My RepRap lives!!!

It’s been forever, but I’ve finally got my RepRap printing in a usable format. I still can’t make small prints — I’ve got issues with my extruder not extruding smoothly which I don’t think can be fixed with anything other than a new extruder. I also see why people use T5 pulleys instead of printed pulleys — my printed pulleys are quite elliptical — though less so than my previous pulleys.

I’m actually getting excited by Junior’s Resin Printer. I’d love to get better resolution parts than is possible with my RepRap. Nonetheless, it’s still cool to watch mine in action:

My RepRap almost fully printing

Hi All,

My RepRap is almost fully working. I only have a single issue left to fix. Getting the “blobs” out when I print. Any thoughts on how to do it?

A layer from my reprap with blobs on it

How to un-deform a Medela bottle

We use Medela bottles that came with our breast pump. One thing we don’t like about the Medela bottles is that they deform under heat — like when you’re warming milk to feed to your baby. We’ve learned how to un-deform the bottles. We also switched to Ameda and Evenflo bottles for cold storage. They don’t deform when heated.

I’m assuming you’re trying to un-deform ( restore ) a bottle full of milk, rather than an empty bottle. An empty bottle is easy — open it, toss it into boiling water, blow into the hot bottle, rinse in cold.

1. Heat the bottle up to the same temperature as when it deformed. You can also use boiling water, but that’s overkill. You use the hot water for avery short time — just enough to heat the bottle surface, not the milk inside. If the bottle has deformed, the milk inside is too hot to feed to baby!
2. Open the lid a little — not al the way, or you risk spilling milk — just enough to let some air in.
3. Gently put pressure on the sides of the dents. They’ll slowly move, then suddenly “snap” at the end.
4. immediately rinse the sides with cold water. You can also put it into a cup of cold water. Be careful not to let the water enter the bottle.
5. Remember, the milk is too hot to feed to baby, and will re-deform the bottle if you grab it hard. Do not put pressure on the bottle, and wait until the milk has cooled to a reasonable temperature. The bottle will be fine then.
6. We’ve found the bottle is not damaged by being de-formed. Once you restore it and cool it back to room temperature, it will work just fine. It will de-form whenever it gets too hot.

Why we don’t invent.

Steve Denning recently wrote a Forbes Article about Why Amazon can’t make a Kindle in the US, even if it wanted to.

He essentially wrote a general version of what I had perviously written about when I was lamenting howmass scale up of the RepRap project can only happen in China.

for the most part, Steve’s article is on target. But he’s missing the bigger picture. He thinks that the problem is a cultural one — the Culture of accountants, CEOs, Economists all following short-term interests. He doesn’t realize it’s not a cultural problem. I have training as an Economist. We Economists don’t believe in cultural reasons — we think that all people respond to immediate incentives. We believe that humans are naturally impatient, and naturally self-interested. We call this person Homo Economicus.

Homo Economicus is fully rational and self-interested. (S)he will always follow the immediate, self-gratifying response. And I see evidence this is correct — How many people do you know who, if they lived near a free wi-fi coffe shop, would drop their own broadband to abuse the coffee-shop under them? How many people pirate music, software, or movies online? If people can get something for free, they will do so — even defend it as just, even if it meant harming the artist. It doesn’t matter how much money you have — Thomas Edison was a pirate!

The problem Steve mentions is real. Already, in my RepRap, I’ve had to run into people who know where to order hard to find parts in China. Hard to find here in the US — but awash in China. Linear bearings, Shaft couplers. Hollow rods. Simple stuff. None of those are in hardware stores here, or can be ordered here. I have to Ebay those parts from China — no-one in the US can sell them to me. I use them in inventing things. My ability to invent is harmed in the US by lack of parts, due to outsourcing of all our manufacturing. It’s hurting innovation — far more than anything else ever will.

The answer is structural — we need new import duties, for a time. We likely need a cyclical duty cycle — sometimes having duties to encourage innovation, and sometimes removing them for the same reason. No import duties hurts innovation, as do import duties that never go away.

Some tips and tricks from my RepRap

My RepRap is no more.  I’ve taken it apart to use its parts for another robot — a hybrid Mill and Printer I’ve designed, called EasyMaker.  Here’s a list of some of the things I did to make my Prusa a more tolerable bot when it was still intact.

