What is RepRap & RapMan Z-Axis Wobble?

I'm fairly confident that any issues with the Y-Axis alignment and the Bed Leveling alignment on my RapMan has been successfully solved using the new tools that I designed to make the process more precise.

But, when printing at .125mm, it is apparent that one more issue may need to be tackled.  And, that is probably some issue with some relatively minor Z-Axis wobble.

This video isn't all that great.  The lighting is poor and the image is 640x480 because it was shot at 240fps so we could analyze the image in slow motion.  I'll try to get better images of all four threaded rods this evening.
However, it is still useful enough to use right now.

What this video shows is that if there is any wobble at all, it is very. very minor.  Yet, because we are working with such tiny tolerances, it is still noticeable in the printed output.  As the following samples show.

Here is the test object.  It's a tower having 3 equal sides.  This shape was chosen because it results in 3 sharp edges.  It was printed at .125mm resolution.  And, as you can see, there are some visible ridges that probably indicate Z-Axis wobble.

Test Tower

Looking at a crop of the image, we can see the ridges a bit more distinctly.

Test Tower - Crop showing ridges more clearly

By laying the tower on its side and angling the light to create shadows, the ridges become more identifiable.

Lighting to accentuate the ridges

While we can see an interesting pattern in the above picture, it's not so clear as to how many layers there are in the repeats of that pattern.  For that we need a microscope.  Again, the following picture was created using the worst microscope I have in my collection and the camera was hand held to the eyepiece.  So, it's not the best we can do.  Even so, it is helpful to see for this article.

Ridge pattern through a 20x microscope

The most important thing about this image, and something with which I want to follow up, is that the ridge pattern looks to be about 12 rows.  If 12 (or so) rows equates to a full turn of the Z-Axis threaded rods, we have evidence of Z-Axis wobble.  Yes, it's on a small scale.  The wobble appears to be less than .5mm.  But, it is there.  And, theoretically, we should be able to get that down to virtually zero.

In subsequent posts, we'll explore some of the solutions that other 3D printer users have come up with to deal with this issue.  But, before we leave this subject, it might be interesting to see what we are up against in dealing with the threads of the threaded rods.

Threaded Rob Up Close and Personal

If you click on the above image, you will see that threaded rods aren't always as cleanly threaded as we would like.  In fact, I don't believe I have ever seen a perfectly clean threaded rob.  This one is as good as any I've seen.  Yet, it clearly has some defects and/or debris that might affect the print.

While looking at the screw, it dawned on me that I should be able to place the test tower next to the threaded rob and take some macro images to see if the threads match the pattern of ridges.  I'm guessing they do.  :)

Fine tuning RapMan 3.2 - Hot End clearance

The RapMan gives us several tools to raise and lower the hot end relative to the bed.

The first, and most basic, way to set the distance between the hot end and the bed is a long screw that hangs down from the extruder assembly.  Each time we select the bed height option on the console, the printer homes the machine so that this bolt can activate a switch and then the printer uses that position to move to the center of the bed and lower the hot end to the position called for the bolt's length.

The manual calls for adjusting the hot end so that it barely touches the bed.  "Barely" is the operative term.  I'd like something a little more measurable.  To get the most precise setting, I decided to use a mechanic's tappet gauge.  So, I started with the 0.102mm leaf on the mechanic's gauge to get the hot end as close as I am able to measure. But, through trial and error, I found that my particular printer responded best (laying down an undistorted raft) at 0.254 for PLA.

Here are the steps I use.

1. Press the Z-Height Selection
2. Make sure the Z-Height Offset is 0
3. Try the 0.254 leaf of the gauge under the hot end.
4. If there is a lot of clearance, tighten the adjustment bolt.
5. If there is no clearance, loosen the adjustment bolt.
6. Exit Z-Height adjustment

Repeat the above steps until the gauge just slips under the hot end.  Do NOT make changes to the Z-Height offset.  You are setting the base point and will use the offset to further fine tune for different situations or special cases.

I understand the critical nature of getting the hot end (Z-Axis) height right for the raft.  But, it's still unclear to me that it makes much of a difference in subsequent layers as the Z-Axis increments should take care of itself in spite of the starting height as long as the height was sufficient to create a starting raft.

And, the optimal height for any given printer with any given material might be a bit different.  That is because the setting you end up using is the setting that is able to lay down a nice raft without tearing it or distorting it.

The point is that we can get more precise in by using tools, like a mechanic's tappet gauge, we are better able to control our printing environment on a repeatable basis.

