thereprapkitstore.com Prusa Mendel construction Notes/Discussions

The single biggest step improvement I had was in calibrating my extruder. If you don't do anything else, do this!

It's quite funny. The first thing our machine prodices is a funny, molten lump and we are as happy as can be. My wife was not as easily pleased!

Pratick Wrote:
-------------------------------------------------------
> And finally the first print ... not really
> convincing.
>
> [www.freeimagehosting.net]
>
> If anyone can make me benefit of his knowledge,
> don't hesitate ;o))
>
> I haven't checked the temperatures measured by the
> board, I'm still waiting for my temperature probe
> and I also didn't read anything else in the wiki
> to improve the quality but of course, I will.
>
> Thanks again to all that have helped and more
> specifically nophead, I think that James should
> pay you for doing the support in its place.
>
>
> Patrick

My ABSPrusa has come of age. It has now gone forth and multiplied!

ABSPrusa parts printed in Clear PLA

Now to take a couple of days off to re-aquaint myself with my family before getting ready for the SouthWest RUG meeating in Ledbury, Herefordshire this weekend. I have ordered a 300mm digital vernier and a TDI from Amazon which should be arriving tomorrow.

TDI
300mm Digital Vernier

Great job MotoBarsteward!!!

If I want to calibrate the extruder, I'll have to re-compile a firmware and so to re-calibrate the axis and the termistor as James didn't indicate those parameters in the Wiki. So did you calibrate all ?

And did you have to fine tune all parameters in Slic3r to get such good results ?

Patrick

I assume you are using Sprinter? If so, there are only two numbers that need to be changed. The first is the motherboard type and the second is the extruder steps per mm.

Extruder calibration

Setting Motherboard

The default thermister worked for me.

After extrusion calibration, setting the z axis home is the next thing to do. If you find you have to keep adjusting it, check the threaded bars aren't working their way out of the holders. This has happened to me twice. I'm not sure why. I'm still working on this. If its too close, the first layer is too squashed which causes bobbles on the surface. This catches the head on subsequent layers and causes missed steps. Too high and the first layer doesn't stick. We are adjusting the height and level to 0.1 to 0.2 mm. It's not easy but I'm going to try some of the devices on thingiverse

Pratick Wrote:
-------------------------------------------------------
> Great job MotoBarsteward!!!
>
> If I want to calibrate the extruder, I'll have to
> re-compile a firmware and so to re-calibrate the
> axis and the termistor as James didn't indicate
> those parameters in the Wiki. So did you calibrate
> all ?
>
> And did you have to fine tune all parameters in
> Slic3r to get such good results ?
>
> Patrick

Looks like the filament is coming out too long and thin for the layer height you are trying to print. Try slicing with thinner layers.

---

[www.hydraraptor.blogspot.com]

Was this comment to me or Patrick?
nophead Wrote:
-------------------------------------------------------
> Looks like the filament is coming out too long and
> thin for the layer height you are trying to print.
> Try slicing with thinner layers.

It was in response to Patrick's picture of a cube. Sorry I should have made it clear. Your parts look very good.

---

[www.hydraraptor.blogspot.com]

Patrick you seem to be one step ahead of me! I tried to calibrate my extruder before printing anything and it was way off, extruding nearly 40mm of plastic when I insturcted it to extrude 30mm at 50mm/min. I then contacted James to ask for his Sprinter files but if it only involves changing 2 numbers I'll just use the latest version on github.

I have put my endstops on the wrong ends of the X and Y axes, can I change how these 2 work in the firmware without having to move the actual switches? The Z axis endstop is working as it should.

A pic of my completed kit is attached. I'm waiting for a new desk so the cardboard box will have to do for now! You'll notice I fitted the electronics underneath the print bed for better cable management. I've just ordered 2 10cm white cold cathodes to mount on the front 2 angled threaded rods to provide lighting for the print bed. I'll design and print some reflectors for the cathodes to sit in and fit some reflective material inside them, I'll post the thingiverse link here when it's ready.

Edited 1 time(s). Last edit at 06/17/2012 09:45PM by remondo.

Your wiring appears to be a lot neater than mine. I appear to have wires everywhere.

remondo Wrote:
-------------------------------------------------------
> Patrick you seem to be one step ahead of me! I
> tried to calibrate my extruder before printing
> anything and it was way off, extruding nearly 40mm
> of plastic when I insturcted it to extrude 30mm at
> 50mm/min. I then contacted James to ask for his
> Sprinter files but if it only involves changing 2
> numbers I'll just use the latest version on
> github.
>
> I have put my endstops on the wrong ends of the X
> and Y axes, can I change how these 2 work in the
> firmware without having to move the actual
> switches? The Z axis endstop is working as it
> should.
>
> A pic of my completed kit is attached. I'm waiting
> for a new desk so the cardboard box will have to
> do for now! You'll notice I fitted the electronics
> underneath the print bed for better cable
> management. I've just ordered 2 10cm white cold
> cathodes to mount on the front 2 angled threaded
> rods to provide lighting for the print bed. I'll
> design and print some reflectors for the cathodes
> to sit in and fit some reflective material inside
> them, I'll post the thingiverse link here when
> it's ready.

