4/20/2017

Fix Wobble on Disc Sander

Back in 2014 i build a 12" disc sander using an old furnace blower motor.  I used melamine for the 12" disc and built the frame out of 2x4's.  It wasn't perfect but it's worked fine for years.  The biggest issue was that the disc wasn't perfectly balanced and it wobbled.


Fix Disc Sander Wobble 

https://youtu.be/PDb5_I42sdk

And here's the original video from when i built the sander.

Disc Sander - Make DIY Build

http://youtu.be/v0whmYkAV7U

The problem occurred when i made the steel mounting flange between the motor and the disc.  I welded a large washer to a steel pulley.  Somehow during the welding it shifted and wasn't perfectly 90 degrees.  So when i say it wasn't balanced what i really mean is that it wasn't perpendicular to the motor and that caused the wobble.
weld pulley flange, 90 degrees, belt disc sander

It looked ok, but not balanced and at 90 degrees.
mount disc to sander, metal pulley, electric motor

Parts to attach flange to disc.
how to fix wobble in sander, disc, disk

Lots of people complained that it was dangerous...they were probably right.  They said that the unbalance would wear out the bearing and cause the disc to break apart.
diy disc sander, make, build

So 3 years later i decided to try and fix it.

I started by spinning the disc by hand and marking the parts of the flange that high and low (1,2,3,4).  Then i loosened the 4 bolts that held the disc in place and shimmed the low area with some paper shims.
how to shim, shim disc, disk, sander, belt

I then shimmed it on the 2-3 side, with trial and error, until the wobble was virtually gone.
fix unbalanced disc, mower, blade, sander, shim, how to

It took a lot of trial and error to finally get it right, i ended up having to put several shims at different angles to get the balance correct.  But i finally got it so that it was almost perfectly perpendicular to the motor and the table.
build tool, disc sander, easy, cheap

Had i known it would have only taken a few minutes i would have done this years ago.
how to build a sander


The next thing that needs to be done is to add a guard/shroud over the disc.  That would block any debris that may get clogged and shoot up into the air.  Or if the disc breaks apart it would keep it from flying in every direction.
easy to build disc sander, shim 12" wheel

Definitely safer now than it was before.
fix an unbalanced disc sander

4/18/2017

Glass Print Bed - For 3D Printer

3D printers can come with different types of build plates.  I decided to convert my Monoprice Select Mini to print on glass.


Glass Print Bed - For Under $1 - 3D Printer - MP Select Mini

https://youtu.be/vy30E6wJIz4

The most common build plates are aluminum and glass.  The advantage of aluminum is that it's cheap, durable, and the heated bed cartridge can be attached directly to the underside.
aluminum build plate, mp select mini


To print on aluminum you need to have some type of covering like masking tape.

The advantages of a glass print bed is that it is perfectly flat (will not warp or bend), easy to clean, does not need any type of protecting tape, produces a super smooth shiny surface when printed on.

I have the Monoprice Select Mini and it comes with an aluminum build plate.
mp select mini, add glass build plate to 3d printer bed

Which is fine, i printed several parts onto blue masking tape.  It worked well and had fairly good adhesion.  But i decided to install a glass bed, for a few different reasons.  First i got sick of adding and removing the blue painters tape.  Second i liked the idea of printing directly onto glass and being able to clean it up by running it under water in the sink.  And third i was intrigued by the shiny surface when printed on.
3d printing onto glass

In the very early days of 3D printing, people tried all sorts of different build plates, but glass and aluminum kind of became the standard.

So what type of glass do you use.  When you read about 3D printer glass beds and hear what people write about in forums, the name Borosilicate Glass comes up.  Borosilicate glass is what's used to make test tubes and beakers for chemistry class (Pyrex).  The advantage of this glass is that it can withstand very high temperatures.  And since it is a 'Heated Bed', borosilicate glass is an obvious choice.

So i went on Amazon and looked for 3D printer glass beds that i could use.  It turns out that everyone is charging a minimum of $20 for a sheet of glass.
borosilicate glass, amazon, cost

Another option of boro glass.
borosilicate glass for 3d printer bed

I wasn't really happy with the idea of spending $20 for a sheet of glass.  So i continued to read about other people's experience and learned all about what people have used in the past.

