Category Archives: reprap

Slic3r

Okay, I’m a bit sick of fighting ooze at the moment (see last post for more details), so I thought I’d get in and print some useful objects.

When browsing Thingiverse the other day, I saw this design for a holder for Apple earphones.

I thought that these might make ‘stocking stuffers’, and a good answer to the question ‘Well, what can you make with a 3D printer?’ that you often get asked.

Not willing to just print something out (heaven forbid), I used the opportunity to also give Slic3r a try. Slic3r is an alternative skeining program, different from Skeinforge and SFact. Unlike SFact, which basically works as a ‘plug-in’ to Pronterface, Slic3r is a stand-alone program. I’m not sure what advantages this gives, but it’s extremely fast to skein, which is probably due to running natively vs running interpreted Python code.

One of the supposed strength’s of Slic3r is in thin layers, so I thought I’d try something a little different.

I printed up two earbud holders. One, using Slic3r, would be at 0.2mm layers, but printed at 60mm/s. The other, using SFact, would use 0.4mm layers, and print at 30mm/s. So they should have the same printing time, but each have a different area of focus.

Here’s the results.

Slic3r’s output is on the right, SFact on the left.

I’m not totally impressed with Slic3r’s results. It’s clearly missing a lot of the fine tuning which has gone into SFact. I think that the 0.2mm layer was just a bit too thin, and the walls came out a bit unevenly.

I think that it’ll definitely be worth keeping an eye on Slic3r. It’s only very new, but doing pretty well so far.

More Ooze Fighting

Unfortunately, I didn’t have much luck getting help for my ooze problem in the Reprap forums. The only respondent suggested that the best way to fight it is to replace the hot-end, with a J-head nozzle.

While I do have a J-head spare, I’m not quite willing to give up on the Budasnozzle yet. I thought I’d sit down with the ‘daily branch’ version of SFact (which has more retraction-related settings), and battle my way through the various settings, see what the effects are.

Here’s my output from my tests:

Retraction settings:

v1 – Use Fixed Retraction
Retraction speed – 13.3mm / s
Retraction distance – 1mm
Restart Extra Distance – 0.1mm
Result – Corner bulge worse than SF default

v2
Retraction speed – 13.3mm / s
Retraction distance – 2mm
Restart Extra Distance – 0.2mm
Result – Even worse.

v3
Retraction speed – 13.3mm / s
Retraction distance – 0.1mm
Restart Extra Distance – 0.2mm
Result – Really terrible – filament everywhere. Did I save the second one correctly before skeining?

v4 – retry v2 again, slow down filament speed to 30mm/s just to get a better idea of what’s happening.
Retraction speed – 13.3mm / s
Retraction distance – 2mm
Restart Extra Distance – 0.2mm
Result – The same as V2. Notice that the Z-axis bars are moving around a bit. Probably need to tighten up X-axis bars again. Maybe print some Z-stabilisers.

v5 – Change settings again
Retraction distance – 3mm
Restart Extra Distance – 1mm
Result – Okay, it looks like the ‘restart extra distance’ is causing a lot of the blobbing. It’s the extra filament that gets fed into the extruder before starting the next section. Take this back to 0, I think.

v6 – Restart Extra distance at zero.
Retraction distance – 3mm
Restart Extra Distance – 0mm
Result – Much better. Internal blobs lowest of all prints. External still higher than default settings. Can you set a negative Restart extra distance?

v7 – Restart Extra distance at -1.5.
Retraction distance – 3mm
Restart Extra Distance – -1.5mm
Result – Very good. Improved internal blobs even further. Corner blob improved but still larger than defaults

Here’s some of the results from the tests;

While I wasn’t successful in removing the ooze, I’d still call tonight a success. I’ve learnt a lot about SFact’s retraction settings, and feel like I have more control over the machine, in general.

Calibration Time

While my Prusa is printing fairly well, there’s still a lot of room for improvement. My calibration methodology so far has involved just fixing the glaring problems, rather than going through a systematic calibration process and optimising the printer’s performance at every step.

The top two tasks on my ‘to do’ list are calibration related, so it makes sense to tackle them all in one go. Seeing the success that Julian has had with his calibrations has inspired me to sit down and go through the calibration profile described in the wiki.

First off: Thin-walled cube. This one is used to test the layer thickness. As per the calibration procedure, I started off with 0.4mm, working my way down in 0.01mm increments – all at 30mm/s speed. 🙂

As you can see from the photos, they all turned out great, with no issues at all of the extruder tip plowing into the previously deposited layer. SFact is obviously doing a really good job in controlling the extrusion for all these different heights. As the layer thickness decreases, the fineness of the layers becomes extremely apparent.