Fine Tuning RapMan 3.2 - Precise Bed Leveling

Making sure that the RapMan 3.2 bed is level is probably among the most important things we can do to ensure better results.

The build manual and the display panel gives up some tools to level the bed using three bolts.

But, my eyes were having a hard time seeing the hot end height.  So, I decided to make some tools to help me do this more precisely.  First, I bought a set of mechanic's valve tappet gauges.  Using a gauge under the tool that I am going to describe is the most precise way to ensure that all points are even.

First the tools...

Bed Level Tools

 Basically, these two tools are hung over the X-Carrier rails and hang down.  The four points are an even length.  Here is how they are used.

Tools hung over at each end of the X-Carrier rails.

Notice that that a tappet gauge is being slipped under one of the pointed rods.  Adjust the height of the bed using the console until the gauge can be just slipped under the point.  It should NOT lift the tool.  Now, by simply using the bed leveling bolts, ensure that the gauge just slips under each of the other points.

Do this front and back.

Gauge being used at the back of the bed

These tools are a LOT easier to see than the tip of the hot end because you can place them so close to the edges of the adjustable bed assembly.  You can get up close and personal.

Finally, I had created an earlier set of alignment tools designed to do the same thing.  However, these sat on the bed, itself and had clips similar to those of the X/Y Carrier alignment tools.  I now use these just to verify that the bed is level.

Verifying that the bed is level

The latter step  is not really required.  I simply have the posts already and it's a good tactile way to verify that the bed is level.  Raise or lower the bed until one of the tools clips easily on the carrier rod and the other tool should also clip easily.

Once bed leveling is complete, we need to adjust the hot end height.  And, for that I also use the mechanic's tappet gauge.

Fine Tuning the RapMan 3.2 - X Carrier Alignment

So far, I have not found a single defect in the design of the RapMan 3.2 that I could pinpoint for you.

However, the printer is only going to print as well as we have built our RapMan printer.  And, I am determined that I am not going to be content until I have assured myself that the printer I have built is as good as any other RapMan out there.  And, that means finding ways to fine tune as many of the variables as I can.  And, at least for me, this means a By-The-Numbers approach to alignment.

Fortunately, the RapMan can help us out here, by allowing us to build alignment tools that we can use to ensure that we are as close to the most precise tolerances as we can get.  I want to talk about some that I've created for myself.

The first is a tool that allows me to align the Y-Axis travel.  The RapMan uses two belts for the Y axis.  And, it's possible that these two belts are pulling at an angle.  The best way to ensure that both belts are adjusted so that the X-Carrier is in perfect alignment is to measure the distance on both the left and the right sides to make sure they are equal.

Here is the alignment tool that I built for this job.  We use two.

Y-Axis Alignment tool

Notice that these alignment tools have a small half circle and a large half circle.  The small half circle fits over the top front rail and the large half circle fits over the front carrier bar for the X-Y carriage.  Clip the tool on the front rod and move the X-Y carriage carefully until it's possible to easily clip the tool onto the first rail of the carriage.  Do NOT force it.  Here is what it looks like.

Left Side Y-Axis Tool Attached

Then clip the other alignment tool to the front rod and ease it down to the carrier rail.  Again, do NOT force it.

2nd Alignment tool attached to front rail

Alignment tool being lowered to carrier rail

If the 2nd alignment tool will not easily clip onto the carrier rail, then the carrier is out of alignment.  Loosen the Y-Axis pulley at the back right of the printer and pull or push the right end of the carrier until the tool can easily be clipped to the carrier.

Carrier aligned

Then tighten the pulley.  The carrier should now be aligned.  But, you may want to remove the alignment clips and try the steps again to ensure that the X-Carrier is, indeed, permanently in alignment.

RapMan 3.2 Unattended Print at .250mm

UPDATE:  I did manage to figure out why the .125mm test was not, initially. printing well.  It didn't dawn on me that because the layers were 1/2 the thickness, I needed to raise the bed to compensate.  Once that was done, it was running fine when I left it this morning.  Hopefully, it completed the job.  I'll find out in an hour or so.  I HATE DC area traffic!  LOL!

Before leaving for home... and hopefully finding a higher resolution print of Peyton Duncan's Chow waiting for me... I managed to capture some better images of the printed model from my RapMan 3.2 printer.

Nobody is trying to fool anybody.  An extrusion printer doesn't cost $400,000.  Neither does it perform like one.  But, it still does a very credible job at rendering what one creates.  And, frankly, I'm quite pleased with the result at .250 vertical resolution.  So, here are some images.

