All posts by Whitney

Meet Gigantor, the printer of unusual size

Here are some pix of my new printer which Andy calls “Gigantor”.  As you can see it is a work of such refined elegant design that it would bring Steve Jobs to tears.  Actually Gigantor is at an awkward adolescent stage.  If you wish to criticize please first change your Facebook profile picture to your 7th grade yearbook photo.

Gigantor was built in an improvisational style using a lot of scrap from my shop.  Most of the non 3d printer specific stuff was left over from other projects.   I started with the guide rods and build out from there.  Rather than give directions to make your own I will point out some of the special or unique features.  I built this printer for myself, not as an open-source project, so it uses tools and techniques which might not be readily available to everyone.  It is the only 3d printer I have seen which has welded and CNC plasma cut parts.  So just for the record I am not suggesting anyone try to duplicate this printer.  Make your own out of whatever you have lying around.  It’s much more fun.

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Gigantor, a breathtakingly elegant design destined for an art museum, or a land fill

 

 

First some general specs:

Build volume: 500mmx500mmx400mm  The z axis could be brought up to the full 500mm with some easy modifications, but I have’t bothered yet.

XY Motion Control Schema:  Modified  Ultimaker style.

Z axis: Welded aluminum and steel frame driven by 2 leadscrews.

Electronics: RUMBA board with TMC2100 silent stepper sticks and full graphic Smart LCD controller.  NEMA 23 steppers on all axes.

Extruder: Initially BulldogXL, currently custom EZ view

Hotend: e3d, currently equipped with volcano mod and 1mm nozzle

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The printer is designed with the x and y axes built on the CNC plasma cut steel frame at the top.  The frame is attached with drywall screws (only the most refined of engineering solutions here) to the rest of the printer which is made of plywood.  Many early 3d printers were made of laser cut plywood.  Being larger than my entire laser cutter this plywood is table saw cut.  This makes the z axis and the x/y easily separable modules.  You could experiment with different x/y designs and easily swap them onto the z axis.  For instance could have a corexy module which I could install in just a few minutes.

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The basic design is similar to the Ultimaker’s crossed guide rods, but I made some improvements (at least I think they are improvements).  The original Ultimaker design uses rotating shafts which both guide the ends of the cross rods and transmit the motion from the steppers to the belts.  It is an elegant design that makes the most of minimal parts and it makes a lot of sense for their commercial design.  But when you scale a printer up the guide rods need to be a lot thicker to be rigid enough over the longer span.  I am using 16mm rods where most smaller printers use 8mm.   I separate the support and power transmission functions which are combined in the Ultimaker design.  The heavy rigid guide rods don’t need to move and the jack shafts which transmit the stepper power to the belts are only 5mm in diameter so they can accelerate and decelerate quickly and smoothly.  The jacks shafts attach to each end of double shaft steppers which avoids needing a belt to connect the stepper to the shaft, or the added width and other problems which could come from having the stepper drive the shaft from one end.

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The rod ends are printed with 618 nylon to withstand the strain from the belts.  The integral belt clamps took a bit of work because they have to carry a lot of tension in the belts to avoid backlash.  The fender washers keep to belts locked in the clamps while the bolts threaded through the layer lines add reinforcement.  Gt3 belts would have been better here, but the gt2’s are cheap and so am I.  I designed all the 3d printed parts in Cubify Design.  The lower stress parts are printed in PLA.  I have reamers which match the bearing sizes so all holes are reamed to size receive their linear bearings.  They fit so precisely that when I ran out of retainer clips I just left a couple of bearings press fit in their housings and they have performed perfectly.

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I used some leftover openbuilds extrusion and v wheels to guide the z axis.  It is very rigid and tight.  If I were starting from scratch with no materials and few tools I would build the whole printer from aluminum extrusion.  It isn’t the cheapest material but it is very precise and easy to work with and can be cut well with wood cutting tools.  The two sides are connected by some TIG welded aluminum tube.

