Using Cura on my Reprap

I got a message the other day on g+ from ultimaker letting me know that Cura was available for Macs. Cura is software that does both slicing and printer control. It has some cool features so I decided to check it out.

The install went very smoothly. It searched for a python module that I didn’t have, then installed it for me. That was it.

Calibration was pretty quick as well. Cura and slic3r both are front ends for skeinforge. EDIT – thanks Gary for the correction. They do a bunch of math behind the scenes so that you can tweak one number and have it ripple through all of the other things that number influences. Cura seems to be even simpler than slic3r, but in my experience that has been a good thing. I had to set my bed size, x,y,z, max length, nozzle size, filament, filament size, and possibly a few other things. There is a first run wizard that guides you through the things that you need to change. The one big sticking point is that you (strangely) need to put your extruder steps per mm into cura. I’m not sure if it was in the wizard. If it wasn’t then you can find it under preferences called “steps per E”

The slicer in cura is well laid out and labeled. It is a little slower than slic3r, but gave me better results. It also allows me to tweak things like speed (by a lot) and have much more consistent results.

There is a project planner feature that is pretty awesome. It is a plater, in that it allows you to gang up multiple pieces in one print but it allows you to apply different slicing settings to each piece. Being able to print a wade’s extruder at .2 layers and the gears at .1 on the same bed is really awesome. The coolest thing about project planner is that you can control whether the separate parts are printed individually or all at the same time. I can’t count the number of times that a 3×3 grid of gears will have one gear come up and then it will eventually knock all of the rest free. I LOVE this feature.

There is also a gcode post processor in cura. This has been a staple of traditional cnc software for a long time. I love this. For example: cura was generating a M190 code in the startup. This means that it waits for my heated build platform to get to temp before moving on. I don’t like to wait that long as my apt is cold, and my bed heats up slowly. I was able to swap out all “M190” codes with “M140” and away I went!

You can’t control the printer without sending a print to it. The overall print section seems to be the least developed part of the whole thing. You can’t select a gcode file to send without generating it in Cura. You can however generate it in cura, then edit externally, and then send it from cura. I have also had far more print freezes and line checksum errors in cura than in slic3r.

I’m stoked on cura. I wish it had a bunch of other features, but it seems like it is developed by a person (? /community?) that has been continuing to add new features and push things. I’m sure that there are some things that I’ll use pronterface for. I may even do my slicing in cura and my printing in pronterface. Either way I am glad to have made the leap, and now I have another software tool in my toolbox.

Hack saturday – spend $25 free on amex @ small business

American express has a one a year campaign where they will reimburse you $25 if you register your amex card online and spend more than 25 at a participating small business. Just to reiterate, here are the two rules
1) register your (amex) card online at
2) buy a minimum of $25 worth of stuff from an amex approved small business. Want to find one? Check out their online small business finder.

Just so you know that this isn’t “too good to believe” you can see that I did it last year and got a bunch of free gear from sparkfun.

So here is why this is hacky enough to go up on my blog. The small businesses don’t have to be local to you. They just need to be on the map. I’ve looked for a bunch of my favorite small open source hardware / reprap stores and have a small list. The most difficult part is that you need to know the store’s physical address, and their name according to amex. I’m sure that I have missed some just because they might have their cc account under a different name than their actual store name.

Here’s my list:
artisans asylumn
hobby fever
DIY Drones (3d robotics)
you do it electronics

NOT eligible – post with the zip code and address if you can find that they are actually there. I would LOVE that.
sparkfun :(

It’s not too late to register, and I haven’t picked out my list yet. PLEASE post your thoughts for any hacker friendly small businesses that accept amex, or even better – check them out on the map and post back here

I’ve been busy modeling!

I’ve put together three entries for the engineer vs designer absurd iPhone contest. It’s been a lot of fun, and it’s a great excuse to jump into openSCAD and start actually creating things, as opposed to duplicating things that others have built.

So far I have built a wheeled iphone case with a broomstick handle,

a shuttered iPhone case

and an iPhone trailer hitch!

Check them out on thingiverse, and design some of your own!

rename your ramps or gen6 ftdi serial connection

You can change the name of your ftdi serial connection with a little bit of magic that piotr whipped up. That means that you can have multiple machines connected and give them logical names. In this example I changed mine from the random character string to PRUSAG6.

All of the info is from dangerous prototypes

This shows the app after I selected my gen6 serial connection and hit read

This is what I changed it to. You can’t give it any more characters than I did.

After a restart, my pronterface clearly shows me which serial port I should be using! It’s not a huge thing, but it does help to take a minor annoyance away. When I have two machines hooked up it will be a godsend though.

Note: this won’t work with an UNO, because it uses a different chip.

OpenSCAD tip: How to get formatting.

