Sticky rafts? Or not sticky enough? I'm having trouble getting the ends of my rafts to stick to the build area of my Reprap. I've had a couple successes by covering the build area with electrical tape, but even then I often have to push down the corners of the rafts just after they are extruded, as they have a tendency to curl up and away from the build area. Any ideas on how to stick the raft down better? Once I get a decent raft, I seem to be able to build on it nicely, but sticking the raft is problematic. I've been extruding ABS at 8mm/s, slowed down to 4mm/s for the double thick first raft layer. 200 deg C seems too cold for the first layer, 215 works sometimes, haven't tried much at 230. Wade https://reprap.org/forum/read.php?14,15945,15945#msg-15945 Wed, 11 Mar 2026 15:07:35 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?14,15945,20279#msg-20279 https://reprap.org/forum/read.php?14,15945,20279#msg-20279
Another variant that might be worth exploring is sugar glass: [www.instructables.com] Not sure if it'd stand the heat, though.]]> degroof Mechanics Mon, 12 Jan 2009 12:59:48 -0500 https://reprap.org/forum/read.php?14,15945,20087#msg-20087 https://reprap.org/forum/read.php?14,15945,20087#msg-20087 www.baking911.com]

I'm guessing what destroyer2012 has would be "caramel - medium brown".

Might be interesting to create "candy" of various forms and see which ones have useful properties. For example, can you extrude "soft ball" sugar?]]> degroof Mechanics Wed, 07 Jan 2009 12:14:03 -0500 https://reprap.org/forum/read.php?14,15945,20086#msg-20086 https://reprap.org/forum/read.php?14,15945,20086#msg-20086
I wonder if the raft is still needed?]]> nophead Mechanics Wed, 07 Jan 2009 12:08:56 -0500 https://reprap.org/forum/read.php?14,15945,20084#msg-20084 https://reprap.org/forum/read.php?14,15945,20084#msg-20084
The "red" sugar seems very similar to the color of the sugar I melted earlier in this thread. It was a brown with a red tint to it that results from the sugar caramelizing. The candyfab folks have some very dark sugar creations as well.]]> Anonymous User Mechanics Wed, 07 Jan 2009 11:53:08 -0500 https://reprap.org/forum/read.php?14,15945,20079#msg-20079 https://reprap.org/forum/read.php?14,15945,20079#msg-20079 -------------------------------------------------------
>
> BTW! Why is your sugar red? :S

No clue. It's baker's sugar, if that makes any difference. Gonna mess with my extruder's speed and try again. Maybe I can get better extrusion thickness. Maybe it has to do with the temperature at which I melted it?

Doing this in an oven seems like overkill. I was thinking of using a heat gun or something to melt the sugar down, or maybe eventually even make the base heat up and re-form the sugar-surface after a model is removed. Even wrapping nichrome wire around a small heat-resistant cup would melt the sugar quickly and efficiently for re-application.]]> destroyer2012 Mechanics Tue, 06 Jan 2009 23:43:29 -0500 https://reprap.org/forum/read.php?14,15945,20074#msg-20074 https://reprap.org/forum/read.php?14,15945,20074#msg-20074 -------------------------------------------------------
> I just tried extruding ABS onto sugar today
>
EXCELLENT! Somebody finally tackled the question of what sort of support material plastic will actually stick to! Bravo!

:)-D

BTW! Why is your sugar red? :S]]> Forrest Higgs Mechanics Tue, 06 Jan 2009 19:29:08 -0500 https://reprap.org/forum/read.php?14,15945,20072#msg-20072 https://reprap.org/forum/read.php?14,15945,20072#msg-20072
I melted the sugar in an aluminum foil 'cup' and then poured it onto an aluminum foil surface, then flattened it with the underside of a pan. The surface was really smooth and flat, but it was not completely flat when I mounted it onto my base (I just taped it to existing paper, and the paper bowed up a bit), so one corner of my raft was sunken into the sugar a lot more than the other corner, but even the non-sunken corners stuck pretty well, and in those cases the tip of the heater barrel was about a millimeter or two off the surface.

