Is it possible that a 220V silicone heater pad may be causing some EMI that would affect print quality (irregularities)? The ABS model on the right was printed with my old printer which is very poorly built compared to my new printer and still the print quality was almost perfect (some minor ringing artifacts). Then i printed the same model with the same settings on my new machine over and over and the result was the middle model in the picture. Over-under extrusion was not an issue and i ruled out every possibility and still got the same results (changed Z leadscrew/ballscrew, changed motors/stepper drivers, tried different temperatures etc.) Then i decided to try a print with white PLA without the 220V heat pad because i read somewhere that they might cause some EMI. And the result was the smoothest wall finish that i ever got on any printer (don’t mind the molten upper part. I printed without cooling fans because i thought they were causing vibrations 
). No wonder, since i tripple checked the sqareness and quality of the linear system. So that confirmed that the mechanics, motors, drivers… were NOT the problem. Any ideas why the heat pad is causing problems? I’m planning on switching to a 24V 320W heater.
A better picture of the last PLA print.
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@Mark_Rehorst I printed again with the bed set to 50°C and the irregularities are there again… It’s hard to see on a picture because of white PLA but they are definitely there… I’ll make another print without the heat bed just to make sure and post a side by side picture.
The pattern is VERY similar to Z wobble because it occurs in ‘‘kinda’’ regular intervals.
I’m controlling it with an SSR and bang-bang. The temperature difference between the max and min of the temperature curve is 3-4 degrees. The bed is a platform moving only in Z (picture) and supported on 3 points. Aluminum thickness between the heater and the glass is 2.5mm… This might be the problem but do you think it would have such a big impact at only 50°C and +/- 4°C?
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+Mark Rehorst Thanks for your great reply! It definitely got me thinking and i will try switching to PID before i try a thicker aluminum plate. The 2nd print without the bed came out almost perfect btw. The rippling effect is much worse with higher bed temperatures so i’m almost sure that your theory is correct.
The bed doesn’t bounce. At first i used a welded Z construction and that bounced like hell, producing artifacts. Now i switched to a screwed construction and it’s much, much better.
There is also a problem that the heater mat has an irregular heat output. The center is almost 10°C hotter than the edges. I already talked to the company who makes these mats (Keenovo) and the next one i take will have more dense wiring on the edges. While we are also on the topic of power supplies… How do i choose the correct mean well power supply? I found some that cost 100€ and others that cost 200€ for the same power. I was looking at this one:
http://www.proconnecting.de/Power-Supplies/Direct-mounting/HRP-450-24::944.html
The reason behind a 24V heater mat is that i’m eventually planning on selling this printer as a kit, and i don’t want the user handling 220V (other than connecting the power supply).
PS: sorry, i actually ment +/- 2°C in the previous post
http://www.proconnecting.de/Power-Supplies/Direct-mounting/HRP-450-24::944.html
How big its your heatedbed??
Maybe you have to insulate the bottom side of the bed, I got same issues, because its a little bit harder control the temperature.
I got the problem with a 388x235 bed. My bed its always going up and donw 1 or 2 degress.
Using cartonage under the beds correct this problem for me.
@MakerGal its 300x200mm. did you glue the inulation to the heater?
I just put it under, not glue or tape, I make the holes in the cartonage fitting the screws and that was enough.
)’
It sounds like flexion of the bed surface due to rise and fall of temperature. This can cause the bed to flex up/down, giving this effect which is often wrongly-diagnosed as z-wobble.
@Mark_Rehorst does the PID control works with the SSR ? I thought only bang-bang control would work with AC heathers using SSR, because the pid would require the heater to be controled like a dimmer to vary the power, Im not sure if the PID and SSR can do it.
it works. the on signal is pulsed about 3-4 times a second. as far as i know, that doesn’t damage the ssr
@Rodrigo_Bugni , the SSR only turns off when the sine wave of the AC “zero crosses”. You’re not using PWM control here (which the SSR cannot do), but rather PID. PID runs rather slowly. FAR slower than the 50/60hz of the electrical outlet.
PWM = Dimmer.
PID = Faster, more mathematically controlled bang-bang. Still slow enough for SSRs.
Bang bang on a bed heater can cause bed heaving that looks like z wobble. It can easily be the problem. I had this trouble myself.
@ThantiK ok you nailed! Now I got it right! Thanks
Does the PID controller works with a regular relay intead of SSR ?
@Rodrigo_Bugni you wouldn’t want to use a ‘regular’ relay. Regular relays are mechanical and wear out far too quickly. Marlin has built-in PID controlling/tuning that you can use, you just have to enable it. You don’t need an external controller.
@Mark_Rehorst It’s hard to say how much power the whole thing needs because the current draw is constantly jumping. Do i have to take the average current draw or the peaks? Up untill now i always had ‘‘oversized’’ power supplies, but now if i want to add a 24V 320W heater and have a MeanWell power supply i wonder if 480W is gonna be enough or if i should go with 600W…
wow that’s quite a difference between the 1st and 2nd image. Ideally i would like to get rid of the glass plate and just have planed aluminum and maybe buildtak on top. Does the aluminum plate deform when you heat it up to 100C?
What is that