The one on the left is 0.4mm layer thickness, and the one on the right is 0.31mm.

Stage two was looking at infill.

The first one I ran, I only had the infill solidity at 0.35. It turned out fine, perfectly flat. The second one I turned up the infill solidity to where it was meant to be: 1.0. In this one, there was a noticeable convexity to the top of the print. It was only minor, but quite noticeable.

However, I couldn’t find the setting in SFact that ‘s meant to fix the issue – ‘Infill width over thickness’. This must be one of the settings that been taken out with the move from Skeinforge to SFact. Maybe the best way to adjust this these days is by changing the ‘Filament Packing Density’ – I’ll have to check. Since there wasn’t anything more I could do here, I moved onto a third test – Oozing.

Oozing has been the biggest issue with my printer since I started printing. There’s two main issues that I have. The first is at the ‘uplift corner’. I always get a bulge at the corner where the printer stops to lift up the layer. The lifting up process causes the print to pause for a second. The ‘dribble’ from the nozzle at that point always creates a slight bulge.

The second issue is a more typical ooze issue – ‘fly aways’ at the start and end of exposed ‘towers’. This can be seen very clearly in some of my earlier prints – seen here. These problems aren’t too bad. The results can be cleaned up with a knife fairly easily, but better not to have the problem in the first place.

Unfortunately, I wasn’t able to make any real headway today into this problem. SFact has two main ooze-related settings – ‘Oozerate’ and ‘Filament Retraction Speed’. I fiddled with these settings, as can be seen the above photo, but without any real improvement.

As an additional step, I went and downloaded the ‘daily branch’ version of SFact. This has a lot more ooze and retraction-related settings. I tried a couple of test prints, but again, had no significant success.

I’ll keep trying with some additional settings, but I think I’ll have to go to the forums’ and ask for some help there, get the expert’s opinion.

Speed Trap

As I commented in Julian’s blog, it’s interesting to see the difference in quality that he gets between the different speeds. I haven’t noticed too much of a difference myself, but I put that more down to my lack of calibration than anything else.

I thought that I’d replicate his three-speed experiment to compare and contrast the results. I used the ‘single-wall calibration cube’ as my test object.

The four speeds were: 30, 45, 60 and 90 mm/s. They’re all looking fairly good up until the 90mm/s one. The main problem there was that the filament was going down so fast that it didn’t give the layer below a chance to cool down before starting the next layer. If I’d had some active cooling, or a larger object, I think it’d have looked great.

I didn’t notice until I’d finished doing these cubes, but my X-Axis belt was slightly loose. I think I could have got them looking even better!

Spool Finished

Finally finished printing the spool. Printed out the last couple of bits tonight, and assembled it this afternoon.

The most difficult part was the support arm that sits on the frame, the spindle. In its standard orientation, it wouldn’t fit onto my print area. I had to load it up into EasyFit, and rotate it 90 degrees. Currently my X-axis only has 155mm of travel, while Y has 175mm. Once rotated the piece fit on fine. However, I printed out the wrong one! I printed out this spindle, but it was too narrow, causing the spool to flop around. I had to print out the spindle from this page. It’s a bit tight, but should loosen up with use (and maybe some sandpaper.) I also printed up a filament guide.

Here’s the assembled spool. Looks great, and will keep my work-area a bit more tidy. As you can see, I’ve almost finished off my first roll of filament!

And a video of the spindle being printed.

Auto-Shutdown

Well, that was easy. Only a minute of searching the Reprap forums yielded the solution to this problem.

To auto-shutdown the hotend and heatbed after a print just go to the ‘chamber’ tab in SFact. Turn chamber on, then check the ‘turn off at shut down’ buttons.

Catching the Marlin

Okay, so that title was pretty contrived.

Last week, when I was having ‘shelling’ (actually backlash) issues, I made a post to the Reprap forums. One of the posters there suggested that a way to correct the ‘wiggles’ in the walls of my prints was to change across to the Marlin firmware.

This is a pretty radical suggestion, as Sprinter is currently firmly entrenched as the favorite firmware of the Reprap community. But, given that changing firmware is pretty much the easiest thing you can do with your Reprap, I thought I’d give it a shot.