The sugar cracked when I tried to remove the sunken-in corner, but it was not very damaged when I tried to remove the other, less molten-in corner of the raft. This definately shows promise! I will adjust my extruder to make sure it's running more consistently and try again.

[www.flickr.com]]]> destroyer2012 Mechanics Tue, 06 Jan 2009 19:13:40 -0500 https://reprap.org/forum/read.php?14,15945,19222#msg-19222 https://reprap.org/forum/read.php?14,15945,19222#msg-19222 -------------------------------------------------------
> I haven't read your blog post about
> scaling up the heated baseplate (I couldn't find
> it :S). So this will have to be a decidedly
> amateur post.
>
No problem...

[www.3dreplicators.com]
>
> What about making a heated baseplate with a number
> of separate controlled regions, so only some of
> the base plate has to be heated at a time. So
> hopefully you wouldn't be drawing near 150w.
> This would only help if you were doing a number of
> separate parts, trying to do one big part would
> mean having it all turned on anyway.
>
> Though I guess this would mean more channels of
> PWM, so were back to the custom electronics.
>
I've got nothing against custom electronics. Right now, however, I'd rather use more electricity for a while and make sure that the heated surface concept really works well before running off and designing a complicated thing like that.
>
> I'm new (..fresh meat..) and don't (yet) own a
> reprap, so I may have missed some crucial piece of
> reasoning.
>
Doesn't sound like you have. :)-D]]> Forrest Higgs Mechanics Mon, 08 Dec 2008 16:34:06 -0500 https://reprap.org/forum/read.php?14,15945,19221#msg-19221 https://reprap.org/forum/read.php?14,15945,19221#msg-19221
What about making a heated baseplate with a number of separate controlled regions, so only some of the base plate has to be heated at a time. So hopefully you wouldn't be drawing near 150w.
This would only help if you were doing a number of separate parts, trying to do one big part would mean having it all turned on anyway.

Though I guess this would mean more channels of PWM, so were back to the custom electronics.

[disclaimer] I'm new (..fresh meat..) and don't (yet) own a reprap, so I may have missed some crucial piece of reasoning.]]> Anonymous User Mechanics Mon, 08 Dec 2008 16:21:28 -0500 https://reprap.org/forum/read.php?14,15945,19055#msg-19055 https://reprap.org/forum/read.php?14,15945,19055#msg-19055
I have tried all sorts of different plastics borrowed from the tech department's scrap bin and nothing worked as the bottom of the raft would not adhere.

I also tried using copper strip board and heating it with a hot air gun and this worked quiet well but it bent the strip board (which could be fixed by holding it down better) and it damaged the strip board when I removed it.

I then tried heating the MDF table I extrude onto but again not much adhesion unless I pushed the plastic into the surface.

Then I noticed some old Evostick glue on the side and painted it onto the MDF and extruded straight onto it while it was wet.

This worked really well. No peeling or warping and when it was time to remove it a swift tap with a screwdiver and it came straight up.

This worked on a 4cm2 raft extruded in HDPE at 230 degrees and the temperature in the garage was about 2!

Tomorrow I will try a large long thin object.
Andy]]> andy hall Mechanics Wed, 03 Dec 2008 16:58:42 -0500 https://reprap.org/forum/read.php?14,15945,18898#msg-18898 https://reprap.org/forum/read.php?14,15945,18898#msg-18898 -------------------------------------------------------
> Doesn't convection swamp emission in this case?
>
You can't swamp radiative loss. You can just add to it with convection.

The little simulation model I did indicated that if you use forced convection on the print surface, a very common option that I think you use, iirc, you are absolutely right. You can see in the main blog that I did a scaling up exercise on the Metalab surface heater and discovered that you need about 150 Watts to properly heat a print table using their design. To get that from a 12 v power supply you're talking about 12.5 amps. My power supply will do that, but I wonder if most of the ATX systems that people are using can supply that in addition to what the Reprap machine needs to operate.

