Print Bed Surfaces: “More than Moore” Edition

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Try this for yourself. Pick up some polished silicon wafers and support our makerspace here: The MakerHive Store

There are two beautiful aspects of the internet.

1. At some point in time bsolutely everything has been / is / will be for sale online for a really good price

2. Thanks to awesome communities on forums and on Twitter the best stuff tends to bubble up so that I actually hear about it before it’s gone.

Such was the case with a case of 8″ silicon wafers from Electric Goldmine. A friend mentioned that these things are so cheap and interesting that they just had to be useful. And he was definitely right.

Round wafer on a very Cartesian printer

Round wafer on a very Cartesian printer

These wafers are an excellent print bed for several reasons, and they’re perfect for me for a few more reasons.

1. Planarity – lithography at sub 20 nm nodes probably doesn’t work so well if a wafer isn’t perfectly flat

2. Heat Transfer – the combination of excellent thermal conductivity (compared to glass) and rigidity in a relatively thin wafer (these are 0.7 mm) allows for quick heat up and cool down and elimination of hot/cold spots on the print surface.

3. (just for me) Copper plated on one side – My Printrbot Simple Metal’s inductive probe looks for metal to tell how far away it is from the bed. Straight silicon doesn’t cut it. But one side of the wafer appears to be copper plated and polished. That creates a really nice surface for my auto-leveling probe to detect.

So how well does it work?

Pretty much like glass. I retried everything the internet told me to do when printing on glass, and ended up using purple glue stick again with really good results, just like on my previous glass bed.

Another huge advantage is that I’m not clamping the wafer to the print bed in any way. It is only resting on the silicone baking sheet which is clamped to the print bed. This way a wafer can be swapped out after a print for a fresh one, without waiting for the entire bed to cool down. I used to tell myself that 10 minutes to heat up here and 15 minutes to cool down there didn’t matter that much, but it does. What other lies am I telling myself?

Scribing wafers without a diamond scribe is a bad idea. At least Maverick is still giving me the thumbs-up

Scribing wafers without a diamond scribe is a bad idea. At least Maverick is still giving me the thumbs-up

1 wafer post-print, another wafer loaded and waiting

1 wafer post-print, another wafer loaded and waiting

Bat Owl rises from the silicon...

Bat Owl rises from the silicon…

To make this a bit more functional on my printer, I had to raise the print bed by about 1 cm. Already having a 3D printer, making standoffs to accomplish this was a breeze. The stack up is shown below.

Lifting the bed

Lifting the bed

Aluminum Bed

Aluminum Bed

Silicone baking mat for high-friction & thermal conductivity

Silicone baking mat for high-friction & thermal conductivity

Binder clips and fragment of silicon for the home position

Binder clips and fragment of silicon for the home position

Wafer on the bed, smothered in purple glue stick and ready to print!

Wafer on the bed, smothered in purple glue stick and ready to print!

 

This effort was much more rewarding than I anticipated, both in sheer fun and in functionality. I’ve expended much more effort for much less improvement in the past.

10/10 – Would buy & build again.

 

Now if anyone has a lead on 12″ wafers at a reasonable price…

Second Steps in 3D Printing – Heated Bed

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As soon as I got the Simple Metal printer working, I wanted to take it apart and make it work better. A heated bed was the most functional upgrade as it allowed me to ditch the blue masking tape and move to glass or kapton tape and remove my PLA shackles, allowing me to print in theoretically any plastic (realistically ABS). The heated bed upgrade from Printrbot was very easy to install and worked pretty well up to about 80 C. I did use thermal grease between the PCB heater and the aluminum bed because the finish was really rough. It might have been too rough for the thermal grease to help but it ended up working. I added some cardboard and a mousepad underneath the PCB heater to help guide the heat up to the print bed instead of down to my Printrboard. With those modifications I was able to reach 100 C in about 20 minutes. Not great, but functional.

Heated Bed with makeshift insulation

Heated Bed with makeshift insulation

Pipe insulation - Not as functional as cardboard, but looks better.

Pipe insulation – Not as functional as cardboard, but looks better.

Fan shroud in "traffic-cone-orange" ABS

Fan shroud in “traffic-cone-orange” ABS

Initially I used the square of Kapton tape provided as my print bed surface. Covering the tape with purple glue stick worked very well for ABS and PLA. But I did not give the Kapton the respect and consideration it demands and ended up with some nasty bubbles.

The heated bed upgrade was not without flaws though. As the makeshift insulation might suggest, there are some design elements lacking here. Some issues that should be resolved for more satisfying prints include:

1. Insulation underneath the heater PCB

Solution: Cardboard, Mousepads, Pipe insulation, anything else that will help keep the heat in. I ended up using lots of binder clips to clamp it all together

2. Heat sinking from the black metal wings that connect to the x-axis belt

Solution: Just print some standoffs! You’ll lose some z-height but the bed will reach higher temperatures and do it more quickly

3. No space under the bed for insulation in the original configuration

Solution: Mount the heated bed on top of the wings. I know it’s designed to be mounted underneath to end up with a flush surface that looks really nice, but form over function is not to my taste.

 

Overall, the heated bed upgrade was an expensive solution for mediocre performance. But it can easily be hacked to resolve some design issues and result in a very functional print bed.