Some of the touted features of Marlin are:

Interrupt based movement with real linear acceleration
High steprate
Look ahead (Keep the speed high when possible. High cornering speed)

Configuration was easy, Marlin uses exactly the same configuration.h file as Sprinter, so all the settings can carry through. One point of note; the Marlin firmware runs at a standard 250,000 baud rate, as opposed to Sprinter’s 115,000. The only trickiness with the firmware was the thermistor tables. Marlin didn’t have the thermistor table for my hot-end, but that was just a simple copy-and-paste job across from Sprinter’s thermistor.h.

Once uploaded, WOW, the difference is impressive. You can hear the difference in the motor control. Much smoother and more finely controlled than Sprinter.

The printer is now exceptionally quiet. It was pretty noisy when I had Sprinter and the PLA bushings, but now with the linear bearings and Marlin, it’s super-quiet. No problems watching the TV with the printer running away behind your head. It’s probably due to the greater stepping control and better acceleration. Less ‘jerks’ on the axes.

The print quality has improved again. One of my banes – non-completely-filled top surfaces – has almost been eliminated. Surface finish is much better, as is layer stacking.

Next on my list of ‘things to work on’ will be to try and figure out how to shut down the heatbed and hot-end after a print. I’m now confident enough with my printer to leave it running unattended (once I get the spool printed for filament feed), but I want it to shut down when I’m finished. I think this can be done by adding the right G-codes to the end.gmc file, but I need to investigate how to do that.

Main things to work on now:

Ooze settings.
Solid infill, particularly on ‘top’ layers.
SD card printing
~~Investigate the ‘Marlin’ firmware (as per this thread)~~
Figure out how to turn off the heatbed and hot-end automatically (gcodes?)

Upgraded

One of the most amazing things about the Reprap project is that the printers can print out their own repair parts and upgrades. Today, my printer joined that club when I installed the linear bearing upgrades that the printer had printed off itself.

The installation process went fairly easily, with the main hassle trying to line up the Y-axis bearings with each other. The best way to achieve this was by only screwing in one of the two screws in each mount, leaving the mount free to orientate itself along the smooth rod.

It was a little bit noisy at first, being metal-on-metal, but a bit of lithium grease on the rods quickly fixed that up.

Main things to work on now:

Ooze settings.
Solid infill, particularly on ‘top’ layers.
SD card printing
Investigate the ‘Marlin’ firmware (as per this thread)

Linear Bearings

I’ve been having trouble printing out the parts to use the linear bearings on the Y-axis. The bases have been coming through fine, but the ‘towers’ have been coming through as blobby messes. Lowering the temperature a bit has helped.

Following on from Julian’s suggestion, I had a look at the Easyfit software he recommended. Using it, I cloned the Y-axis bearing holder three times, so that I had four of the parts on a ‘plate’. My thinking was that by printing four parts, it would give the parts enough time to cool down between each layer. I set them up with 5mm between each piece, which worked great.

This was my longest print so far, at 57 minutes. This is how the parts looked when printing was finished.

As you can see, I still need to work on my ooze settings, but the parts looked pretty good, with no melting around the ‘towers’. My theory worked well. Here’s the parts once cleaned up a bit with a Stanley knife.

I’m really pleased with them, and the linear bearings snap into them without any troubles at all. Next up was to print up an X-Carriage. The main option is Greg Frost’s X-carriage, but I went for Joem’s version, as it allows for four, not three, bearings. However, it’s very large. If it cuts down on the X-travel too much, I might have to switch to the three-bearing version. I also printed out the version with mounting points for a fan, which I think I’ll fit in the future.

This was an even longer print, at about an hour twenty. This print had some noticeable lifting off at one corner, which came up about 1mm. This won’t affect the performance of the part, but I might have to keep the bed temperature a bit higher than 100 degrees for these larger pieces in the future.

Useful Printing

With the ‘backlash from hell’ problem solved the printer’s printing really well, enough that you can actually print useful things with it.

I’ve been experimenting with temperatures a bit, trying to find a happy medium that will print well, and still stick to the heated bed. I’ve found some settings that work quite well.

To start with, I set the heated bed temperature to 130 degrees. This results in about a 115 degree temperature at the top of the pyrex sheet. I also set the hot-end to 230 degrees. Once the first layer is complete, I turn down the hot-end to 220, and the bed to 100, which results in about a 90 degree top temperature.

These settings work great. The first layer sticks really well, and the object stays really stuck for the remainder of the print. Once the print’s finished, the bed temperature usually has to drop below 60 degrees before the object can be removed without major force. The base has that nice ‘glossy shine’

The first objects on my list of ‘real prints’ are some LM8UU Linear bearing parts to put onto the printer, and a spool holder for the filament. Here’s the first spool part: