I was surprised to find that, as I started, I couldn’t even view the website because the hosting company had updated some software without updating all the requisites so the site didn’t even work!  Sigh…

In any case, if you’ve been one of the ones who have been checking in, I apologize for letting this languish and will try to do better in the future!!!

New 3D Printer, busy printing the next thing!

The printer is a ‘resin’ type printer where the print bed is moved (rather than a print head) and is dipped into a vat of resin that is cured using Ultraviolet light.  The pattern to be cured is generated by a high resolution LCD under the vat and selectively passes through UV light from below.  The print bed is then raised to the next position and the next layer is projected on to the last.  It’s a slow process, but very high resolution and, I’m hoping, without the printing gaps that you get with a ‘FDM’ type 3D printer.

The print volume is small, only 4.5×2.56×5.9 inches, but almost all of my printing is smaller than this.  Interestingly, with this type of printer the time it takes to print is entirely determined by the height of the object and the layer thickness, while a conventional 3D printer the time it takes to print is a function of the volume of the printed object and the resolution of the extruder.  Hence, in a lot of cases, the print time will be shorter with this type of printer, especially on complex objects.

So, what have I done since I unpacked this yesterday?

Included with the printer was a sample design file of a mythical WatchTower.  I printed it in a Green Translucent resin purposefully keeping it small to test the resolution:

WatchTower complete with Spiral Staircase in the middle of it.

To give you some idea of the size of this tower, try this on:

WatchTower with some perspective added.

Finally, here is a closeup of the walkway at the top of the tower:

Bird’s Eye view of the watchtower. You can see the stairs descending and the printing on the walkway. Those letters are approximately 150 microns thick…

Here is the replica, mounted on our Garden Shed:

New decoration for our garden shed.

And a closer view:

Here’s a closer view of the branch and ButterFly

And finally the Butterfly:

Closeup of Butterfly

Details of how this was made are down below.

The other recent addition to the Yard is some livestock to entertain our Granddaughter when she comes to visit.

Here is the Sheep looking longingly at the front lawn…

Closeup of the Sheep:

Sheep painted.

The two large pieces, the Sheep and, especially, the Stylized Branch, both required some special cutting techniques because both of them were too large to fit on the CNC Plasma Table.  The table can only cut  23″ in one direction and 25″ in the other.  The good news is that the table is open on the ends of the 23″ axis so, theoretically ^{(see Note [1] below)}, I could cut something as long as will fit in my Workshop.

However, this required multiple steps in both processing the artwork and the cutting process. Each step allowed me to cut a region of the metal, the cutting was paused while I re-positioned and aligned the steel for the next cut, and then cutting was resumed at the next section with the software offsetting the coordinates to match the new position.  The alignment is critical as the cut line is only about 0.050″ wide so any error in positioning would, at best, leave a jog in the cut line, or, worse, an uncut section of steel that would need manual cutting and fixing.

The sheep was used to test and prove the process.  It could have been done by limiting the size to 23″, but using a full sheet gave me a bigger sheep and tested the process.

The first step was to rework the art work:

Maximized Sheep Artwork, rotated and scaled to fit 24×24 piece of steel.

You can see the split line between the two halves of the drawing.  That’s where the art work needed to be separated into to independent groups.  Note that the art work has internal cuts and they had to be separated into the two different cut phases as well.

Using the Sheep project to refine the process turned out to be a wise decision as I learned enough from the Sheep project to do the Stylized branch, which required three sections over a 72 piece of steel, and 4 joints.

Branch Artwork showing three sections and mounting hole locations.

Cutting a 6 foot long piece of steel also required some re-arrangement of my workshop, not only to make room for the workpiece but also to provide support for the portions of steel that were on either side of the table during the cut.   It also concerned me that my Plasma cutter, which is normally kept in a little alcove surrounded by fiberglass welding blankets where most of the sparks are contained by the blankets, would now be out in the open during all the cuts with sparks flying in all directions!  As a precaution I put my fire extinguisher right at my side during the whole operation!

Here is the setup prior to cut:

I had to rearrange my workshop to manage a 6 foot long piece of steel!

And here is the result after the cut:

And here is the finished cut. Notice the lead in and lead out cuts at the joint of each section.

And the final piece cleaned up and ready to paint.

Branch ready for painting!

All in all, the cutting went very well with probably no more than 1/32″ misalignment in the worst case.  As a result of this project, I’m confident that I can reliably do larger pieces still!

Little did I know, that ‘treat’ was merely a trick to get me away from the house so she could have caterers and our daughter’s setup a HUGE surprise party for me.  Several family and friends were there, some having traveled all the way from Maine!  It was great and literally left me speechless.  So… unable to do better than the following photos…

Clare MADE THIS CAKE! Isn’t it GREAT?!

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As you can see, I’ve got a bit of learning on my airbrushing technique.

I cut the stencils out of Mylar on my Laser cutter.  For the most part, the stencils came out fine, but the problem is that the Laser cutter can only deal with 200x300mm material so I had to piece together the 20×30 inch sign and didn’t do as good a job as I could have… sigh.  Next time…

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Just another day at the office…

Here’s my current ‘activity’ as I’m simultaneously debugging code on 4 different processors, 3 of which have radios that are communicating with each other and one is our home server containing our webserver and MySQL database (where all the data is supposed to be going).

Amazingly, it’s all working!

Cheers!

