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Archive for March, 2017

9
Mar

3D Printer Webcam

After doing some testing with webcams I’ve come to the conclusion that you need one wide-angle of a brute to get the job done without having to end up setting the webcam up 30+cm or more away from your print bed.

Awkward to say the least.

What I wanted was to put the camera on one of my delta’s towers and have it catch the whole print bed. Impossible.

I duplicated the setup on my bench so this is what it can see… The webcam, standard el cheapo USB version on the left edge, printed 50mm LED light housing sitting on a 220mm bed.

IMG 0966

Through the web cam, this is what I can see…

Webcam Normal

Ah yeah, that’s useful. More like a macro cam. I had to keep in mind that these are meant to sit on the top of your monitor or laptop and grab your happy smiling face for those online chats. Nothing more.

I couldn’t find a wide angle webcam but I did notice that a lot of eBay sellers had some “wide angle” lens attachments you could use on your cellphone to photograph wide angle scenes. Cheap enough, wasn’t worried about the quality, so I ordered one.

IMG 0969

The description:

fisheye:
Angle: 175°- 180°
Magnification: 0.33X
Lens Construction : 3 Element 3 Group
Max Diameter: 25mm
Length: 15mm
 
Wide Angle :
Angle: 130°
Magnification: 0.67X
Lens Construction : 2 Element 2 Group
Max Diameter: 20mm
Length: 11mm
 
Macro :
Magnification : 10X
Min Object distance : 10-15mm
Lens Construction : 1 Element 1 Group
Max Diameter: 20mm
Length: 15mm

The “wide angle” one is fairly useless but…the fisheye one hits the mark!

I merely held the one marked “Fisheye” in front of the webcam lens and got this:

Webcam Wideangle

Probably some edge distortion, but at least it covers a fair portion of the print bed compared to the standard webcam.

I plan on printing up a simple mount to fix it to the front the webcam.

While I’m at it, I should advise that if you get a web cam, make sure you get one that allows you to adjust the focal ring. I have a couple that are fixed focus and a pain to adjust, whereas most of the budget ones I have allow easy focus adjustment.

6
Mar

Kossel Rebuild Time!

At 2,380 hours, it was time for a major Kossel rebuild. The accuracy was suffering a bit more, not that it was ever 100% accurate in the first place.

Plus I’d used the other printer to design a whack of new parts that I needed to test out anyway…

Kossel Disassembly…

As Johnny Five says, “No Disassemble”…which, looking back now might have been good advice…course the other old saw goes, “If it’s not broken, you’re not trying hard enough”.

It took just over four hours to reduce Bullwinkle to frame parts and a cardboard box of screws, nuts, electronics, and add ons. I could see it was going to take a LOT longer to get it back together.

I was astounded at how loose the parts had gotten in two years. Some were merely finger tight. Like the stepper motor screws. Others like the frame screws felt like I used Lactate when I put it together.

IMG 2433

Missing is the box full of new printed parts. The majority of which I custom designed/modified at some point but never got around to testing. Nothing like an unproven design is there…

Bullwinkle Rebuild

I started with the top frame. My own design. There is a top so the 2020 open beam can’t slide all the way through, a mount for the limit switch and a guide to ensure the linear rail would be entered on the 2020 beam.

IMG 2434

The reason for the tall height (60mm) instead of the usual 20mm, is simple. To make the frame more rigid. If you look at the typical delta printers there are large double mounts on the base, but the top of the frame has a rather skimpy structure that is able to twist without a lot of effort.

The mounts I printed fit the 2020 beam like a glove. As in no play whatsoever. Plus as I said there is a top to them so the 2020 beam butts up against it.

IMG 2339

The top side of the mount:

IMG 2340

Next the bottom frame, pretty much standard for a delta except the bottom of the frame is again closed off so the 2020 beam can’t slide through.

IMG 2436

With the closed off areas top and bottom frame, the belts on the steppers actually pull the top and bottom frames together. If any of the frame screws work loose the belt tension will still hold it together. I see this as a good thing. Just untested at this point.

Once the frame was put together, I added the linear rails. Normally you wouldn’t build it this way because it’s harder to put the rails on. Easier to put the rails on the 2020 beam, then put the beam in the frame parts. But since I had designed linear guide alignments into the top frame, well, frame piece had to go on first.

For the bottom end stop, I redesigned a part to ensure alignment all the way down the 2020 beam.

IMG 2429

Next up I soldered in the wires for the top end switches.

IMG 2441

Finally as the day was ending I put the power supply hangers on the top frame, mounted the power supply and ran the 12Vdc wires (16 gauge for the heated bed, 18 gauge for the hot end) down the left beam, and 16 gauge wires for the power wires down the right beam. I enclosed all the wires in some nylon sheathing to keep them from chaffing and keep them neat.

IMG 2442

I found some Mendal “clips” on Thingiverse and printed up a dozen of them. They work great…

Adding in the Arduino and RAMPS 1.4 board I use my own custom sled design to hold those and it works nicely.

Kossel Assembly – Day 2

Since I was rebuilding, I also rebuilt the hot end and extruder. This, of course was going to come back to bite me in the butt, but I didn’t know it at the time.

