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During warm-up for my first print (and then again during my first print) I noticed the following oddity:

• Bed temperature stopped climbing for entire duration of power supply fan cycle (1-2 minutes?)
• Bed target was 80C, reached 75C stablilized and stayed bouncing there.
• As soon as fan cycled off, bed climbed to 80C target very quickly and started print
• During print PSU fan cycled on again. Again the bed temp (per LCD panel) dropped down to 75C during fan operation.

Some considered possibilities
1.) cooling of bed from air movement
2.) cooling of thermistor only from air movement (direct opening below and very minimal RTV applied)
3.) competitive current draw diminishing available heating power
4.) safety function of PSU limiting current output once fan needed?

I was sort of surprised the software didn't seem to ramp up the current to overcome any potential cooling by wind. of bed/sensor.
Any thoughts?

FIRST PRINT
All suggestions welcome!
to my very noob eyes I suspect:
Underextrusion
Handle 1 --> ABS diameter = 1.62mm average instead of 1.75mm but my calipers were questionable so I've ordered a nicer set. i suspect slightly larger than measured though so error should make worse?
Handle 2 --> extrusion multiplier = will increase by 5% to test
Gaps between infill and perimeter
Handle 1 --> print speed = slow print speed which may improve infill/edge bonding
Handle 2 --> Infill Overlap? is this the correct command? (0.1mm --> 0.2mm?)

I also need to play with retraction a little bit probably since when static my hot-end seems to extrude a 5-10 mm of ABS while idle

[img]http://i.imgur.com/emtjMRp.jpg[/img]
[img]http://i.imgur.com/mOBBasu.jpg[/img]
[img]http://i.imgur.com/iCbKrZI.jpg[/img]

Thats a very useable shroud and for a such a complex object you should be pleased with it as a first print. (consider a drop of hot glue on where the wires come out of its fan as a strain relief.. i had the wires fatigue break their and the short from the break took out a fuse on my rambo)

the master of learning to make perfect prints is MHackney
and this is his good book er post... er how to do it
http://forum.seemecnc.com/viewtopic.php ... 361#p59076

I suspect the problem is mostly from the fan cooling the thermistor, rather than the bed (it would be impressive if it could cool the whole bed that much, but then, the bed is a little precariously balanced at the highest temperatures) there is a plug that SeemeCNC designed to help fix this on repables. http://repables.com/r/726/

yay thanks! good to know I'm not crazy. ill try the tape fix they mention until i can print that out and modify

I think the gap between the top/bottom surface and the perimeter crept in during the MatterControl 1.5 update.
When I switch from matterslicer to cura, I get a good surface.
Anyone else seeing this?

I take it you didn't tape over the center hole like it says in the manual?

g.

geneb wrote:I take it you didn't tape over the center hole like it says in the manual?

g.

No one reads that thing.

@geneb
Maybe i overlooked it but I suspect that advice wasn't there in my version of the build manual. 4th edition has been changed since I assembled the bottom plate in Dec '16. SeeMeCNC doesn't seem good at emailing previous customers about identified issues. Plastic plug design was uploaded a month ago.

Current manual
Version 4.35, March 21st, 2016 Fourth Edition

Can't see revision history of manual but the new picture (Fig. 6.9-3) doesn't even have a base plate with a hole in it so it definitely post-dates my kit packaging.

Current instructions would seem appropriate for construction though:
"If your base top plate contains a hole in the exact center, please cover the hole with tape on both sides. This will prevent the power supply's cooling fan from blowing air on the center of the heated bed."

Anyway, I packed the hole with insulation and taped both sides today. Issue hopefully resolved.

AlanZ wrote:I think the gap between the top/bottom surface and the perimeter crept in during the MatterControl 1.5 update.
When I switch from matterslicer to cura, I get a good surface.
Anyone else seeing this?

I fixed the gap by changing my infill overlap from 1mm to 1.2mm. I'd read that different slicers could influence prints - interesting if that's the cause.
I'd show a picture of the improvement (still one sharp corner with a small gap so will be trying 1.25 today) but my laptop went to sleep an hour into the print... More settings to fix!

I had the exact same experience with the bed heat up at exactly the same temps with the PSU fan cycling on. I'm pretty sure it's the fan air blowing on the bed thermistor (which recovers the instant the fan stops). My upper base plate had a small circular hole in the dead center, through which I had routed the bed wires. It also had a triangular hole torwards the front through which the wires were probably supposed to be routed. So I rerouted my wires and sealed off the center hole with Kapton tape and rtv silicone. Then I realized that actually the triangular hole is almost directly over the psu's fan. So I took a piece of aluminum tape and placed it over the underside of that hole and the wires coming through it to keep the fan from blowing air up through it. I also put a lot more kapton tape over all the wires near the thermistor on the bed underside. Haven't printed with the fix yet, but am designing a wind vane part (using Design Spark Mechanical) and will attempt a print soon.

Eric LB wrote:I had the exact same experience with the bed heat up at exactly the same temps with the PSU fan cycling on. I'm pretty sure it's the fan air blowing on the bed thermistor (which recovers the instant the fan stops). My upper base plate had a small circular hole in the dead center, through which I had routed the bed wires. It also had a triangular hole torwards the front through which the wires were probably supposed to be routed. So I rerouted my wires and sealed off the center hole with Kapton tape and rtv silicone. Then I realized that actually the triangular hole is almost directly over the psu's fan. So I took a piece of aluminum tape and placed it over the underside of that hole and the wires coming through it to keep the fan from blowing air up through it. I also put a lot more kapton tape over all the wires near the thermistor on the bed underside. Haven't printed with the fix yet, but am designing a wind vane part (using Design Spark Mechanical) and will attempt a print soon.

I was in the exact same scenario as you. Even down to the wire routing. I re-routed 2 days ago and packed both holes with small amounts of drywall insulation i had and sealed with a layer of kapton and black electrical tape on both sides. Temps are stable now during PSU fan operation.
(Bed still very stubborn about coming to temperature - might have something to do with the PDI bed calibration not being mentioned in manual.
PDI calibration command is: M303 P1 C8 S90 <-- will fail (time out) getting to 90 from ambient but you can start closer in temp or change temp. I haven't gone through all this yet as I currently switched to dead time mode and upped my max to 255 and seems to be doing better so i got back to working on first layer adhesion/printing)

I do have tape over the hole, and when the fan kicks in, the bed temp drops. Pretty sure it's a power issue, and not an airflow issue.

The center hole only causes a problem with the new power supplies, not the ATX supply.

PID tuning the bed wasn't included in the manual because it's not really necessary.

g.