Build Snafu's

Drill Rod Diameter

I will add many pictures soon (I hope).  So I ran into a couple of build snags, and fixes.  The drill rod measured 10.00mm, 10.00mm, and 9.97mm, which sounds OK, but the linear bearings that I bought are for 9.97mm.  So I had to figure out how to shave .03mm (.0012") off of the diameter.  What I did was wet sand by hand the first rod for 2 hours with 800 grit and got no where.  The next day I chucked it up in my lathe, and used 220 grit, until I got the size right, then went to 400 grit, then a rubbing compound, then wd40.  So these now work great.  Looking all over the internet, there are a ton of bearing complaints.  High quality bearings cost $20 each x12 = $240.  Yikes.  I'll deal with the rod diameter.  I also want to point out that this printer is going to be noisy because of the bearings.  If you don't have a lathe, you may want to consider a plastic or bronze bushing.  They will be quite.  But my goal was the perfect printer (within reason).  Linear bearings are very smooth given the right diameter rod.   Choices, choices.

Bearing Alignment

The next snag was bearing alignment.  I figured a reamer would be expensive, and it's not like you can get one at Walmart.  The problem is that the bearings go in the plastic parts, which will have small imperfections in them.  So it will skew the bearing in the holder ever so slightly.  I came up with an idea that saved me a ton of time and headache.  I found a 3/4" solid rod, chucked it up in the lathe, then added 400 grit sandpaper properly cut, slightly overlapping with rubber bands.  So, rubber band, plastic part, rubber band.  Rotate the part a couple of times, then turn on the lathe for about 30 seconds, and slide the part back and forth down the sandpaper.  This is in my opinion as good or even better than a ream.  The bearings now slide perfectly in the holders.  And on all parts like the Z axis that have 2 bearings, they are 100% aligned.  I have pics, but not loaded in yet.  Stay tuned.

Wiring

Gauge    Amps at 12V
22    5A
20    8A
18    10A
16    20A
14    40A
12    60A
Don't believe everything you read.  Use 14 or 16 gauge wire for your heatbed if your going to power it with Ramps.  You need to be able to use 5A, and 11A.  I like to have a 50% overkill.  Stupid me...  I read that you should only use 12 gauge wire.  So I went to hobbytown USA and picked up some 12 gauge remote control battery wire.  Guess what...  It won't fit into the connecter on the ramps, and looks ridiculous on the heatbed.  There is no way that this gauge wire would do anything but add to your frustrations.  I'm currently replacing it with 14 and 18 gauge blue speaker wire from Walmart.

Pyrex Bed

I had a hard time getting PLA to stick.  I had to run the bed temps up to 80c, and that was still questionable.  I found a simple solution.  Wet sand 800 the top of the pyrex bed.  Just swirl it around every which way, and press hard.  It will look identical to unsanded, but PLA sticks like crazy to it.  You can also feel the difference when you clean both sides.  One side is ultra smooth, the other side is not.