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SLS4All - Affordable SLS 3D Printer

Design, development and build of open-sourced SLS 3D Printer.

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Design, build and test of the open-sourced desktop 3D printer utilizing the selective laser sintering technology (SLS). This printer will have all the features like commercial benchtop SLS printers.

Project homepage: https://SLS4all.com
Discord: https://discord.com/invite/qDFNFASM57
YouTube: https://www.youtube.com/c/SLS4All

<< Design of Updated Version: 15/09/2022 >>

<< Printer Testing: 13/08/2022 >>

<< Recoater after redesign: 05/05/2022 >>

<< Current Status: 04/2022 >>

<< Project Details >>

I decided to use the ordinary arrangement of the SLS printers. It means to have two chambers with the moving beds. One as the powder reservoir (powder chamber) and the second one for the printing outputs (print chamber). The printing material (PA12 powder) will be moved layer by layer from the powder to print chamber using wiping mechanism. 

<< Frame >>

Frame construction is made from the so called 2020 extruded aluminum profiles (20x20mm). All the walls are from the 3mm thick aluminum plates.

Even though I designed the frame as two-skin I had some troubles with the heat in early stage. Therefore, Teflon (PTFE) is used at meaningful frame joints and the rock wool insulates the top skin form the inside heat.

<< Chambers >>

The dimensions of the chambers are 220x175x200 mm for the powder reservoir and 175x175x200 mm for the print chamber. It should allow me to print the range form small to mid-sized parts. I would like to have the effective print volume somewhere around 150x150x180mm.

<< Recoater >>

I decided to go in the way of counter rolling mechanism instead of simple piece of aluminum plate. I choose this way because the quality of the layers is one of the parameters directly affecting printing quality.

<< Heating >>

I proposed quite comprehensive heating system. It can be seen as an overkill, but hopefully, it will do what it should. I want to achieve maximal temperature uniformity possible across the material in both powder and print chamber. It means I want to have the temperature control on every single side of both chambers, including the beds. Another 4 independent halogen heaters will be used to heat the top layer surface.

<< X & Y axis >>

I want my printer to be quicker that FDM ones. Therefore, I have to avoid common Cartesian X and Y axis layout. Why? Even if the X and Y moves would be at the same decent speeds as the FDM printers do, total print speed will be much slower because of layer preparation time overhead. Therefore, I decided to go in a way of galvanometers (galvos).

<< Laser source >>

Laser source will be the 5W blue laser diode (wavelength of 445 nm). It is the most cost-effective solution but as with anything, you pay for its low price in another way. This mostly relates to the shape of the laser beam source and specifics while focusing it – especially for the relatively long distance.

<< Hardware >>

Summary of requirements placed on the printer’s control hardware interfaces:

  • 3 step motors and their drivers for Z1, Z2 and R axis. I decided to use the latest TMC 2209 drivers because of their quietness and power. I also intend to use the sensor-less homing functions
  • interfaces for driving X and Z axis by galvanometers
  • number GPIO interfaces for the heating system and for fans. It means 10 GPIO pins for chamber heaters, 4 pins for print area surface heaters, 2 pins for fan groups (air in/air out), pins for IR thermo-camera
  • PWM regulation possibility. I need at least one hardware PWM pin for the laser power regulation and software PWM abilities for the heater’s power output regulation
  • interface for the on-board camera
  • interface for the touch screen LCD
  • I2C and SPI bus interfaces for internal communication
  • BigTree Tech SKR 1.4 Turbo to control laser, steppers and galvos
  • Raspberry Pi 4b 2GB, to control heaters, video camera and thermo camera
  • Solid State Relays for AC heaters switching (sides of chambers, halogen heaters)
  • 30A MOSFETS for DC heaters switching (print and powder bed)
  • Own PCB, called Inova Driver Board, for thermistors reading and the galvo signal processing
  • 3x stepper motor NEMA17 for Z1, Z2 and roceater

Basic electronics arrangement is as follows:

  • BigTree Tech SKR 1.4 Turbo to control laser, steppers and galvos ...
Read more »

  • This Will Be An Open Source - Updated Version Of Inova Printer

    Tomas Starek09/17/2022 at 13:07 0 comments

    Based on the recent print tests I realized I am much too close to the physical limits of the current printer prototype to get the best print quality I can. Therefore, I decided to focus my efforts on the development of the updated version which addresses these limits. From my perspective it is more time effective than to upgrade first prototype.

    I have already finished the design of the bottom printer's part. The top printer’s part is finished from say 80%, so I think I will start building it in about a month. If it works well, I plan to gradually release this version as an open source.

  • Printer testing video is here!

