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Pocket Printer Upgrade - hybrid roller slides

by dkennell, published

Pocket Printer Upgrade - hybrid roller slides by dkennell Mar 24, 2012

Description

This printer won't quite fit in your pocket, but it is very easy to take with you. I designed the printer around two constraints. First, the high mass motors and extruder are stationary. This allows smooth high speed printing, as only the print bed moves. This keeps the forces on the slides low as well. This will also allow dual extruders on a very lightweight printer. Second, the slides are all integrated, using PLA bearing surfaces running on the extrusions. I wanted to try this on all the axes of a printer since it works so well on my Aluminum Mendel. It is self-contained, with power supply on board. It is very robust, and makes top quality prints. I made this printer to test the above constraints, but it works so well I decided to publish it.

The print volume is 120mm W x 100mm D x 65mm H. This could be expanded a little by getting longer extrusions.

Pocket Printer on Marlin - http://youtu.be/lAwCmbKS-yQ I have comb activated, so it travels around the cord cutout on this iPhone dock at a very rapid travel speed.

Watch this printer and my Aluminum Mendel http://www.thingiverse.com/thing:16076 print side by side here http://youtu.be/JysNv3Hi67k

I posted a video at http://www.youtube.com/watch?v=4tpOokI6_Z0 I wanted to see if it could print vertically. It is printing a stretchy bracelet - http://www.thingiverse.com/thing:13505.

I hope this inspires others to expand on this design.

Recent Comments

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There really are no detailed instructions. You pretty much have to figure it out from the exploded drawings and photographs. Sorry.
Hi where are all the instructions to build this, i simply cannot find them :-(
LOL this is cute :D

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Instructions

I added the controller with sd card reader and click encoder as seen in tommyc's excellent tutorial - http://tommyc-reprap.blogspot.com/2012/03/panelmax-tutorial.html. Now I can grab a coil of filament and the printer and print anywhere.

This is printed in PLA. Drilling and tapping small parts is necessary to build this project. A drill press is nice, but it could be done by hand. The sliding surfaces fit well with my printer settings, but you can use a new, sharp file to remove a little material if necessary. Take your time with fitting the slides, a good fit without too much friction is needed. The x and y inner slides can be adjusted externally for a perfect fit. I use a very light film of silicone lube on the slides. I tried many different designs on the slides, but this one really works the best.

The exploded view and BOM should provide enough info to make this project. I zipped the stl files because there are 22 total. I also zipped the entire Inventor project. I did not provide all the limit switch or power supply and switch mounts.

4/24/2012 I upgraded the slides to a hybrid roller version that is easy to print and assemble and has low friction and good precision. All the stl files are in the zipped folder. I was unsuccessful in simplifying the pulley arrangement by combining x and y movement, so I added a small, lightweight stepper for the x axis. This motor weighs only 4.9 ounces, compared to 12 for the standard steppers, so moving mass is still low. The motor should be run near its maximum current of 500 mA, so I recommend making the x motor mount out of aluminum plate to dissipate the heat. A drawing with dimensions is included in the zipped file. I also upgraded to the Misumi belts and pulleys. I think the smooth action is worth the extra cost.

4/27/2012 An exploded view drawing of the hybrid roller slide has been added below. The BOM is on the exploded view drawing.

Hi where are all the instructions to build this, i simply cannot find them :-(
There really are no detailed instructions. You pretty much have to figure it out from the exploded drawings and photographs. Sorry.
LOL this is cute :D
Hello,
Great design! We're about to order parts to build two of theses but we are a bit confused about the 3 BOM. Which one should we use to build a complete printer with the upgrade slide? Is there mix and match to be done? Do you have a BOM that is up to date?
Any info would be appreciated!!

Cheers

Marc
Sorry about the confusion. I am trying to do a better job with my newer postings. I think you need the parts on the original BOM_Aluminum_Pocket_Printer (minus the x and y slides and a bunch of idler pulleys) plus the parts on the BOM on the Exploded_hybrid_slide_assy.
Hi, great printer, one of the best frame designs out there I think. I am designing a derivative to allow for big extruders so I can print in new materials and have 3 extruder heads. I am hoping to fix the extruder heads and put Z movement in the bed. Is there any way you could upload .STEP files of your Inventor parts? Solidworks user here. Thanks!
OK, I added a zipped folder of the STEP files. Good luck.
Thanks a lot!
Dave - FYI, I just completed my first successful print on my Pocket Printer derivative. I'll post the details soon.
I'm having two issues with the z-axis.

