Heated bed

Got my heated bed sorted. Used the silicone heat pad like Sublime suggested. Works great:

Printing with a heated bed makes all the difference, nice job, I like the thumb nuts for the trimming.

Looks really good but in some ways I have to disagree with Robonz assessment of a heated bed making all the difference (if that means improves things).

It causes whats known as Elephant foot where the bottom of the part stays soft enough that is deforms. You can not use lots of cooling of the printed part which means lower definition corners. The extra power it takes means it is less portable or at least requires a much larger (or two) power supply(s). The heat it gives off can cause the bed arms to soften. The heat it gives off can cause the electronics to overheat. The soft nature of the bottom of the part can cause extra wobble on tall parts.

I am not trying to say they do not have some benefits. The fact it keeps the bottom of the part soft means the warping forces from the above layers do not pull the part off the bed, and for ABS this is a must. But the part does still warp its just that the bottom is soft enough it can stretch so that the bottom of the part is still touching the bed while the middle is warped.

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The one I hate the most is the lubrication drys out much quicker. But having flat prints (for me) is worth al the other troubles.

Interesting points Sublime. I will have to keep an eye on the arms. I'm confused about one point though. Why does a heated bed limit the amount cooling?

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wingnut
Interesting points Sublime. I will have to keep an eye on the arms. I'm confused about one point though. Why does a heated bed limit the amount cooling?

The reason the heated bed stops the part from warping and coming off the bed is because the bottom of the model stays warm enough that it does not shrink. But if you blast air at it to cool the part you are also causing it to shrink which pulls it off the bed. If you are printing PLA on heated glass it can shrink enough that the part just falls right off. So for smaller detailed parts where warping is not an issue I would not use the heated bed. If the part is large enough that it has time to cool without the use of fans then using the heated bed makes sense since that size would most likely warp enough that you need the heated bed.

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Thought I'd give an update of my experience with a heatbed so far.

The short answer is that it's the best upgrade I've added so far. I now run the fans at 100% all the time and get no curling at all. Having the fans on all the time means that I can run the hot end much hotter and I still get good results with small details. Extrusion pressure is also reduced. I haven't heard the extruder skip once since the upgrade. I've been keeping an eye (or rather a finger) on the bottom of my build stack paying close attention to the temperatures at the support arms and it's just ever so slightly warm. My prints do have a little bit of the 'elephant foot' that Sublime pointed out but it's only a little worse than the flaring I get normally from the compressed first layer. An easy fix with a small file. So lots of benefits and no negative side effects. Highly recommended.

Glad to hear you are not having any issues. I am sure it will be good news for those wanting to install one.

I am surprised to hear the fans do not effect bed adhesion. But I guess with the fans fixed at the top and the bed going down the bed is not subject to the airflow for very long.

Are you printing PLA on glass? ABS on Kapton? PLA on tape?

Also I am sure people would love to hear where you got the silicone pad and your experiance with the supplier and how you go about ordering one to fit Tantillus.

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I got my heat pad on ebay. The seller will configure the pad for whatever power and size you want at no extra charge. I asked him to make me a 100x100 pad for 70Watts at 12V. He didn't have any at the time with these specs but I see he is selling them now:

[cgi.ebay.com]

It comes with andhesive backing to aid installation. I backed it up with a sheet of 1/4 plywood scrap cut to size. The plywood provides some insulation that I believe accounts for the low temps at the the bottom of the stack.

For the thermistor I bought one of these:

[cgi.ebay.com]

I mounted it by drilling a 1/16 hole into the side of my aluminum plate and packing it with heat paste. The hole doesn't have to be very deep as the thermistor is tiny. It's not held very securely but strategic use of tie wraps to secure the wires keeps it from getting pulled out. I didn't want to glue it in out of fear that the super thin wires would eventually break off. I thought about just laying the thermistor between the heatpad and the aluminum but I figured that would mess with the temperature readings since the heatpad heats up much faster than the aluminum.

I'm currently printing PLA on glass with elmers glue. Right now, the adhesion is actually too good. Getting parts off can be a pain. I'm going to try experimenting with printing on clean glass with no glue.