    Tomas Starek08/14/2022 at 10:19 0 comments

    It's been a struggle with time, but finally the video is out showing the testing of the printer :-)

  • Q: Will be kits sometime available? A: YES!

    Tomas Starek06/26/2022 at 11:03 1 comment

    I had some time to think about "the kit" and I have, I hope, a good news because your interest persuaded me to do it.

    My short-plan is as follows: 

    1) I need to tune the printer to make nice, repeatable prints. I believe it should not take too long. It could be done in a couple of weeks. Simultaneously, I plan to start some preparatory activities for kit. These will mostly relate to organizational and logistical aspects.

    2) Make design changes I am calling v2 and do the documentation - drawings, assembly manual, source codes, etc.

    3) Build and test v2. Here will be also a good space to fine-tune assembly manual, etc.

    4) Finalize all the manufacturing and logistical aspects, announce prices, delivery dates, etc.

    5) Open pre-orders, start making kits and publish the Inova documentation (DXFs, STLs, manuals, FW, SW, ...)

    6) Support you in building your own Inova (kit or your own build from scratch) :-)

    When it will be?

    It is not a small bite but I will do my best to be able to deliver first kits to you by the end of autumn. Let's fingers crossed. I will keep you informed about the progress of the steps above on a regular basis.

  • Print bed surface heat consistency

    Tomas Starek05/20/2022 at 15:25 0 comments

    As a result of the last print test I spent many hours by finding the right way how to ensure the best possible heat distribution/consistency across the print bed surface. Problem was, some areas of bed surface were under or over heated.

    I ended up with new halogen shielding and quite simple procedure how to tune it. Unfortunately, current design of the topFrame limits me in making heat distribution good enough for the whole print bed area. As a result of that I must use smaller print space in the Y axis for further testing. It will be around 130mm instead of 150mm. But good is, that it should not be problem to fixed that. So, the final working area will be still 150x150mm 😉

    Here is the pict of what I am talking about. The orange rectangle is the 150x150mm effective print area - it is rectangle because of camera view perspective. I need to have the temps diffs max about 2.5°C. Therefore, the top and bottom row inside the rectangle is a bit problematic. The test was done for 100°C.


    When I checked video from the last print, there was a diffs range up to 5+°C :-o

    I will make the next print test in coming days.

  • Initial test prints: the PA12 print profile experiments

    Tomas Starek05/11/2022 at 20:02 0 comments

    I did 3 tests past two weeks and here are the results. If you are intersted in more details please join Discord - https://discord.com/invite/qDFNFASM57

     Test nr. 1 - first few sintered layers on my printer ever!

    Test nr. 2 - moving forward, now it starts to be really 3D :-)

    Test nr. 3 - last time numbers were not printed. Now they are! Few more print tests like this one and then Benchy is waiting :-)

  • Recoater rebuild: Part 2

    Tomas Starek05/03/2022 at 20:40 0 comments

    Recoater rebuild is done. I did a few tests today and it looks very promisingly. It is smooth, silent and rigid enough. I will heavily test it in next days.

    -

  • Recoater rebuild: Part 1

    Tomas Starek04/27/2022 at 18:15 0 comments

    I moved on a bit with the recoater remake. I have printed out and fine-tuned all parts I will need - the blade holders and pulley holders. I made it from the ASA so hopefully it will be able to withstand the high temperatures (if not then it will be CNC machined). ASA is more temp resistant (temps just below 100°C are OK) than ABS and more rigid. Good thing is that it also prints easier than ABS.

    Blade itself is ready as well - CNC machined from aluminum, as planned. Linear rails are just perfect.

    I will mount everything into the printer in coming days.

  • Recoater Redesign: Blade Insted of Roller

    Tomas Starek04/21/2022 at 12:55 0 comments

    As written on my blog and meant here before have been still facing some troubles with the recoater. Therefore, I decided, even I really didn't want to, to change its design.

    Main problems are with the roller part. Unfortunately, I have made its diameter of 38mm, which implies high rotating speeds and causes layer shifts. I spent some time to come up with the solution how to incorporate roller with smaller diameter into the current printer design. But due to space constrains it's not easily possible.

    Another issue is that once the roller, being from PTFE, starts to warm up, it starts to deform a bit due to nonsymmetrical heating of it. I eliminated this by "grilling" the roller during the printer heat up, but I cannot be sure that it is perfectly circular and concentric with the axels. As we are speaking about the hundredths of millimeter which plays a role, it is a problem.

    It is not all. Last problem is related to smooth rods which are approx. 550mm long. I thought it will be OK without support, but it is not. And again, you cannot ensure layer thickness precision which is needed.

    Here are intended changes:

    1) Replace smooth rods with the linear guides

    2) Change the recoater from roller to blade. I will come back to the roller in v2.