You're also talking about a 0.9 ohm heating element to deliver that kind of wattage at 12 v.]]> Forrest Higgs Mechanics Fri, 28 Nov 2008 11:40:36 -0500 https://reprap.org/forum/read.php?14,15945,18895#msg-18895 https://reprap.org/forum/read.php?14,15945,18895#msg-18895
Would a low wall around the edge reduce the convection loss by preventing cold air from being sucked in sideways.]]> nophead Mechanics Fri, 28 Nov 2008 11:31:10 -0500 https://reprap.org/forum/read.php?14,15945,18891#msg-18891 https://reprap.org/forum/read.php?14,15945,18891#msg-18891 Forrest Higgs Mechanics Fri, 28 Nov 2008 11:22:58 -0500 https://reprap.org/forum/read.php?14,15945,18890#msg-18890 https://reprap.org/forum/read.php?14,15945,18890#msg-18890
@forrest: i was thinking along the same lines, of using nichrome and cement to build a heated plate without needing the power-resistors. i am curious how it would work out, but i have a feeling that the thin layer of cement would have a high tendency to crack, what with the different coefficients of expansion and all the heating and cooling... if you try it let me know how it works.

another thing people could try if they have the resources, is just to extrude onto a commercial hot-plate.]]> pumpernickel2 Mechanics Fri, 28 Nov 2008 11:08:29 -0500 https://reprap.org/forum/read.php?14,15945,18713#msg-18713 https://reprap.org/forum/read.php?14,15945,18713#msg-18713 nophead Mechanics Sun, 23 Nov 2008 14:32:46 -0500 https://reprap.org/forum/read.php?14,15945,18710#msg-18710 https://reprap.org/forum/read.php?14,15945,18710#msg-18710 -------------------------------------------------------
>
> i think so. Although it's hard to measure this
> accurately. we baught one of the laser temperature
> measuring devices but it doesn't give good
> readings on shiny copper.
>
You can correct those readings by plugging in the temperatures you're getting into the Stefan-Boltzmann equation and solve for energy assuming a 0.9 emmisivity, which is what most IR thermometers assume (check the product literature to be sure). Then use the radiant energy figure and plug it back into the same equation along with the book emissivity for polished copper.

In both the 1.6 um region you get an emissivity of about 0.03.

[www.raytek.com]

while for the 8-14 um band it runs about 0.02.

[www.infrared-thermography.com]

Mind, if you've let it get oxidized, which it will pretty quickly if it's spent siginificant amounts of time at temperatures > 100C, that emissivity is going to climb up to about 0.7.

Anyhow, plug those figures back into Stefan-Boltzmann and you can get pretty good corrected temperatures.

One thing that you need to keep in mind if you are using a non-contact IR thermometer is to get it quite close (maybe a cm) to the target, take the measurement and then pull it away. The cheaper IR thermometers typically have a fairly wide view factor (you can check in your product literature), so it's easy to either be measuring too big an area and, as a result, losing resolution, or measuring off the edge of your plate which gets you an average of the plate temperature and the background, too. They also tend to use cheaper IR sensors, too, which measure only the part of the blackbody radiation in the 1.6 um region and then basically guess about what's going on at longer wavelengths (8-14 um). This last, however, is really only a problem if you are measuring temperatures in the vicinity of room temperature. At temperatures ~100-150C the 1.6 um region sensors should work just fine.

I've done a LOT of this kind of stuff.]]> Forrest Higgs Mechanics Sun, 23 Nov 2008 11:34:04 -0500 https://reprap.org/forum/read.php?14,15945,18709#msg-18709 https://reprap.org/forum/read.php?14,15945,18709#msg-18709 -------------------------------------------------------
> Hi Wizard23,
>
> Is your heated plate hotter in the center than the
> edges and if so has that been a problem?

i think so. Although it's hard to measure this accurately. we baught one of the laser temperature measuring devices but it doesn't give good readings on shiny copper.

> If it is a problem, you could change the script so
> that a double loops starts around the outside
> with the edges close together, then as it gets to
> center the edges would be slightly wider apart so
> that there will be more heating at the edges of
> the plate to compensate for the extra cooling at
> the edges. Then the temperature across the plate
> could be constant.