Here's a list of some of the different materials people have tried, other than just buying the borosilicate 3D printer glass:
- Mirror glass
- Window glass
- Tempered glass
- Frosted glass
- Heat treated glass
- Floor tile
- Marble tile
- Granite tile
- Aluminum sheet (may oxidize)
- 9h Glass laminate sheet protector for tablet (gorilla glass)
borosilicate glass in laboratory

Here's another story i saw where someone said the 3D printed part stuck so well to the borosilicate glass that it took a chunk out when they tried to remove it.
glass print bed damaged

When i heard someone say that they just went to the dollar store, bought a picture frame, and was successfully using that glass for their print bed, i knew that's what i was going to do.  Before spending $20 i was going to try the cheapest glass i could find.  The fear is that when the bed heats up, the ordinary glass might crack, but for $1 it was worth a shot.

I actually ended up going to Lowe's and looked in their glass and lexan cutting section.  It turned out that i could buy a piece of 10"x12" glass for $3.
lowes, home depot, lexan, glass area, plexiglass cost

But then i went to the back of the store and saw that they sold a 6 pack of 12"x12" mirrored glass for $10.
mirror glass pack from lowes home depot

I figured that things weren't going to go perfectly and i should probably have some extras.  Whether i broke a few pieces while trying to cut it, or whether some cracked during printing.  So i bought the box.  And it turns out that i only needed the glass to be roughly 6"x6", so i could get 4 pieces out of each sheet, which means i could get 24 sheets from the box.  So i was getting 24 glass print beds for $10 ($0.42 per sheet) versus 1 print bed for $20, which is 48 times the price.

Also while i was at Lowe's i saw a piece of 12"x12" marble tile on the clearance rack for $2.

I decided to buy that too just for experimenting.  And i also remembered that i had some old 12"x12" granite tiles in the garage from a project we did on our house.  Both the marble and granite tiles had a super smooth shiny surface.
12" marble tiles on clearance

Leftover granite tile in the garage.
3d printing on marble, granite

This will be for an experiment later... if i ever get around to it.
how to print onto tile, marble, granite, 3d printer

One big advantage of the stone tiles would be their ability to retain the high temps.  With aluminum and glass the bed heater is constantly turning off and on to maintain the temp.  The stone tiles are almost 1/2" thick and would hold their heat a lot longer.  But installing a marble / granite tile print bed is another blog post.

So now i had these glass sheets and i had to cut them to size.  So here's the quick lesson on how to cut glass or a mirror.  This is from another post that i did earlier about cutting glass.

Some of below is from my blog post about How to Cut Glass
http://davewirth.blogspot.com/2017/03/how-to-cut-glass.html


How to Cut Mirror Glass - QUICK

https://youtu.be/uniR7W9U5gM

Here's the quick lesson on how to cut glass or a mirror.  I needed to cut some glass for my 3D printer.
cut glass for 3d printer

First, about  what you are cutting.  I used a mirror which was about 1/8" thick, which is pretty standard.

how to cut glass, how to cut a mirror, glass cutter, tool

I bought a 6 pack of 12"x12" mirrored glass at Lowe's for $10.  

where to buy mirror glass, lowes, home depot, 12 inch glass, mirror


where to buy mirror glass, scrap book

Or you could buy individual pieces of glass.  For example a 10"x12" piece of glass is under $3.

buy individual glass, mirror, lexan

Second, you need the right tools.  The main tool is obviously the glass cutter.
glass cutter, cheap glass cutter, diy glass cutter

I have a fairly cheap one, which you can buy on Amazon for $5.

glass cutter, amazon

The way that the glass cutter works is that there's a tiny wheel on the front which is made of carbide steel, which is able to "score" a line into the glass.

how a glass cutter works, how to cut glass

Other tools are safety glasses, gloves, straight edge, a metal file for rounding the edges, and a work surface with a towel.



tools to cut glass, tool to cut mirror, how do i cut a mirror

For some small cuts you may need a wrench to snap off the glass piece.

wrench

Another thing you need is some type of oil, i used 3-in-1 oil.  Because the cutter needs lubrication in order to sline smoothly.

oil, 3 in 1 oil

Once you know where you want to cut the glass, apply a thin line of oil over the line, hold the straight edge tightly to the glass, then in one smooth movement firmly score a line in the glass.  It should take a lot of force pushing down and you should hear a crackling sound.

need oil for cutting glass

Make sure the score line goes from one end to the other, if there's a gap you can go back and score the ends.

how to cut glass, corners, straight

Then use the ball end of the cutter to gently tap on the glass near the score line.  This will help promote the score line cracks all the way through the glass.

quick glass cutting



Next it's time to snap the glass on that score line.  Wearing your gloves, hold the score line on the edge of the table.  Then slowly apply pressure on the overhanging edge until it snaps (hopefully on the scored line).