1. The lead screw nut pulls out of its seated position slightly while descending, making it impossible to get a consistent z-axis home. I'm seeing about a half-millimeter (max) play due to the nut unseating, making calibration and subsequent printing impossible. If I tighten the self-tapping nut hold-down screw enough to keep the nut seated, the nut hold-down screw puts a torque on the nut, orthogonal to the lead screw z-axis, and the lead screw loads too heavily due to friction. I very nice break, BTW. Occasionally, I find a M8 1.25 nut that is so far out of tolerance, it makes a poor candidate for the lead screw nut. This is not the case. I hand-selected the nut. I am considering using JB Weld epoxy to permanently bind the nut in the seated position, and not use the nut hold-down screw. I would hold the nut in place using a M8 1.25 bolt and temporary opposing nut, to make reasonably sure the lead screw nut stays on axis while the epoxy sets and cures.

2. The linear slides want to "stick and walk" slightly during both ascending and descending the x-axis, essentially causing the extruder to wobble roll about its y-axis -- if it had a y-axis. This also impedes x-axis homing and subsequent calibration. There is some play in the slides, in yaw, pitch, and roll -- not a lot, but I think enough to prevent calibration. I have yet to prove the walk is a calibration show stopper, because problem 1 above, impedes accurate measurement. I applied a lite dose of 3-in-one oil, but it does not help. I experimented with different loads, both positive and negative. The wobble is not caused by the weight or moment of the extruder and extruder arm.

What did you do to fix these problems? How do you increase the size of the slides to take out the wobble? I considered using JB Weld (or other brand) epoxy to add dimension to PLA bearing surfaces, then filing them to fit more tightly, but the coefficient of friction between epoxy and the Aluminum extrusion is prohibitive. I used waxed dental floss on the x and y-axis to solve a similar problem, but I think the geometry of the fixed z-axis slides makes it impossible to wrap dental floss.

Help me Obi Wan. You're my only hope? :-)
1. Maybe a second screw opposite the first would help.

2. Check that the z inner slides are snug.  Also check that there is no wobble in your threaded rod or coupling.

3.  You might try a better quality bearing, or use two thrust bearings.  To get started, you should be able to push the z down when in the home position.  It is all up from there, so backlash shouldn't be an issue.

Good Luck
Simply clever. Thank you Dave. I am thoroughly enjoying this.
I finished building my Pocket Printer a few days ago. I am calibrating it now. I have a question about xy axis scaling. Here is my thinking.

1. Both x and y steppers are 200 steps/revolution.
2. Both x and y pulleys are 15 mm diameter.

If I did the math correctly, I come up with 200 step per revolution divided by (Pi x 15 mm) pulley circumference ~= 4.2551 step/mm

That is a HUGE difference between the default Marlin scale of:

DEFAULT_AXIS_STEPS_PER_UNIT   {78.7402,78.7402,200*8/3,760*1.1}

To confuse matters more, when I advance "10" units from Printer Interface, the Pocket Printer responds with an actual displacement of about 12mm, which is pretty close to what it should be, suggesting my calculations and reasoning are way off.

What am I missing?
 If you are using the 24 tooth pulleys with 2 mm pitch, the travel distance is 48 mm/rev.  If your board is set up for 1/16 stepping, you actually have 3200 steps/rev divided by 48 = 66.666 steps/mm.
I will be installing the xyz-axis optical limit switches soon. I am assuming a right-hand coordinate system, where the optical limits switches close at position zero.

Here are my assumptions, Let the y-axis points north and south, east is on the side of the y-axis motor, west on the z-axis motor side.

x-axis - positive counts toward the west, zero origin on the far east
y-axis - positive counts toward the south, zero origin on the far north, closest to the z
-axis vertical extrusion.
z-axis - positive counts upward toward the ceiling, lowest relative point is zero origin.

Does this seem reasonable?
FYI, I temporarily scrapped my optical sensors, and replaced them with smaller mechanical micro switches. I was running into too many space constraints with the optical switches. The circuit boards are too large. From what see from others, this is a common issue.
This is a little confusing. Let me explain this way: When at the origin, the extruder is in the SW corner of the build platform according to your terminology, at the extreme left of the platform. The build platform is to the right and towards the z axis. Positive x the platform moves left, the extruder moving to the right relative to the table. Positive y the platform moves toward you away from the z axis, the extruder moving towards the rear of the platform.
It seems I'm on the right track for a right-hand coordinate system. I can see what appears to be part of a z-axis limit switch near the base of the vertical extrusion in one of the photos. I cannot see the x or y switches, so I'm assuming you found convenient locations hidden from view, at the far ends of x and y travel.

BTW, I've nearly completed construction. All that remains are the limit switches (I'm using optical), and electronics installation. It's really a nice looking product. The mirror print bed surface gives it a special look. I'll be posting notes and photos soon. I've started writing an eBook about t
he pocket printer.
You are right about the limit switch mounting. The x limit bracket is shown on the Hybrid Exploded pdf, #21 on the parts list. I used mechanical switches, which are pretty small. Looking forward to seeing your finished product. Sounds like you may be printing soon.
What distance should I raise the heated aluminum print bed plate from the PLA x-axis slider plate? I'm concerned the bed heater might warp the PLA x-axis plate.