A friend of mine als suggested this. And so i wanted to do it like that in the script. but as i did not have any real values on which to base the density distribution along the radius (and because the serpentine script was already finished :) I went for this design. But its on my todo list...still it will not be easy to figure out how to distribute the lines without one of these super expensive thermal cameras :) I don''t think the temperature gradient is a real problem though (but for bigger areas it might well be)]]> wizard23 Mechanics Sun, 23 Nov 2008 11:12:27 -0500 https://reprap.org/forum/read.php?14,15945,18707#msg-18707 https://reprap.org/forum/read.php?14,15945,18707#msg-18707
Is your heated plate hotter in the center than the edges and if so has that been a problem?

If it is a problem, you could change the script so that a double loops starts around the outside with the edges close together, then as it gets to center the edges would be slightly wider apart so that there will be more heating at the edges of the plate to compensate for the extra cooling at the edges. Then the temperature across the plate could be constant.]]> Enrique Mechanics Sun, 23 Nov 2008 03:54:13 -0500 https://reprap.org/forum/read.php?14,15945,18705#msg-18705 https://reprap.org/forum/read.php?14,15945,18705#msg-18705
I'm wondering if I couldn't rough up the back of an aluminum plate like you all are using above, apply a thin layer of Cotronics or Cerastil ceramic like Nop and I use to secure nichrome onto our extruder barrels, then lay down a length of nichrome and bury it in another layer of ceramic?

Mind, I've got a pile of power resistors that I'm not using for anything and a BUNCH of epoxy. :-D

I LOVE this project! :)-D]]> Forrest Higgs Mechanics Sat, 22 Nov 2008 19:53:25 -0500 https://reprap.org/forum/read.php?14,15945,18693#msg-18693 https://reprap.org/forum/read.php?14,15945,18693#msg-18693 Have you tried having it hot for the first layer to stick and then dropping the temperature a little below the melting point of HDPE (130 IIRC) while building the rest of the object?]]> nophead Mechanics Sat, 22 Nov 2008 12:47:35 -0500 https://reprap.org/forum/read.php?14,15945,18692#msg-18692 https://reprap.org/forum/read.php?14,15945,18692#msg-18692
each resistor is 32 ohms. they are in parallel, which gives 8 ohm total resistance, chosen because extruder heater is about 8 ohms also. each resistor has a power rating of 25 watt. there is a 100k thermistor glued to center bottom of plate.

a stand-alone arduino running some simple code runs an extra pwm-driver-board to run the heater. this runs on a big separate 24V supply. 24V is needed to get the plate hot enough. a temperature of around 150C to 160C seems to get HDPE to stick pretty well. takes about ten minutes to warm up at full-blast 24V.

a word of caution to any of you folks who might want to try this at home: the plate gets HOT!!! you obviously need to be careful around it and not leave it running by itself.

so now the big question: does it help the plastic stick? well, yes. but the part also melts and oozes out a bit at the bottom as the build proceeds. to get the part off, turn off the plate and let it cool. with hdpe the part separates from the aluminum easily and is left with a nice flat surface. warping is also greatly reduced.

now, whether using a plate like this is better than using a raft like other folks, i'm not sure. both have good points and bad points - and i haven't tried using a raft. but i think the raft may be the better way to go, considering the hassle of the heated plate and the relative minor advantages...[attachment 1228 heatedplate.jpg]]]> pumpernickel2 Mechanics Sat, 22 Nov 2008 12:17:38 -0500 https://reprap.org/forum/read.php?14,15945,18642#msg-18642 https://reprap.org/forum/read.php?14,15945,18642#msg-18642
And then i remembered some old heating-elements i scavanged twenty years or so ago:
[attachment 1213 Heizplatten1.jpg]

This are heaters with 115V AC and 150Watts each.

Connected sequential i can plug them direct to the line.

Mounted under an aluminium-plate and with an old but working temperature-controler and a PT100-resistor as temp-sensor this would be a perfect heating-bed.

I think with some heat-insulation beneath i should be able to set and control the average plate-temp between 30]]> VDX Mechanics Thu, 20 Nov 2008 14:52:03 -0500 https://reprap.org/forum/read.php?14,15945,18634#msg-18634 https://reprap.org/forum/read.php?14,15945,18634#msg-18634
For other things or for people who want to try out the heated base plate as it is it might be usefull. Might also be usefull for our planned plastic recycler - which would basically be a modded old school meat grinder with lots of nicrome around it.]]> wizard23 Mechanics Thu, 20 Nov 2008 12:14:19 -0500 https://reprap.org/forum/read.php?14,15945,18606#msg-18606 https://reprap.org/forum/read.php?14,15945,18606#msg-18606
You effectively create a small switch mode circuit, controlled by firmware, which you configure as either buck or boost depending on whether the resistance is too high or too low. If you are interested I can sketch the circuits.

