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printrbot

If you missed the story so far.

Printrbot is a cheap 3D-printer kit designed by Brooke Drumm which was offered on kickstarter.
http://www.kickstarter.com/projects/printrbot/printrbot-your-first-3d-printer
Brooke was hoping to raise $25,000 to start making bots and bot kits at a reasonable price.
He didn't raise $25,000 he raised $830,827.
Instead of building 50 kits in his garage he set up a factory to build 1400 (and more after that).
Understandably this delayed the estimated delivery date by about two months.
As an early backer (number 53 of 1808) I have an early kit and there were a few wrinkles still being ironed out.
My kit is a "printed" kit - the much of the kit is comprised of plastic parts which were printed on printrbots.
Printrbot HQ has about 20 printers running long hours to print parts. This means they can tune designs by just altering a computer file or two.

Printrbot is a reprap derivative. It builds upon a decade of open-source 3D printer research.
As it is a printer which can print parts for printers it is possible to print replacement parts for itself - you can also customize or improve them. You can also use it to print parts for a different type of reprap or some totally different type of machine.

The future has arrived and it is sitting in my house.


26'th April 2012,

My printrbot kit arrived today.

Above are the parts after unwrapping.
I'm am working through the assembly video here. http://www.printrbottalk.com/wiki/index.php?title=Assembly_Videos

Above is the progress after video 1.

Brooke doesn't explain that the two small motors are the Z motors till after they are fitted.
The two Z motors are wired to a single plug.

Snag one.

I hit my first snag in video-4.
Brooke has the bearing pre-pressed onto the Y-belt guide. When he says it is tight he isn't wrong.

I used a vice to press the bearings flush but they have to go further up the plastic shaft to make room for two washers on each bearing.
There isn't enough thread on the 16mm screws to screw into the motor until it is pressed home.
I used a loose motor, a screw and a single washer to pull the bearing alone a bit.
Then repeated with two washers two force the bearing (and washers) into place.
The washers must be manually lined up so it is easier to do it on a loose motor than on the mounted one.
Alternatively you could probably assemble the Y guide onto the motor before fitting it.

Above shown the Y guide bearing thingo after I've pulled the bearings into place.

This is the state of play after video-4.

Annoyance one.

No power supply. We were expecting the kit to come with one. Not sure if this was a mistake or deliberate. Either way it would be silly to import one from the US.

Annoyance two.


The printer is now WAY too wide for the bed. The width need to be reduced by about 25mm. The alignment as in video-2 was a waste of time as I'll have to do it all again.

Annoyance three.

If you assemble the bot as you go through the videos you'll find you've mounted the Y motor and guide - then you'll be advised to file a flat on the shaft with the motor shaft in a vice :-(.
This shaft is so tight I doubt it will slip even without the screw.

Minor design flaw.


The holes for mounting the wooden bed to the rails are too far apart (or the rods are too short).
I can make it work but it would be better if the rod went all the way through the mount.
I think some people drilled new holes and that newer kits have this fixed.
Moving the mounts in a bit will of course reduce the bed travel and work volume.
Later I was drilling holes to ziptie the temp sensor leads so a added two holes to fix the problem.
The hole have to be at the opposite end to the heated bad.
Also,
The hotbed holes don't line up perfectly with the holes in the bed. The hotbed mounting holes are also a bit close to the mounting brackets and they will probably need trimming to get the nuts on the mounting screws.

Possible flaw.

I'm not at all happy with the recommended heat sensor attachment. The coupling to the heated bed is poor and one side of the sensor is exposed to ambient air. I've made a minor mod by taping a wad of tissue over the sensor as a token attempt to insulate it.
Gluing the sensor in place with thermally conductive adhesive would be better.

Minor printing part defects.

The quality of the parts varies from very good to not so good.
My filament motor gear has a piece of tooth missing but should still work ok.
One Z rod is quite loose - ie the hole in the base piece is too large.

Minor part failure.


My Y motor gear is cracked near the screw. I don't think this was from tightening the screw. I think it was when I tried to get the gear off the shaft and gave up. If it fails I can probably repair is enough to print another. Look like a PITA to replace.

Day two.


Reduced the base width and re-aligned. I don't think Brooke mentioned the obvious that the base pieces have to be parallel so that the Y bars are parallel. Then worked my way through the videos.
The design has been changing and my kit is a mix of old and new versions. I don't have a "zest" in my kit - this is a mount for the Z axis home micro-switch. No suggestion was made for how to mount the switch.
The mounting of the X-motor and belt was missing from the videos. I think I worked it out.

The filament drive looks like it will never slip - very aggressive. Brooke says to loosen the screws to insert filament but I found putting a point on the end of the filament let me wind it in without loosening them.

The hardware is complete apart from hotbed mounting nuts.
Tomorrow I will add electronics.

Day three.

A slack day. I had to shop and vote and didn't put much time into the build.
I got everything together and wired but haven't mounted to Z limit switch. Brooke calls them end-stops but end-stop means something else to me.
I had a couple of problems.

The PC power supply has two 4 way plugs not one. The wrong one also fits into the printrboard PCB and does bad things like short rails together.
No harm done though (I think).

The other problem is the cable on the E motor is too short for the wire routing Brooke recommends. I managed to make it connect but I'm not happy with it.