1. How to tighten a belt.

Take the ends of the belt and form small loops using zip ties. Connect the belt together by running a zip tie through the loops. This gives you a belt you can tighten on the fly.

2. How to reduce current needs/noise/skipped steps.
Use linear bearings on your smooth rods. It takes 10 for a Prusa Mendel, but the smoothness from bearings means less current needed to move your bed/print-head. I use only about 500ma for my X and Y motors, and I never skip steps on those. My Z and E motors still draw a bit of current, since bearings don’t help as much there. For my Z motors, I’ve found that using a bubble level to level the X carriage true stops me from skipping steps. On my Extruder, I’ve turned up the current and set the spring tension on my Wade’s extruder — this helps it not skip steps. Luckily for me, when I skip steps, it’s pretty obvios — I hear a sick, clicking sound. With micro-stepping from my RAMPS kit, my bot is very quiet — Here’s a video. I can also run my bot fast — the bearings enable very fast motion — I’m limited in the max speed of my extruder.

3. How to calibrate your extruder.
I was writing a PERL wrapper around Skeingforge to modify the G-Code to calibrate my Prusa. It was a very simple script, and it worked for large prints, but not small. Then I learned how to calibrate my  extruder(E).  The method is simple.

1. Take a clear, straight drinking straw and cut it to 100 mm. Mark it at 25mm, 50mm, and at 75mm.
2. Take off your hot end. (Though you can skip this step if you don’t mind a little error)
3. feed 50 mm of filament.
4. Use the straw to see how much you fed. If you fed exactly 50, great! If not, modify your extruder steps per unit in the firmware. For sprinter, it is the last element of the float axis_steps_per_unit[] array in Configuration.h. You multiply your existing value by a fractions — 50 in the numerator, and the measured movement in the denominator. So, if I tried to feed 50mm, but really get 60mm, I would multiply the final element of the array by 50/60 ( aka 5/6th ).
5. Recompile and upload the changes to your electronics.
6. Repeat the last two steps until you get exactly 50.
7. Load your hot end, heat it, and load filament.
8. Feed 50mm of filament.
9. The extruder should feed exactly 50mm of plastic. If you don’t, you’re skipping steps. Increase current to your extruder motor, and/or change the tension on your extruder 608 bearing.

5. How to calibrate any other Axis (X, Y, Z).
Stepper motors work by having a single step being some degree of rotation.  Most commonly, steppers are 1.8 degrees per step.  You need to determine how many steps you need to move your motor 1 millimeter on that axis.  Most people sort of guess, or use the defaults.  But, the method to calculate this turns out to be really easy.

1. figure out how many steps is 1 full turn of your motor. This is easy — take 360 degrees and divide it by your angle per step. Most motors are 1.8 degrees per step, so for most motors, that answer is 200. Some motors are 0.9 — hence the answer is 400.
2. Adjust for micro-stepping. If you have micro-stepping, you’ll need to multiply by the inverse of the microstepping ratio. So, 1/16 microstepping means you have to do 16 micro-steps to get 1 full step.
3. An example for my Motor. I have a 1.8 degree stepper motor with 1/16 micro-stepping(common on RAMPS) you would take [360( the degrees of a circle)/1.8(the angle per step from your data sheet)] * 16(The inverse of the micro-stepping ratio). 360/1.8 = 200. 200 * 16 = 3200. Viola — that’s how many steps for 1 rotation of my motor.
4. See how much your axis moves for 1 full turn of your motor, in the unit of measure you’re using.
5. Divide the the steps for a rotation by the amount moved.
6. Enter that number into your firmware.
7. An example from my Z Axis. My Z axis is a screw axis, so a full turn moves about 1.25mm. Hence, I take 3200/1.25 = 2560. That’s my steps per unit.  You can do more than 1 full turn if it’s small — try 10 full turns on something like the Z axis, then divide the amount moved by 10.  So, 10 turns is 12.5mm.  Which is easier to measure, especially if you have calipers.  The X axis on mine does about 40mm for a full turn — so that comes out to around (3200/40 = 80) steps for 1 mm.

