Printing at wrong height & other problems

Hi guys,

I'm starting to get a little frustrated trying to set up my printer so I thought that I would ask for help before I end up like the dude who took a sledgehammer (and his dog) to his machine. I have a few problems that I would really appreciate some help with. PS This is all with ABS as it is all I have (didn't get any sample filament).

1. I level the z-axis so that it seems at the right height on both sides of the bed around the middle (I think my glass might be warped slightly), then I tell it to print but when it goes to do so it is about .5-1mm above where I levelled it to be. I don't know if there is some setting I am missing (I am using repeteir-host & slic3r) or whether there is something else I am missing.

2. Sometimes if I manage to lay down the first layer it tries to do the second and it manages the perimeters ok, but when it tries to do the infill it stops extruding. It does this because the hobbed bolt has stripped the filament. I don't know if I have the screws done up too tight or whether it is just because the first layer was too close and it struggled to push filament out and so when it tries to extrude quickly it skips.

3. The heated bed does not seem to stay at the set temperature for the whole print. I have had to do the Solid State Relay mod which does work, but the bed will sit at about 85 when I have it set at 95. Not sure if it is something I have done wrong or something as it functions correctly other than that. It gets up to the right temp before the print starts, just doesn't hold it throughout.

There are a couple of other things but that is a good start. If any of you glorious forum members are able to shed some light I would be very much greatly appreciated.

While I don't want this to turn into another thread of the Robo3D Bashers Vs Defenders I am pretty disappointed considering the massive delays, then added extra costs to my postage so they could save money sending a bulk order to Australia, I got NO sample filament (I was hoping to try the PLA before moving onto the ABS I bought) I had to do the solid state relay on the second day so that the bed didn't turn off after a few minutes, the bed seems warped, the z-axis limit switch looks really inaccurate (planning a mod once I can print something half decently). Oh and before the "you were a backer so you knew what you were getting into", I was NOT a backer, I was a customer from the website.

 

I'd highly recommend getting some PLA to really start learning the printer. It will alleviate some of your frustration since it's easier to get going with it versus ABS.

Repetier has a first layer height setting. If you followed the recommended settings, this is set to 0.35mm which is why when it prints that first layer, it moves up slightly before printing.

When I level my Z axis, I get it to where a sheet of paper _barely_ goes under the hot-end and is the same on both sides of the printer. I then move the Z home axis stop screw so the Z stop goes a little bit further down before engaging. At this point a sheet of paper should not be able to go under the hot-end nozzle but going home should not throw your nuts. When it begins extruding you should get a slightly flattened look in the skirt.

Filament that fails to extrude could be due to several reasons:

1) Your hot-end isn't hot enough. Some filaments if they go below a certain temperature will immediately freeze (T-Glase is a good example of this)
2) Your filament is too wide or is not round but oval. Check this by pulling the filament and checking the diameter at just before the melt site with calipers. I find that anything over about 1.90, my extruder stops cold.
3) Not enough pressure on the extruder bolts (less likely)

For me, right now, it's almost always #2. Filament sizing that isn't constant is driving me nuts.

hrm. Not sure why it wouldn't hold the temperature. The bed, as it cools, should be registering its temperature via the thermistor on it and the s/w should be compensating. Only thing I can possibly think of here is the heater just doesn't have enough oomph but that doesn't really make sense to me.

Sorry you're having such a hard time. Not getting the sample filament is frustrating. They didn't give you alot but it's enough for several calibration cubes for sure. Did you check the orientation of the Z axis stop switch? Alot of them came out of the factory reversed and it wasn't on the checklist of things to check. Look at section 0, checklist item #1 on the Robo 3D User's FAQ which you can get to via http://melodybliss.org/robo3d/

 

The warped bed can be fixed, or at least helped a lot by tightening the belt below it. Put a straight edge on it, tighten belt and check it. You can squeeze the belts together to tighten them while looking at straight edge to see what its doing. Mine was .008" or better off and now I can just start print and walk away.

What is your first layer temp? The temp for layers after that? It sounds like the first layer temp is good but second is too low. try raising both by 5c

 

Hi guys,

First off thanks for your help. I had a look at the getting started guide again but it doesn't say anything about changing the first layer height, it just says that the recommended layer height is 0.3mm. In the image they show the first layer height at 100%, although I am trying putting that to 120% which is pretty much what you recommended.

My issue with levelling is that I can try to get it to the right height they way you suggest but because the bed is warped it is not constant throughout. I don't have a good straight edge but I did tighten the y-axis belt anyway because it seemed a little loose. I might try to print out the bed levelling parts someone on here created, hopefully I can manage to print them, every now and again I have some mild success.

