Heat bed Study for Scalar XL

image_pdfimage_print

Few words

The goal of this study is to type of heat bed to use on the Scalar XL 3D printer.
It allows to compate different solution that focuses on spreading the heat over the whole print surface in a reasonable time laps.

We will show during this study the different solution and also the temperature profiles obtained for each of them.

Main constraints

  • Our study is focused on a 320x435mm heatbed surface
  • The base plate of the heatbed is standard 10mm thick medium (polywood).

Measurements:

Measurements have been made using an infrared thermometer

It was also confirmed by the thermistor of the 3D printer by reading the value on the LCD screen.

The use of an infrared thermoteter is always to be made on a non metalic surface, or surfaces covered with paint, tape and so on.

On the aluminum plate we measured the temperature on the white protective film provided with a brand new aluminum plate.

Variables:

The parameters that we will change are:

  • The type of insulator used below the heating element
  • The type of heating element used
  • The amounts of heating elements
  • The print surface material
  • the position of each insulator

Test 1 – Initial solution

Test 2 – Insulator change

Test 3 – Use of Cork as insulator

Test 4 – Use of an aluminum print surface

Test 5 -Use of insulator foil instead of cork

Test 6 – Adding Cork below the insulator foil

Test 7 – Insulators swap

Test 8 – no insulators

Test 9 – Use of a silicone heater 700W 220V

Conclusion:

In order to illustrate all those test results you will find below a graph showing the sum of tests from 1 to 9.

This graph is a temperature profile when heating the print surface.

  • Horizontal axis shows the temperature in °C
  • Vertical axis shows time spent to reach a target temperature.

The curves at the bottom of this graph are those where the heating is faster!

Here the purple curve corresponding to test 9. This test has the 700w silicone heater + insulator foil . Both allow to reach 110°C in nearly 3 minutes.

The closest test would be test 2 with the same insulator foil and 2 standard MK1A and MK2B heatbeds and their associated 20x20cm mirrors

Here are the main observations:

  • The heating time increases when we are using the aluminum plate
  • Insulation below the heat element greatly increases the performances of the heatbed and also reduces power consumption!
  • The insulator foil allows to gain between  30% to 40% performances compared with a cork insulator.
  • The max temperatures reached decreases when using the aluminum plate when using standard reprap heatbeds.
  • The aluminum surface increased the heating surface by 74% compared with the surface of the 2 mirrors.
  • The aluminum setup is more simple as all the elements are pressed one against the other. Also the use of 4 screws at each corners is also possible!
  • On the aluminum sheet we can see that the temperature delta between the center and the sides of the plate is only 10°C.
  • With mirrors we have a greater temperature delta on the corners or each mirrors (this also depends on the curling of the mirrors when heating).
  • The silicone heaters can reach 1W/cm² maximum. So for this surface (1392cm²) we can reach 1392W .The silicone heater that was tested was designed to use half of this potential.