Posts Tagged ‘ aluminum

# Overview

I’ve been using removable glass build plates for years on both my Makerbot Replicator 1, and my custom C-Bot:  I get double-thick glass cut at my local hardware store (Orchard Supply Hardware has had a great price on this), always thinking it was ‘totally flat’.  But is it really?  My C-Bot has a 12×12″ heated build platform.  When I go to level it with the glass, I get each of the four corners dialed in perfectly.  But the middle always sags slightly… even though it’s glass.  Double-thick glass.  But glass is actually somewhat plastic, and this sag has always bugged me.

Back in December I assembled my 1000mm X-Carve CNC, and it’s been so much fun cutting wood.  I knew it could do aluminum as well, but needed  a project.  And that’s what this post is all about:  Using my X-Carve to machine a new removable build plate out of .25″ mic6 aluminum for my 3d printer.  I am so happy with the results.

# Sourcing the material

Before I started this, I had no idea what ‘mic6’ aluminum was.  It’s also referred to as ‘cast aluminum tooling plate’ or ‘ATP’, since mic6 appears to be a trademarked brand name.  Simplistically, it’s a standard for (among other things) a very flat aluminum plate, to .001″.  After reading a plethora of forms, and researching my local options, I settled on Midwest Steel And Aluminum’s “Cast Aluminum Tool & Jig Plate“, .25″ thick, 12×12”, which came to about $20, and the ground shipping another$20.  I could have bought it locally for \$45 + tax (ugh).

A note on the order:  The plate was packaged in one layer of cardboard, that was it.  It appeared to have been dropped several times in-transit, 3 of the 4 corners were blunted, and there was an small indentation in the middle of plate itself.  If I was using this for something really precision I would have returned it.  Just a note to tell them to ship it better if you go this route.

Once it showed up, time to make some cuts!

# Initial cuts

When I first got the plate I knew I had to notch a section out of each corner, since the heads of the bolts that hold the MakerFarm heated build platform stick up about 1/8″ish from it:  I didn’t want the plate resting on the bolt-heads, so I need to make little pockets for each.  Before I even considered my X-Carve CNC, I figured I could use my drill-press to pocket these.  Long story short:  It did not work well, and made a mess of the corners.  Based on that frustration I went down the ‘how about I use that dormant CNC right next to the drill press…” road.

For all below cuts, I used the same 1/8″ 2-flue upcut carbide endmill.

Since these cuts were so simple, I used Inventable’s Easel: I designed a circle with a diameter of .4″ across, .175″ deep, and used that to pocket each of the four corners already mangled by my drill press.  I used the default ‘aluminum’ Easel setting (5 ipm, .003″ doc, DeWalt on speed 1) with the first pocket (which took about 20 minutes), then started cranking it up: By the final pocket I had it running at 20 ipm at .01″ doc, with the DeWalt on speed 2, taking about 5 minutes..  It did great, and the bit was cool to the touch after the cuts.  When all four pockets were complete, it fit right on the bed with no collision with the bolt-heads:

All the rough stuff to the right of the bolt-head was the abuse by the drill-press.

I have four bulldog clips that hold the plate on, one on the middle of each side.  The issue is even though I’ve bent them down to move them out of the way, parts of them still stick up slightly, and on a large print the nozzle could collide with them.  So going back to Easel, I designed a new rectangular pocket that would keep the bulldogs out of the way of the toolhead.  These were 2.25″ x .3″, cut .075″ deep.  I positioned them in the center of the left\right sides of the build plate, but had to offset them on the front\back based on my leadscrew config.

An in-process cut:

And all four final cuts:

Installed on the printer:  No more clearance problems with the bulldogs!

# Prepping the plate

I use a highly secret (50% wood-glue, 50% water) slurry on my build plate to get PLA to stick.  But the mic6 is so smooth, I first scoured it with steel wool for several minutes to give the glue something to bite into.

Note for the future:  First, use something like lacquer thinner\acetone\mineral spirits to clean the plate of any oils:  Quite to my surprise, after many minutes of scrubbing, I could clearly see my handprint on it.  The oils deposited from my hand actually protected it from the steel wool.  So I went back and liberally scrubbed it with lacquer-thinner soaked rag, then went back to the steel-wool treatment again:  No more handprint.  Be sure to wipe it down with lacquer thinner after the steel wool too:  The wool actually leaves quite a bit of itself deposited into the aluminum.