After doing the Pottery Logo project, I realized that I need to have air jets to both cool the router bit and clear away chips.  With plastic especially, but even with wood, the chips, if not cleared, will collect in the channels and create friction, and, eventually, burn the router bit (and scar the walls of the workpiece).  I found some nice flexible hose components that allow you to easily guide the air to specific spots.  The ‘hose’ consists of small hollow knuckles that snap together like beads and, with the friction fit, stay where you bend them.

Here is the setup I’ve installed on the Router:

Z Gantry with new air cooling/clearing jets added.

The mounting block moves with the Z Gantry and keeps the air nozzles pointed at the router bit.  I’ve supplied the air through a solenoid valve that is controlled by the CNC commands so I can turn on the air only when the ‘chips are flying’…

Vacuum Chuck

In the course of doing various projects on the router, I’ve concluded that ‘hold downs’, the devices needed to keep the workpiece in place, are the biggest nuisance of doing any CNC routing.  The first problem is that they inevitably get in the way and, being in the way of a XYZ gantry, with a very sharp tool spinning at 24000 RPM, is generally not a good thing…  Bad things ALWAYS happen in this case.  The hold downs get in the way because they aren’t part of the model that you’re working on and are ignored in the ‘flight path’ when generating the CNC commands!

The second problem is, they don’t always hold the material flat.  If you have a thin, eg 1/4″ thick, strip of wood that is 6 inches wide, holding down just on the edges is not sufficient.  It will most likely bow, to some degree, in the middle.  If you’re trying to engrave with a V bit and the total depth of engraving is only 0.032″, even a 0.010″ bow renders the engraving useless – there is too much width variation in the engraved lines.

So, what’s the answer to both these problems?

I’m hoping that it’s a Vacuum Chuck.  A Vacuum Chuck in a device that clamps to the CNC Router floor and uses vacuum to hold down the workpiece.  How well does vacuum work?  Let’s see… if the chuck is 12″ x 6″, that’s 72 square inches.  If the vacuum can be >10″ of mercury, that’s equivalent to 5PSI.  5 pounds per square inch x 72 square inches is a hold down power of 360 pounds!  Probably ok for most things…  AND the pressure is evenly applied across the entire surface of the workpiece.  Consequently, that 1/4″ thick piece of wood is FLAT and stays FLAT!

Since I have the equipment to do vacuum pressing for bent laminations and that included a plexiglass block with a vacuum port, all I had to do was use the router to create air passages across the face of the block and, with the Pottery Logo Project, I had just the router bit to machine the plexiglass!  Here is the result:

Vacuum Chuck with a mesh of air passages across it’s top. The air passages all lead to the vacuum fitting at the left, center of the plexiglass block.

With Chuck all machined, I was anxious to try it out.  The first thing I did was put a piece of 1/4″ MDF on the top and turn on the vacuum.  Boy, did THAT suck!  Or, I should say, it didn’t suck.  I was hardly able to get 5″ of vacuum (perfect vacuum is approximately 29.9″ or 14.22PSI)!  Major disappointment!

After trying various things to seal the edges, thinking this was where the air was being lost, and actually sealing the edges with double sticky tape, I realized that I was losing air THROUGH the MDF!  The MDF is so porous that it was actually letting air bleed through its entire surface.

Hmmmm…  I looked around and noticed one of my scraps of MDF had been sprayed with Shellac.  I grabbed that piece, put it on the double sticky tape and the vacuum immediately rose to 17″!!!  Then, further realizing that that piece of MDF had never been sanded after the Shellac, I sanded down the ‘fuzzies’ with 600 grit sand ‘paper’ and was able to get as much as 22″ of vacuum.  GREAT! That’s over 770 pounds of holding power!  Now we’re talking!

This was great news, because part of the plan was to use MDF as an interface between the chuck and the workpiece if I need a ‘spoil board’.  A ‘spoil board’ is a board that gets ‘spoiled’ in the process of routing a workpiece when the workpiece needs to get cut all the way through.  You can safely cut through the workpiece into the spoil board and won’t dig into your CNC Router bed or, in this case, vacuum chuck.  Basically the MDF spoil board will provide air passages from the chuck to the workpiece and the workpiece will hold the spoil board sandwiched to the chuck.  Key is that the air passages in the spoil board need to be placed where the workpiece won’t get cut through, otherwise the vacuum will be lost and, uh, bad things will happen…

Good examples where I’m hoping to use this method is when I’m making small pieces like key fobs or coasters.  I can set up a spoil board for each type of project and reuse it as often as I need.

Another thing I need to do, where this chuck will help, is in cutting up printed circuit boards (PCBs).  I’ve been doing a few electronic projects recently and some of them are fairly small boards (1″x1.9″).  PCB manufacturers generally try to get you to fit your board within certain fixed sizes, with the smallest size typically 5cm x 5cm (1.93″ x 1.93″).  Obviously, I can fit two of these designs on to this minimum size.  In the ‘old days’, when I’ve combined boards into a single PCB, I’ve used a bench shear to cut the boards.  This works ok, but the boards get scuffed and slightly bent in the process.  A better approach is to cut a V groove on the dividing line on both sides of the board so it can be simply snapped in two.  Hmmmm, sounds like a job for a CNC router!

So, may I present, for your consideration, an MDF alignment/vacuum interface board for cutting a PCB:

Vacuum Chuck with MDF interface providing an alignment well to machine the PCB. Note the air channels in the PCB well and the holes leading down to the chuck.

Here’s a close up of the PCB after being machined on both sides. This is perfect! Very ‘snappable’! The PCB is 1/16″ thick.