Heatbed warping causing ridging? [HELP]

I've been running into some problems with my printer for some time, and a couple of chats on the Reprap IRC pointed me towards Z wobble as a source of problems. I realized that the wobbling that most people are having from bend Z rods, was unfortunately not my problem. Someone on the IRC pointed out that between the layer time, and the increments of the ridges, the "smushed" layers may be caused by the heated warping when cycling on and off. Can anyone confirm that hypothesis, or point me towards another fix? I've always been a little worried about how the hotend was mounted; its a little bit wobble and with some force it wobbles around ~5mm. how stiff does a mount need to be?

Edited 4 time(s). Last edit at 06/30/2015 01:39PM by Montiey.

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Master Tinkerer

The hotend should not wobble at all. That will cause way to many errors in your prints.
you can set PID on the Heatbed, I have I have no real proof that that works to correct the Z axis issue, but have read and heard that solution many times. I would also check and make sure your settings are correct for you Z axis steps, it maybe making a correction if you do not have that configured correctly or if you are not using the proper layer height.

Just as a test, I printed a test cube with the heated bed totally off. The cube came out with really nice layers. So my question now, is what is happening to the heated that is causing the ridging on the layers? Is it heat flexing?

Edited 1 time(s). Last edit at 06/29/2015 04:41PM by Montiey.

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Master Tinkerer

Would be nice if you specify these specs first

nozzle size, print layer height, print speed, wall count top/bottom, wall count sides, bed temp, nozzle temp, plastic material

These are helpful in identifying what might be causing this problem

Try lowering acceleration or your temp, don't know which temp since you didn't specify bed/hotend temp

Sorry for the lack of info.
Here are all the specs I can think of off the top of my head
Hexagon hotend 1.75mm
Inland brand black PLA
hotend: 210°
bed: 55°
Layer hight: 0.2
Nozzle diameter: 0.4, brass
print speed: ~60mm/s
infill: 20% for almost all prints

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Master Tinkerer

bump

I did a bunch of research on heatbeds and bowing.. There is simply nothing out there that matches the problem i'm having. Just wondering if anyone has switched from a PCB heater (thats what I have) to a silicon stick-on type heater. Also, would using a milled aluminum sheet help to reduce the bowing?
I'm getting very discouraged at this point. All my prints without the heated are absolutely superb, while i'm starting to wonder if its just the heat of the bed affecting the bed, and not actually the "bowing" that may or may not be happening. Does anyone have experience fixing either of these two problems? ANY advice is greatly appreciated.

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Master Tinkerer

bump

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Master Tinkerer

I had wobble with my hot end moving in the mount. I put a shim between the hotend and extruder and the "Wobble stopped"

I would say that that could be he problem, but it totally dissapears when the heatbed is disabled.

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Master Tinkerer

This doesn't help much as we didn't reach a complete answer to what was happening, but your problem sounds a lot like the one described in this thread:

[forums.reprap.org]

That thread is pretty much the problem I'm having, but I think it may be that the bed is actually causing extruder inconsistencies, due to the heatbeds load on the ramps. I noticed that in large, flat surfaces there are waves of filament that are shiny, and then matt. The shiny spots are also looking like they have been under extruded to the point that the strings aren't even connected that well and bubble up minuscule amounts. I also measured the 12v pins on my power supply and they were are 12v while idle. I bumped them up to 12.65 or so and i'll see if that makes any difference. Also, where should they be set? 12 seems like the logical answer, but If I wanted to account for the load drop, where would that put me?

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Master Tinkerer

If the power supply can't handle the load, get a supply that can. Take a PSU that can provide twice what you're asking from it. Hotend = 40W, heated bed = 150W, stepper motors max. = 5x12x2A = 125W. Total 315W. Get at least 500W. If you get an ATX PSU you need to dimension it even bigger, as about 30-40% of the wattage is for 3.3 and 5V lines.

I use a separate 300W 24V PSU for the heated bed (which is rated 12V, I use 75% duty cycle to reduce power, works a treat, heats up very quickly!).

I'd also enable PID and tune it before using it, the bed temperature shouldn't deviate more than half a degree during print.

Check the hotend temperature during printing, if it's not within half a degree deviation then you either need to tune PID for the hot end as well, or you need a more powerful power supply.