Also, I'm considering using a glass mirror plate over the aluminum plate. Thoughts?
Use at least 1" long screws to attach it. It must be high enough so that the extruder will reach the bed when z is at minimum. Heat will not be a problem at this height, at least with PLA bed temps. I have very good luck with the aluminum/mirror print bed. Be sure to ground the aluminum plate if using a 120 V heater.
I modified the x-axis slide assembly. The bearings pinch the y-axis rail far too tightly, and when I did manage to get the bearing posts to flex enough, the bearing posts that share the rail guides lift and rotate the guides enough to significantly bind the slider. There is a larger bending moment on these posts, because they are longer than the opposite posts. The opposite posts have to be shorter to clear the x-axis motor mount. I think the longer posts will always bend farther sooner than the shorter posts. I drilled out all four bearing fastener holes, and elongated the bearing mounting holes on the short posts, increasing the spacing between opposing bearings so that the overall pinching force is just enough to keep positive pressure against the rail. I used longer fasteners with locking nuts on the x-slide mount. It's temporary, until I can print an improvement.

I'm curious if anyone else has run into this, and what the fix was.
The y-axis idler pulley appears to be about 5mm too high. It will not align with the y-axis belt. The 5mm offset is too much to cut from the end support, so I'm going to drill new blind extrusion holes in the end support, and drop the end support enough to bring the pulley back in line. I'll have to add 5mm pads to the rear feet to level the printer. Has anyone else run into this, or did I make a mistake in the assembly?
Your problems stem from changes I made to give you a larger print area. I should not have made those changes without building them myself. I think this printer is best used as its original design as a small, portable machine.
I think this is going to be a great printer. Little glitches like this are to be expected when operating on the cutting edge. Being able to create prototypes rapidly like this is a wonderful thing. Electronic systems became softer with programming. Then electronics itself became soft with programmable logic cell arrays. Now mechanical components are soft. Before long, we will be printing polymer transistors and carbon fibers. Yeah, rapid prototyping is cool.
I started aligning the z-axis tonight. Do any of you have a favorite technique to align the z-axis? I'm still experimenting, but I made the following "obvious" observations.

Errors are most noticeable when the z-axiz slide travels toward the highest and lowest positions.

The fastener holes in the PLA parts are not perfectly located. Some reaming is needed I think.

The flex motor coupling hides errors. I think it's a good idea to pre-align with the threaded rod float
ing or hovering over the coupling bore.

The z-motor shaft and the z-axis threaded rod and bearing receiver are mounted on different rails, and the rails are neither coplanar nor perpendicular in practice. How do we deal with this? I squared things up during assembly the best I could, but I wonder i
f it's enough.

The z-axis motor mount may not be flat .

My threaded rod is black steel with sharp threads. I cleaned up the threads with a die. Because only threads contact the inside do the flex coupling, it slips easily. Some clutch action might be desirable to prevent disasters, should binding
occur, but since we do not have position feedback, slippage could cause z-axiz errors or even print head crashes, as the advance fails to match the print. So, how do we prevent z-axis slippage? Thread filler?

How do we measure the threaded rod parallel and perpendicular planes? When they are severe
ly off, I can feel the extra drag at min and max height, while turning the z-axis motor with my fingers, but that's not a very good measurement.

Ideas?
To align the z axis I like to get it in about the right position by measuring. Run the z all the way to the top, loosen the screws on the bearing bracket/handle and move to position where z screw moves freely. Ream holes in handle if nececcary. Run z all the way to bottom and adjust motor. Repeat if necessary. I have stopped using the spiral cut aluminum couplings because the last 5 I bought had the shaft hole bored out of alignment. They all wobbled when installed on the motor without the leadscrew connected. I use either the resin or alumunum couplers from Misumi with good results. They have set screws which grip the leadscrew better than the clamp style.
I think I have the z-axis aligned now. My coupling may also be out of true, but other than that, the z-axis drive looks good to me.

Here is how I aligned the z-axis.

I measured x and y deltas relative to the z-axis rail, to the threaded rod starting with the top, with the 608zz bearing removed, then proceeded to duplicate the x and y deltas near the z-axis motor, with the z-thread at the lowest possible position. I found a li
ttle surprise. The z-axis motor would not allow me to pull in the y delta. The body of the motor was flush against the horizontal apron rail, the rail with the two rear PLA feet. I have a theory if you are interested. I removed the apron, and elongated the holes in the brackets, so that the apron co
uld be adjusted away from the z-axis rail by about 2 mm max. Since the z-axis motor is attached to the apron, I then had some room to adjust the y delta. I made sure the apron rail was square with the z-axis rail. I then reamed out the holes in the bearing bracket/handle so that the 608zz bearing ea
sily dropped in without adding friction to the threaded assembly. The threaded rod feels smooth throughout full travel. Nice.
Thanks Dave. I'm starting to understand the z-axis. There are many more degrees of freedom than I first supposed. For example, the z-axis PLA motor mount has a large moment arm from the extrusion fasteners, to the motor shaft, so any non-flat protrusion from plastic "burrs", can tilt the threaded rod significantly.

