Wednesday, August 31, 2016

Mini printer mods - printing on glass

After the first couple of prints, I wanted to get read for regular use, so I cut a piece of glass to use as the regular print surface. I have had little luck with printing on glass in the past but decided to give it another try.

The main problem that I had is that there isn't enough adjustment in the Mini to allow for a sheet of normal window glass on top of the print surface. I may come up with a more elegant solution later but for now I just bent the lever on the microswitch up to get the Z zero within adjustment range.

I hit another problem in that the preheat menu only allows you to go up to 60 degrees. You can adjust higher than that after the print starts, and the GCode can call for higher, but you can't preheat up to the 70 degrees you want for PLA on glass.

I am still working on the startup gcode for this printer, so I wasn't getting the glass quite hot enough. For now I used a bit of hair spray on the glass and it's printing fine.

I will probably put kapton on the back of the glass and flip it for ABS.

As you can see below, the glass is just held down with a couple of small bulldog clips. You can also see that I need to do some tuning - I thought I had the retraction set at 4 or 5 mm but it's only at 2, therefore the stringing. You need a lot of retraction with a bowden tube system.

Tuesday, August 30, 2016

New printer: Monoprice MP Select Mini

I recently decided to look at tiny printers for travel and to clear up some space in my workshop (I will keep the big printer but 95% of the time a much smaller printer will do the job).

I wound up ordering a Monoprice MP Select Mini. It is truly amazing what you can get for $200 these days.

Hackaday did a good review and teardown, here is a link to it. They did a spot on excellent review. I agree across the board. The 32 bit processor and display are great. The control dial is a bit fiddly, I may print some glue-on aids to rotation. The PID on the temp control is horrible. I'm going to see if it's possible to tune the PID manually if it still doesn't have auto-tune.

My printer came with two problems out of the box which were trivial for me but which would probably have greatly frustrated a newbie.  First, when I hit auto-home, it spiked the hotend into the bed. I hit the power switch, then used manual motion controls to retract the Z back up again.  I discovered that the connector for the Z axis endstop switch had fallen out.  This is actually visible without any disassembly. I was able to just push it back in place with a butter knife.

Second, the Z axis was level but far too low. I suspect that an impact during shipping, or perhaps final assembly, might have knocked the Z switch and the wire downwards. I screwed all four adjustment screws down 1.75 turns to reach a good zero height.

For me, this was a 5 minute trivial inconvenience. For a newbie, it would have been at the very least a call to tech support, and possibly a very frustrating reason to return the printer.

The minor issue is that the square spool holder on the side will not allow you to put on some of my spools that have a solid core. I had to bend down the retaining tab on the side a bit to allow them to go on.

Those things aside, I love this printer. I do not hesitate to recommend it, I will be using it as my primary printer instead of the CTC which will go on the shelf unless I need dual extrusion or a big print area.  If I were buying a big printer again at this point I would also definitely take a hard look at the larger Monoprice units, which Hackaday also gave great reviews of.

Friday, August 19, 2016

Laptop mainboard - ALMOST right

My last post was about a laptop mainboard that I dropped in, and that it only had one thing different - a different connector for the feature buttons.

Well, then I noticed that the touchpad buttons didn't work.  And it didn't think there was a battery plugged in.  And the LEDs up front (power, battery, wifi) weren't lighting.

I opened it up again, and found that there were no switches installed on the mainboard for the mouse. I surmise that it was for a slightly different model that had buttons in the touchpad (there is also a populated connector on this mainboard in the right place, which is probably for that purpose).  So I got the hot air out and removed the switches, and moved them. I also desoldered the LEDs from the old board and moved them (no mean feat - they are 0603 LEDs).  I plugged in enough to power up, and no luck. The LEDs didn't light, and the mouse buttons still didn't work.

I compared the boards and determined that the mouse button switch leads go through a couple of 0603 100 ohm resistors. One was still on the board, so I moved that one. The other one was probably lost when I swept the switch off with the hot air, so I put in a 330 ohm resistor which I have on hand. This worked.

The LEDs, probably a similar story because I noticed that it had LEDs already in place elsewhere on the board and those were working. I just drilled three holes in the top of the laptop to let the LEDs shine through and covered it with tape.

The battery - that was another story. Turns out the battery connector was about 3mm shorter on this board than the other one. I did manage to remove the connector from the old one and get it on the new one. This took over an hour. Lead-free solder is a pain in the ass when desoldering large connectors with through hole physical stakes.  On the old board, I ripped the via rivets out while desoldering, so I was super careful on the new board. I tried hot air on the old board first but it was just not working and I decided if I was going to have to use other means on the new board, best to practice on the old one first.

Anyway, that's all working now, the LEDs are shining through the lovely bodged holes drilled in the case, the battery is charging, and the mouse buttons work.

I would NOT have been successful at this stuff without the microscope that I bought last week. The parts are just too small for my eyes.  I think they're probably too small for anyone's eyes when you consider you need to examine the solder after your work is done. Maybe you could do it with a 10X loupe but I'm happy to have the microscope.

Monday, August 15, 2016

Laptop repair

Just a quick heads-up - we had a laptop die in our household a few months ago, and didn't have time to mess with the repair so we just bought a new one. Last week I started messing about with the repair and spent several hours looking for a crack in the circuit board or a bad connection to a component (would only power up if pressure was applied to the board).

After a couple of hours of this, just out of curiosity I checked ebay to see what a new mainboard would cost. Turns out, $30.  Well to heck with fixing the old mainboard then. I'd already wasted more time than that.

2 days later, the mainboard arrived. It was new in box, slipped right in with one exception - it had a 0.5mm pitch connector instead of the 1.0mm pitch connector in one place but it was just for the options keys.  I ordered new connectors off eBay, it'll be a few weeks (China) for $3 for 5 of them.

Moral of the story, check the prices for all the options before spending much time on a repair. I just assumed mainboard replacement would be uneconomical since the last time I tried to buy a laptop mainboard they wanted more than the cost of a replacement laptop. These days if the laptop is more than 2 or 3 years old, likely there are repair depots liquidating excess inventory for a song.

New printer: JGAurora A3

This week I decided I'd had it with all the other printers in my stable.  The CTC is stable and decent but it just bugs me (can't st...