Playing around with a heated chamber design.

For quite some time I have lusted after a 3D printer with the following specifications:

  • A 20x20x15cm build area
  • A heating print bed
  • A heated build chamber (ambient to 100C) to possibly eliminate warping.
  • A respectable print resolution and speed

Over 12 months ago I made my first serious attempt at satisfying these by designing and half building a rep-strap based on the mantis CNC design. However serious limitations in the design and a lack of free time have resulted in the ‘gunstrap’ collecting dust for over 12 months.  Among others, the problems with the gunstrap were:

  • High rolling resistance due to metal on metal sleeve baring
  • Slow speed due to needing to physically move the heavy print bed and print head. assembly.
  • Poor resolution due to the design of the Z and Y axis.
  • Extruder stepper located within the build chamber.

To overcome each of these limitations I have spent some time designing a replacement in SketcUp, as seen below.

What you see above is a fully enclosed build chamber that will be constructed from 12mm wood fibre board or similar. The blue transparent section is a double layer glass viewing window that is opened by the handle below it.

When opened, the two axis print head and print bed are accessible. To the right of the window will be a 16 character 2 line LCD display for temperature readouts and the like.

This design features the following:

  • All electrical components and motors (ex end stops) are located outside of the heated build chamber.
  • Print head weight has been reduced to as little as possible to increase print speed and resolution.
  • Rolling resistance is lowered through the use of ball bearings.
  • Scissor lift Z axis for increased stability

The scissor lift Z axis will be constructed by modifying a  lab jack similar to the one shown here. If the wooden shell, which also acts as the main structure of the printer, is removed then the workings become more clear. The modified lab scissor jack coupled to a stepper motor can be seen below (click image to enlarge).

Looking from the front top down on the two axis print head stage its seen that its composed of stainless steel shafts for guides like a Mendel, a PTFE sleeve bearing for the print head holder similar to a Ultimaker. Rather than an expensive belt I plan on sourcing some fine braided wire to use as a pulley which I have seen work quite well on older mechanical pen plotters for lab work. I plan on cutting box section aluminium from corner to comer to make L pieces to hold the guide bearings.

Feeding filament into a wades extruder on the side of the printer will be a mounted filament spool. The wades extruder will force the filament up a PTFE tube which enters the printer at a hole located at the top of the printer.

Finally, in a side compartment insulated by double thickness paralleling will be the electronics. This includes a RAMPS based stepper driver system, ATX powersupply and cooling fans.

As no low melting point plastic components or electrical equipment is contained within the build chamber I believe the high build chamber environment of 100C should be achievable. The heat will be provided by the heated print bed and print head only and will be actively circulated by a fan at the top of the chamber.

I am plananing on sourcing the bearings from smallparts.com.au and modifing them to include a flange. The stepper motors will come from robotgear.com.au for around $85 for 4,  including shipping within Australia. I have a month off before starting a PhD in 2012 so hopefully that allows enough time to get this all built and calibrated.

You can find a copy of the 3D model from here. Some parts of the model were sourced from Googles 3D warehouse including the Steep Reel, bolt, Arduino Mega, character display and ATX powersupply.

I would love to hear what people think of this design and so welcome all comments and criticisms. If you have any suggestions for improvements or alternative ideas please leave a comment!

Happy new year to all!

Advertisements

About Richard

I am a Materials Engineering working in the field of Magnetic Materials in Melbourne, Australia. This blog covers my personal interest in all things CNC.
This entry was posted in A Reprap Project and tagged , , , , , , , , , , , . Bookmark the permalink.

5 Responses to Playing around with a heated chamber design.

  1. Andrew Diehl says:

    I have serious doubts the scissors jack will remain perfectly level during movement. It is not made for precision.

    Filament is going to get squishy in the bowden tube/pre-nozzle with chamber temp of 100C

    Heated bed/nozzle will not provide enough power to get the chamber to 100C, without the bed temp being unreasonably high.

    The ptfe bearing on the print head will absolutely have to be some other non-plastic material. The glass transition temp of ptfe is only 30C from your chamber temp. Not good for something that needs to be low friction and low wear.

    • Richard says:

      Hi Andrew

      Thanks for the comments. The scissor jack I have is a little different to the one I linked to in the post. Here is a photo of it. An uneven surface is a real possibility, especially at full extension. I may need to limit my build height in order to get it level, but I wont know until I try.

      As for the heating of the filament within the Bowden tube, it appears this problem has already been solved by commercial machines. They use an large diameter feed tube into which the filament and wiring is placed. This tube then has ambient temperature air forced into it in order to keep everything at an acceptable temperature. The air then returns out of the chamber by a secondary tube. This cool air stream could also be run over sealed heat sink at the print head in an effort to keep the transition zone as short as possible. I was going to try and avoid using this system due to the obvious complexity, but I may have no choice.

      The heated bed I am using employs power resistors and consumes upwards of 350W. Im hoping that this in combination with a well insulated build chamber will allow me to get reasonable temperatures. If not, then a hair dryer like heating element with a fan could be used. I would also like to be able to strictly control the cool down rate so this may be something else I need to add.

      Lastly, I couldn’t agree more about the print head bearings. I will put an order in for some LM8UU linear bearings.

      Thanks

      Richard.

  2. Beau-James says:

    Hello, I like the ideas you’re working with on this project.
    Are you still working on it? I’ve nearly finished building an enclosed design with similar thoughts to heat the chamber.

    • Richard says:

      Hey

      I am still working away on a 3D printer, at the rate of about 5 hours a year… Work has taken over completely unfortunately.

      I would love to hear how your own experiences go with a heated build chamber. Do you have a blog or forum that your posting your progress on?

      Cheers,

      Richard.

      • beauxlabs says:

        My blog can be found at beauxlabs.wordpress.com.
        Unfortunately, I rarely have the time to update it with what I’m working on,
        but I put up a new post for my 3D printer project. I’m beginning to put more detail.
        The whole frame will be encased in laser cut acrylic and a thermopile will control ventilation to maintain constant temperature. I’m assembling much of the information I’ve gathered into a paper which will be ready by March at the latest.

        Best Regards,
        Beau-James

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s