My motor coupling looks okay, but I have not run it out yet. I located some Misumi couplings that look promising. I'll order a few samples to try out.

When I was a kid, I used Tygon or rubber tubing to couple my motors to drive shafts for model boats and cars. I did this mainly because my alignme
nt was usually not very good, and tubing was very forgiving. Why exactly do we use flex couplings on the Pocket Printer z-axis. Is it because of alignment, shock, or both? I guess with belt drives, we have built in shock, but with threaded drive, something has to give.
Hi All.

I'm making progress building my new Pocket Printer, but I'm stuck on a problem with x-axis slide binding throughout the range of motion. The x-slide mount pinches all four bearing on the sides of the 20-mm Misumi extrusion. It looks correct, but I think the pinching force is too great. Nothing els
e is binding that I can see - certainly not the PLA rail guides. Loosening the guides make no difference. I experimented with a single rail with same binding problem.

I see no easy way to reduce the bearing pinch force, assuming that's the problem. I suppose I could fill the bearing fastener holes,
and redrill and tap, but I can see in my mind's eye, the drill going where it wants to, with or without my drill press. Perhaps I could remove the bearings on one side, and kludge a fixture to reapply an adjustable reduced bearing pinch force.

Any suggestions will be appreciated.

Thanks in advanc
e,

Ron
Ron,

You could try drilling the holes to about half their depth with a larger drill, first on one side, the the other if the bearings are still too tight. That should allow them to spread apart slightly while still maintaining enough thread to hold them in
That's a simple solution that makes a lot of sense. Afterall, it was designed to be a cantilever spring post, correct? Drilling the hole reduces the spring forces I guess. Lets it bend farther.

I thought about applying a heat gun and bending the post, but I don't have the experience yet. I envisioned my results, and it wasn't pretty.

I also considered removing the two bearings on the inside of the slide, and replacing them with a single bearing centered between the vacant posts, support
ed with a springy lever with a slotted position adjustment. The lever rotation axis would be parallel to the slide plate or print bed. The lever would have to be small enough to clear the carriage works. Later, after I could print, I would print another slide with tweaked post positions - or somethi
ng. Being able to print, changes everything.
Correction. The lever rotation axis would be normal to x-axis bed, such that the fulcrum would be a pin or screw through the bed.
The bearing support is meant to flex. When designing a larger x carriage for your larger size, I added a buttress to each bearing mount for a little added strength. I shouldn't have done that. If the drilling doesn't solve the problem, I will go back to the original design.

I have tried using just 3 bearings, but it did not provide enough stability. A spring lever might work, although I tried several variations without success until I came up with this design. I am sure the design could be improved, but I use my printer almost daily and it has held up well.
I discovered the source of the x-axis binding. It was not the bearing post spring force like I thought. I originally loosened the PLA guide fasteners to eliminate the guides as the source of the binding, assuming they floated, then "bore sighted" the length of the extrusion, looking for changes in the air gap. Tonight however, just to avoid butchering the slide unnecessarily, I tested the slide and bearings over a single rail, without the PLA guides, the slide inverted, flat on the bench. The slide moved freely (yahoo!). I feel silly for having missed something so obvious, but it was not obvious to me at the time. I think the bearing rims were breaking against the slides. The bearing, being typically out of round, exhibited near friction free movement for about 4 mm, until binding again. Dave, I think you invented a really cool miniature break pad. Keep that filed away. I'm sure we'll need it someday.

Out of curiosity, I took some measurements with the "break pads" removed. I held the rail and slide vertically, while balancing a disposable plastic cup on the rail, carefully filling the cup with water just enough to overcome the stiction. It took 1.5 dL of water. That's about 5 oz of force, assu
ming gravity is working correctly in the Great Northwest. That "feels" high to me, but I have no other data to compare.
I'm still having trouble with the x-axis binding. I can tweak the rail guides and get smooth action, but after a couple test slides, the assembly jams. I still think the rails are acting like break pads because the bearing post spring force is too high.

I have not yet drilled out the posts as you had suggested. I'll go ahead and use the drill trick, but I was wondering if it made sense to file off the bearing post buttresses, to give them more flex like you originally intended.

What do you think?
I have a question about the horizontal extrusion attached to the back side of the z-axis extrusion. I'm not sure what to call the backside extrusion, but the rear feet are attached to it, so l'll call it the "apron" for now. Feel free to correct me.

How does the apron attach to the z-axis extrusion? In other words, how do we make a perpendicular connection with extrusion?
I use Misumi right angle brackets for this.
David, your vertical printing experiment at (http://youtube.com/watch?v=4tpOokI6_Z0) looks interesting. I have a future need to print unsupported horizontal surfaces.

What did the print quality look like up close? Was the bracelet functional?

