A few new repraps underway in central auckland

There are a few of us slowly building some machines in Auckland. It started as a group venture for one machine but seems to have quickly morphed into three mendelmaxs and four mendel prusas with a possible rostock. I'l let the group know if any of these print before Christmas. There are some doubters who think they will end up a pile of bits under various desks but the enthusiasm ids hot at the moment.

Awesome, some pictures of your machines please.

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Richmond, New Zealand
Thingiverse ~ YouTube

Here is one of the Mendelmax's, one other is moving on all axis and awaiting calibration. There is an almost completed Prusa V2 the rest of the machines are in parts gathering mode.

Hi there,

I'm really interested in building a 3d printer this coming summer, however I haven't actually had the opportunity to see one in real life, or see the models they can produce. Your machine above looks great!

I was wondering if there was any way I could get in touch with you to have a look at your machines, and get some ideas? I'm considering either the Rostock, or a Prusa Mendelmax I2 currently.

Regards,

Jack

Sure we could arrange this. There are a couple of machines nearing completeion at TVNZ. Just a question of lining up a time when a Prusa and Mendelmax are there together. The mendelamx is printing but needs tuning (that's an important part of the process) the mendelamx is close to moving, wiring is underway. That will give you some idea. The mendel prisim that various people (especially wired1) is working, is well worth consideration. All depends on the depth of your pocket. If you have a little cash to spare the kit way is the best as you get everything together and it all fits. Having seen Blomkers kits here in New Zealand, both his price and quality is great. You would find it hard to get one yourself cheaper. However that is a Mendelmax only. A Prusa could be chaeper depending on how much you can scrounge.

Hi All,

I have to put my hand up as to the builder of one of the machines referred to here. Oatridge & I have the pleasure of being employed by the same institution.

I part way through a Prusa build - fits & starts, but getting there slowly. The PLA parts have been produced by another of my workmates, so I think there are at least 3 printing with mine and at least a couple of others underway

I've completed most of the physical build, and am at the stage of getting in the heated bed, shaft couplers power supply etc when $ allow.

Nice bed base, like the black plastics too, they look good against the zinc/alloy.

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Richmond, New Zealand
Thingiverse ~ YouTube

Thanks, the bed base was inspired by your one piece carriage. I've just mounted standard bearing blocks directly under the plate, a will mount the heated bed straight off that, and already have a set of your thumb wheel adjusters

I have also put the rails above the front/rear top threaded rods. I just need a 10mm spacer to bring the belt clamp level with the idler.

Hopefully there will not be too much heat transfer to the PLA bearing blocks.

Hey folks
Another Aucklander here. This may not be the exactly right place to introduce myself, but here goes.

I have a Prusa Mendel. It prints, but I have issues with the bed not heating enough. It hits the wall at 63 degrees. I can wait hours. I have no inspiration as to how to get it hotter. There are four heating elements and they all seem to be working (using the very scientific finger test), but 63 just isn't enough to get decent adhesion in the first layer for ABS.
I could go with PLA instead of ABS, but I really want to do some things in ABS.
Also, my software isn't perfect with Python to handle STL files to I have to convert to gcode first, which I can do but isn't ideal. Would love to be able to fix that, someone who knows how to configure that stuff could probably sort it pretty quickly, it's a pathing thing, I don't think I have the files in the exact place it is looking but I can't figure out where that actually is.
Also, keen to get in contact with others in the area and share the knowledge, although mine isn't very much to be honest.
Feel free to PM me.
Rob

Why don't you download the "ready to run" software suite (Windows 32 or 64)?

To be honest, I thought I had.
Happy to give it a try though. Where can I find it?

Get it here Rob...

[koti.kapsi.fi]

Don't forget to replace the included Slic3r package with the latest 0.98 version (slic3r.org). And make a copy of your existing slic3r Config.ini file before you delete the old program. (Unless you already have it of course!)

Edited 2 time(s). Last edit at 01/22/2013 05:14PM by waitaki.

Hi Rob,
Some more details on your heater setup might help get more suggestions on how to fix it.