5. Picking and loading a software stack.
I used to use the SF-ACT modified skeinforge to generate G-Code from a model, pronterface to send that G-Code to the robot , and sprinter to run the G-Code on the robot as my software stack.  Now, I use Slic3r to generate,  Pronterface to send, and Marlin to run.  Reptier works really well as a sender, but is a pain to get working on a Mac.  However, if you have a Linux or Windows box, then it is a good choice instead of pronterface.

6. Leveling the print bed.
One trick, and this should just become standard design for the Prusa, is to mount the screws that link your frog-plate to your print bed upside down, and use wing-nuts on the top side to secure it. This way, you don’t need a screwdriver to adjust the bed’s level — just turn the wing nuts. Removing the bed — say to remove a very well stuck on, large object, also become easier this way — the upside down screws become posts that hold your springs in place, even with the bed removed.

7. Mount linear bearings with zip ties.
I use linear bearings in my prusa, to reduce current, help prevent skipped steps, and for better speed/quiet. I’ve found that holes cut into your mounts combined with zip ties provides a nice, easy to remove solution. It allows for relatively quick tool-head changes, though it does turn zip-ties into a consumable. Luckily, zip ties are cheap and easy to get.

8. Upgrade to an EasyMaker.
Really, anyone with any form of RepRap should upgrade it to an EasyMaker.  The design is open source, and up on ThingiVerse.   Still a prototype, and already far better than a Prusa, MendelMax, Makerbot, etc…

Breast Pump Reviews

It’s been almost a year since our little one was born. My wife is an engineer, and has been working since recovering from childbirth. She wanted to get a nice, electric pump for use at work. Something she could conceal and use while working. She got 3 different electric pumps and one hand pump — an Ameda Purely yours ultra was on close-out at the local Baby’s R Us about a year ago, so we got that for a song. It was nice, but the breast-feeding center recommended the Medela Pump N Style, and she also tried out a whisper-wear she got off Craigslist.

She tried many, and decided to use the Medela, but it didn’t do everything she wanted for a concealable, work-friendly pump.

Ameda Purely yours ultra

We liked this unit. The horns on this pump are very good — easy to use and easy to clean, even when hand-washing. The air hoses attach to an area with little mini-pumps for each breast in each horn. This means there’s no way to spill milk when you move around — a very nice feature. The pump adjusts well, and has different settings. It did a good job, and the Ameda bottles are just awesome. It doesn’t have a stimulate feature, and the breast-feeding center in our hospital kept recommending the Medela for this reason. We did switch to the Medela, but the purely yours ultra was a good pump at a good price. You don’t get as much milk out, it seems to us anyway, with this pump. She always felt like there was left-over that the pump didn’t get out, and stopped using this pump. However, that’s subjective — she used the pump earlier after birth than the Medela, and I think she would eventually have gotten the same result with either pump. This pump is not concealable under clothes — but it’s fairly quiet. You might be able to get away with using this at your desk.

Medela Pump N Style

This unit has a nice stimulate feature, which my wife does feel helps with let-down. It also is very adjustable, and the back-pack is a nice way to carry it around with bottles and horns. It’s a bit loud compared to the other two pumps, but it seems to have the most power. The bad thing about this unit is the horns. If you bend over, you can spill milk out the back. The horns have lots of small crevices you can’t reach when hand-washing, even with a nipple brush. We always have to dish-washer them to feel that they’re properly cleaned. The Medela bottles deform sometimes when sterilized or when warmed in a steamer, and their plastic is softer. We don’t like their bottles — the deformation is annoying — imagine you have a crying baby who is hungry. You take the bottle out of the fridge and stick it in a bottle-warmer. The bottle deforms, making getting the cap off difficult, and you have to re-heat the bottle to get the shape right. It drove us nuts a few times. We switched to Ameda and Evenflo bottles using the Medela pump. The evenflo bottles don’t deform, are really cheap, and do a great job not spilling milk when inverted, like when you take the bottle out of the baby’s mouth. My wife hates that she has to sit upright to use the horns, and it restricts her movement a lot. But, it does have the best suction, and she gets the most milk using it. You can’t conceal and use this at work — it’s just too big and too loud. If your work has a mother’s room and you can take a pumping break, this is a good pump.