We often dealt with gravity and print nozzle misdirection in the 2D printer world. We compensated with time-of-flight, drop mass, drop viscosity, firing time, etc.

In our new 3D world, do you think we could compensate fo
r gravitational trajectory by managing viscosity and x-y position, or do we need a more clever solution?
I did't spend too much time wth vertical printing. It was more just wondering if it would work. The print quality was equal to horizontal. Since the extruded plastic is adhering directly to a solid layer, I don't think gravity plays much of a role. It later occured to me to try a bridge test, but I have never taken the time to do it.
I now have most of the parts to build my new Pocket Printer hybrid.

How exactly does the z-axis extrusion fasten to the base (y-axis) extrusion? (I have the coordinates right, correct?). It looks like a butt joint, which implies I must use brackets. I don't see any brackets in the photos or drawings. It looks like Entropy85 used brackets in his derivative. I would
think we need brackets both fore and aft, to insure a stable joint.

Can you please advise?
Is this a "blind" butt joint that requires drilling through the y-axis base extrusion to match the z-axis extrusion end taps? The Frame_Exploded.pdf may suggest so.
Yes, that is correct. I used three blind screws, HTJ5, to secure the butt joint. That requires drilling tool access holes in the Y axis. You could fit in a couple of angle brackets on the front side, but I did not need them. The Frame Exploded.pdf on the Aluminum Mendel thingiverse.com/thing:16076 shows a detail of how the blind screws work if you need clarification.
Aluminum Mendel
Thanks Dave. That clears things up a bit.

Some Misumi docs, e.g., us.misumi-ec.com/pdf/fa/2010/p2389.pdf
, suggest the end tap need not be tapped. Are the Misumi blind joint screws self-tapping? Do you prefer to pre-tap them?
They are self tapping, but a little oil helps.
Yesterday, I finished ordering the last of the parts for my new Portable Printer, including the controller and power supply, plus selected spare items. I just have to click my shopping cart "ship" button for the Kapton tape and a set of metric tap and die . This really is too much fun.

BTW, I was fortunate enough to get the two Raspberry Pi computers I ordered. The "Pi" is a business card sized computer that can run Debian Linux. I will eventually run my 3D printers using Pi computers.
I have a few questions about the print bed.

It looks like many people apply Kapton tape over the surface of the print bed. Kapton tape is a technological marvel, and justifiably expensive. Do you guys have a favorite vendor that delivers Kapton tape at a great price?

Do you ever have issues at the seam, where the wide strips of tape meet?
For example, do you get undesirable print artifacts when the printed object touches the tape seam, or is it negligible?

Some people suggest using glass plate over the surface of the print bed. I'm not sure that is a good idea, as the glass may not conduct heat very well.

Your thoughts would be app
reciated.
Kapton on an aluminum bed with a silicone heat pad underneath has worked well for me. It is expensive, and easily damaged. The seams do leave small mark. My vendor has always been Ultimachine. I saw a suggestion a few weeks ago for printing on a mirror. It seemed like the metallic coating could help heat transfer between the aluminum plate and the glass. A local hardware store cut me a few pieces, but I never really tried it until tonight. The results of a few small print jobs were quite good, so I may use this for a while. It is a perfect durable surface, and with the mirror you can really see the first layer as it is going down. I clipped it to my bed with some binder clips. I have also tried a piece of plexiglass from a storm door. The part stuck so hard I could hardly get it off. Maybe it would work if it were not heated. The glass definitely adds mass, so we'll see how it works on some faster prints.
Thanks Dave. A mirror? Sounds innovative, clever. Got t' love this open source community.
I would like to order additional Misumi die cast brackets to keep in my inventory, mainly for test fixtures and other kludges. An assortment might be nice. For starters, what Misumi part numbers do you guys use for the Pocket Printer rear support? The term "die cast brackets" gets zero hits on the Misumi site.

Extrusions are too cool. I thought up a hundred uses last night when should have been sleeping. :)
The ones I use are HBLFS5 for 20mm and HBLFS6 for 30 mm extrusions. You can find more brackets at

Automation Components
&
gt; Aluminum Extrusion Components
&
gt; Brackets
I have some questions about filament.

I plan to use the recommended Prusa Stepper Plastruder Kit for 1.75mm filament. It appears to me that narrower 1.75mm filament might provide smaller streams/drops per step, resulting in better resolution. I helped design hp Color DeskJets, and small drop mass, among other things, helped us produce
high resolution photo quality prints. Your thoughts on 1.75mm filament would be welcome. Why do you guys prefer 1.75mm filament?

Do you ever switch to thicker 3mm filament? If so, why do you use wider filament, and how do you configure the 1.75mm extruder to accept 3mm filament? Or do you?

