Very Strange here.. temp holds great for first layer.. then drops like a rock  

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Scott,

I'm going to guess the part fan turns on at the second layer and the air is either being deflected up from the bed towards the nozzle, or what happened to me is that I damaged the fan shroud at some point and it actually started leaking air directly out on the nozzle.

That is where I would check first.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Ok will do.
It is doing a abs print ATM just fine. Temp is constant at 255 for the nozzle. Heating the bed to 90 was a nightmare to figure out.
Will let you know once this print is finished.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Hi Scott

I had the same issue heating the bed when I printed some ABS (or HIPS; can't remember which). Initially when I printed HIPS some months ago, all was OK, but on this occasion, it took forever to heat the bed over 60 degrees.

In addition, the heater was only working when the bed was as in the back half of the printer.

I found that due to constant movement, the heater cable had broken internally just past the cable tie on the RAMBo housing. The plastic cable sheath had melted and a couple of strands had poked through the sheath.

I replaced the cable and all is now OK again, but I am expecting this to happen every few months. It would be worth you checking for this. In any event, can you check the resistance of the bed heater at the RAMBO connectors (remove connector first). It will be a low resistance, so you should also measure the resistance of the meter's leads and take that into account. The heater should be 1.2 to 1.6 Ohms I think.

Peter

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Thanks Peter. I am printing an abs part right now. Its been going for hours with holding a constant nozzle temp of 255. The bed is holding at 90. I did what you suggested in another thread and put cork under the bed too (was such a pain finding cork on Easter Sunday lol). Plus my enclosure for it is helping to get the abs temps needed. Only takes like 8 minutes to get to the temps and its been going strong.
This happened when I went to pla last night trying to get a part out quickly. It would heat up to 200 for the nozzle and 50 for the bed. Start to print the first layer. All was good then went to do the second layer and the temp dropped. Nothing has changed as far as telling it to modify the temps. It was to hold at 200 for the nozzle. It decided differently. All I saw was 200/200 199/200 198/200 etc etc until it gave the error due to low temps.
Once this abs part is done I'll take it apart and see if its the blower or what. Just very strange. I tried it in both simplify and slic to make sure it wasn't a programming bug. Its not. So has to be hardware.
Fun times!

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Hi Scott

Yeah, I didn't refer to your issues with PLA as Richard had covered my thoughts about the part fan. I redesigned the part fan outlet slightly to overcome the temperature drop; I did upload some test graphs using the original and revised fan holder here a while back, but I would guess that your fan holder has melted slightly due to your high temperature ABS printing without the fan.

As you have applied cork to the underside of the bed, I really would suspect the heater cable as mentioned above. If you do replace the heater cable, please ensure that you install at least a 15 Amp cable.

Let us know how you get on.

Peter

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Hmm well can't wait for this piece to finish now to play around.
Ok if it did melt. Need a better design and if I need to buy different fans so be it. And print in abs? Pla? Or something else...
Any ideas on a good design and material?
I cut the cork away from the cables too. Wasn't going to do small adjustments of cutting to get around them. Just cut a big hole for the wires.
Thanks Peter!

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Scott

I printed the fan housing using PLA. It is a few millimetres away from the heater block and is fine when printing ABS or HIPS (but I print those at around 225 degrees). It seems that others have had issues when opening my reworked fan housing with a slicer, but it works fine for me with KISSlicer.

Peter

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Awesome. Will get it when home. Now speed up time so I can be home lol.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Will try as well, I have also important nozzle temperature drops when high ventilation is needed.

Peter, do you have a Thingiverse/Youmagine/ other account where you share your modification ?

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

I printed your modified fan housing Peter.
I also reprinted out a couple of the pieces due to the x carriage was broken (the top screw for the fan housing broke).
I just did a print. It still drops but not as fast.
Now I am really confused as to what is going on here...

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Hi Scott

Did you measure the heater cartridge? Best to do it at the screws on the RAMBo connector.

Any change you could upload a photo of your hot end? That may show up something that is not correct.

Peter

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Peter,
No I have not measured at the pins.
This is what it looks like now.
It isn't dropping like it was last time. but it is still dropping. It holds the temp great for the first layer so I am leaning towards the fan blowing on it but can't see how that is happening now.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

I am trying to lower the fan speed.. see if that will make a difference in the hot end dropping the temp.
Only happens when the fan comes on.. otherwise it holds the temp great when warming up.
Changing the fan speed to 80 seems to be working.. need to play with it some more but will see when the piece is done.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Scott

When the nozzle is down low (< 1mm) there will always be some airflow across the heater block. Usually the heater cartridge has sufficient power to react and counteract any lowering of temperature.

It is therefore important to find out if your heater cartridge is underpowered (by measuring its resistance) and if it is, you should be able to contact support and get a replacement sent out.

If you position the nozzle in the centre of the bed and do the following:

1. Heat extruder to 215 degrees
2. Turn on part fan at 100%
3. Note the temperature every 30 seconds for 3 minutes

Repeat this test at Z heights of 1mm, 10mm, 25mm and 50mm.

You should find that at greater heights, the temperature does not drop at all. This will also identify a lower powered heater.

Peter

P.S. the photos look good except for your colour choice!

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Lol that is my son.. he though purple would be cool...

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Well I did that.. all seemed good. I ran a program.. all seemed to work..
so hopefully it was a oops and it has worked itself out.

Trying a larger print now...

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Lol that is my son.. he though purple would be cool...
Yeah, but it looks like hot pink in the photos (at least on my monitor...

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

NOOOO it is purple!!! purple i say PURPLE! lol

Might have to remake it again then... lol
Seems to be working. Once the first layer is down.. I adjust the fan speed from 255 to 140 and temp is holding nicely...
Might have to invest in a new hotend though soon and see.. Between the prusa and now the Robo i am printing like mad..
It is nice to print parts for the one on the other... very helpful.

Re: Very Strange here.. temp holds great for first layer.. then drops like a rock

Scott

OK, but it's not right. When you get a chance, please check the resistance of the heat cartridge.

A new 40W cartridge is only £4.50 - 40W is the one now currently being supplied as standard with the printer. Josef found that many 30W cartridges being supplied were only 24 to 27 Watts, so they are now shipping the higher power (but that also brings different issues with it.,..).

http://e3d-online.com/Electrical/Components/Heater-Cartridge-12v-40w

Peter