I either have to rotate the printrboard or lengthen the cable. It is tempting to shorten most of the other cables but this might be a problem if I decide to expand my bot.

The X limit switch isn't well aligned and I intend to print another version of the piece the screw goes through. The hole needs to be moved down a bit.

I also installed the windows USB driver for printrboard.

Powered up.

Motion in X Y and Z seem OK.
There is a lot of wobble when moving up and down but I expected that because one bar is loose.
Homing X works.
Homing Y doesn't work.
Homing Z will work when I attach the micro-switch.
Extruder works.
Hot bed doesn't work.
Not too bad for first power-up.
I was half expecting trouble with the X motion because the belt is so tight it feels hard to move the carriage by hand.
It is also good that prontoface connected OK and seems to work.
Later,

I can see the Y-micro-switch isn't being hit - should be an easy fix.

Also - Printrbot have let us know the lack of power-supplies was an error on their part and they want to work something out to compensate.


Day four


I bought a bamboo serving tray from K-mart for $10. Now I can move the printer and PSU around together and don't have to unplug the 12V supply.

My solution for the short e-motor wires was to use a spare 4 pin cable from the power supply to make an extender.

My solution for the misaligned Y limit switch was to extend the micro-switch arm with a carbon fibre rod and heat-shrink.
Just about anything would do - a matchstick and zip-ties might work.

For a temporary Z limit switch location I just zip-tied to the smooth rod.

I've also super-glued the loose rod (the other rod).

One more snag - literally?

Everything seems to work but the home position is slightly off the hot-bed. During the homing cycle the nozzle tip runs into a hotbed mounting screw. A simple screw adjustment on the X-limit should fix that. Done.

First blog,block and jaws.

Like many others I had trouble getting the ABS to stick to the printbed.
Cleaning it seem to make matters worse. I tried several solvents and printing on tape with no luck.
I notice that if you peeled off a failed print the ABS would stick ok the next time. So I thought the must be a way to condition the surface.
Maybe painting on ABS glue and peeling it off again?
It also stuck better where the surface had been printed.
I figured it surface was just too smooth, so I took the shine off with a scouring pad and the problem totally disappeared.


I figured the small single walled prints were failing because there wasn't enough time for the layers to cool. So I printed something bigger.
The results were pretty good for an uncalibrated printer.

So for fun I printed jaws.

It turned out well except for a little curling at the ends. This may be because I didn't roughen the bed as well at the edges.

Day five.


To test my cooling theory some more I printed four test squares at once to slow things down and the result was much better.

Out of action.

I did a lot of printing today and started to have serious problems.
It turned out the extruder motor cog was slipping.
Later the Y stage played up and I suspect that cog is loose or broken.
Some of the problems may be showing up now because the motors (shafts) are getting very hot after extended use - commonly reported issue.
One Z linear bearing has slipped out too.
I need to give this project a rest and do some other stuff.
But I'm sure I won't be able to stay away from it very long.

BANG!!!

I was settling in to have another printing session and picked up the PSU to move it into a better position.
It went bang and tripped my house circuit breaker.
No printing tonight :-(

This is the track that went splat - a 3mm track to the 250V caps.

2'nd-may-2012

I created a thingyverse account and uploaded my first two things.
http://www.thingiverse.com/thing:22357
http://www.thingiverse.com/thing:22358

Dead Printrboard.

I replaced the supply but the printer won't connect via USB.
The AT90USB1286 micro appears to be somewhat alive in that it will talk to my ISP (in system programmer).
The micro comes with a build in boot-loader and is usually programmed using an atmel utility called "FLIP".
Without USB FLIP can't work.
The micro did seem to reprogram OK using ISP.
I'm guessing a spike along the earth line fried one or more USB pins on the micro.
A new AT90USB1286 is on order but could take a week to get here.
I should be able to get another board ordered as well.
So no printing for a week or two :-(
Also my PLA sample pack and red ABS has arrived.

4-may


I removed the micro from the board in preparation for soldering in a new one when it arrives.
I tried using hot air on my rework station but I wasn't happy with the amount of heat I was applying. No doubt this is lead free solder which has a higher melting point to what I'm use to. I went back to my proven method of cutting the pins off with a sharp blade.

5'th-may

I ported the tooth-belt pulley into sketchup (hard work) and beefed it up a bit because others are also having them crack.
http://www.thingiverse.com/thing:22530


8'th-may

My replacement chip arrived 5 days later and I managed to fix the board. This was a good thing because the replacement board took 22 days to arrive.

Above is the new chip being held in place with magnets waiting for me to solder it.

The solder rework wasn't as tidy as I would have liked and this is probably caused by obstacles in the way and because I was used lead soldered to rework a lead-free board. I had to touch up a few bad joins but it has now been running reliably for a few weeks.

Continued on printrbot mods


Internal

Image gallery
3D-thingys some modified and original printer parts.
3D-printing
http://nerdipedia.com/tiki-index.php?page=printrbot+mods
3D CAD

External

http://nerdipedia.com/tiki-index.php?page=printrbot&structure=index
http://www.printrbottalk.com/forum/index.php
http://www.printrbottalk.com/wiki
You can watch the activity at Printrbot HQ live here: https://www.dropcam.com/p/cL4RuS

Created by eddie. Last Modification: Thursday 24 of May, 2012 20:42:44 AEST by eddie.

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