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Rather than rely on spring loaded screw for bed leveling I use a printed knurled thumb nut on the top and the bottom.  The screws allow you to push up or pull down on the build plate.  The built plate assembly weighs around 40 pounds so it was difficult to find springs which would support it rigidly yet still be easily adjustable.  It is a little more difficult to adjust but it locks the bed in place much more positively.  I basically leveled the bed once, locked it in place and haven’t touched it since.  I think this system is far superior to usual spring arrangement.  Some of the thumb nuts have encapsulated steel hex nuts, but I found that wasn’t necessary.  I printed them in solid 618 Nylon with a pilot hole and then tapped them with a regular taper tap.

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The build plate is a 24″ square 3/8″ thick tempered glass table top.  It was on sale at Pier One.  It is remarkably flat and with 4 point leveling screws it can be made almost perfect over its entire area.  Of course I am generally printing with thicker layers than most smaller printers.  If I wanted to print something at 0.1mm layer pitch I would probably need to modify the first layer to get a good stick.  It would benefit from enclosure and a heated bed, but I haven’t gotten around to that.  It would radiate enough heat to essentially heat the room as well.

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The first iteration used a NEMA 17 stepper to drive each of the two z axis lead screws.  It worked fine except that when the power went off or the stepper drivers were disabled the weight of the build plate spun the lead screws and the whole thing went crashing to the bottom.  The current version uses a single NEMA 23 coupled by a gt3 belt to both lead screws.  I prefer this design because it keeps the two lead screws synchronized.   The large sprockets on the lead screws make the z-axis extremely accurate and there is enough resistance in the system that the bed stays in place by itself.  I threw it together quickly to test the system and left the old NEMA 17’s  in place as bearings for the bottom end of the lead screws.  They make great bearings and are cheap enough to leave them there.  I could eek out a few more cm of z axis if I used a more compact bearing set up but I haven’t bothered so far.

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This is my rough and ready belt tensioner.  It is adjusted to the right tension and then screwed into the plywood to hold it in place.  The stepper is just screwed to the plywood with long deck screws.  It works perfectly and costs essentially nothing.

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This is the first iteration of my new EZ view extruder.  I designed it especially for work with flexible filament.  I was sick of flex filament squirting out the side or wrapping around the drive gear.  Neither is possible with this design.  Plus you can see what is going on inside and easily break it down if you ever need to.  It isn’t quite ready for the world but I will release the design once I am happy with it.  This extruder and the leveling screw design are the two elements of this printer which I think could have broader utility.  Most of the rest of the design just resulted from me improvising with what I had on hand.

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So how does it work you ask?  With a regular .4mm nozzle printing PLA it is pretty good.  It isn’t the best printer I have,  but I don’t have anything else in its size class to compare it to.  Not having a heated bed or enclosure somewhat limits how large a print you can make reliably.  At the moment I am using it to print ridiculously large flexible prints.  I am running an e3d volcano with a 1mm nozzle.  This is a wearable top hat.  The print is a bit rough because I am having trouble with the new extruder design, but it prints  TPU much more reliably than the bulldogXL.

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This is the largest print I have done so far in terms of xy area.  The tikicaster was printed in 3 parts, front, back and sides.  This way the build plate surfaces of the prints are all on the inside.   This is the same way Telecaster Thinlines and Rickenbacker 360’s are made.  There were some shrinkage cracks and lift up issues from printing such a large piece on an unheated bed in an unheated room, but nothing a little bondo couldn’t fix.  You can see and download all the parts at http://www.thingiverse.com/thing:890969

Building a Desktop Scanner part 2

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I used an arduino mega, but any micro controller will do.  The mega has the advantage that it can take an inexpensive lcd display shield and still have lots of i/o pins easily accessible.  The arduino can’t safely drive a stepper motor directly so we connect it to a stepper motor driver.  I used an EasyDriver board which is inexpensive and lives up to its name.  The chip at the heart of the EasyDriver needs a heat sink to reach its maximum output, but in this application you probably don’t need one.  You won’t be running it very hard.  I run the arduino, the lcd and the EasyDriver all off a 9V battery.  This power supply somewhat limits the torque that the stepper will produce so if you are planning to turn a large turntable you might need a larger power supply and a heat sink on the driver.

