Building a 3D Printer, RepRap Mendel Prusa2 by craynerd

[raynerd]

After finishing my CNC machine, I`d quite like to have a go at a 3D printer as the concept amazes me.

I received my parts a few days back, really chuffed with them...


M8 threaded rod and 100 nuts and washers, along with a mix of other fasteners came to about £12


Started on the triangular sides:




Next step is to connect the sides together.

[pete3000]

Looks interesting from reading the reprap wiki, need to finish my seig x3 cnc conversion before I start on more shiny toys .

Few questions I noticed several extruder design, which looked over complicated and a bit cobbled. could you use a mini glue gun element/soldering iron element for melting the plastic wire?
The feed grip looked to be a weak point, could a mig welder pulley and tensioner feed be adapted with a stepper. Much harder wearing?

Just ideas.

Wher did you get your kit from?

[ParCan]

looking good already craynerd.

Pete3000

Most Glue guns work on 240 volts. Just no thanks !
I tried a weller soldering iron heater based hot end. The thermal Junction was to big to hold the temperature where it's needed.
Hot End / Nozzle design is a black art at the best of timee.

The Wade and Gregs Extruder designs work fine.
The hobbed bolt does have to be well made, and believe me it's not easy.

Alex.

[j45on]

Looking good 
I have a Printrbot 3d printer coming soon 

[raynerd]

Hi guys, sorry, missed these replies! Thanks for looking and commenting

Pete3000 - ParCan printed the parts 

Ok, so I have been busy with work but spent a little more time yesterday on the Prusa:

So got all the cross members on to link the two sides together and then jigged it out. Now I must admit, I spent about 1 1/2 hours getting it square as it kept twisting!


8mm linear bearings clipped into printed bearing holders


Then mounted the ply bottom table onto the silver steel using the bearings.



At this point I realised I`d mounted the bars on the wrong side of the frame. On the Prusa2 the clips should hold the bars at the top of the threaded rod and not hanging as it is in the photo.

So I`m now running an evening behind as I`ve now flipped the bars around and mounted the motor and timing pulleys... update tomorrow!

[j45on]

Chris are you running the bearings on silver steel ?
I had trouble with my first cnc using bearings on silver steel as the bearing balls are harder than the shaft and it scored the shaft rather than running smoothy.
I now have lots of silver steel now as I had to buy hardened and ground shaft 

[raynerd]

Jason, I didn`t think about that...just presumed silver steel would be better than mild steel. I`m guessing I`ll have to change it to hardened rod at some point.... ohh dear, more ££££!!

Ok, we`ll in the little bits of time I pinch in the workshop, I`ve made more progress.

I`ve put the 6mm ply table on 225x225mm with the belt and motor in place for the Y motion:


I`ve gone for a double bearing rather than using the printed bearing holders... tough one as lots in the IRC said there bearing guides worked fine but a few said this method is better:


Bearings in position and belt grips shown:


The the x axis built and clipped into place:


Carriage running on linear bearings on the X axis


Lead screws for the z axis along with nuts and springs:


Turned down some little couplings for my lead screws as the printed ones wouldn`t hold. They are M8 one end and grub screw 5mm bore the other:




and currently as it stands:


Next job is to add the belt to the carriage and mount the motor and then I think I`ll be looking at assembling the extruder!

[ChrisC]

The printed couplings are normally designed to have a piece of 5mm bore PVC tubing slipped onto the motor shaft before assembling.  It is intended to allow a bit of flexibility to take up mis-alignments between the motor, leadscrew and the Z axis nut.

Chris

[raynerd]

The printed couplings are normally designed to have a piece of 5mm bore PVC tubing slipped onto the motor shaft before assembling

Yes, I believe so but unfortunately I didn`t see this in any of the assembly tutorial videos or guides. A little tube would have been useful to counter some misalignment but I`ll see how these solid ones work. I must admit, they both turn just fine but one does look at a slight angle. However, since the x axis idler is fixed in its position of the flat bar in relation to the lead screw, I don`t see how there is anything that can be done about it! I`ll have to see how it runs with the motors attached.

