A new filament feed for the UP!

My UP! came with a 800 gram reel of filament.  I also bought thee 1 kg reels from the Delta people along with the UP!  Not long afterwards I bought a rather large spool of ABS filament from my usual supplier and had been putting it onto the empty 800 gram reel as I needed it.

This spool to spool transferring was a bit of a pain so when I bought a large consignment of ABS from New Image I had them put it on their own 1 kg reels.  New Image reels looked nothing like Delta's and would not fit onto the UP! spool holder, so I new I was either going to have to print a new spool holder or continue reel to reel transferring.

I was in a hurry with a mechatronic hand project, so rather than use the New Image spools I just unpacked one of my Delta spools instead.  Imagine my surprise when I discovered that the 1 kg Delta spools won't fit on the UP! spool holder, either.  Totally shocking.

In any case, I went down to the hardware store, bought some plywood, a large diameter bolt and a Lazy Susan turntable assembly.  Here is the new spool holder that resulted.

It works beautifully with both my wide New Image spools and also the 1 kg Delta spools.

Is Reprap UP! to the Chinese challenge?

It appears that Delta Micro's UP! and UP! Mini are aiming to be a serious threat to Reprap and other personal 3D printer offerings in very short order.

Some months ago, a long term technology friend of mine acquired an UP!  While Peggy has been a inspired developer of educational technology for years, she did not, to the best of my knowledge, have any prior knowledge of the ins and outs of 3D printing on personal printers.  In spite of that, Peggy whipped her UP! printer out of the box and did a brilliant print first time out. That really caught my attention.  I'd been working on the Reprap project for years and still, when I bought a Rapman, a greatly enhanced Darwin-derivative, several years ago it had taken me the better part of a month to get used to the quirks of printing on it to the point that I could get reliably good prints.

The UP! 3D printer by Delta Micro

At the time I had abandoned my effort to build a second generation Darwin-derivative printer as simply taking too much time and getting in the way of other design work I wanted to do.  My Rapman, however, was getting a little long in the tooth and, should parts break I would not have the means to print replacements.  Clearly, I needed another printer.

I had been idly interested in the UP! for some time.  Delta Micro, which makes the UP! is the Chinese equivalent of Stratasys here in the US.  Some years ago, I suggested to Stratasys that they leverage the highly sophisticated solids model processing app that they supply with their high-end printers to promote a inexpensive, personal 3D printer in the Reprap price range.  To Stratasys' credit, they eventually did introduce such a printer that they marketed though Hewlett Packard.  Unfortunately, their price point, which was around $14K, was well beyond the means of most pocketbooks for personal use.  Delta Micro, on the other hand, did leverage their high-end solids model processing app to promote their own personal printer, the UP!.  The UP! was priced at about $1.5K, roughly the same as my Rapman costs currently.

After much agonizing about abandoning the Sampo printer I'd spent considerable money in developing, I went ahead and purchased an UP!.  My notion was to get a close look at it to see how much of what Delta Micro said about it was true and how much was hype.

Out of the box, one thing that immediately struck me was the tiny size of the UP! The 140x140x135mm print volume reminded me a lot of the old Makerbot Cupcake.  It took me about half an hour to get out of the box and set up, ready for operation.  While the manuals indicated that I might have to level the print surface, this was not necessary.  Calibrating the printhead height took about ten minutes.  When I ordered the UP, I was very worried about print adhesion to the print surface.  Delta Micro offered three solutions; perforated printed circuit board, painted glass and Kaplon tape covered glass.  I had had so much drama with prints peeling off of the print table with the Rapman over the years that I ordered all three options.

As it turned out, I need not have bothered.  The simplest option, perforated printed circuit board, clipped onto the print table with standard office clips,  has proved perfectly adequate.

Printing on perforated printed circuit board

I had been assured by the American distributor that the UP! had a heated print table.  It certainly didn't look that way out of the box.  The black iron print table is heated by a central heating element in the middle of the table.  This arrangement struck me as dubious.  The control app that goes with the UP lists the table as heating to 105 degrees C.  I was worried about the temperature gradient of the print table and did a bit of thermal imaging.

