Thanks KK, I was already wondering whether 4mm float glass would be better. It wouldn't work with the bed clips from The Range 59p photo frame because they are barely able to handle the 3mm glass + alu + bed heater + mdf tabs, but I've ordered these clips which should handle the extra 1mm easily.by dc42 - Ormerod
Right above the hot end heater connector is the mosfet that controls it, and next to the mosfet is an LED (D7) and resistor. Does the LED come on when you command the heater on? If the LED doesn't come on and you have a DMM then you could also check the voltages on the mosfet. Should be +12V on the drain with the heater off, 0V when on. The gate should be +5V when on, 0V when off. Source at 0V aby dc42 - Ormerod
Doing a binary diff of the RepRapFirmware.bin file I built with the one on github, I get much the same thing. There are quite a few sporadic diffs, mostly values increased by either 0x1C or 0x38, so probably jump/call destination addresses. Then starting at offset 0x3948 the file is completely different. So the code at that address has apparently changed and grown. Maybe Adrian is using an olderby dc42 - Ormerod
Thinking further about it, I'll replace the 2 outside front screws by short ones, that clamp the aluminium and bed heater together but do not penetrate the MDF.by dc42 - Ormerod
Quotekwikius The flyback diode would be connected with anode to TR2 drain and cathode to Vin, basically across the bed heater inductance. On switching off TR2 the diode starts to conduct with 10 A running through it into Vin. Not quite, the current circulates round the bed and the flyback diode only, so your decoupling capacitor isn't involved. However, your decoupling capacitor (or my 1uF oby dc42 - Ormerod
I finally got the firmware to build, by a combination of installing 32-bit Eclipse instead of 64-bit, choosing a path for my Eclipse workspace with no spaces in it, installing Arduino 1.5.4 in a path with no spaces in it, and editing lots of paths in the configuration files (looks like it was the same changes 3DES made). I'll test whether the rebuilt firmware works later today, but right now I neby dc42 - Ormerod
Dieter, I did add a flyback diode, but I removed it when I added the resistor in series with the mosfet gate. The back emf from the bed heater inductance isn't really the problem, the problem is the abrupt removal of a 10A load from the 12V supply along with the lack of local decoupling. Adding the gate series resistor to slow down the turn off speed alleviates both. I added a 1uF ceramic local dby dc42 - Ormerod
The label on my PSU says the 12V supply is rated at 32A. If you are exceeding that because of a short, I would expect you to find scorch marks. It could just be that you have a bad PSU. Do you have another one you can try?by dc42 - Ormerod
Hi Dieter, I believe the biggest problem is that the bed heater mosfet switches off very abruptly (in <20ns) and there is no local decoupling. This leads to a short, sharp positive spike on the 12V supply in the locality. Switch-on is less of a problem because it is much slower, around 2us. Using PWM to do a soft start and finish would result in many more of these spikes being generated. I haby dc42 - Ormerod
Surely the bed is essentially supported at 3 points, with the two outer corners not really providing support? I'm tempted to remove those 2 screws completely. With the printing plate made of rigid glass, and the heater PCB being rigid too, I don't think it makes much sense to support it at more than 3 points. It is the MDF plywood ribs that keep the 3 support points stable relative to the bearingby dc42 - Ormerod
Ian, thanks for the instructions. Unfortunately, I'm still having problems. When I try to open the project in Eclipse, I get these errors from the Arduino plugin: Then when I try to build the project, it says it can't find make.exe. I guess I can edit the path to fix that one (shame Eclipse doesn't come with an installer that sets it up already), but I don't know what to do about the null poinby dc42 - Ormerod
Quotemarkbee Hi dc42, the part is only 1.2mm in depth so countersunk screws would protrude from the part. That would be counterproductive to the space available between fan and Duet board mounting that remains when the X-axis is homing. Markus Given that my fan is currently attached using cap head screws that sit on top of the fan, and this gives 4mm clearance between the head and the electronby dc42 - Ormerod
Can anyone advise me which is the best free CAD package for a novice like me to learn, so that I can design my own objects? I run apps mostly under Windows 7.by dc42 - Ormerod
Hi Markus, Why not put countersunk screw holes in the part, so that the existing cap screws holding the fan can be replaced by slightly longer countersunk ones, to hold everything in place?by dc42 - Ormerod
I let the bed cool, then try to push the piece off sideways. If that doesn't work, then I push a paint scraper under it. At the start of the next job, I spray a little isopropanol on the bed and wipe if off with a duster. But I'm a novice when it comes to 3d printing, so there may well be better advice available.by dc42 - Ormerod