The firmware is pretty simple.  One set of buttons allows you to select the number of exposures to make per revolution. One button starts and stops the scanner.  One button takes a single exposure and then rotates the stepper one increment.  This manual mode is handy with subjects which require each shot to be manually focused.

When I use the scanner I place it on a work table in my shop and mount the camera on a tripod next to it on the floor.  I use a cheap macro rail ($25 on amazon) to help position the camera.  The rail has more flex than is desirable, but it works okay since you aren’t actually touching the camera to trigger the exposure.  I use https://www.thingiverse.com/thing:548006 to hold a sheet of paper as a seamless background.  I also sometimes punch a hole in a sheet of paper and thread it on the stepper shaft to mask out the motor.  This approach might work well for you guys because you can cheaply replace the background if anything drips on it.

As you know lighting is critical for photogrammetry.  I use 3-4 JANSJÖ led desk lamps from Ikea to light the subject.  These lamps are very easy to position, and put out a lot of light.  They have small heads which makes it easy to light small subjects.  They are LEDs so they put out very little heat.  You can improvise diffusers with regular paper and tape.  Plus they are $10 each!  I also sometimes use a cheap LED ring light on the camera lens which provides nice diffuse light, but since it is attached to the filter ring of the lens it tends to get in the way with macro shots where the subject is almost touching the lens.

Another approach to lighting is to put the scanner inside a light tent.  This gives you a lot of diffuse even light and a clean background.  They sell small kits for photographing jewelry which are designed to minimize reflections and glare when shooting shiny things, so they might help with your stuff.  Also a circular polarizer filter would be a good thing to have on hand.  It can be helpful reducing glare.

 

Building a desktop 3d scanner part 1

We have talked about many different options for 3d scanning over the years, but we always come back to photogrammetry.  The process involves taking photographs of an object from all angles and then using software to identify and triangulate the location of parts of the object.  After a lot of number crunching you end up with a 3d scan of the object in the photographs.  The quality of the output is entirely dependent on the quality of the set of photos you start with, and that is where the skill comes in.  The software is pretty easy to run and there aren’t that many options on how to process your data.  The big learning curve happens with the camera.  This simple scanner makes it relatively easy to capture high quality photo sets which will produce high quality scans.

The basic setup is simple: An arduino controls a stepper motor and an infrared LED.  Using the multi camera control library from Sebastian Setz  and the IR LED the arduino emulates a wireless remote for almost any DSLR camera.  It fires off an exposure then rotates the stepper motor to the next position and repeats.  The result is an evenly spaced set of photos ready to feed to your photogrammetry software .

screw scan

By automating the movement of the camera you are guaranteed sufficient overlap between the shots and complete coverage.  So you can concentrate on the quality of the exposure.

Properly exposed razor sharp images are critical for photogrammetry so it is worth talking a bit about the basics of photography.  The two most basic exposure adjustments are aperture (also called f-stop) and shutter speed.  No lens can keep the entire image in focus at one time.  There is always a limited depth of field, the range of distances from the camera through which the image is in focus.  Objects closer or farther away than this focal range are blurred.  Blurring introduces noise and errors into photogrammetry so we want the greatest depth of field possible.  On most cameras this comes about f/11.  Lower f-stops have lower depth of field.  Higher f-stops introduce diffraction errors which can be just as bad.  Shutter speed is critical if you are holding the camera in your hand, but in this case it is on a tripod so it is less important.

The drywall screw example here uses a macro lens to fill the frame with the relatively small subject.   Autofocus generally doesn’t work well with macro photography so you will probably need to focus manually.  An object like this drywall screw is predominantly cylindrical so if it is centered on the axis of the stepper it will stay at the same distance from the camera throughout the revolution.  That means you can set the focus and exposure once and it will work for the entire revolution.  Other shapes of object may require you to focus each shot individually.  If you scan a larger object you may be able to use autofocus to keep the images crisp.