The only thing that was tricky to source was the aluminum plate. I acquired mine by bartering with a colleague who is into CNC. If anyone is interested, I can ask him how much he would charge for a few more. Maybe I can even get him to mill a little slot for the thermistor. One side benefit of the aluminum plate is that I was able to recess the screw heads. That allowed me to go with an over sized glass plate so it's much easier to clip from the sides and alignment is less critical

I want to eventually try printing ABS but the heatbed temps will have to be much higher. I'm afraid what that would do to all the PLA parts in the printer. Maybe with some extra cooling directed at the bottom of the stack?

Excellent. I have placed an offer on one just to play with.

WWFP put a heated bed on his metric machine and he added fans to the bottom plate of the bed (the one that attaches to the arms). I think he still has PLA arms and if memory serves he has printed abs with it.


The countersunk screws is a nice touch and is possible with the original bed parts as well. It just added a lot to the manufacturing process so I did not do it for production since a laser cutter can not cut them.

Yeah PLA on heated glass with glue must stick like nothing else. I find even with cold glass and a thick coat of glue that has been scraped or sanded and then washed with acetone, the parts can stick so well you can end up with the bottom layer becoming part of the bed. In those cases it helps to just soak the glass with the part on it in the sink until it releases.

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Sweet! I think I have my next upgrade :-)

How did you hook up the heat bed/thermisor?

Hi SkyArcher

I made a video on my Tanty heated bed
https://www.youtube.com/watch?v=GFj2S6i-FGs


I have printed ABS and PLA on it.The video shows where the thermistor connection goes. You need to modify the firmware too. From memory you just make bed 1 instead of 0 or something like that. My bed quite happily runs at 110C. I have not tried to go any hotter. Blue painters tape works fine at 110 with ABS too.

Cheers
Keith

Thanks Robonz. That was a very interesting video.

I made a silicone pad/ aluminum/ wood bed like wingnut's bed then I hooked up my power supply to both 12v input on the Ramps board. Then connected the headed bed to D8 and the 100k thermistor to t1. Then defined the bed thermistor in configuration.h as #6.

Also un commented
### ENABLED BED_LIMIT_SWITCHING

But I'm not sure that is right. I'll try commenting it out and see what happens.

I ran a print and the bed heated up quickly but I think that I need to move the thermistor so that it has contact with the glass plate for a more accurate temp reading.

Edited 2 time(s). Last edit at 08/28/2014 09:03AM by SkyArcher.

Is there a way to turn off the heat bed in the middle of the run? I think that once you've laid down the first 5-10 layers, the heat is no longer needed.

For Kisslicer

M140 S0 turns off the heated bed, just stick that in ptr gcode-> N* layers set the layer number to the layer you want to turn it off at. I have not tested this but it should work.

Personally I leave it on for the whole print but if I was to turn it off I would run at least 20 to 30 layers at 100um layer height

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SkyArcher
... I think that once you've laid down the first 5-10 layers, the heat is no longer needed.

Well, this is simply not true. Once you turned the heat off, the parts start cooling down and warping appear.

Some are lowering the temperature just below the glass transition level. Though it's just a few degrees (5-10), it may help in improving one of the well known artifacts - the elephant foot.

Quote
Robonz
For Kisslicer

M140 S0 turns off the heated bed, just stick that in ptr gcode-> N* layers set the layer number to the layer you want to turn it off at. I have not tested this but it should work.

Personally I leave it on for the whole print but if I was to turn it off I would run at least 20 to 30 layers at 100um layer height

I've been running my bed at 50c and it is working very well at reducing warp.

However, I need the exact code for turning off the heated bed mid print.

Or how do you turn off the headed bed at the end of the print?

This is how I see the heated bed temperature. Your bed should be as cold as it can go without warpage that "is bad". The bed adds stress to the model and reduces warpage so you want that happy medium.

To turn the bed off at the end of the print I do this. In postfix of kisslicer I have this code. Its more code than you need but it makes for a nice print ending. It mainly drops the bed before homing so the hotend doesnt drag across your nice new print. It also pulls the hotend away from a print that could be sitting around home.

; Switch to relative coordinates
G91

; move down so tip does not drag on work
G1 Z5

; Switch back to absolute coordinates
G90

;home xy
G1 X0 Y0 F6000

; turn off extruder hot end
M104 S0

;turn off heated bed
M140 S0

; shut down motors
M84

I have done a lot of prints like that and it has worked out well.

Cheers
Keith

Thanks Keith, I'll try it tonight.