Chris

[ChrisC]

Yes the quality of the build info is a little variable! I'm not sure how useful the PVC tube actually is.  My Prusa has it fitted, but I'm building a second system at the moment and I'm trying a printed coupler without PVC tube.  It will be interesting to see how the rigid couplers compare to the more flexible ones.  In theory you do need some compliance here to protect the motor bearings, but the whole frame is so flexible that I doubt it actually makes a huge difference.

Your build is looking good.  What electronics are you planning to use?

Chris

[raynerd]

I`ve just purchased RAMPS 1.4 and I`m going to use an ATX supply for power....however, I`m not sure if an ATX will cope with both the motor current and that pulled by the heated bed as well! I believe my ATX is rated 24A on the 12V line but I`m not sure....think I might run the heatbed on a second ATX or purchase a dedicated unit. Just seems a shame with the ATX available.

I`ve got a little issue at present with the misalignment of the x axis belt over from the motor end, over the carriage and to the bearing on the idler end. It seems to be no where near in line with the belt clamps!!

Chris

[ChrisC]

12 Volts 24 Amps should be just about ok.  Hot end resistor is normally 6.8 Ohms = 1.7Amps.  The motor current draw is unlikely to be greater than 8 amps, but best to measure it.  So that leaves 14 Amps for the hot bed.  I assume you are using one of the PCB hot beds, the guy I bought mine from says they have a resistance when cold of 1 ohm (resistance increases as it heats up of course), but I have seen reports of resistances around 0.8 ohms.  A 1 ohm bed will draw a maximum of 11 amps, but a 0.8 ohm bed will draw 15 amps.

Chinese 12Volt 30amp power supplies sell on ebay for just over £20.

I initially used a Gen 6 board, which is not ideal: it is acoustically very noisy, has a design fault with the thermistor input circuit and doesn't support a hot bed.  I'm in the process of building a Sanguinololu; I'd be interested to hear how you find the Ramps 1.4 shield.

Chris

[ChrisC]

Oops hit Post too soon!

Sorry to hear you're having problems with the X belt alignment.  There are a lot of variations to the designs of the X carriage and the motor and idler ends.  In the end you sometimes just have to come up with a compromise... once you get it running you can re-print a better part!  One problem I found was with the X idler.  The design shows a 8mm bearing with two fixed penny washers.  The belt running on these fixed washers caused too much friction on my system and caused missed steps (worked ok on the Y axis though).  I turned up an aluminium pulley which I glued onto the bearing using loctite.  The flanges now rotate with the pulley, it does mean that the diameter of the idler is too large, so the belt runs up hill on one side.  I'll replace it with a smaller pulley in due course.  There are designs for printed parts to fit onto the bearing to achieve the same result.

Chris

[ParCan]

Hi

Your build is coming on really well. I like your Z Couplings. They are very similar to what I have.
See how you get on with them.

The X Belt can be a real pain.
See if you can find a couple or 3 washers that fit inside the penny washer either side, thus allowing the penny washer to rotate.

I have run with LM6UU's on my Huxley on silver steel with no ill effects. I'd see how you get on. Just give them 1 or 2 drops of thin oil every 10 or so hours to keep it all free and nice.

24 Amps is enough for a Heat Bed and the machine.
You may need to put a load on the 5V rail to keep tthe 12 V up.
My advice for the heated bed is also to run it through a relay or somethign to keep all that current away from your RAMPS.

It's all looking rather good I have to say

Alex.

[Noitoen]

A good source for guide rods is on old Xerox machines or printers.

[raynerd]

I`ve come quite a way with this build and have managed to do some prints:

Here is the extruder built up:


the extruder has some gearing which ultimately turns a hobbed bolt which grips the filament and forces it down through the nozzle:


All the electronics are wired up. I`m using RAMPS 1.4 with polulu drivers. The wiring is a mess and is the next step - getting it all tidy!!


So I didn`t do any calibrating and managed to get the motors moving. I didn`t realise that pronterface software had an extrude button and so I printed a test cube which didn`t turn out great but I was chuffed to bits!


...so what do you print when you`ve just built a 3D printer.... ?

A Ring Mustache of course!!!