After the plate was scrubbed, cleaned, and glue-slurry applied, I did some test prints.  And while the flatness was super awesome, I realized something very quickly:  The slicer said the bed heated up waaaay faster than it actually did:  For big prints in PLA, I’ll heat the bed up to 60c.

It dawned on me that the thermistor that does the temp reading is taped to the bottom of the MakerFarm heated build platform, while the thing being printed is sitting above it on .25″ of aluminum… that is taking much longer to heat up.

After brainstorming, I came up with the idea of cutting a groove into the bottom of the plate, that I could tape the thermistor into:  It should then be reading the temp from the removable plate itself, providing a much more accurate temperature.  This means I’ll also need to snip the leads running to the thermistor and install a barrel-jack into the mix to allow for the plate to be removed, since there’s now a sensor taped to it.

# Secondary cut

Going back to Easel, I designed a .5″ wide groove cut .0312″ deep that I could recess the tape into, then another smaller groove .2″ across and .1″ deep to run the wires to the thermistor.

Here it is mid-cut:

Cut gotchas:

• Easel has (based on what I’ve experienced) no idea of conventional cuts (bit spinning in the direction of travel) and climb cuts (bit spinning opposite direction of travel).  From what I’ve read, climb cuts can provide better finish, but only on ‘professional\beefy’ machines:  not the X-Carve.  Conventional cuts fare much better on the X-Carve.  This (as I found out) can cause dangerous problems.
• When the top cut started, it was all conventional cuts, and cut fine.  But when the next layer started, and for every layer down, it was climb cuts.  Because of that, I noticed a lot of bit defection, chattering, and even gouging.  To avoid catastrophe, I had to manually monitor the cut, and really crank up the spindle speed as needed to compensate.
• Note that MeshCAM gives you the option in the rough-cut to do either conventional or climb cut:  For future aluminum projects I’ll be using it for sure.

To help with heat transfer (that is only a theory of mine) and to prevent any sort of plate-slip (which is legit), I shoot the bottom of the plate with rubberized undercoating.  I then snipped my thermistor line, soldered barrel-jacks onto either side of it, then taped it into the groove on the bottom of the plate:

Putting it back onto the HPB, I reconnected the barrel-jacks:

# Final thoughts

It works, great.

When the HPB heats up, and it finally gets to temp…. it really feels like the top\bottom are the same temp.  And I can level each of the four corners, and the middle is the exact same distance as the rest of them from the toolhead.

Super rewarding project with one machine improving another.

## Making (real) aluminum boats in Maya : The Results

Back in Feb I blogged about how I collaborated with my father (in Alaska) to help him design a new aluminum boat.  Using Autodesk Maya, and a napkin sketch he made, we worked together (remotely) to susout the dimensions.  By giving him files he provided to the local plasma cutter, by Feb (nice and cold up there) he’d got the bulk of it welded together.

A week ago I was able to spent a week up there, an amazing experience as always (pics here).  And one of the highlights was being able to finally (drive &) ride in the boat.  Was a great experience, and super interesting for myself to recognize the physical representation of the Maya model floating in the water.  It’s a thing of beauty:

I only wonder how long until he builds another…?

## Building the C-Bot 3D printer: Part 4 : Cutting the linear rail

While I really wanted to use this printer build as an excuse to get a chop-saw (and I could have done this on my table saw), the offer of my buddy Mason to go to his house and borrow his sounded pretty good too:  While I’ve used quite a few tools in my life, I’ve never actually used a chop-saw, and it’s always nice to do something with someone who has experiencing doing it themselves.  Not that chop-saws are rocket-science.  But after using one, I think I’ll add one to my Christmas list…

For my build, I ordered nine meters (in one meter sections) of the 20x40mm, which would get cut into 14 separate pieces.  I would have needed more but Mason had an extra length of it, plus the 20x60mm I need.  +2 more cuts…

I hauled all my OpenBuilds v-slot linear rail over to Mason’s and spent the next few hours marking them, and cutting them up (along with the two Acme lead screws).  Could have gone a lot faster, but we were in no hurry, and time was spent staring at his C-bot and dreaming of the future

Overall it went very smoothly, nothing outstanding to note.  After I brought them home I spent a good amount of time with a dental pick (they’re awesome) and steel file de-burring all the cut ends, and cleaning them up.  Next up will be tapping the ends for the metric bolts (part 6).

