27 June 2015

Ghetto 3D printer heated bed

Written by 
Rate this item
(1 Vote)

Recently both of our primary 3D printers went down for maintenance and servicing, which was inconvenient since we needed to prototype some work and deadlines were tight. So we pulled out an old veteran back to operation. Although our backup printer has only a small build volume, no worries as we could cut and dice the model and print each part separately.

However, the problem was that parts were coming out warped because the printer doesn’t have a heated bed and filament extrusion was being dragged over certain layers.


Ok, so we thought, let’s mod this guy with a quick hack heated bed, probably an hour-long hack no less that could potentially improve the quality of hours of printed parts.

To get started, we have lots of these versatile 5x15cm heating pads lying about. Cheaper ones are available from Chinaland to build your own, utilizing various scrap materials we had around the lab, we got to work.



The area of the build stage is about 20x25cm, and some arrangements were considered for maximum heating area. We cut up a small thin sheet of aluminum for the plate mount.




Eventually the linear arrangement of two pads side by side was decided so that wire management would be easier on each end as opposed to four different sides. The pads were taped down, wires soldered and sleeved for a little heat protection.



Thermal grease generously applied.


The setup looks good so far! The edges were all taped down with Kapton polyamide tape for high-temperature resistance.


Our K-type thermocouple placed right in the centre of the plate.


Preliminary tests look good! A start-up at 5V ramps up nicely to 49.8°C very quickly, but it’s already running at the maximum amperage that our power supply can provide, which is 3A, this design might prove a tad too much on the Power Supply Unit (PSU) for four heating pads rated at 600mA each.


A box of binder clips always proves handy to hold things together. 



Powering up the printer and doing a re-leveling of the build stage. The binder clips holding down the ghetto heated bed all around the circumference. Looking good, let’s do a test print.


The moment the printer started printing, we could see something wasn’t quite right. The aluminum sheet wasn’t completely flat throughout the surface area. There were “blobs” or “hills” where the sheet wasn’t completely flat and the extruder head would scratch along the surface, causing the deposited plastic to be scraped away. The problem is that the sheet is just too flexible and warps along the center or at unpredictable areas and would “pop-up”, changing the leveling profile.


Areas where the extruder head scratched the ghetto aluminum sheet.


Plan B: Use something more rigid. We had a stainless steel plate lying around which would do nicely.


With a smaller surface area, we only needed three heating pads, which should ideally reduce the amperage to manageable levels of our PSU. We only need to maintain a warm temperature, and not to really melt anything.



Side by side comparison.


Thermal grease – check. Kapton tape down – check. Wire sleeving and soldered joints – check.

Powering the new plate up. 5.1V gives us a nice 42.6°C at only 2.15A, looking great so far.





Ramping up to 8V gives us a nice 70°C, topping off at close to 24watts on our PSU channel. Three pads at full power give us a comfortable 70.6°C.



Time to install the plate into the printer.


FULL POWERRRRR.


Another roadblock. This time the plate is too thick to properly level the stage on each calibration point. Even with the leveling screws tightened all the way to their maximum depth, the stage is now too high and collides with the extruder head. Bummer!

A corrective fix would be to remove the existing build stage and replace it with a thinner custom glass stage with the same mounting screws tapped into the same location and then placing our DIY heated plate on the new stage and installing it into the printer.

That kind of work would exceed that of a single afternoon, which is more than we’re willing to spend on this project anyway. Bummer! We are just gonna wait for our main printers to be operational again then.


All is not lost though! Our printed parts with warping defects can still be placed on the heated plate to soften and flatten them back into shape.



A colleague found a very practical application of the heated bed. It makes a great cup warmer! 24watts of heating power, careful hot surface though!

There are already ideas for improvement. Next we'd probably plan to add in a temperature controller hooked up to a variable power supply unit that linearly controls the temperature via voltage variation based on readings from the thermocouple. That would be a very simple but useful add-on to accurately control the temperature profile of your heated bed.Until then!


Hope you like this article, and get some ideas of your own. Do post comments or subscribe.

Bazinga!

Read 8561 times Last modified on 28 June 2015
More in this category: « Lights for your plants

Leave a comment

Make sure you enter the (*) required information where indicated. HTML code is not allowed.