A Return to Posting

I have decided to start posting on this blog again.  I doubt that there are many folks out there who are waiting breathlessly for information on what I am doing but this was always intended to just be a record of my progress for my own use.

Things have actually progressed here even though I have not documented them.  After the extruder "blowed up" on my classic Mendel I decided to build a Prusa rather than repair the old one.  It has turned out to be a great decision.  The build went quickly (for me anyway) and I am just waiting for the dual extruders to arrive before firing it up. 

Some specs on the new machine:

• Prusa Mendel (parts bought on Ebay)
• Ramps electronics (came with a full wiring set for a Prusa)
• Full hardware set bought online
• LM8UU Linear bearings
• LCD screen extension for Ramps
• Dual QU BD universal extruders (1.75mm)
• PCB heated bed kit

I financed QU-BD on Kickstarter so I have had to wait a while for them to get their first shipments out.  It took a couple of months for me to build the Mendel anyway and they have just announced that they have shipped all of their Kickstarter related hardware to their backers so I am hoping that the extruders will be here within the next few days.  I have both ABS and PLA filament in the 1.75mm size so I will probably set up the extruders by material rather than with various colors.

I also bought a small power supply on Ebay.  This is one of the ones intended for automotive lighting systems.  They are becoming very popular for Repraps as they are smaller than the older PC power supplies like the one I used on my last machine.  I plan on printing a case  that can combine the ramps, the power supply and the LCD screen into a single compact unit along with a cooling fan.

Construction on my DIYLILCNC is also progressing.  The main parts of the gantry have been assembled and the parts for the bed have been cut.  All of the mechanical and electronic parts are here, I just need to get the time to complete assembly.  It will be great to have something that can cut sheet parts for projects as a complement to the plastic parts created by the Mendel.  Note that the design for the 2.0 version is now out so I am, once again, constructing a machine that is one version behind the rest of the world.

Much Progress, Some Issues.

It has been a while since I posted, mostly because I have been meaning to take some pictures of various things to show what I have been doing.  Since I still haven't taken those photos I decided to just go ahead and post an update anyway.  Maybe I can get the pictures taken this weekend.

Things were going fairly well for a while.  I finished making a circuit board clamp that I found on Thingiverse and it works fine (my first multi-part object).  In the process I used up the last of my grey PLA and switched to the 5lb roll of Green that I had purchased.  I found that the green filament melted at a lower temp and would turn black occasionally at the temps I was using previously.  After some experimentation I found that printing at a set temp of 187 worked fine but I still have to do some tests on the actual vs reported temp to see whether it is reporting accurately.  Also, it appears that all PLA is not created equal and I may have to make adjustments every time I change a roll.

I removed the spool from my electrical cord reel, sawed it in half, and dropped my green filament in.  I managed to remove the winding handle without breaking it so I can use it to lock the halves of the spool together whenever I drop a new roll of filament in.  I had tried to print a Thingiverse object that was intended for that purpose but found an interesting issue instead:  The large body of the plug printed fine but the fill (set at 60%) began to sag in the middle so that after about 2" of height there was a dip of about 2mm in the center of the object and when the extruder attempted to print the prongs in that spot it was too high above the existing layer to bond.  I believe this is caused by the plastic being too soft and spreading out too much horizontally after it is laid down.

I also started to encounter some missing steps in my prints.  Since my first prints did not encounter this I know that it is not caused by electronics or firmware.  It is happening consistently now but only in one direction on the X-axis, so my prints slowly lean over as successive layers are laid down.  I have increased the current to the X-axis as well as adding heat sinks to all my stepper controllers (in case I need to increase current to others).  I also loosened up the bolts holding the X-axis bearings.  They were quite tight when I checked them so they may be my problem if they were restricting the bearings rotation.

My biggest problem is that I have large blobs of plastic oozing out of the extruder somewhere hidden by the X-carriage.  It started slowly but got progressively worse over time.  I am sure that the original problem was caused by an extruder crash into the print bed.  Since I did not have my endstops working I was manually zeroing the print head and then removing the home instruction from the G-code.  Of course, the inevitable happened and I forgot to remove the instruction once.  That resulted in a full speed crash on all the axis.  I wanted to print instead of taking the time to resolve the endstop issue and so I must pay for my impatience.