What type are your heaters?
What resistance?
What voltage are you running them at?
Are they wired in series or parallel?
Can you check that they have the correct resistance?
What is the material/construction of the heat bed?
Where is the thermistor located?
Have you any way to verify the thermistor reading?
Do you have the back insulated?
Do you have fans running during the warm up and first layer?

If all that fails to provide a solution then I have some 100W silicone rubber heater mats with integral thermistor listed on my website that will hit 100°C no problems.

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[www.makershop.co.nz]
Makershop - Reprap parts, adding new stock almost daily.
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Hi all,

Just thought I'd say hi - I'm in Takapuna and have just got my MendelMax up and running (PLA parts printed by a friend on his Prusa, and everything else sourced myself). Stoked with how well it's printing already - been an awesome project to work on so far :-)

Cheers,

Matt

Sorry for slowness of response, I need to follow the topic so I get notified.

I have no idea about the bed heating components, they are four resistors that were supplied mounted on the bed already. They are in little metal housings that look like heat sinks which are labelled WH5 2R2 5% but I suspect that has nothing to do with the heaters themselves. I can't see anything anywhere in the documentation I was supplied that tells me more.
HOWEVER
I think I may have spotted something in the way they are wired. If I assume red wire is positive, it runs the first two heaters in parallel but then the negative comes out of them and powers the other two. The diagram I do have in my documentation is not consistent with that and would suggest that the positive goes in to all four in parallel and the negative comes from all four in parallel.
Is changing the wiring layout likely to help? My schoolboy electrical knowledge would suggest the second two resistors are getting a lower power.

These are simply power resistors, being used as heaters, quite common on repraps.

details on the part [nz.element14.com]

Depensing on how this is wired, combination of parallel and serial will determine the final resistance and have a bareing on how hot it can get.

If you description is correct you have a resitance of 5.5 ohms, wich sounds really high (my PCB HBP is about 1ohm)
Running them all in parallel the resitance would be 0.55 ohms, wich would be a lot better.

Other things that can limit HBP temp are :

Not enought power.. check you power supply is really putting out 12volts when the HBP is on. Annother common issue is the wires from the powersupply to the HBP, they must be capable of 11 amps, Ie thick wires. If the wires arent thick enough the wire itself warms up and not enough current get to the HBP. Thirdly you should isulate the underside of the HBP, so all your heat doesnt just bleed out into the air. Even cardboard would work.

Edited 1 time(s). Last edit at 01/30/2013 08:38PM by Dust.

Hmm, the wires seem thick(ish), not really thin electronic wire like in basic toy motors, but not 230 volt or oven thick. I just measured wire thickness and the gauge of wire appears to be pretty much the same all over, except for the ones going to the power supply. I traced the cables back to the board and they are coming from the pwr/bed source on the board, next to the pwr/tip socket. The nozzle heating doesn't seem to be a problem.

The picture on that link looks to be the right one, well spotted, thank you.
I can try insulating underneath.
So I should try running them all in parallel? That meaning (for the avoidance of doubt) that I run the red/positive in to the "top" end of all four resistors and the black/negative from the bottom of all of them.

I don't have the gear to check output voltages.
Thanks for input.

Yes I would try running them all in parrallel

Also check what amperage you power supply can put out on the 12v rails (should be written on it) Should be at least 16amp.

Supply will need to be more than 16A at 12 volts if you're running them all in parallel won't it?

if resistance is 0.55ohms and voltage is 12V then I=V/R = ~21.8A ! (which is about 240W at 12V)

Not sure how that combination of resistors is supposed to provide circa 120W at 12 volts?

Sounds to me like 3dRob was saying that the resistors are grouped in parallel in twos, and that the two pairs are then in series, which gives an overall resistance of 2.2ohms.

Even so, that's going to be about 60W at 12V....

mind=blown

I am sure I could work it out if I had to, but I am using a pretty bog standard PC power supply, 400W, it has two +12v supplies, 14A and 8A.
My rudimentary understanding would suggest that I should be better off with supplying all four heaters in parallel rather than two pairs serially. But I am reluctant to fire up the soldering iron if it is unlikely to help, or possibly could make things worse.