Thermogram of the bare printer table

Interestingly, the thermal gradient between the center of the table to the edge was only about 5 degrees.  When I laid the perforated printed circuit board over the print table, I got about a 10 degree overall drop in the print surface.

Print table with the perforated print circuit board

The addition of the board evened out the print table temperature quite nicely so that there was very little in the way of a gradient from the center of the table to the edges.

Construction of the UP! was quite simple.  The enclosure is basically stamped sheet steel.  Positioning is done with stepper driven belts and flat plate linear guides with grooved edges.  It is very simple and very robust.  I found out how robust when I accidentally knocked the UP! off of the stool it was sitting on in the first picture in this article.  Horrified, I picked it up and could see no damage.  With considerable dread I restarted the printer and discovered that it hadn't even been knocked out of alignment.  It had fallen about 80 cm onto a linoleum covered floor.  This is not something I'd recommend be made into a regular practice, mind.

While the UP! uses an SD card like the Rapman, it is permanently mounted on the controller board. You load the card via a USB link to your computer and start up the print.  After the print is started, the printer no longer needs a USB connection to your PC.

As I mentioned earlier, one of the original attractions of the UP! was that it had leveraged the software app from Delta's high end printers.  I was especially struck with the sophistication of the structural support capabilities reflected in this picture.

Teapot printed on the UP! with breakaway structural support

One thing that I noticed about the UP! was that I had far less trouble printing tiny objects than I had with the Rapman.  The UP! is a bit different than Reprap machines in that it extrudes ABS at 270 C rather than the usual 235 C that the Rapman allows.  The thermal footprint of the 1.7 mm filament extruder is much, much smaller than the extruders that I've had experience with it the past and rather looks like the one that Adrian Bowyer, the father of the Reprap project, designed for the Reprap Huxley machine.

Delta had one picture, since removed from their website showing how you could stack objects on top of each other spaced a centimeter or so and the support capability of the system would print them quite nicely.  Frankly, I had severe doubts about the ease with which print rafts and structural support could be removed.  Experience with the printer, however, has proved those doubts to have been unjustified.

As an example, I recently printed parts for a hand movement sensor for a haptic telepresence robot on the UP!  You can see here a particular print positioned in the print volume.

Finger rings for a hand motion sensor as seen on the UP! solids processing app

Printing the support structure of the rings

Completed print

Support material removed

I was able to recover the printed rings from the support material and clean them as you can see here in less than a minute without hurrying.  When Delta says breakaway support material, they aren't joking.

One of the apparent drawbacks of the UP! is the implication that it only uses Delta supplied polymer.  At roughly $25/lb, it is a bit pricey for an old Scots-Irishman like myself, so I inquired if using third party filament would void my warranty.  I was told that I could use whatever I wanted in the printer, but if I burned out or otherwise damaged the extruder it cost less than $300 to buy new one.

One thing that created a problem is that the UP! uses 1.7 mm filament whereas the standard for Stratasys and an increasing number of Reprap machines is 1.75 mm.  Fortunately, I have a good working relationship with Jim Waring at New Image Plastics.  I have had good results using his 3 mm filament in the past and was able to get him to extrude several pounds of that polymer in 1.7 mm diameter so that I could try it out with the UP!.

The last exercise with the finger rings was done with New Image filament.  There appears to be no substantial difference in print quality between the ABS polymer which he makes, which is manufactured in Taiwan and what Delta supplies with the UP!  Jim's filament, however, sells for $9.95/lb rather than $25/lb, a considerable savings.

Finally, it appears that Delta Micro is going for the throat of the manufacturers of Repraps in the US and elsewhere.  They are now offering a slightly smaller printer, the UP! Mini! with a 120x120x120 enclosed print volume which uses standard 1.75 mm filament for less than $1,000.  The UP! Mini appears to be a serious challenge to both the Reprap variations and to the 3D Systems Cube system.  It strikes me that unless the quality and ease of use of UP! competitors makes a rather quick quantum leap they could easily find themselves to be a historical footnote in the history of 3D printing rather than a new paradigm of virally diffused technology.