I think my temps might have been a little low (extruder was 220 & 210) because I put that up 5 deg and it extruded better without stripping the filament. I am wondering if perhaps the temp of my bed is why it it curling off. I currently have it set to 100 & 95 deg but for some reason even though I have a relay in place so that the ramps doesn't shut itself off, the temperature through the print is more like 80-85 deg. No idea why it would be struggling to keep it up to temperature. It looks like repetier is trying but can't do it. I might try setting the whole print to 100 deg and see what happens. Is there a maximum temperature that the stock extruder and bed can get to?

As for the z-axis limit switch I have already rotated that (bit dodgy that they used oversized nuts as spacers) but the screw still hits the switch around the middle rather than the end. Once I can get semi-acceptable prints that will be a simple part to design and print though I think.

It is a bit frustrating but to me the saving grace of the Robo3D team is that they have a forum full of really friendly and knowledgeable people. I just can't wait to have this thing working reliably. Thanks again guys.

James.

 

Hi Ziggy,

Mine does this on every print. Sometimes I get lucky and the print stays stuck, but I set both the "first layer" and "other layers" setting to 100 deg and it still dips down sometimes all the way to 80, but usually hangs around 85. Repetier knows they temp is wrong, and shows that the output is at 100%, but it just doesn't go up.

The bit that confuses me is that it has no trouble keeping the temps at the desired level when it is warming up and even when it is doing the first layer. Then it goes to do the second and third layer and drops down.

I have put a relay in because the heat bed use to turn itself off after 10mins so I'm pretty sure it has nothing to do with the polyfuses, although I guess it is possible that I did something wrong with the relay (other than this issue it works perfectly though).

Hopefully someone smarter than I with the software/electronics can shed some light on this!

James.

 

Does it completely drop off if you leave it or will it maintain 90C?

What happens is the polyfuse on the ramps board gets too hot and it's current rating drops below the drawn current and it trips open.

Robo 3D is now giving out fans and brackets for the ramps board to fix this.

 

That is not what is happening. As I stated a couple of times, I already have a relay in place because initially that did happen. As Ziggy stated a couple of times he does not believe that is the case because he has bypassed the polyfuses. As we have both stated a couple of times it will hold at between 80-90C when it's target is 100C.

 

That's a really unsafe idea, but ok.

I haven't run into this myself but I replaced the polyfuse on mine rated to 14A.

What's the ambient temp of your printer? If it's too cold it might not have the wattage to maintain 100C

The power supply is rated to 30A. The extruder takes around 3A, the HBP takes about 9, and I don't know for certain on the stepper motors but I'd guesstimate around 1A per motor. So this is well within the operating range of the power supply so it shouldn't be causing issues.

Out of curiousity where on your kapton heater is your thermistor secured? Do you happen to have an IR thermometer to verify the actual bed temperature. When I got my printer my thermistor was located neat the edge of the kapton, and resulted in a large delta T across the bed when maintaining 40C. When I moved the thermistor to the center of the bed it dropped the delta T to below 5C.

 

Not too sure of the actual ambient temp but I am in Australia so I can't imagine that being an issue.

The weird bit is that is seems to drop down when it gets to the second layer. Holds it fine for the first but then drops, even though I now have both set to 100C.

I will have to have a look at the thermistor placement but I can't imagine that being an issue because it manages 100C for the first layer. It is also recognising that the temp has dropped and has the output set to 100%, so it's not like it doesn't realise it should be heating it up. I don't have a thermometer I'm afraid but if it looks like it will be useful then I can certainly look at getting one. Any recommendations?

Thanks for your assistance.

 

What is your temperatures per layer set to in your slicer settings.

If it does 100C for the first layer then drops off to 90C for the rest, that's a slicing thing

 

Both are set to 100C (I had 100C & 90C but was seeing if having them both the same would get it closer to the desired temp). Repetier sees this and shows that it's desired temp is 100C, but does not manage to get it there. Seems like the slicer has successfully told repetier what the temp should be.

 

Hey Ziggy,

I could very easily be wrong, but are you sure that the power supply is split evenly into 15A and 15A? For some reason I have it in my head that one was lower than the other. ie. One is suppose to be dedicated for the logic and the other is higher to power motors, heaters etc.

Just a thought.

 

I'm fairly positive the power supply is a single channel 30A. I can't actually get mine out but I seem to remember seeing the 2 pairs of positive and negative terminals are jumpered together. The polyfuse splitting the current is a protective measure and doesn't care if the supply voltage is common to both circuits.

That's true but the power loss from going between 12.24 and 11.75v is only like 5W of power. So not a big loss.

Well the bed should only be pulling around 9A. But you can measure the resistance and verify.

If you do decide to get a secondary power supply it would be better to get a 24V supply and use a relay to bypass the ramps board. This will provide more power to the heater and help get things more stabilized.

Though honestly I can think of no hardware reason why the power would drop off like that. Unless your power supply is faulty or something. I'm assuming you're in Australia like jim? The ambient temperature does play a role in how hot you can get.

 

I'm at a loss man. What happens if you preheat before starting the print?

 

Mine gets up to the right temp and holds it just fine. stays good for the first layer and then drops down.