    3) Change the drive train, to be able to worh not only with the steel rope but also to test special heat resistant GT2 belts.

    4) Change the cover of linear technics parts to be comfortably accessible for maintenance.

    I have proposed this design:

    It consists of MGN9R rails with the MGN9H trolleys. Aluminum wiper will have precisely flat bottom (will be CNC machined). I read research papers related to the blade shape and I was really surprised that flat bottom is better than symmetric, asymmetric or rounded. But it has some logic.

    You can see the design in deep detail here: https://sls4all.com/fusion360-model/

    I would like to rebuild printer in this way in two weeks or so. Hopefully, it will work as intended. There is one thing which makes me worried - I can't pull the trolley exactly on the axis direction of the rail... will see.

    I expect from this change to be able to focus on the sintering parameters and be sure that there is one layer like each other.

  • First Real Test: Search for PA12 print profile parameters

    Tomas Starek04/19/2022 at 13:20 0 comments

    I did my first sintering test past weekend. Goal was to start tests of the sintering parameters (laser power, scanning speed, hatching distance, layer thickness, temperatures...) to find best setup for PA12 powder I am using.

    Test objects

    • Rectangular pattern of squares/cubes 20x20 mm across whole bed size.

    Key parameters of the test

    • Printer preheat: 1:20 min to 145°C
    • Surface temp: 171°C
    • Layer thickness: 0,15mm
    • Laser power: 4900mW
    • Laser spot size: approx: 0,25mm
    • Energy density: 22 mJ/mm2
    • Nr. of outlines: 2
    • Hatching overlap: 25%

    Bed preparation

    • Surface temp: 160°C
    • Nr. of layers for bed preparation: 30 (it will be higher during parts printings)

    Cooling procedure

    • Controlled cooling was not set. Printer was opened a few minutes after the printing had finished (reason why is below) During part printings will be controlled cooling function set to 0,5-1°C/min. (upraveno)

    A few pictures from the testing

    1. Nesting of test object

    2. Print parameters setup

    3. Sliced test object

    4. Plot feature of the laser scanning process

    5. Printing/Sintering of the test object

    Until now it was just WOW ... but than it went wrong ... Recoater failed to complete next layer.

    Reason was that I used wrong ratio of the volume change after sintering. Therefore, the next layer has not enough powder. But that is minor issue - just SW setup.

    From now on, I will calculate it dynamicaly for each layer based on the sintered surface area.

    So, the first sintering test results: 

    1. Amount of fresh powder was not OK for such a huge sintered area.
    2. Surface temperature was a bit low. The print cake was not at expected structure.
    3. Sintering in XY axis was relatively OK - for the first attempt. I will set up the hatching overlap to 30% next time.
    4. Sintering in Z axis was poor/undersintered. I made mistake in setting the energy density. Based on this number scanning speeds are changed dynamically across print bed. It is based on the laser spot size change due to its defocus. I set it for 22mJ/mm2 but it was my base point for 0,1mm layer thickess not for 0,15mm :-(
    5. After deep look at the sintered squares, it was possible to see big layer shifts. I am persuaded it is caused by the big speed of roller surface rotation. It is the real problem because I can't to significantly change it easily. It is an mechanical design issue I didn't count with. I can decrease it by say 30% in Klipper but it will not be enough. As I am facing also other mechanical issues with recoater I really think of major changes even it is complicating my life. I will let you know soon.

    Here is one of printed squares. This one was placed in the bed area where was recoater able to wipe more than one layer. These are I think 3 or 4 here. It is warped a bit because of really really quick cooling.

    -

    So, this is my base point for further tests. I hope to see first Benchy before I will be in my 60's :-)

  • Heat insulation improvements & Halogen shields

    Tomas Starek04/17/2022 at 09:51 0 comments

    I made some improvements of the insulation. Main reason was to protect the thermo camera, but I used it also at another places. It is made from the so called “stove paper” which is 3mm thick and heat-resistant up to 1260°C. Its heat conductivity is also great: 0,07 Wm-1K-1 at 200°C. (upraveno)

    I have also made shields for halogens allowing me to direct the heat towards print surface in the better way - halogen tube with shield can rotate in the r7s socket. You can see it in place in previous picture.

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    https://SLS4All.com

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technical.jw wrote 08/14/2022 at 15:51 point

have a look at high speed sintering, a dark part profile on white powder is sintered by passing a halogen heater across the surface, leaving the white powder unsintered.

means having a printhead instead of a laser.

  Are you sure? yes | no

Tomas Starek wrote 08/15/2022 at 09:05 point

Thanks for the tip, I will definitely look at it.

  Are you sure? yes | no

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