The UP! Mini

Bought a Chinese UP! printer

Got my 3D Up! printer running.  There was some drama with installing drivers.  The manual instructions were written for Windows XP and I was using Windows 7.  Slightly different way of doing things which I managed to puzzle out.

Tested the extruder.  It prints at 270 C.  Now I understand why they designed the extruder head the way that they did.  You'd be hard pressed to print at that temperature with a Reprap extruder head.

Solving a nagging question about print adhesion

Unlike most of you, I don't use an electrically heated print surface.  Some time ago I bought a Rapman 3.1, which used an acrylic 3 mm print table.  I soon discovered that 3 mm was far too thin and quickly warped beyond use.  Switching to 10 mm solved that problem.


After a long time of successful prints, I noticed that with winter causing colder temperatures in the print room I was having more and more trouble getting my prints to stick to the acrylic.  I tried cleaning it and sanding it with little avail.  Electrically heated print tables were just coming available but insofar as printing was concerned, I thought that things were already complicated enough without adding that sort of equipment to my Rapman.


I had an IR heat lamp in the lab, detritus of another experiment, and discovered that using it on a tripod to raise the temperature of the acrylic print table above 40 degrees Celsius measured with a non-contact IR thermometer gave me consistent adhesion.  I soon discovered that I could turn off the IR lamp after 4-5 print layers with no ill effects.  It was not needed for the rest of the print.


The rig looked a bit like this...

Note that the lamp is placed at a 45 degree angle to the acrylic print table.


I soon noticed that adhesion at the near side of the print table was much less firm than that at the back and less firm at the left side than the right.  I attributed this to various things, uneven heating being one of the possibilities.  While the left/right difference made sense the front/back difference didn't seeing as the IR lamp was aligned with the left/right axis.


Cranking the terminal heating temperature before starting a print to about 50 degrees solved most of the problem for the center of the table and I was able to print along the front/back axis with reliable success.  Unfortunately, the back side of the print area seemed to have the print pad melting into the acrylic while the front side would separate easily.


It made no sense.  I thought for a while that it had something to do with the acrylic plate and rotated it with no effect.  Swapping ends and sides always left the back side of the print table very firmly attached to the print pad.  While that wasn't a horrible situation it was annoying, because it meant that processing the printed objects after separation became more time consuming.

A few weeks ago, I purchased a FLIR E30 thermal imaging camera with the intention of learning more about what was happening with prints as they were being laid down, the ultimate goal being building in advanced heuristics into my Slice and Dice app which converts STL files into Gcode.  I also had hopes about eventually doing some research into what actually happens thermally with extruder hot ends with the notion that I might be able to design a better one.


Yesterday, the E30 arrived and I decided that a good beginning exercise might be to look at the distribution of heat on my acrylic print table when I used the IR lamp in its standard configuration to heat it.  The results were quite unexpected.

>




The lamp put down a marked hot spot at the upper right rather than at the right as I expected.  The upper right was exactly where I had the most trouble with print pad melting.  Obviously, the IR lamp did not give even heating when tilted but overheated in on the upper right.


This was nasty.  I had previously thought about using several smaller IR lamps at the corners of the Sampo printer that I have been developing.  If the smaller lamps behaved like my single, large one, however, this might not be a good idea at all.


I then got to thinking about how IR lamps are actually used in food heating cabinets.  They are almost always placed point straight down.  I rearranged my tripod to place the lamp almost vertically over the acrylic print table.

That sorted out the temperature distribution problem...

A new acquisition...

Details

Sampo's touch screen begins to work...

Adriaan has been working hard learning the TFT programming protocols and has his first touch screen menu working on the Sampo controller board.

Bogdan makes a measurement suggestion...

After I got the x and y axes operating independently, Bogdan suggested that I measure the steps between the limits switches to see how much difference in measurements might be attributable to the mechanical microswitches that I am using.  I had already been recording that with the y axis, so I decided to extend the monitoring code a bit.