For the wiring from the hot end down to the RAMPS, I had a thermistor, heating element, 12V fan wire, and variable fan cooling wires. I put them all in a sheath like the 12V and 110Vac wiring. To keep it all neat.

And it was time to test out a new fan setup. On the left you can see the original fan setup I used. Axial 4020 fans, same as the cooling one that runs all the time. And they do work but axial like to be mounted vertically or horizontal, not on a slant. Plus axials don’t like back pressure.

Hence the middle design of the 4020S blower fans. These work absolutely super! BUT, for the variable speed controller I use (a 12V PWM controller from eBay), I had a few fans that didn’t want to spin up unless the full 12Vdc was going to them.

Recently I came across some 4010 blower fans. I redesigned the housing for them and they work better when you want to get out near the edges of the print bed. Plus they weigh 40% less than the other two fan set ups. Win win. Sort of. These fans blow more air than the 4020 blower fans do and don’t like to go as slow. Always trade offs.

IMG 2416

Ultimately, now, I can say that there isn’t a huge advantage over the standard blower fan (4020) other than the weight or size. That doesn’t appear to affect anything as far as I can tell.

The next area I had redesigned was the bed mounts. Every delta I have seen has these tabbed mounts of some sort, with a clip/clamp on the top to hold the glass and heated build plate down. I’ve seen a lot of them made out of PLA. The glass transition point of PLA is lower than what you need to heat the bed up to if you’re printing ABS. Things can get a little squishy. I’d think.

I could have printed some out of ABS, but that stuff gives me such a headache I try to avoid it where I can. Unless it’s summer time and I can vent the shop. So I did the next best thing. I used some silicon (high temp RTV) on the heater.

Silicon Adhesive

Then I put a layer of cork on the bottom.

Cork Mount

Trimmed the outside with a box knife. Mounted the bed right on top of the 2020 beam with the mounts next to it. My logic was that the normal glass mounts could be tilted because of the beam so what difference would it make if the bed sat right on the beam? As it turns out, it works just fine.

Finally the whole thing was back together, levelled, and I was test printing…

IMG 2443

Fail – Opps

This is the part where I say that it’s working absolutely perfect and a 100% successful rebuild.

Except I’d be lying through my teeth if I did.

First thing I did was print a quick bookmark, which incidentally I’ve printed about 100 times because I know what to look for and it doesn’t take long to print…

IMG 2447

See a problem? Yeah. This has got extrusion written all over it. So..

  1. Too far above the bed for first layer? Nope.
  2. Hot end too cold? Nope.
  3. Extruder not putting enough PLA through? Nope ***
  4. Extruder Tension too low/High? Nope ***

Notice the “***”… yeah those are hint giveaways. I used the old extruder and I only replaced the spring in it. The drive gear on my extruder, an MK8 was actually worn to the point that the filament was slipping on it. So 2,380 hours and by sheer chance I rebuilt it at the same time it decided to quick working.

I grabbed one of my spares from my parts bin and within a few minutes, the old gear was gone and new one in it’s place.

MK8 Gear

And all was right? Not. Even. Close.

I had the extruder “clicks”. These appear when you’re trying to shove filament through the bowden tube faster than the little 0.4mm nozzle can let it get out. The extruder skips and clicks. So yeah it printed better but ugly too…

Take a look at the “fingers” on the bookmark and around the eyes at the blobs. Obviously something still amiss.

IMG 2449

But what? At this point, I’d like to say, it was the “A” thing. Except, it wasn’t. It was still a BUNCH of things…things I’d never encountered or even thought of before.

I don’t what made me do it, but I took the bowden tube out of the hot end, sent an M302 code to the printer, and told it to extrude 100mm of filament. I fully expected 100mm of filament. I got 104.7mm on average. Say what?

As it happens, these MK8 gear things are not all made the same. Mine was extruding more than the original worn out one. Some rapid math calc and I had a new step value to put in Marlin for the extruder.

And all was fixed? Nah. Like I said, multiple issues. Now I was squashing the filament so hard with the new spring it was binding. Ah HA! A quick and easy fix.

I loaded up some freshly opened filament, printed again. Finally getting much better…however…if you look at the bottom you’ll see a line of fill that shouldn’t really be there. It’s in the solid fill so I’m over extruding so the solid fill ended up on top of the solid file (Slic3r tends to fill all over so it can and does backfill on itself).

IMG 2445

Didn’t make any sense to me, so I grabbed the old extruder gear, popped it in the extruder, asked for 100mm and measured what I got. 98.4mm average.

In a lot of slicer programs they tell you to set the extrusion multiplier to .9 for PLA filament. Purely by accident when I built this one two years ago I’d plugged in the right steps to give me about .94 and it had worked. Right up to the point where it wore out.

My choices were either to correct this in the firmware, or do it in the slic3r I use. I did it in slic3r and all came out like this:

IMG 2446

Summary

I swear I spent more time troubleshooting this rebuild than I did just rebuilding it. I learned a whack in the process, grew some more grey hairs and stressed out trying to figure it out.

In the end, I got the printer working like it should, it’s more accurate than it was and it’s really nice to have it in one piece again.

But the old adage is true, when you spill something out of the bucket you’re going to need a bigger bucket to get it all back in.