 

My daughter likes the mustache!!!


So then onto something a little more tricky! Which first required me to calibrate the system. It wasn`t far off which is why it allowed me to get something half decent in the mustache and the square.

I decided to give this a go: It isn`t anything functional but it has a massive overhang and imagined it would be pretty tricky!
http://www.thingiverse.com/thing:15364







Video coming shortly...

[raynerd]

[ieezitin]

Cray

nice build i am watching closely. Sweet daughter its nice to include your family with the hobbies more people should do it.

Anthony. 

[ParCan]

Hi Chris

You have got your printer together really nicely.
A bit of fine tuning and you'll start to get some really nice prints from it.

My Thoughts are:
Nozzle temp may be a tad high - maybe 5 degrees. That should help with the Strings and Blobs.
1st layer Z Height is definately to low for the Cube. Set the nozzle 2 A4 paper thickneses above the bed.
Maybe a touch more retract.

I saw the scrape mark in the Blue tape - we have all done that ;)

Congrats on a really nice build.

Alex.

[raynerd]

OK, I`ll bring the temp down and raise the z axis.

I have a problem! - I noticed this evening that on the, what should be verticals, they are sloping back slightly and not perfectly square to the table!!!!

Chris

[ChrisC]

Hi Chris,

Your build is coming on really well, your first print is much better than the first print I did when I built my Prusa! As Alex has said, the initial Z height is quite critical, it is also crucial that you get the print table parallel to the plane of the X Y movement.  Which slicer are you using with Pronterface?  I moved to Slic3R from Skeinforge a few months ago, and have found it a great deal better.  Which ever one you are using I would suggest you set the Z home position as Alex has suggested, and then use the Slicer software to tweek the Z offset.  In the case of Slic3R there is a Z offset parameter under the "Printer and Filament" tab, in Skeinforge  it is in the "Bottom" tab.  You need to be able to set the Z height to an accuracy of perhaps 0.1mm or better.

Chris

[ChrisC]

One other thing I meant to mention; a small fan directed at the printing table makes a huge difference to the print quality. Ideally it should be directed at the point where the printing is taking place.  The idea is to quickly cool the molten plastic before it starts to slump.  It is particularly important for small features.  The best results can be obtained with a fan which can be turned on and off during the printing, but even a fixed fan makes a big difference.  You don't need very much air flow; obviously too much will cause cooling of the hot end.

Chris

[raynerd]

Hello one and all.
Chris, I`ve set the height OK and my prints are sticking but I think my z axis is not vertical to the table but slanting back and to the right. Here is my bad attempt at yoda:

[ChrisC]

Hi Chris,

Your Yoda isn't too bad, it always takes a while to get things calibrated.  Setting everything square is a bit time consuming, but one advantage of the Prusa is that you have plenty of degrees of freedom.  I normally start by choosing one of the Y axis bearing rails as a datum and then setting the second Y axis rail parallel and the X axis perpendicular to it.  You can then use a large square to set the Z axis perpendicular to the plane of the top of the two Y axis bearing rods.... it is more difficult to describe it than to do it, but I'm sure you know what I mean.  I apologise if I'm stating the obvious.

The shield print on your Yoda shows that the table isn't level, you can see it is much thinner at the bottom of the photo than at the top.  The Z height and table level are about more than just getting the print to stick, if you are too low you will notice that the first few layers tend to bulge out a bit.  If you aren't already using it I would strongly recommend that you use Slic3r  (www.slic3r.org) as a slicer, it is much easier to use and understand than skeinforge (it is also slices very much faster than skeinforge).  Boring calibration cubes are the best way to make progress with print quality.

I saw on another thread that you have just got your hands on a Raspberry Pi, so I expect the Prusa is taking a bit of a back seat at the moment.  I'm following your experiences with the Raspberry Pi with interest.

I've got my Prusa Air working, I'll post some photos when I get a few spare minutes.

Chris

[DavoDavo]

I just found this thread, I'm fascinated with the concept and will be following with interest. Whether I'll ever build one myself is doubtful but I find it all so interesting watching the build progress. 


Good work and keep the pics coming.