With the y-axis, I had been simply writing the number of pulses to an SD card whenever a limit switch was tripped.  In that I was running the axes at 65 mm/sec, I was getting a rather substantial thump whenever a switch was encountered.  When I thought about it, I began to suspect that the impact was a result of the time it was taking the write to the SD card to happen in that I was doing that immediately after the switch was tripped.  I changed the code to record a set number of triggering events for each axis and then exit the stepper loop and print the whole set of measurements at one time.  That reduced the noise of switch triggering on the x axis to almost nothing.  It also reduced the noise from triggering events on the y axis, but not as much.  Considering the y-axis is shifting the whole weight of the x axis assembly, the extra momentum generated thereby is probably causing the larger thump.


I first took a set of 50 triggering events running at 65 mm/sec.

You can see that the two limits switches on serving the x axis trigger with slightly different sensitivities, one triggering about 0.3 mm greater than the other {transition is running at 0.89 mm/step for both axes}. The both y axis limits switches trigger at the same place except that occasionally one gets moody and triggers 8 steps {~0.6-0.7 mm} longer than the first.


I then took another set of measurements at 32.5 mm/sec. The NEMA 23s were near resonance frequencies at this speed raising the noise level of the printer considerably. I will have to see about damping this.

What you can see is that the variation on the x-axis stayed about the same while the moodiness of the one limit switch on the y axis disappeared. Notice also that the steps between switches are down.


From there, I took a set of measurements at my usual printing speed for Rapman at 22 mm/sec.

Decreasing the transition velocity got us further away from the resonance frequencies of the NEMA 23s. It must be said, however, that the printer was still louder than when I was running it at 65 mm/sec. You can notice here that the variation in limit switch triggering has dropped to 1-2 steps.


This has been an interesting exercise. One thing that is obvious now is that to control noise levels I should be controlling the stepper speed both by the delays between steps and by adjusting the level of microstepping that I am using.

X & Y Axes operational from the controller

I was finally able to get time to integrate the full anti-bounce board with the x and y axis limit switches.

The two axes are playing ping pong and running at a speed of 65 mm/sec with no slippage and no heating of either the steppers or the driver chips. I've run them all morning with no mishaps.


Now I am going to have to see to writing a gcode interpreter and taking a shot at the TFT 320x240 graphics touch screen for system control.

Leveraging Bogdan's anti-bounce circuit for Sampo...

In developing the Darwin-derivative, Rapman-derivative Sampo 3D printer project as a kaizen exercise I utilized the same sort of microswitches for limits checking as are specified in the Rapman design.  I soon discovered that the switches have a formidable electronic bounce.  I was able to control that using the button function in my firmware compiler for the y-axis.  The computations taken for a firmware fix, however, were going to put a terrific drag of my MCU that I didn't want to have to deal with.


Enter Bogdan Kecman with helpful suggestions on how to put together an antibounce circuit for the limits switches.

I had last built an antibounce circuit in 1981, so his help was greatly appreciated.  I built a lashup of the circuit to check to see that the component values were right and then went on to design a board to handle all six limts switches.  I wanted six instead of Rapman's three because a lot of problems that I'd had with Rapman stemmed from the fact that it has limits switches only on one end of its axes.  When things went bad one could find steppers trying to skate off of the unchecked far end of axes.  As well, Rapman limits checking only seems to be done when one is resetting the axes at the beginning of a print.  I want to do better than that.


I bought components and dug out my stripboard and had a go at the design.  Some time before I put together a stripboard design program after having had no luck with the ones I was able to access on the web.  Eventually, I evolved this board.


Frontside...

Backside...

It has been some time since I built a board, so I found putting this one together quite frustrating.  I was about to give up this evening after making a bunch of mistakes and then got angry to the point of rage.  The adrenalin let me get the @#$#@$ thing finished.

Tomorrow I will drill out the breaks in the strips, check the board for continuity and, if I have enough time, try to rig it into Sampo and extend the firmware to utilize it. I suspect that will have to wait till the weekend, however.