The actual aluminum build plate size is 6 1/4" x 5 1/8", but there are adjustment screws in the corners that need to be accessed from above.  Some printers have thumb screws that can be adjusted from below, which are better.

So i had a few options.  First i could have cut the glass the exact size of the print bed, then when i needed to level the print bed i would have to move the glass back and forth to get access to the screws.  Second i could cut the glass smaller so that i would always be able to adjust the screws,  5 5/8" x 4 3/8".
binder clips to hold glass build plate

For a while this worked fine, but it became a paint to adjust the bed level, since the allen screws were covered by the glass.
prototype 3d print bed, glass, material

Originally i decided to go with the full size glass, but later i learned that i could actually cut the corners off.
glass print bed, version 2, 3d printer

This is great because i get the full bed size, but also can access the leveling screws.

Next is when i learned more about how the printer actually works.  The Monoprice Select Mini actually has little switches for the X, Y, and Z axis that tells it when it's come to the end.
z axis switch, limit switch, monoprice select mini

Other more advanced printers have a little feeler arm near the nozzle which detects the height of the bed and automatically stops.

But with the MP mini you have to add a spacer.  The printer doesn't know you added a piece of glass and without a spacer it would continue to try to go down to where the aluminum plate is and probably crack the glass.

Luckily, i again learned from people who had done this before me.  There are some spacers that people have drawn in 3D, that you can snap onto your arm.  Here's the first spacer i used.
z axis spacer for glass print bed, mp select mini

Here it is on the printer.
z spacer for glass print bed

One shortcoming of this spacer is that you have to remove the back plate of the printer to install it.  That means that you have to take the bottom off and remove 6 screws.  It can be a bit of a pain if you are constantly doing adjusting.
disassembled 3d printer, monoprice

There's another spacer that someone drew that has little handles and you can snap it into place without removing the back plate.
different spacers for glass print bed

One thing to note is that the thickness of the spacer should equal the thickness of the glass.  I didn't really think about this and my glass was slightly thicker than the spacer and that meant that i had to crank down the adjuster screws all the way to the bottom.
adjustment screws size for 3d printer

So instead of redrawing the spacer, i just super-glued a piece of plastic to the bottom, it worked great.
shim spacer, 3d printer, how to modify

Another view of it on the bar/arm.
glass spacer

Later i used TinkerCad and modified the spacers thickness for glass and stone tile.
tinkercad to modify stl obj

Another view of the large spacer.
large spacer for granite and marble print bed

It was actually pretty easy to go in and add a square piece on the edge to match the thickness.
how to use tinkercad, autodesk

Another thing you have to consider is how you are going to attach / hold the glass to the aluminum bed.  There are 3D printed clips you can use, but i didn't have a lot of luck with them.  Also you have to use a smaller piece of glass.

Lots of people used simple metal binder clips.  The trick with those is that you need to use the smallest ones you can find.  The big ones work ok, but get in the way and hit the X-axis arm.  So you have to remove the metal clips from the black part every time.  Once i found the small ones it's been a lot easier.
binder clip size, 3d printer, glass print bed

Smallest binder clip that fit.
smallest binder clips for print bed

Another view of the sizes
binder clip sizes

After you add the glass and add the spacer, you will need to re-level the print bed.  Then you should be all ready to print on glass.

Some people just print directly on the glass, with the heat set to 50 or 60 deg C.  That does work and produces an amazingly smooth shiny surface.
how to 3d print directly onto glass

However it doesn't always stick throughout the entire print.  I've found some PLA where printing directly on glass is fine, but other PLA and especially PETG doesn't stick.

So for the majority of my prints i use a glue stick.
gluestick for 3d printer bed adhesion

I use just a regular Elmers white glue stick.  After the bed is heated i lightly wipe it on, the heat makes it slide like melted butter.

I can usually print this way about 5 times in a row before i need to remove the glass, run it under water in the sink and wipe off the glue residue.

Now i know that some people use Aquanet hairspray with great results.  I've tried this a few times but didn't get good enough adhesion.  They say to spray the hairspray on the glass, let it dry, and repeat with 3 or more coats.  It does give a slightly tacky surface, but in my experience the parts come loose while printing.  So i stick to just glass or most of the time, glue stick.

The convenience of printing on glass alone is reason for me to use it, with the amazingly shiny surface being a perk.  I would hate to have to go back to using masking tape.
adjust screws for glass print bed

Another view of the print bed.
how to attach glass print bed to 3d printer bed

And once i get around to cutting the marble and granite i will make another video and write a blog post about it.

Oh....and (knock on wood) i haven't had any of my glass break from the temperature.  But if it does i'm only out $0.42 versus $20.