts were mainly printed on my Mendel, some of the smaller parts like the gears were printed on HydraRaptor. See [hydraraptor.blogspot.com]

Good to see it working. Looks like your PLA got a bit too hot. Small things like that print a lot better if you do a few at a time.


[www.hydraraptor.blogspot.com]
Re: Temp problems with gen 3 electronics
October 17, 2010 09:03AM
ill give that a try, thanks for the tip smiling smiley
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