Mendel z-axis stepper mounts done

I managed to get some hours together to do some more work on my son's Prusa Mendel, the z-axis stepper mounts this time.

I printed the z-axis stepper mounts at a 45 degree angle to minimize parts preparation time and avoid warping.

I'm now working on the x-axis stepper and idler mounts.  My son processed the stepper mount last night and I did the idler mount this morning.  They're printing this evening.

Mendel frame takes shape...

I had a major crash of the Rapman 3.0 printer and for several hours I thought I was really knackered. One of the leads to a phase of the extruder stepper parted because of fatigue from thousands of hours of vibration. The system shut down and reset. At first I thought I had a simple static discharge event, the first in many months. I fired the system back up and discovered that the extruder stepper would dance around but wouldn't pump filament.

After serious prayers that the stepper driver chip for the extruder hadn't fried I rewired the connector and got the extruder pumping ABS again only to discover that the intense vibration from the stepper before the reset had actually shaken apart the Arcol extruder hot end that I had bought from László Krekács in Hungary.

This sounds worse than it was. I simply screwed it all back together and cleaned the extruder end and it worked perfectly again. Unfortunately, I will have to recalibrate Rapman now. That should take a few hours that I didn't have available today.

In any case, I was able to cobble the Prusa Mendel frame together this morning.

It's a dinky little thing, but interesting all the same.

Printing a Mendel derivative

After talking with my son recently, I concluded that he needs to start printing a lot faster than I'm going to have Sampo debugged and duplicated. I have a lot of 8 mm linear shafting and linear bearings in stock, so I decided to build him a Mendel derivative using Sampo firmware and controllers. That should get him printing a lot faster than would otherwise be the case.

I started printing parts for a Prusa Mendel yesterday. So far, so good. Got the gantries finished and am printing the rest of the parts now.

5/16th inch threaded rod is pretty much a one on one replacement for M8, #8 machine screws replace M4s and #4 machine screws replace M3s.  I couldn't see much point in printing the SAE Mendel.  I'm going to have to redesign the extruder carriage to seat linear bearings instead of those strange PLA things it ordinarily uses.

Picking up speed

The MIPS core that PIC32 uses is a very high performance CPU that was used in high end Windows workstations in the early to mid-1990s. It doesn't behave much like the 8 and 16 bit PIC chips, so it's taken me a while to get down the learning curve. The button function in the Mikroelektronika compiler library works, but requires about 10 msec to filter out the bounce when a limits switch is encountered.


Processing a button function for each step when I was running at half step slowed the y-axis down to 12-15 mm/sec. To get around that problem in firmware I wrote a smart limits switch routine that runs slow until it finds the first limits switch and then kicks the stepper motor up to full speed until it nears the other limits switch.


Using this approach lets me increase the maximum transition speed for the y-axis from 15 mm/sec to about 65 mm/sec for my firmware testing as you can see in the video clip.

It's worth noting that the Allegro driver chip has a maximum rating of 0.75 amps and the NEMA 23 is a six wire model drawing 0.5 amps per phase. I've wired it in series which brings that amperage down considerably. In spite of this I'm getting 65 mm/sec and both the stepper and the NEMA 23 are running quite cool. The driver chip requires no heat sink or fan.

Y-axis test firmware operational

After a delightful chat with Bogdan this morning about the PIC32's MIPS core processor, I was able to get the y-axis test firmware working.  Bogdan has done a lot of work with the PIC32 and is very generous with his knowledge.  A few hours later, I had the y-axis responding to the limits switches.

Right now with sampling from the limits switches in the same loop that runs the stepper I'm getting 15 mm/sec.  On its own the stepper can do about 52 mm/sec.  I suspect that the speed of the axis will be getting a lot closer to that upper limit once I get the limits switches into an interrupt loop.  :-)

Printing flexible cable guides...

