One of the major reasons contributing to failed prints is compromised build plate. It may be not levelled well or it may heat incorrectly causing warp and detachment. Our Magigoo was invented to provide adhesion and prevent warp, but even we calibrate our printers monthly to rule out any inconsistencies. Here is our recipe for the heated bed calibration.
Why is the heated bed calibration so important?
Let’s start with the build plate today. Say you are printing in ABS, so you set you print bed to 100 °C. When you look at your printer hardware closer you realise that the temperature of the bed is often measured by a single thermistor, which is placed in the centre of the bed in the middle of a PCB. This PCB is then covered with some type of metal plate which is then often covered with a glass plate. So basically there may be 3 layers of material, with varying thermal properties and conductivities and between each of these there might be either a layer or pockets of insulating air. Also it is likely that the bed radiates more heat from the sides rather than the centre, as its losing heating effect from centrally located PCB. So, is the bed temperature 100 C? Your display is showing so, butin reality its hard to answer. You are going to have to check it out yourself and we can tell you how.
What do you need
The method is pretty simple and cheap to do, all you need is a
- glass of water (ideally deionised but for this purpose tap water should do)
- hot plate (or kitchen stove),
- multimeter with a thermocouple,
- bulb thermometer and
- thermal paste
- ohh yes, and a 3D printer.
First things first, lets make sure our thermocouple is giving us the correct readings
- Fill beaker with 200 mL deionised water
- Place beaker on hot plate and boil
- Measure temperature with mercury bulb thermometer
- Place thermocouple in beaker and allow to equilibrate for 2 minutes
- Take readings every minute for 5 minutes
If you do not have a bulb thermometer in this case you could assume that the water is boiling at 100°C. The errors from the current printer displays are surely greater than the error you have here so you are already gaining a lot of information.
Calibrating heat bed
- If you have five thermocouples, place one of the calibrated thermocouples at each corner of the bed and one at the centre, as shown in Figure 1. If not just repeat the following steps at each point
- On each spot, place a drop of thermal paste and fix in place with a strip of tape.
- Raise the temperature of the bed using the preheat setting to 40 °C. Allow to equilibrate for 15 minutes and take note of the reading. I have put in a table at the end of this post which you could use to collect your data.
- Repeat step 3), raising the bed temperature to 110 °C at 10 °C intervals.
- Repeat 1)-4) with the printer open
- Repeat 1)-5) with for aluminium surface
Doing this once is not enough. In house we calibrate our printers monthly and sometime we get a lot of variation. It isn’t ideal method, but at least it is a starting point by ruling out bed heating problems and to figuring out how to solve any printing problems you are facing.