Whisper-wear

The company that makes this pump seems to be out of business. This pump is worn on the breast itself, and is fully self-contained. No bottles, no horns, no wires. Very silent, and for some very small-breasted women, concealable. If your have normal or larger breasts, it will not be concealable — you’ll get a “Dolly Parton” effect. This pump system is, in our opinion, not very good. Not enough power from the units. Low durability of the units. Maybe it’s because we bought off craigslist, but the units broke very quickly, and we didn’t get to really use it. My wife was hoping for something she could use at work — but this wouldn’t work for her due to low power and the poor durability.

Bottles, horns, etc

As mentioned earlier, we liked the Ameda bottles best. They held up the best in the milk warmer, and had the best overall feel. Coming in a close second was Evenflo. The evenflo nipples are great — better than the ones from either Ameda or Medela, as they don’t spill as much milk when the baby is not sucking. “Born free” is even better for both bottle and nipple, but doesn’t fit the horns for either Medela or Ameda. Evenflo bottles fit both, and are available in glass. That’s great if you’re worried about plastic leaching contaminants into the milk when warmed — glass is the least toxic and most environmentally friendly material we know of in baby bottles. We worry about glass breaking when heated in the warmer, though. It has never happened, but every time we heat glass, we worry. So, we use the Evenflo plastic bottles in day-care, and the glass ones are for at-home occasional use. Horns are another big one. Get yourself sized for your horns at your local breast-feeding center. The ones that came with the pumps were too small, and caused lots of pain for my wife. If you find pumping hurts, your horns are the wrong size. My wife also borrowed a pair of freemies from a friend of hers when we went on an overseas trip. This is the kind of horn that is also a milk storage unit — you don’t use any bottles, but pump and store in the horn itself. These horns are concealable — she could wear them on the plane, and although she looked like Dolly Parton wearing them, the did a good job allowing both pumping and storage. The downside of these horns are two-fold. One — they’re really hard to take apart to clean. Two — they don’t provide as much vacuum as normal horns.

For the horns, invest in a pumping bra. This is a bra that holds the horns, so you don’t have to. We have friends who hold the horns instead of using a pumping bra, and we can’t imagine it.

Anyway, keep your stick on the ice!

OSX Lion Review

I work at a university. As such, I often support new computers when professors purchase them — regardless of platform. Recently, I setup a macbook air with Lion. For the most part, it works just like snow leopard — except that it has a couple of UI improvements and web browser improvements.

1. The new Safari is awesome! Firefox, Chrome, and IE feel slow and outdated compared to safari. I like how safari now has a page stack, and using back/forward buttons just animates a page from the stack. It also doesn’t cause a full postback cycle, since the page was never unloaded, but rather, live cached, making browsing very fast. The back/forward tackpad gesture is now reversed — swipe right to go back, swipe left to go forward. The animation reminds you, and you adapt instantly.

2. Spaces/Expose is much more user friendly. While mac has supported a large virtual desktop, getting to it was a pain, and it looked messy. I hated using it, and so I just turned it off in Snow Leopard. In Lion, the UI improvement has made it a useful feature.

3. Launchpad now exists, but you don’t have to use that view. Launchpad is like tossing in iPad home screen in your dock. You push it, and suddenly you’ve got a desktop full of application icons. I’m not sure I like it — I might. I certainly feel frustration at finding my installed apps in my Applications folder on 10.6. I can see this being a viable solution. It’s better than just tossing a folder in your dock, as it can be organized like iPad’s apps are.

Other than those changes, it looked/felt the same as Snow Leopard. Coupled with the quickness of the AIR, it was a really nice experience using it. It made Windows 7 on a Dell feel outdated and clunky. Fast boots, slick UI, not too much clutter. It was the opposite of Windows — no annoying tray icons, no annoying pop-up balloons. Growl exists — which is a shame. I don’t see why developers EVER need to have “balloon” notifications of any type. Both MS and Apple should dis-allow any apps that do that ever — even their own. I hope Apple’s App store guidelines reject any apps that use growl notifications. Too annoying!