There is not much to say about this.  Once I got two of the links printed and assembled so that I knew everything fit together, I bought a few hundred #4-40 3/4 inch machine screws and nuts to hold the parts together.  I'd designed the parts to perfectly seat a 3/4 inch machine screw and nut.


When I got home with my trove of fasteners from my stockist I discovered that his Chinese supplier had been making a little extra money by trimming his 3/4 inch screws (0.75 inch) down to 0.714.  What that meant was that the screws went all the way through the guide assembly but didn't emerge on the other side to allow the nut to be seated on the end of the machine screw.


My stockist is getting me some 7/8 inch machine screws as replacements and writing a hot note to the warehouse.  Quality assurance at the Chinese plant needs a bit of a rework, I think.


Interestingly, I had designed the holes for the #4 machine screws so that the threads engaged the sides of the holes, so actually nuts weren't required.  With that in mind I went ahead and assembled the flexible cable guide for the x-axis.  It seems to work perfectly.

I get a tight turn like I'd hoped with no clashing.  Right now I am up to 16 inches of a 24 inch assembly for the x-axis.  When I get the full 24 inches printed and assembled I will design and print the end mounts.


It will be interestingly how many hours of operation this kind of flexible cable guide will handle before something wears out.  

Flex cable carrier

I've never been happy with the way that Rapman handles axis and extruder cabling, so I decided to print my own flex cable carrier system.  I saw several possibilities in Thingiverse.  Most of them were knockoffs of existing injection molded parts, however, and printed very poorly.


A few looked as if they were designed specifically for a 3D printer like this one...

I didn't much like this one largely because of the large turning radius for the flex.  I wanted something more like this...

Since my wiring was considerably more modest, however, I wanted something with a bit sharper turning radius still.  After several hours of trying out alternatives in Art of Illusion, I came up with this as a first try.

It is shown here with #4 bolts 1.5 inches long.  It can work interchangeably with #4 UTS/SAE - 3/4 inch or M3 - 20 mm bolts.  With fasteners it costs about $1.50/ft.  Commercially available alternatives average about $12.50/ft.

The system can make a 180 degree flex within 50 mm.  The next move is to get a couple of packets of #4 bolts and nuts and print a few feet of this to try with the x-axis cabling.

A "string wars" approach to the y-axis

Darwin and it's direct derivatives uses two belt loops driven by a shaft connected to a NEMA 23 stepper.

In Sampo, that dual loop arrangement has been replaced with a single large loop

The belt guides are equipped with standard 608 skateboard bearings with printed fenders.

Topologically, the y-axis is simply an attenuated version of the x-axis.

Print table installed

I had gone to considerable trouble to make sure that I sited the bolt holes in the MDF {medium density fibreboard} print table properly. To that end I designed a template for each of the brackets that would show me where the guide holes should be put.

Once I had the table suitably aligned, I was able to drill the guide holes with my Dremel tool quite easily.

I then removed the table and took it to the workshop to drill out the holes to #8 bolt diameter.  When I returned and tried to mount the board I discovered that the holes didn't line up.  I had neglected to mark the lower left corner of the print table and had no way of knowing which side our orientation matched my drilled holes.  We are talking about a few mm here, mind.   There were 16 possible orientations and that was complicated by the fact that the brackets were able to rotate around the z-axis linear shafts in  the xy plane.  After about the tenth possible orientation, I found one that fit 3 of the four brackets and just redrilled both the MDF and the bracket.  Mercifully, solid ABS is very amenable to drilling so other than having the lower right corner showing an extra set of bolt holes, it all worked out quite well. 


Hopefully, I will remember to mark the lower left corner the next time I build one of these.  The print table moves quite freely as the video will demonstrate.

Now all that remains is for me to reprint the z-axis cable grippers and mount them and the z-axis will be complete.

Ready to install the print table

I got the last of the y-axis brackets printed and light mounted.

It looks like the print table with be 420x420 mm.  I've designed a bolt-on template that seats the table on the brackets and shows me where to site the guide holes for the mounting bolts.

And here is the first drill template mounted on a z-axis bracket.

Got it right on the second try!  :-)