Who is
your preferred vendor for filament?
When I started printing, I chose to go with 1.75 mm filament for the very reasons you stated. I have never tried 3 mm, so I can't speak to how it works. I'm sure people are getting good quality prints with it. If you want to make your own extruder, my guess is that it is easier to hob the bolt for the larger filament. I have always gotten my filament from Ultimachine.
Here are several BOM questions for a Pocket Printer I'm building. I want to extend the length of each axis to create a larger print envelope. I'm an electronic/firmware engineer, not a mechanical engineer, so please bear with me :)

I how can I locate the end-stop datum points on each axis? Once I know the end-stops, I can verify the current print envelope, and calculate my desired envelope, given the longer extrusions.

BTW, I'm thinking of adding approximately 50mm to x, y, and z axis.

I assume the cantilever beam (part 23
in the exploded frame) allows the calibrated placement of the print head (extruder) nozzle to rest over the center of xy bed, when both x and y axis are at 50% full travel. How much longer should I extend the cantilever beam to guarantee nozzle placement at the extended xy bed center?. I guess I ne
ed datum for part 23 as well.

Now for the fun part - the belts. Now I studied statics and dynamics under Dr. Meriam, the man who wrote the text books, and I did pretty well. But my point is, that was a long time ago.

The y-belt looks easy. Do I simply add twice the extended y-axis length to the be
lt circumference?

The x-belt looks complicated. Would I add four times the x-axis length to the belt circumference?

I'm comfortable with firmware, so after I get my Pocket Printer working, I would like to try the alternative "more efficient design" depicted in the pulley arrangement. Could you sim
ilarly help me with the alternative pulley lengths? The Y-axis looks the same in both configurations. True? The X-belt looks very different. Not sure where to start, and I pulley block dimensions are a little fuzzy to me.

Thanks in advance,

Ron
If you wait until tmw, I will post my pocket printer derivative. I've extended the frame to fit a 200x200 Prusa PCB print bed.
How is the 200x200 bed working?
Fanstic, I look forward to seeing that project.
I uploaded it as a derivative. Check out entropyprojects.blogspot.com for the full details. Thanks for the inspiration!
Thank you Entropy85.
Ron,

The measured travel on my current build with the extrusion lengths listed in the BOM is: x = 120mm, y = 100mm, and z = 70mm. The extra length you get should add directly to the travel on each axis. The beam for the extruder will have to be extended the same amount as the y axis. The extruder plate allows quite a bit of adjustment for fine tuning.

I never got the "more efficient design" fully implemented, so I strongly suggest that you use the hybrid roller slide upgrade, and my x and y belts are about 465mm and 525mm respectively. If you are adding 50mm to each axis, each belt will be 100mm longer. If you buy the suggested Misumi GBN9942GT-60 belts, they are 994mm long and are cut to length required. I got both my belts out of one, but 994mm is the longest in this series, so you will need two. For your larger build area I also suggest using the Pololu #1209 stepper.
It looks like the Pololu 1209 stepper comes in several variants/torques: 2.5 oz-in to 44 oz-in, in various steps. The 44 oz-in appears similar to the Kysan 1124090 Nema 17 steppers, close to the same mass, 340g vs 350g. I assume we want to reduce the inertia of the top-most axis (x-axis), which suggests to me I need to choose one of the smaller variants of the Pololu 1209, e.g., the 20 oz-in variant, with 20 oz-in which weighs 180g.

Can you please advise?

BTW, I already ordered three identical Kysan 1124090 Nema 17 steppers, for the x, y, and z-axis, assuming I could boost the height of the feet for the large x-axis motor. If the x-axis motor produced too much inertia, I could switch to a smaller motor, e.g., one of the Polo
lu 1209 variants.

What are your thoughts on this? Is the large Kysan 1124090 Nema 17 stepper too heavy for our x-axis? Will the x-axis motor overshoot too much, skip steps, etc?
My bad. The Pololu 1209 does not have variants. Selecting the variant, changes the URL and subsequent part number. The Pololu 1209 delivers 20 oz-in torque, and weighs 180g
It looks like the longest printed part is the x-slide mount (part 17), or the x-slide hybrid mount (part 13). The one I have in hand is approximately 180mm long.

Two questions.

1. The x-slide mount I have in had looks different from both the exploded and hybrid exploded views. The tabs appear longer than in the view or the STL file. Which x-slide mount should I be using for the hybrid model?

2. I would like my Pocket Printer to be able to reproduce its p
rinted parts. The long slide mount I have in hand is 180mm long. I was planning to increase my print envelope to x=170mm, y=150mm, z=120mm. I obviously need to increase the x-axis travel something greater than the slide mount (180mm). I know Entropy85 increased his print bed to 200mm x 200mm. Given
the current design, what is a reasonable print envelope for this design? Is the 200mm x 200mm bed reasonable?
Actually, it looks like the x-slide mount length due to the tab lengths are somewhat arbitrary - just a convenient bed mount. That would imply I can print a shorter slide mount. True?
I decided to stay with the plan, and extend the print envelope 50mm in every direction. I should be able to print the x-slide, as long as the tabs are not too long. I ordered all the extrusions. It should be easy to add longer extrusions and belts later if needed.