I hope you get well soon.]]> nophead Mechanics Wed, 19 Nov 2008 17:50:41 -0500 https://reprap.org/forum/read.php?14,15945,18605#msg-18605 https://reprap.org/forum/read.php?14,15945,18605#msg-18605 -------------------------------------------------------
> To fix the resistance you could just attach a wire
> to the centre and link the other two connections
> to get 9R.
>
>
> Edit:
> On second thoughts that would of course give 4.5R,
> doh.

Yes it would be 4.5ohm. Still this could at least be driven with the PWM board (althogh the transistor would need a fat heatsink to drive that and survive). so this would actually work...too bad that i glued it together with another epoxy plate in an effort to make it more flat (which did not really help) so i cant access the centre anymore.

I'll just increase the trace width in the existing board and etch it next time i'm at the lab. It sucks to be sick and sit at home...but at least i have time to read and post to the reprap forum :)]]> wizard23 Mechanics Wed, 19 Nov 2008 17:19:38 -0500 https://reprap.org/forum/read.php?14,15945,18602#msg-18602 https://reprap.org/forum/read.php?14,15945,18602#msg-18602
To fix the resistance you could just attach a wire to the centre and link the other two connections to get 9R.


Edit:
On second thoughts that would of course give 4.5R, doh.]]> nophead Mechanics Wed, 19 Nov 2008 16:54:10 -0500 https://reprap.org/forum/read.php?14,15945,18597#msg-18597 https://reprap.org/forum/read.php?14,15945,18597#msg-18597 degroof Mechanics Wed, 19 Nov 2008 15:43:15 -0500 https://reprap.org/forum/read.php?14,15945,18596#msg-18596 https://reprap.org/forum/read.php?14,15945,18596#msg-18596 -------------------------------------------------------
> Now that is a cool idea! Please post the details
> on your new PCB - I'll be etching one myself very
> shortly!

If you are interested in the pcb: I made some python scripts that generate the serpentines as a kicad .brd file. The rest (adding some more traces and vias for mounting i did in kicad). the python scripts and the board I actually etched (generate_meander2.py and reprap_heaterv03.brd) are in our subversion user directory:
[reprap.svn.sourceforge.net]

I calculated the pcb with this PCB track with calculator to be 8 ohm at 100C:
[circuitcalculator.com]

but when I etched it it had more than 18Ohm so something must have gone wrong or the PCB trace calculator is wrong. A friend who is very much into analog electronics built a small cuircuit so we can now drive it with 30V from an arduino but because the standard reprap PWM board uses 12V I want to redo it with thicker traces

A the moment I'm sick and so I can't go to the lab and test our new designs but I will post updates as soon as I etch a new version.]]> wizard23 Mechanics Wed, 19 Nov 2008 15:37:21 -0500 https://reprap.org/forum/read.php?14,15945,18593#msg-18593 https://reprap.org/forum/read.php?14,15945,18593#msg-18593
Wade]]> Wade Mechanics Wed, 19 Nov 2008 15:18:08 -0500 https://reprap.org/forum/read.php?14,15945,18592#msg-18592 https://reprap.org/forum/read.php?14,15945,18592#msg-18592
[reprap.soup.io]

In the next version we just etched a long winded trace of copper as a heating element. Sadly the resulting resistance was much higher than the calculated value so it needs way more than 12V to be heated, so we'll have to redesign this one.

One word of caution: While the heating helps reduce the warping stress don't overdo it. If the base plate is too hot the material sticks very well but also shrinks and gets crunchy. About 100C seems to be the best value although I don't fully trust our readings.

All I wrote here applies to ABS we haven't tested it with other materials yet.]]> wizard23 Mechanics Wed, 19 Nov 2008 15:12:07 -0500