Focus tip: Many DSLR cameras allow you to zoom in on the viewfinder preview image which will allow you to focus even more precisely.

Jpeg compression is another source of noise in your images so you will want to shoot at the highest image quality your camera will allow.  You can shoot RAW and develop as uncompressed TIFFs, but for most scans I just use the highest quality JPEG copmression.

Driving your SLA printer

Your DLP type SLA printer will need to manage 2 basic tasks in order to print.  The first is to adjust the Z-axis for each layer and the second is to send the appropriate slice image to the projector.  This is pretty simple stuff, but unfortunately it is beyond the ability of a simple Arduino.  It is within the realm of possibility for a RaspberryPi (they come with HDMI ports), but no one has written the software yet.  So at this point the best solution is a Windows machine running Creation Workshop.DSC_0020

The Windows machine USB’s to an arduino based board (I use a ramps 1.4, but any will do) to interpret the gcode and control the z-axis stepper.  If you have an old Windows box, or an old laptop lying around you may already have what you need, but if you don’t there is a perfect solution.  Finally a good use for a Windows tablet!  Perhaps because no one has found another good use they are practically giving Windows Tablets away.  You need one which has an HDMI output and will drive two displays.  You also need a usb port to connect to the ramps board.  I also recommend you get one with 2gb of ram.  I started with a Winbook TW700 which worked well except that if you had a large or complex model it tended to crash while printing.  This wouldn’t be such a big deal except that it failed with the projector blasting pure white.  If you weren’t right there when it happened this tended to cook off all the resin in the build vat.

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It made an interesting brick like print, not to mention an awful smell.  I only did this a couple of times before I upgraded to the Winbook TW802 which has double the memory and hasn’t crashed yet.  This one cost $159,  the TW700 was only $59, less than a retail license of Win8.

Speeding up your SLA printer

With all the hype Carbon3d has gotten lately about how it has revolutionized 3d printing with its continuous printing system, I started to ask myself what was stopping me from doing the same thing?

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The standard layer cycle for top down machines is to expose the layer, lower the print into the vat, let the resin flow over the print, raise the print back up to the position for the next layer, wait for the resin to flow out evenly, expose the next layer and repeat.  This may be faster than the peel cycle of a bottom up printer, but it still isn’t as fast as it could be.  With the right resin and a good DLP projector the exposure time can be as little as a second or two, yet the whole cycle can take as long as 8-10 seconds.  Now we are only talking seconds here, but an 8 second layer cycle takes 4 times as long to print as a 2 second layer cycle.  That’s the difference between a 1 hour print and a 4 hour print.  What if we could trim out the extra time so we are exposing resin for the entire layer cycle?  It turns out it isn’t that hard to do. Creation Workshop gives you enough control over the program that it is quite easy to make your machine print continuous layers.  You set the Z-lift distance to 0mm and the lift and sequence time to 0sec.  The machine exposes a layer then drops to the next layer and exposes it with only a brief flicker of the projector as it changes layer.  You will probably have to tweak the exposure time and layer height to optimize things, but it is pretty easy.

There are a few problems with the continuous printing system.  First the initial layers on the build plate sometimes have trouble because there isn’t enough resin on the surface until the build plate is well submerged.  A perforated build plate helps, but isn’t a perfect solution.  The second problem is that the resin doesn’t flow out as quickly as we would like.  The perfect resin would be water thin and would level out instantly.  It doesn’t exist (yet).  As print slowly submerges in the vat it sometimes takes too long for the resign to flow in and be exposed.  This results in defects and sometimes entirely failed prints.  My next project is to heat my resin vat to try to reduce its viscosity.