On the lighter side, I've been thinking about a special sound effect for my first print -- maybe in a month or so. I'm considering the opening stanza of Eric Clapton's Layla. I can hear it now! :)
Extending 50 mm on all axes sounds wise. I did modify the x slide for you and made the tabs longer. The way I set up the build plate, the mounting screws are outside the normal print envelope. Therefore, the space between the screws is longer than the Y travel. You might be able to make a different style mount that would get around this limitation. I had never planned to make this a true reprap, one that could reproduce itself. Adding that constraint didn't make sense. All I wanted was a very compact, portable printer. If you want a larger printer eventually, you small printer could print an Aluminum Mendel, everything but the vertical braces.
I am anxiously waiting for the new BOM! lol I purchased all of the extrusions so far. I'm making my build area a little larger so I can take advantage of the Prusa PCB HBP. Is the X axis motor a NEMA 17 or 14? If 17, what is the torque on a small motor like that?
I'll work on the documentation this weekend. The x motor is a NEMA 14, from Pololu - #1208. It is 28 mm high with 14 oz-in holding torque (compared to 44 oz-in for the standard motors). You might want to use the Pololu #1209 which is 36 mm high with 20 oz-in holding torque with your larger platform. That motor weighs 1.4 oz more, but is still about half the weight of the standard motor. You would have to increase the height of the feet 10mm to have clearance for the larger motor.
Awesome thanks! I have a '14 with 26 oz-in. I'll have to check out the height on it. How important is PLA for the slides given the new hybrid design? I don't have any PLA currently, so I was thinking about printing it in ABS. Thoughts?
I haven't tried ABS for this application, but I think it should work. There is actually very little weight on the printed part of the slides. Try it and let us know how it works.
Will do. How were the shipping prices from misumi? (In the US)
Shipping for all the extrusions, plus hardware and pulleys was $13.20.
Misumi order is place and on its way. I increased the extrusion sizes by like 30-40% to compensate for the larger bed. I may need to cut them down a bit.
Something seems a little off. I printed the Y roller slide from the hybrid roller files and I'm not seeing how it matches up to your updated exploded view/BOM. The Y slides in the exploded view look much different
It seems the y slides shown on the new exploded view are the same as the derivative you made. The y slide included in the "hybrid roller files" is different?
So sorry, I had an old file for the y slide by mistake. You are right, the y slide is s the same as the derivative. I am uploading a fixed version with the right part.
No worries. I was just confused and thought originally that slic3r sliced it weird or something. I'll proceed with the other design instead. I may need more help as I start the assembly process.
FYI youtube lets you rotate videos. When logged in, go to your video page with the sideways video (when you are logged in)"

youtube.com/watch?v=4tpOokI6_Z0

And click "enhancements" at the top. There is an option to rotate!
Hey thanks. Got it fixed.
This is really a professional job. BOM and drawing is top shelf. We are going to use this as a project at the HS STEM lad where I am a mentor. Well done! Looking forward to the CNC mill design.
Is it possible to save this as a file which can be opened in Inventor 2008?

Thank you

:)
I checked with our Autodesk person, and he did not think this could be done. Maybe another user could help us find a workaround or knows how to do this.

Sorry
Try saving in STEP or IGES? Either of those are very portable.
Will do, thanks.
Would a long drive shaft and a sliding pulley (dragged with the X motion) work for the Y?

I like your idea of dependent coordinates and handling that in the firmware. It should be a trivial change. For linear motion, you could just hack the positions with a post process of the gcode:
#!/usr/bin/perl
while(
&
lt;
&
gt;)

{

if(/^(.+s+X)(-?d+(.d*)?)s+Y(-?d+(.d*)?)(s+.*)/) {

print("$1$2 Y".($4 - $2)."$6n");

} else {

print $_;

}

}

:)
A post process of the gcode sounds like a good idea. I am afraid I do not know how to implement your script. Is there a fairly simple explanation of how to use it? I can do a little programming in the Arduino environment, but that's about it. Would it be possible to translate your script into C and insert it into Marlin or Sprinter? I nearly have it working in Sprinter, but it X drifts off slightly on each layer so it doesn't print quite vertical. Maybe its a rounding error when it calculates its position.
Assuming you save that text to foo.pl:

cat thing.gcode | ./http://foo.pl
&
gt; new_thing.gcode

It should be pretty easy to verify with diff (or tool of your choice). The regular expression syntax, which is most of that script, is fairly similar across languages.