NOTE:  Any lint, etc. comes from the fact that this poor guy spent all day in my pocket.  :)

Click on any image to see larger versions... 

Peyton Duncan - Chow View #1:  .250mm

Peyton Duncan - Chow View #2:  .250mm

Peyton Duncan - Chow View #3:  .250mm

Peyton Duncan - Chow View #4:  .250mm

Peyton Duncan - Chow View #5:  .250mm

For these next two images, which only appear to be identical, I raised the F-Stop for each to try to get a bit more depth of field.  I think it helped.

Peyton Duncan - Chow View #6:  .250mm f16.0

Peyton Duncan - Chow View #7:  .250mm f18.0

As you can see, the RapMan, once properly set up, begins to crank out some very nice 3D prints!  And, that is even at the Mid-resolution.

Note for Peyton...  I KNOW that is a DIME in the image and not a quarter as you asked.  How in the world did you think I might have a quarter to my name left while I'm spending all my money having fun buying tools and materials for my RapMan???   LOL!

Note for everyone else...  Peyton is my nephew.  And, I have a LOT of respect for his work and for him personally.  Both Peyton and my artist daughter Cheryl continue to amaze me with their talent. Here is just a sample of Cheryl's beautiful sculpture that got me interested into digital photography and  3D printing in the first place.

Fleurette by Cheryl Meeks

I'm surrounded by geniuses and loving it!

Now... I gotta get out of here to see what awaits me at home... a mess or a Chow!!  :)

RapMan Reel Holder Using MOI 3D

Moment of Inspiration, or MOI 3D, is an absolutely wonderful application.  I installed it two days ago and was immediately able to design some things that will be not only useful to me; but, other RapMan and RepRap users as well.

One of the things that became immediately apparent when my RapMan was completed was that unless I baby sat the printer, the filament would not feed well.  As soon as enough filament had been used that more should be unreeled, the drag simply was too much for my extruder.  That may or may not be the fault of my extruder roller pressure.   But, if so, with my lack of experience, I couldn't trust I would set it right.

So, I determined that roller bearings would probably solve the problem.  And, it did!  I cab now leave the printer unattended for hours on end without a failure to feed.  That was a MAJOR breakthrough!

So, I want to show you how MOI 3D enabled me to go from having absolutely NO experience with the program to creating hubs permitting me to use bearings to support my RapMan filament reel,  My first hub probably took an hour to an hour and a half.  All the subsequent designs took well under an hour and most less than a half hour.  This is remarkable since (1) I am NOT an artist; (2) I am NOT an engineer or draftsperson and (3) I'd not even seen this program before installing it.

I not only created one roller bearing hub.  I refined the design a number of times with different goals in mind,  MOI 3D allowed me the freedom to do this in very easy fashion.  Here is my first design.

First MOI 3D project.  A filament reel hub with roller bearing

As you can see, this is a relatively simple design.  But, it has some features that might not be apparent.  One feature is that it accommodates two different 8mm Inside Diameter bearing sizes, 16mm and 22mm.  This nested design was easy using MOI's Boolean operations that make it easy to remove material.  The lofted shape was accomplished using MOI's scaling.

I then felt I wanted a lighter weight hub.

Attempt at lighter hub using MOI 3D

This design definitely created a lighter version of the hub.  And, it retained the design allowing for a choice be two different sized bearings.  But, it did not allow me to use the 8mm bolt that came with the RapMan reel holder kit.  The bolt wasn't long enough.  So, I used a 5/16" threaded rod to see how it worked.

It worked BEAUTIFULLY.  What a difference!  The bearing allows the filament to be played out with no intervention by me at all.

But, if a hub was to be useful to a wider audience, it should probably be designed to be used with the bolt the user already has.  So, back to the drawing board.

Hub designed to work with the original reel holder bolt

 This design accomplished several goals.  First, it was light.  Secondly, it was designed so that the 8mm x 7mm x 22mm bearing I found at a hobby store would mount flush to the top of the hub.  This meant dropping the ability to also use a 8mm x 5mm x 16mm bearing.  But, the flush mounting was critical to being able to be used with the 8mm x 120mm bolt used with the RapMan Reel Holder.

Here is the above design being used to print the final design.  Note, too, that MOI 3D allowed me to design a base for the filament reel holder that keeps it locked into place.

Test Hub in use with original bolt

While the above design worked beautifully, I still felt that I could lighten the hub even further.  So, I came up with one more design.