You can also drill out the heated bed holes a bit bigger so that there's more space and less mechanical tension on it. When heated the tension can get bigger and bending it as a result.

I have a 30 amp power supply with triple 12v outputs (1 for hotend heatsink fan, other 2 powering ramps through standard speaker wire). I'd assumed 30 amps is enough, and it seems like plenty for a 8"x8" heatbed and a hotend. As for temp consistency they are pretty solid. I ran PID tuning on both the heatbed and hotend, and they have very straight lines in the octoprint temp graph. What you said about the heatbed.. It makes sense, but the way mine is the bolts are angled in towards the center of the heatbed going up towards it, so if anything they will be pulling the heatbed taught like a sheet or something. If the hotends temp doesn't fall under the beds load, then what else could cause inconsistent extrusion like that?

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Master Tinkerer

To answer your suggestions, I have a 30 amp power supply with three 12v outputs (1 for hotend heatsink fan, other 2 powering ramps through standard speaker wire). I'd assumed 30 amps is enough, and it seems like plenty for a 8"x8" heatbed and a hotend. As for temp consistency they are pretty solid. I ran PID tuning on both the heatbed and hotend, and they have very straight lines in the octoprint temp graph. What you said about the heatbed.. It makes sense, but the way mine is the bolts are angled in towards the center of the heatbed going up towards it, so if anything they will be pulling the heatbed taught like a sheet or something. I measured a small drop of 0.03 volts when the heatbed is powered on, so this really confuses me. I bought a 12v to 12v heatbed relay from Makerfarm (elderfarrer) on eBay. Hopefully this will let me take the stress off of the ramps and fix things.
If the hotends temp doesn't fall under the beds load, then what else could cause inconsistent extrusion like that?
I just got some more red and grey PLA from Inland so I'll have more data to work with form the different filaments.

P.S I really have no experience, but Inlands PLA is actually pretty nice, and for $15 per kg its a steal!

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Master Tinkerer

Just hoping to get some answers here; I installed a 12v to 12v relay from Maker farm's eBay shop, and the relay part works perfectly. I changed the "deadzone" in marlin to 0 since the relay is binary and not gradual. However, this also causes the hotend to have horrible fluctuations +/- 3 degrees. Is there any way to disable PID just for the bed?

There is no obviously noticeable difference between the test cubes printed with the relay, and without, but the test cubes printed with no bed heat have near perfect layers. This really leaves me stumped. If the heatbed were to be warping and squishing the layers unevenly, I have a sheet of window glass over the whole thing, and that stuff doesn't really bend, does it?

Is my power supply big enough to run everything + the bed? Its a 30A "ebay" brand supply.

Any help is greatly appreciated.

Edited 1 time(s). Last edit at 07/26/2015 12:46PM by Montiey.

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Master Tinkerer

The photos of the red cubes look ok to me. The sides look a little wobbly on one of them, but I thought your problem was inconsistent layers, and the layers look pretty consistent.
Is it worse with the black PLA? (I noticed the first photo you posted was of a black test cube.) I have seen many people on this forum say they have issues with black filament.

I think you really need to fix up the movement in your hot end. Until you know that is not contributing to the problem, you can't trouble shoot.
What extruder do you use? I have the Wades and when I noticed movement in my hotend, I drilled one of the mounting holes out to 4mm and screwed in an M4 screw (I saw someone else on the forum had done the same). It was pretty tight, but that nozzle didn't move anymore! Better prints instantly. (The nozzle would move as it would drag - only slightly - on the material it was laying down, you couldn't see it move as it was slight).

Fix your nozzle movement, then see how you go.

I would totally investigate a loose hotend, but I know pretty certain that the mount is very solid. It isn't a solid block of titanium, but you have to really push it a bit to get the nozzle to wobble at all; but if the bad quality only surfaces with the heatbed on how could it be a loose nozzle? I'm using the printed wades extruder that came with the kit (Makerfarm Prusa i3v 8", and a hexagon 1.74mm hot end. The heatbed is a single sided PCB heater w/ glass on top (single sided would cause warping as that side would expand/contract and bend the plate?). Ramps 1.4 electronics, pre-tuned stepper drivers (haven't touched them). The only thing that I can think of to be causing the randomly squashed layers is a fluctuating heatbed.

Edited 1 time(s). Last edit at 07/27/2015 09:52AM by Montiey.

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Master Tinkerer