I’ve been diving into learning openSCAD lately, and it has sometimes been a rough road. One thing that has really helped me has been occasionally copying my script into a blank arduino window, letting it auto-format (command-t) , and then pasting it back into openSCAD. The formatting really helps illustrate where the brackets line up. You could do this with many other coding apps (ie not arduino) but that is the one I have handy, and one that most people who print will have installed as well.



How to monitor your reprap remotely with skype!

I was pretty pleased with myself when I thought of this. It is super simple, but it works well. I have been very nervous to run down to do the laundry, or to check the mail while I am printing. Not that my machine has problems, but I want to be there if it does. I looked into all kinds of different nanny-cams, and streaming webcam setups before I figured out the absolute simplest possible option.

1) Set up a new skype account on the machine by my printer.
2) In the privacy setting of the preferences, configure skype to only allow calls from people in your contacts

3) in the calls section, set it to auto answer calls and automatically start video when connected.

4) add yourself to the contact list
5) call yourself from your iphone!

Now, smarter people than I will pipe in here and say that having an always-on video conncetion on the internet is a setup for disaster. I only turn this on when I am running out of the room for a bit, and I turn it off when I return. The security settings ought to do a good job of not letting strangers peek in on your prints, but I don’t think I will run naked in front of the camera just to be safe.

recovering from a pause in pronterface

Today on IRC Kliment was kind enough to help me figure out something that has bugged me for quite some time now.

Whenever I pause a print in pronterface, jog the z axis, and then resume the print it slows down to a crawl. Kliment explained to me that the z jog sends its own f command, which is a speed setting for the next move. The z axis moves much slower than any other axis, so that when I return to the unpaused print, all of the axis are moving at the (slow) z speed.

Even if my explanation of the problem doesn’t make much sense, the fix is easy. Just jog x or y before you unpause the print. I usually jog .1mm right and then left and then hit resume. Now it starts right up again at the correct speed!

10 seconds away from a quieter reprap

I made this video so you could listen to the before and after. Unfortunately, I’m in there yappin’ for most of it.

I was recently at a reprap meetup and there were two brothers with mendelmax machines there. They were eerily quiet. The printers, not the brothers. I was thinking about it on the ride home today and I remembered that they were also on a padded table, so I decided to test it out.

Now don’t get me wrong. I’m still itching for a mendelmax. This helps in the meantime though.

how to salvage a failed print

Today I was printing a part on my prusa and it stopped extruding. I still don’t know why, but I do know that the printhead was a full cm above where the piece was, and it was happily just spinning along.

Since my part was essentially the same outline at the point where it was as where it stopped extruding, I thought up a quick hack to salvage the print.

In pronterface I paused the printer. Next I got it extruding again. I typed M114 and then enter into the dialog box at the bottom right corner. That sends a command to the printer to report back its position. Check out the Z value that it gave back to you. I then jogged the extruder down until it was just smushing into the print. I typed “G92 Z” ,then the z value from above, and enter.

That tells the printer that it is now at the point that it was really at previously. Since I lost all of that print while the printer wasn’t extruding, it essentially just chops that part out and tells it to start printing on top of the print again. I feel like this isn’t making any sense, so hopefully I can clarify it later. I then hit resume, and watched my new (shorter) print finish up!

Note: as you can see in the top photo, there is a line that is probably pretty weak on that part. A bit of ABS glue will definitely help strengthen that up (while making it look ugly) and I think that if I were faster to catch the stopped extrusion, then the print still would have been hot enough for it to bond properly.

Using a Bowden cable on the reprap prusa cold end

This post is to document something that I thought was fairly standard , but after talking to a few people I discovered it isn’t. Some people (I’m looking at you jkeegan) even thought it wasn’t possible. I have been using thin hdpe tubing for some time to enable my extruder to unspool filament by itself.

The benefit of the tubing is that it removes the effect that pulling has on the carriage positioning. The cable has a small washer between it and the extruder, and butts against a 3mm hole I drilled in the handle of my extension cord reel. That arrangement allows all of the pulling force of the extruder to be focused on spinning the reel as opposed to lifting the z axis off of the bed.

I used this setup most of the time I was working with the cupcake, and just set it up again for my gen 6 prusa.

Downsides: it does probably require more torque. You also need to be smart about using as little hdpe tubing as possible, as it seems like the friction scales non linearly. You also want the line to be as straight as possible between the spool and the extruder. My setup in the video is about as long as you want it to be. I could easily see using 10cm of tubing and simply setting the spool on the top of my prusa. That ought to have very little drag compared to the current rig. PTFE tubing might be worth looking into as well

I may end up building a bracket to allow mounting the reel on top. That seems like it would be a pretty manageable setup.

Just because I know someone will end up asking where I got that reel from: home depot is the answer, but you can also find it at amazon here

The hdpe tubing I believe is used for cold water lines such as ice makers. I picked it up at home depot as well.