Building a basic SLA printer part2

As you can see, even the most basic top down SLA printer is capable of making ridiculously detailed prints.

tiny 3dpt penny

The top down system has advantages and disadvantages compared to the more popular bottom up system.  On the advantage side, it requires no peeling.  It needs no fancy vat coating or tilt or twist peeling mechanism.  Because it doesn’t need to peel each layer it can run amazingly fast.  Carbon3d’s secret sauce is a fancy technology to eliminate peeling on a bottom up machine.  Top down machines are all just born that way.

A disadvantage of the top down system is that it is difficult to calibrate to make precise parts.  The resin contains an inhibitor which prevents it from curing in the presence of oxygen so the layers are actually cured somewhere below the top surface.  How far below depends on the projector and the pigmentation of the resin.  The surface level of the resin is difficult to control which adds another layer of uncertainty.  Plus the resin is viscous and forms a meniscus on the top surface (see your middle school science notes if you don’t remember these terms).  Combine these factors with the spreading of the projector beam and you can see why it is difficult to make a finely calibrated print.  It is difficult to know exactly how large the projected image will be at exactly the location where the cure takes place.  The bottom up machines solve this problem by curing layers on the bottom of the build vat  which is a readily defined and easily repeatable location.

Another disadvantage of the top down system is that it requires a build vat that can hold the entire finished print submerged.  This requires a lot of resin unless you resort to trickery.  The simplest solution (the one I use) is to fill most of the build vat with a saturated solution of salt brine.  Mix salt into boiling water until no more dissolves.  Once it cools to room temperature and the excess salt settles to the bottom it can be poured into the build vat.  The saturated brine has a high enough specific gravity that the resin will float on top of if (think Dead Sea).  This works for the most part if you keep a fairly thick layer of resin on top.  If the layer gets too thin you can get drops of water where the resin should be which causes defects in the print.

Building a basic top down SLA printer part1

The debut of Carbon3d’s layerless continuous SLA system certainly caused a splash in the 3d printing world followed quickly by the less well funded, but equally amazing Gizmo3d.  DSC_0020These innovations made me yearn to tinker with SLA printing, so I set out to build my own SLA printer using primarily 3d printed parts and parts left over from previous printer builds.

A top down SLA printer is ridiculously simple to make.  In its simplest form it consists of nothing more than a video projector and a z axis.  All the magic is done by the video projector, and you just buy that part.  If you buy the right one (I use an Acer H6510BD) you don’t need to modify the projector at all so it still works to watch movies.  The software is the other part of the package.  Creation Workshop provides a very simple easy to use solution.  The package is free to use for individuals, but they license it to printer manufacturers, and make custom versions for different machines.  The software is rather basic, sort of the RepG of the SLA world, but it works well enough and can be easily customized to run almost any configuration of SLA printer you can come up with.

In its simplest form the printer projects a slice then lowers the z axis and projects the next image.  Unlike bottom up printers, top down machines require no peeling, so they don’t require special vat coatings or tilt mechanisms.  The part is simply lowered into the vat in preparation for the next layer.  Creation Workshop allows you to inject G-code at almost any time in the printing sequence which makes it easy to activate any sort of peeling mechanism or re-coating blade depending on your machine’s design.

Makerfaire 2015 Part 1

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Andy talks with Claudio Donndelinger about the latest from Lulzbot.

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No more Buddaschnozzle!  Lulzbots now feature the improved hexagon hot end.

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Brandon Climson with his proud teacher.  This high school freshman completely customized and upgraded his Robo3d.

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This is Brandon’s tricked out Robo with dual ezstruders and led lighting.

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This is Brandon’s liquid cooled computer.  This is a young man to watch.

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Andrew Boggeri of FSL3D gives Andy the run down on the Phoenix their new super DLP printer.  It overcomes the resolution limitations of conventional DLP by automatically moving the projector to 3 different positions per layer.  By using an industrial UV projector they are able to achieve 5 second layer cycles at triple the standard resolution.


DSC_0043Whitney talking with David Rorex of Made Solid.  The only company out there making both resin and filament.