Final RapMan Filament Reel hub Design

As you can see, this final design is very, very light.  Yet, it has turned out to be as effective as all the other designs.  Here is an image of the final product.

Final RapMan Filament Hub Printed

While I am very grateful that I was able to come up with something that allows my RapMan to run for hour on end with attention, I am even MORE grateful to have found MOI 3D.

Here is the final version of the reel hub being used with the RapMan filament reel holder, including the original bolt.

Final RapMan Filament Reel hub Design in the Reel holder

I will be putting up all these designs onto various sites.  The last design will be uploaded to 3D Systems' Cubify site that is now in beta.

I'm loving this software and printer combination.  And, I look forward to the new Cube when it arrives.

Follow the Directions!

I have good news and bad news.  First, the bad news.

The Bad News.

My precariously built hot end has failed.  It has clogged.

The Good News

The good news is that the failure had nothing to do with the quality or reliability of the RapMan kit.  It was all me.  And, the reason why that is good news is that, hopefully, I can help other new builders avoid the mistakes that I have made.

Mistake #1 - Cutting the PTFE insulator too short.

The directions call for cutting a small slice off the end of the PTFE insulator.  The operative word here is SMALL.  I sliced off a tad bit too much and, from my research about clogging problems, this is DEFINITELY not a good thing.  It apparently allows melted plastic to rise up and cool, clogging the hot end assembly.

I am ordering a new pre-built hot end.  But, I am also ordering a non-built hot end kit so that I can demonstrate the RIGHT way to do it.  At least the RIGHT way is the plan.  LOL!

But, for now, make sure you cut just enough of the material to square the end, taking off as little as possible.  Put that squared off end into the PEEK insulator leaving you enough room to cut it again when you assemble the wooden MDF plate.

The directions were absolutely clear.  I wasn't!

Mistake #2 - Not paying attention to the material type before taking it from the box.

In taking out the material I've been using for the duck tests, I failed to pay attention to whether it was PLA or ABS.  I simply made the assumption that it was ABS.

That meant that I was selecting a test model that was built for ABS, which requires a hotter temperature than PLA.  This overheating also probably contributed to the results I'd been seeing and the ultimate clogging of the hot end.

The type is not printed on the reel.  It is only printed on the box in which it is shipped.

I usually toss boxes immediately.  But, fortunately, I had not tossed it yet.  So, I was able to correctly identify the correct material type.

I'm learning that a perfect build is all about paying attention!  Fortunately for me, Bits From Bytes makes a very high quality product, has anticipated people with my building skills and makes a pre-built hot end available on their store! :)

V-Flash 3D Printer - Early Info & Specifications

As we sit here in the heat with a dead air conditioning compressor, which will take some steamy days to replace, we're wishing that the whole personal fabrication revolution was mature enough to allow us to build our own! But, we're not quite there yet.

We needed something to brighten our day. So, it was very welcome news to hear from Buddy Byrum, the product manager for V-Flash with answers to some questions we had about the V-Flash 3D printer. And, now we hope to make your day by sharing them!

The image, above, is of an item created with the V-Flash 3D Printer. From the stop motion animation the V-Flash web site (http://www.modelin3d.com/Vflash_animation.shtml) we already knew that objects were built from the bottom rather than adding top layers. Here's how it works.

• A disposable pad having small break away supports is suspended from the build platform at the top of the build chamber.


• A film, at the bottom of the build chamber, is retracted into a container of liquid photo curable resin where it is coated with the resin and then pulled out across the floor of the build chamber.


• The disposable pad, or partially completed model, is lowered into or near the liquid resin on the film.


• A light system photo cures selected portions of the resin to form a layer of the 3D object.


• The build platform is pressed down onto the film and then lifts up.


• The film is again retracted to pick up more resin and the process is repeated until the 3D object is completed.


• The object and disposable pad are taken from the machine and separated.
  

The fact that the material used is a photo curable resin in liquid form rather than a powder should make this a very clean machine to operate in an office environment. The fact that the object is built from the bottom as it hangs, also means no waste of materials since no extra support materials are required. Any liquid not cured is reused. It is obvious that the V-Flash system is very efficient with material utilization.

Unlike some of the powder systems that use a sprayed binder, the parts come out of the machine fully cured and ready to use. (The Desktop Factory is also good in this regard because it binds its powder with heat rather than a sprayed liquid.) That being said, the V-Flash is being marketed as a concept modeler with material properties similar to general use SLA models. Of course, they are hoping to develop future materials that may actually be strong enough to be used for production pieces. Other future materials might have different color, flexibility or hardness properties. So, the technology looks very flexible.