So, before I try printing again to see if my adjustments to the x-axis solve the missing steps problem I am removing the extruder to rebuild it.  I have additional brass tips, PEEK sleeves and a couple of removable heaters from Techzone that I never used so I should be able to get it back in service fairly quickly.  At the same time I will install microswitches to replace the opto-endstops that I have never managed to get working.  I tested the mechanical switches with the sanguinololu and they worked fine so I just need to remove the optos and get them mounted.

Hopefully these changes will give me a stable platform so I can proceed with some of the backlog of print objects that I want to produce.  At the very least I can say that I am having a great time after such a long time building the machine itself.  Fine tuning and repairing are a lot more fun.

And I promise, pictures soon!

First Printed Object!!

Huzzah!  After two years of muddling about I have managed to coax my Mendel into actually printing something.  And it turns out that I didn't even need a new main board!

I had noticed that the electronics would work for about 20 seconds before shutting down so I knew that the problem was not in the stepper controllers but it seemed to me that overheating could be causing a shutdown.  Then, when things had cooled down, it could be made to work again.  I reasoned that perhaps I had the current set too high on the steppers so I turned them all down and tried it again.  Lo and behold everything began working correctly so I proceeded to try printing some small parts.

I managed to get some small things to print correctly, if a little sloppily, so I decided to go for it and try to print a shot glass for the traditional toast to a new machine.  The results (.4mm layers, 200C, 50% infill and no heated bed) are below:

In the picture it appears to narrow towards the bottom but that is caused by the camera angle.  It actually came out great.  There are quite a few blobs but I will experiment with the settings to resolve that.  I suppose it is either too hot or the print head was moving too slowly.   In any case, it is water tight and shaped like it is supposed to be shaped.

I still don't have my endstops working, which means that I have to set everything up manually.  I have been editing the Gcode to remove the homing instructions before and after the print.  The most difficult part is setting the position of the Z axis prior to starting.  Since I am doing it by eye it is hard to get the height set consistently and I have had to stop several prints because I started them with the print head set too high.I could make a spacer to set the height but I think fixing the endstops is a better use of my time.

I have gone through the few feet of grey PLA that I had and I will be starting into my 5lb lot of green PLA so I went to Lowes and bought an electrical cord reel to wind it on.  

Quite a few people are using these now.  They are cheap and sturdy.  the only problem is that the reel is not split in the middle.  that means that I have to wind the whole lot of filament onto it by hand instead of splitting the reel and just dropping the roll in.  There are a number of mods for this reel on Thingiverse including a spindle for 5lb spools and some connectors that allow you to modify it so that the reels can be removed and changed.  I believe that I also came across an actual printable reel designed for these but I have to go find it again.

I have a few items that I want to get printed now that I have it working.  The highest priority, now that summer is coming again, is an  adapter to mount a set of relays under the hood of my Jaguar XJS.  I installed electric fans last year and the relays that came with them do not fit on the mounting bar of the car.  I will have to print those from ABS since it gets pretty hot under there when running the V12 in the summer heat.  I think it may get above the melting point for PLA.

I also want to print a set of clips to reinstall a piece of glass in our stereo cabinet.  None of the mirror or glass mounting clips available locally will fit this oddball installation.  The best thing about this one is that I get to show my wife how useful a Reprap can be!

A satellite of your very own!

I am still waiting for my replacement Sanguinololu but here is a really interesting story to help pass the time:

The folks at Evadot have designed a board to be the brains of your very own satellite.  A CubeSat is a low cost micro-satellite platform that universities and others have been using for a while.  Of course, "low cost" is relative.  A basic CubeSat kit costs anywhere from 7,000 - $10,000 and the launch costs are another $40,000 at the moment.  On top of that you would have to add your own sensors, etc. for whatever mission you have in mind.  Evadot wants to open things up a bit by offering a much cheaper alternative to the present CubeSat kits on the market.

Give the article a read and keep an eye on these folks.  These boards can also be used for a variety of other cool hackerish purposes, including robotics.  Keep in mind however, that launch costs are dropping and you might actually be able to afford to launch your own satellite in a few years.