A guide to basic regular expression syntax:
http://en.wikipedia.org/wiki/Regular_expression#Syntax

Try the hackish script firs
t, and if this does the trick, then it should be trivial to integrate something like this into whatever tool you want (or the firmware).
Thanks for your help. I will give it a try.
I love the design of this, looking at getting a 3D printer for my schools engineering workshop and this works in a similar way to our CNC milling machine. Would be great as the students can see how this works which isn't possible on the mill and get an understanding of both mechanically.
You know, if you could add an automated build platform to this it would be the basis for a phenomenal little manufacturing facility :-)
This design is begging for a dremel or router attachment to make it a mini mill. I could use a small sawdust producing device, and now I have a good start. Thanks, Dave!
Hey thanks. I agree. As you have noticed, the layout is a cnc mill. I am working on a heavier model for circuit board mill that will also cut soft metals.
I think with a flexible shaft attachment for a router, you could keep the design largely the same. Flex shafts don't hold up to heavy use, but I think it would work for circuit boards and soft woods.
Im currently mounting my flexible shaft on my huxley MD printer and works well. Still need to play with designs before upload, but yeah, it works!
Is it possible to eliminate one of the Z steppers? You should be able to mount the Z in the middle somewhere.
Actually there is only one z stepper. The x,y, and z are all lined up along the back.
working with stepstruder mk 7?
I have always used MakerGear and had good luck, so I have not tried anything else.
I love the shape of this printer. That photo of it being carried by hand is really awesome! This really seems like the ultimate in portability.

I am probably asking for too much, but did you happen to measure the weight and power consumption of the machine?

This is very high on my list of printers I would love to have given enough time/space/money.
This printer weighs 9.5 lbs (4.3 kg) versus 19.5 lbs ( 8.8 kg) for the Aluminum Mendel. The power is probably similar, given they both have RAMPS and the same motors and extruder.
Hi could you please add a DXF of the extruder plate so that this can be cut on a laser cutter?

Much appreciated for your Pocket Printer.
Sorry, Inventor wont export DXF files. Will some other format work?
inventor does= right click surface -
&
gt; export face
Thanks for the tip, see uploaded dxf file.
Would there be a significant disadvantage to mounting the x motor to the x axis (or y on the y) rather than having it stationary with the pulley system? You mentioned increased resistance, would this be similar to the resistance of increasing the weight? Just curious. Love the design.

Also, in the firmware, if you knew of much the x would change based on y G-codes, you can have the firmware calculate it's own G position for x. i.e. x needs to move back 1 for every 5 that y moves forward so when the firmware gets a 5mm movement for y it also moves the x back 1. You would have
to have a linear relationship between x and y movements though.
I think keeping the moving mass low is critical for high speeds. The accelerator firmwares are great at reducing jerk, but it is still an issue. I notice a big difference between my mendel and this printer running the same file. The mendel will shake the workbench, the pocket printer is much smoother. Watch the video of the pocket printer on marlin, with fast travel. Also I want to minimize forces on the pla slides.

Conceptually it is pretty simple to combine x and y, but it is pretty difficult in practice. I will keep working on it so that the friction can be reduced in the belts.
Hey, this is the one, great idea and great design!!!
Fabulous printer, now this is the one I want to make after I commission my Prusa, it was going to be a Medel90 or Wallace, but this has to be the one. When can you add the missing parts that you mentioned? Limit switches, Power supply and switch mounts. I like the way the controller is hidden behind the printer with the PSU above it and a nice power switch on the side, this is really cute and I want to make one!
See the new zipped file of accessories. The power supply bracket and the x limit switch bracket I made out of scrap aluminum angle, and don't have any drawings. let me know if you need more info
Many thanks, I will look at the way you implemented it in the photos, but any help

making these parts would be useful. Thanks again
This is great! We have been working on an HBOT design that I believe would work for your machine. We have a friend that helped us with the correct firmware

you can check out the Hbot prototype here: phlatforum.com/viewtopic.php?f=294
&
amp;t=3495

as for the firmware you will need to talk to Jovian on the Phlatforum, unless he finds you here first :) You could always shoot him a PM there.

Great job on this cool machine
Thanks, I will join your forum and find out more about what you are doing. I am making a CNC micromill for circuit boards and soft metals. It is a heavy duty version of this printer with lead screws instead of belts.
This is looking so awesome! Can you make a video with it? Would love to see it move around too!
I posted a video, see link above.
Maybe add a belt to it so you can carry it with you on your sholder? Add a battery and you can carry it with you while it's printing!

See Joris: blog.ultimaker.com/wp-content/uploads/2011/10/2.jpg
Looks like a great printer!

Makeslide is another good choice that integrates the slides into the extrusions.

inventables.com/technologies/makerslide?selected_variety_id=32854
I agree. I have a design for a MakerSlide version, but I need help to modify the firmware so that the design can be implemented.
I cant see how the x axis moves left to right acuratly when the y axis is moving forward and backwards. does the firmware cause the X motor to turn in order to compensate for the movement of the y?
I posted a pdf of the belt/pulley arrangement along with an explanation. The present design automatically compensates for y axis movement.
Absolutely great job! Thanks for sharing!
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