We were not able to get firm estimates on material costs per cubit inch.

The detail resolution is .0088 inches. That translates to 114dpi in the 2D printing world. For most of the tasks for which it is being designed that should be plenty. But, if not, the printed objects can be sanded and printed. The material is said to take paint quite well.

None of the under $10K printers are speed demons. The V-Flash builds, vertically, at a rate of .06 to .75 inches an hour. But, remember, multiple items can be built at the same time provided they fit in the build chamber.

The unique hanging build technique does offer one design challenge. One of the capabilities of 3D printing system is that of building loose items within a cage or gears that are built right onto their shafts. In powder systems the loose powder or other disposable material is used to support these free floating items while being built. The V-Flash methodology will require the user to design small breakaway supports to hold the free floating items in place as the build is being processed. It's isn't a big thing; but, it is something that one has to consider when designing.

The software that will be delivered with the V-Flash system will accept .STL files and will be able to resize and reorient the models to be printed.

The ship dates are still expected to be early fall. Possibly September. So, it may be the first commercial 3D printer to break the under-$10K barrier. We are really looking forward to it. Again, thanks to Buddy Byrum for this helpful information!

It Ain't Smoke and Mirrors!

Back in the early days of video games we were constantly hearing this rumor or that rumor, only to learn that it was all "Smoke & Mirrors". In other words, if it sounds too good the be true, it usually isn't.

We had our own lingering doubts about both of the low-cost 3D printers that are being promised for delivery in the next few months. If the V-Flash actually kicks out some parts in front of the crowd at EASTEC 2007 we can rest a little easier. We'll see.

But, on the Desktop Factory front, we're beginning to see some real movement. Visit their web site and then compare the sites' images with the parts you see here. It is evident that they have been very busy experimenting with ways to help their future users get the most out of their machines when they finally ship.

This image was very important for me. First, it tells me that the surface of the parts created in the Desktop Factory can be polished, smoothed and/or coated to a beautiful finish. Furthermore, they appear to take paint extremely well. Click in the above image and see if you don't observe a fingerprint in the silver gear. It takes a pretty shiny surface to show a fingerprint!

But, it also tells me that Desktop Factory is willing to show its warts, too. The first image that I posted on this blog of a Desktop Factory part came from this larger image. That item and others in the picture, while polished or painted, still reveal the original surface characteristics in interior areas. They could have turned them so it didn't show up; but, they didn't. That's class.

What is unclear is whether the surfaces were polished in some way or that the coating was simply used to smooth the surfaces. If anyone has any information as to how these items were processed please let us know. But, DON'T contact us about using the word "Ain't". We're from the South and Tom taught Science, not English!! Feel fortunate that we didn't use "Ain't Not"!

Yep! It's right around the corner and it truly ain't smoke and mirrors! We just wonder if Tom can actually clear off a large enough area on his desk by the time they are ready to ship. His wife is betting that he can't do it! But, we're pulling for him. There's a desk under there somewhere!!!

3D Printing is Coming Your Way!

Make no mistake about it. 3D printing is on the way to our desktops.

This blog is being created as a place where we can follow the development of Desktop 3D as news and low cost products are released. Right now, we know about several potential candidates for that desk space now occupied by other, less fun, items.

Among the Build-It-Yourself candidates are the Fab@Home project (www.fabathome.com), RepRap (http://reprap.org). We even have an 'Evil Mad Scientist' creating a 3D printer that relies on sugar as the media! And, I'm sure more are on the way.

But, we'll also be following commercial 3D Printers. Two relatively low-cost 3D printers are nearing their target dates for shipping, Desktop Factory and the V-Flash from 3D systems. Information about both is rather sparse right now. But, we have been able to learn a few facts about the Desktop Factory and have obtained some new images which we will share. The image at the top of the post is the latest avaialable for the Desktop Factory.

We understand that the Desktop Factory is actually going to be introduced at the target price at $4,995. This quickly raised its profile on our radar screen! Initially they stated a range of between $5,000 and $7,500. That savings of $2,500 adds up to a lot of materials for experimentation! We like that.

There is something a bit odd about the image of the Desktop Factory printer that we obtained. The buttons and display just don't seem 'real' enough. And, we'd feel a bit better if there was some loose powder in the chamber. But, we'll take what we can get right now and this is the best we have at the moment.