## Making (real) aluminum boats in Maya

Maya render of the boat

Current state of the boat, with my father and brother.

My father has been building boats since before I was born and running them on the rivers of Alaska:  Fiberglass canoe?  Check.  Flat-bottom wooden riverboats with dual outboards?  Check.  Should I mention the hovercraft? 😉  Over the past decade he’s branched out into welded aluminum flat-bottom riverboats with great success:  Make one, use it for a few years, sell it and make an upgraded version.  (On a side note, I can’t wait to retire… <wink>)

Late last year he came to me wondering if I could help with the design:  Could I create the 2d design files he would provide to a local plasma-cutter to cut the main boat forms?  Sounded like a good challenge, and a great opportunity to collaborate with my father (He’s in AK, I’m in CA).  Up until then he’d get the huge sheets of aluminum and cut them by hand.  Having a plasma-shooting robot do that sounded like a more exciting (+ accurate/faster) solution.

My father provided me the drawn plans with angles and dimensions:  I started the process of turning those into real 3d forms.

Initially I attempted to do the whole project in Autodesk Fusion 360:  I’d been teaching it to myself, but I was still very much a noob in the software.  Unfortunately I just couldn’t get it to do what I wanted:  Most importantly I couldn’t ‘unroll’ the 3d forms to 2d forms, which is needed for plasma cutting.  I worked directly with their support on this, but the software just wasn’t quite there yet.

So I decided to do it all in Autodesk Maya (which I’ve been using since it was released in ’99).  While Maya is great for games\film\vfx, I’d never much considered it for accurate CAD-style modeling.  However, it ended up working great. Here are the main takeaways on how I built the boat:

The initial boat model:

• I started by modeling the real-world size sheets of aluminum out of NURBS planes.
• I snapped and rotated the pieces together to get the overall shape of the boat based on the provided angles.
• I applied bend deformers on a single axis to shape the NURBS into the correct swept forms.
• Based on all the intersecting NURBS, I created curve-on-surface intersections:

Right side bent NURBS intersection, with curves-on-surface, before trim.

• Based on those intersections, I trimmed away the excess aluminum (NURBS).
• Boat model complete! (see above render)

The unwrapped form:

• I needed to ‘unwrap’ all the bent surfaces back to flat planes for export.
• To do this, I would duplicate each of the bent/trimmed NURBS, convert them to polygonal mesh, and wrap deform the polys back to the original bent NURBS.
• On the original, I’d access the bend deformer, and zero it:  This would flatten out the wrapped polys.  I’d delete history on the polys, leaving it flat, then bend the original piece back.  I’d then scale it perfectly flat, since the wrap wasn’t 100% accurate.
• I’d repeat that process on each bent piece, ultimately giving me unwrapped flat pieces for all parts of the boat:

Unrolled polys

Exported 2d data:

• I exported each polygonal mesh as obj.  I then used online software to convert the obj to pdf’s, which the plasma cutter could use.

After my father got the 2d data he printed a scale model on paper, affixed it to poster-board, and made a small-scale mockup as a sanity check:

From there, it was off to the plasma cutter…

And the most amazing part?  It all worked:  After my father got the pieces back from the plasma cutter and starting tacking them, they all fit perfectly.  Sighs of relief on all sides.

While it’s been fun to 3d print small items, it was super rewarding to see a much larger-scale 3d model become reality, and do some ‘real’ work with my father.  I can’t wait to ride in it!

Update:  See the final results here!

## New 3D Print & sandcast : FFF Necklace

I wanted to design a necklace for my wife, and put on it the three things I find most important in life: Faith, Family, & Friends.
It was also a good test to see how small I could print legible text, and when cast in aluminum, how much detail would come through.
The images are of the aluminum cast, based on the 3d print. Designed in Autodesk Fusion 360.