Thanks to everyone for offering their thoughts. It feels like the community in NZ is way bigger now than a year ago. I just saw some guy on reddit who has got his printing in three days. I will not embarass myself by admitting how long mine has taken, but I have been distracted with other things. I am keen to finally get it going, however.

You really need to check the wiring of the HBP and verify the resistance with a multimeter
if its 5.5 ohms you need to lower it.

I have 30A 12 volt supply, but since you dont. I wouldnt put them all in parallel either.

So you should try a combination. Join the red to the input of two resitors, connect the other ends two each other and the input of the other two resitors and then end of that to ground

Here is a primitive drawing

      |--R1--|          |--R3--|
-----|          |--------|          |------
      |--R2--|          |--R4--|

This should be 2.2 ohms, 5.45 amps

1.2 ohms would be ideal, using 10amps and 120watts, but this is not possable with any combination of 4 * 2.2 ohm resistors. And just using 2 wouldnt spred the heat evenly.

Edited 4 time(s). Last edit at 01/31/2013 01:31AM by Dust.

Pretty sure that is exactly what I have it like now.
I may have to get myself a multimeter.

Can I ask where you got your hot bed plate from? See if their web site says anything intersting.

I got the whole lot as basically a ready to go kit from a guy called Gary in Nelson.
I know very little about the individual parts supplied.
The documentation I received included a wiring diagram for the resistors that suggested a parallel arrangement
|--R1--|
-----| |----
|--R2--|
|--R3--|
|--R4--|

The bed was already soldered up with the resistors and thermostat. All plugs were on wires, I didn't have to solder anything (if you saw my soldering you would see this as a distinct plus). Except for the wire I cut by accident....

The build wasn't too bad, there were a few extra bits and a few short, which could well have been me cocking things up, but it wasn't anything serious.

So changing to all in parallel would be more than my power supply can handle? Do I just find a bigger power supply? It's just a PC one, I am not sure they would ever supply a lot more amperage would they?

That sounds more like it - If you put all 4 in parallel it has the equivalent of 2.2 ohms divided by 4 = 0.55 ohms and on 12 volts this will use 21.8 amps which is OK if you have a 30 amp power supply. It will produce 261 watts of heat on 12 volts and be quick about it but with only 4 resistors you may get hot-spots on your printer plate if it is too thin.

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Richmond, New Zealand
Thingiverse ~ YouTube

The other option is to consider changing the resistors

4 * 4.7 ohm in parallel would be 1.175, ie 10.21amps, this do able with your power supply. 122.5 watts

eg [nz.element14.com]

Hi 3DRob,
A bigger power supply might not be all you need. your switching circuit needs to be up to switching 22 Amps as well.
The RAMPS boards are only good for switching 10A or so. They have a fuse that will stop it pretty quickly if you exceed this.
Although the MOSFET is rated to 55A the PCB tracks wouldn't be up to 20A and the heat sink on the MOSFET would need to be bigger.

Your best bet is to replace the resistors with 4.7ohms or 5 ohms or see if you can fit one of my heated mats in instead. It will depend on whether you have an open area of 200mm square on the bottom of your heated bed plate.
Check heaters on my website.

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[www.makershop.co.nz]
Makershop - Reprap parts, adding new stock almost daily.
+++++++++++++++++++++++++++++++++++++++++++++

I think the other problem with Gary's suggestion that you use the following layout:

|--R1--|
-----| |----
|--R2--|
|--R3--|
|--R4--|

is that the power dissipated in each resistor won't be even.

Total current through that resistor network would be 3.147A

Total Power dissipated through R1 would be 21.79W

Total Power dissipated through R2||R3||R4 would be 15.97W

which is only 5.32W through each of R2, R3 and R4. You would have 1 corner of your heated bed warmer than the others! I say warmer, because total power dissipation of les that 40W is not going to make your heated bed very hot.

I can't see any combination of 4x 2.2ohm resistors that will give you power in the circa 120W range...