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Made Solid was showing off a Gigabot.  This beast makes my huge printer look small.  Look at the drill bit to the left of the machine.

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Now look at Andy holding the same drill bit print.  Look at the size of that thing.

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Shhhhh!  Top Secret.

DSC_0047Andy talks with Frank Peng of XYZPrinting.

DSC_0049XYZPrinting breaks through the price floor with their new $1500 laser SLA machine.

DSC_0052The first prints look great.


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Patrick Degrendele, CEO of Velleman, a large electronic kit manufacturer now making forays into 3dprinting.

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The Velleman K8200 is sturdy and precisely made of aluminum extrusions.  It features an unusual design where the bed moves in both X and Y and the extruder moves only in the Z axis.  This makes it easy to add all kinds of different print heads.  Next week we look at one modded to print Chocolate!

DSC_0073Andy talks with Ford Fraker of Formlabs.

DSC_0068Formlabs is amazing as always

DSC_0078Their silicone coated tilt vat seems to do the trick nicely.

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Andy chats with Fred Kahl aka The Great Fredini.  Fred is a pioneer of 3d portraiture.

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This is Fredini’s home built kinect based full body turntable scanner.  He ran a scanning booth at Coney island for several years.

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Aaron Jennings from polymaker describes their product line of unique filaments.

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PolyMax, the PLA that’s stronger than ABS.  This stuff is tough!  I bent this sample back and forth like this and I couldn’t break it.  It’s not cheap, but its practically indestructible.

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Brook Drumm, the proud daddy of printrbot, always has a smile when he’s describing his new creations.

 

 

 

 

 

 

 

 

 

 

 

 

DSC_0129A few of my big prints on display at Chimera Art’s booth.

We will see you all next week for the rest of our report from Makerfaire 2015

Using a glass build plate with a Metal Simple

Printrbot with glass build plate
A thin sheet of steel lets your inductive sensor “see” the bed through the added glass build plate.

One of the great features of the Printrbot Metal Simple is its automatic bed leveling sensor.  When properly calibrated it greatly reduces bed leveling hassles.  The sensor works by measuring the bed height at three points and then calculating z height offsets for every location on the bed.  The sensor uses induction to sense the location of the bed without touching it.  This works very well in the printer’s stock configuration, but if you want to print on a glass build plate it calls for some trickery.

Everyone has their own favorite build surface, but for my money you can’t beat glass.  Glass is smoother and flatter than any other material you can easily find, and combined with a bonding agent such as Aquanet hairspray or PVA glue (either glue stick or white glue work) it provides an ideal combination of stick, while you are printing, and release once you are done.  Aquanet has enough stick for most PLA and ABS prints, while PVA can give you a stronger stick useful for printing troublesome materials like nylon.

The problem is that the sensor used in the Metal Simple doesn’t have enough sensitivity to pick up the height of the bed when there is a sheet of glass on top of it.  The inductive sensor can’t “see” the glass, but with the glass in the way it can’t get close enough to the bed to see it.  You could replace the sensor with a longer range unit, but the range of error of the sensor is a percentage of its total range, so longer range means less accurate.

The simplest solution I came up with was to increase the inductance of the bed. The Printrbot Metal Simple is beautifully made of very precisely fabricated aluminum, so I didn’t want to permanently modify it.  I tested a bunch of different materials and discovered the best one was 24ga. galvanized steel.  I sheared a piece big enough to fit under the build plate.  The steel has enough inductance that the sensor can see it from a distance greater than the thickness of the added glass build plate.  You will need to adjust the z height offset in the firmware the same way you probably adjusted it when you first got your machine.  Once you get it dialed in it is very reliable.

DSC_0010Andy came up with a great trick using crimp-on electrical terminals as hold downs for the build plate.  Use slightly longer screws and a couple of washers to shim them up and you can hold your glass build plate in place without making any permanent modifications to your printer.  Just cut to steel sheet and the glass build plate to fit between the bed mounting screws.  With this solution you don’t lose any of your build area.