QuoteRory166 I think for safety the sensor should be 1.5mm from the reflective surface as a minimum. Your new design looks even better. The sensor face is somewhat above the edge of the sensor board. On my unit, this puts the sensor face about 1.5mm above the nozzle already. QuoteRory166 I am almost certain that RRP use only PLA from Haberdashery. I think there is a bit of a green agenda hereby dc42 - Ormerod
Ah, I haven't installed KiCad yet - looks like I had better do that to better understand the board. Avalanche breakdown occurs at about 50V for these mosfets. When the mosfet turns off sharply, the inductance of the bed + wiring causes a back emf to be induced across the bed heater, giving rise to a spike at the mosfet drain, even though Vin stays close to 12V.by dc42 - Ormerod
Thanks Simon, I'll print a new part just as soon as I have some more filament. Does anyone know whether the original parts in the kit are ABS or PLA? I don't yet know how to tell the difference, other than by applying acetone.by dc42 - Ormerod
AFAIR, Ian said the bed current was 9A by design, and someone else on this forum reported 11A. I've just measured the resistance to be 1 ohm at the bed, and there will be some resistance in the ribbon cable. So 9 to 11A is believable. I think the board has a ground plane as one of the inner layers, in which case the stepper driver decoupling capacitors will help suppress the transient when the bby dc42 - Ormerod
The important bits of the firmware that drive the stepper motors and heaters seem to work OK, but I agree that the rest of it is very buggy. I'd rewrite it myself, but RRP have acknowledged that it is beta firmware (I'd call it alpha myself), so I'm expecting them to improve it quite quickly. The few minutes wait after kicking off a print are for the bed temperature to reach 65C. You can go to tby dc42 - Ormerod
@Treth, if there is any ground plane noise in the area of the voltage regulators, then an increased dropout margin will certainly help. I suggest you don't go above 5.5V. There may be some ground plane noise and 12V noise generated when the bed heater turns off, which is why I added a 1uF ceramic capacitor between the bed heater +ve connection and the Vin -ve terminal.by dc42 - Ormerod
Hi Radian, I suspect that your issues with automatic Z axis homing are due to sensitivity to ambient light and/or using reflective aluminium tape. I mentioned in another post that with the aluminium tape, I found that if I moved the Y position in 1mm steps, the G31 value I read varied enormously. I found that white PVC tape gave far more consistent results. Also I changed the component values onby dc42 - Ormerod
QuoteRadian If those mods include adding a few thousand uF across C1/C3 to keep the ATX 12V from browning-out then I mostly agree. I've found this to be absolutely crucial to minimise sudden lock-ups during printing. Unfortunately it hasn't made it 100% reliable but I report that on the basis of only a couple of lock-ups since I did the mod. 470uF was all I could fit in the space, but I would hby dc42 - Ormerod
Quotekwikius So my proposal is to hang some hefty capacitance off the input leads where they enter the enclosure I ignore the existaing capacitance at the ATX PSU, which I believe is stated by Rory166 to be 2200 uF somewhere, but its 2 ft away down the leads. I assume the ATX PSU can handle the large extra capacitiive load I plan to add! I also ignore the hot end heater and concentrate on the Beby dc42 - Ormerod
You could feed the 5V from the ATX power board into the ATX_5V_EN jumper for the same effect.by dc42 - Ormerod
Hi gregstah, I set the bed temperature using the facility provided in the web interface. Don't worry about the duplication of the bed temperature in the extruder window and vice versa. It doesn't actually do anything with those figures unless you press the corresponding Set button. You are not the first to be confused by this.by dc42 - Ormerod
Hi gregstah, I agree with you, needle files are essential too.by dc42 - Ormerod
Hi Ormerod276, Unfortunately the downloads of slic3r and Pronterface don't include an install package. So under Windows, you need to unzip them into a convenient directory, create a shortcut to the .exe file, and move the shortcut into your Start menu. To get the latest firmware, go to this github repository, change the branch from 'master' to 'duet' (not 'due'), and click on "Download zip". Thby dc42 - Ormerod
Hi Treth, I think the 3.3V regulator dropout margin is sufficient when it is running from the 5V switching regulator output. I haven't seen any problems when I power the Duet this way (although I did make a couple of mods). The 3.3V regulator dropout voltage specification is 1.25V max @ 500mA and the output voltage is 3.365V max, giving a worst-case margin of 0.385V when operating from 5V, and aby dc42 - Ormerod
Here is a picture of some things I printed with my Ormerod: For those of you still struggling to get this far, here are my top tips: 1. Be patient. I believe the Ormerod is a sound design, however it seems to have been released before some of the teething troubles were ironed out. Ian has done a superb job of supporting us over the holiday period, and has been very willing to supply replacemeby dc42 - Ormerod