I've managed to upload Sprinter to the board using Arduino 0023. The thermistor values are completely wrong now though, the extruder says 8C and the bed says -28C, hopefully James will send me his Sprinter config. The z-axis motors make noise but they won't move despite turning the pot up. The same goes for the extruder motor, it skips steps even though the pot is in the same place which worked fine before I uploaded the firmware. The status LED now lights up which is useful. I've noticed the chip on my board is the ATMEGA644A but I only have an option for Sanguino ATMEGA644P in Arduino, could this be a problem?

Did you remember to change the motherboard number?

remondo Wrote:
-------------------------------------------------------
> I've managed to upload Sprinter to the board using
> Arduino 0023. The thermistor values are completely
> wrong now though, the extruder says 8C and the bed
> says -28C, hopefully James will send me his
> Sprinter config. The z-axis motors make noise but
> they won't move despite turning the pot up. The
> same goes for the extruder motor, it skips steps
> even though the pot is in the same place which
> worked fine before I uploaded the firmware. The
> status LED now lights up which is useful. I've
> noticed the chip on my board is the ATMEGA644A but
> I only have an option for Sanguino ATMEGA644P in
> Arduino, could this be a problem?

Yes, I downloaded the Melzi version from here so it was already set correctly. James just got back to me with his Sprinter files, I have attached them below. The correct thermistor tables are defined in the configuration.h file.

Edited 1 time(s). Last edit at 06/18/2012 11:26AM by remondo.

Great job Remondo.

You seem to be a wiring specialist, I admire, that's nearly art ;o))

Thank you for sharing the sprinter configuration with all of us, you also look like having a direct link with James, he even didn't answer to any of my mails concerning the missing parts, it doesn't matter anymore.

About your endstops, in the file configuration.h, you will find these lines:

// Sets direction of endstops when homing; 1=MAX, -1=MIN
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1

They're all set to the minimum (-1). In your case you should change the value to 1 for the inverted axis (I didn't try).

Now I'll be able to do what MotoBarsteward adviced me which seems to be really important: I'm going to pay a special attention to the extruder calibration and the heatbed alignment.

I hope I'll come back in a few days with a better result, also applying nophead tuning in slic3r.

Edited 1 time(s). Last edit at 06/18/2012 03:00PM by Pratick.

I changed that line you mentioned and the motor wotor would only turn 1 way so that is not the solution, I ended up moving the switch to the other side. I had to open a Paypal dispute before James responded to me regarding the missing parts. Just finished my first print and the results are better than expected but certainly not perfect.

You also need to change the pin definition to be a MAX end stop instead of a MIN endstop. E.g. for Sanguinolu

#define X_STEP_PIN         15
#define X_DIR_PIN          21
#if X_HOME_DIR < 0
# define X_MIN_PIN          18 
# define X_MAX_PIN          -1
#else
# define X_MIN_PIN          -1
# define X_MAX_PIN          18
#endif

#define Y_STEP_PIN         22
#define Y_DIR_PIN          23
#if Y_HOME_DIR < 0
# define Y_MIN_PIN          19 
# define Y_MAX_PIN          -1
#else
# define Y_MIN_PIN          -1
# define Y_MAX_PIN          19
#endif

#define Z_STEP_PIN         3
#define Z_DIR_PIN          2
#if Z_HOME_DIR < 0
# define Z_MIN_PIN          20 
# define Z_MAX_PIN          -1
#else
# define Z_MIN_PIN          -1
# define Z_MAX_PIN          20
#endif

---

[www.hydraraptor.blogspot.com]

Not sure whether or not to start a new thread or add this to the wiki somewhere.

A problem I've had from the start with my ABSPrusa is the the J Head Mk IV b wobbles whilst printing. This is because the mounting slot in the top of the head is slightly wider than the aluminium mounting plate. This means that it can wobble backwards and forwards.

The last time I dismantled the extruder I tried packing the gap with thin copper wire by winding it round and round in the gap. This worked reasonably well but, after about 20 hours of printing, worked loose again.

Copper wire packing (sorry for Mr Blurycam)

Today, I dismantled the extruder again to inspect the knurled bolt and bearings so I thought I'd have another go at the head wobble. Whilst printing the Wade parts for my brother, I noticed the holes passing from the outside of the extruder into the recess that the end of the J head sits in. I put four screws into these holes and found that they held the head very securely. However, the two on the cog side fouled the cog. I took these out and made a shim from a pie dish for that side and used the other screws to tighten the head down. Problem solved.

Shim and screws to hold J Head still

Pity I broke my thermistor dismantling the head. The head is covered in PLA. The thermistor was glued in it's little hole by PLA. I used a gas powered soldering iron with the heater head on to heat the print head to melt the PLA.

Anyway, hope this helps. nophead did say something about the holes in passing but I didn't understand until I was faced with the problem.

Edited 2 time(s). Last edit at 06/18/2012 05:32PM by MotoBarsteward.

I fitted 1 screw to support the nozzle as I noticed this problem too.

I'm getting to grips with sprinter and pronterface now but my prints are still failing at the end of each layer where the head stops momentarily and oozes a mm or 2 of excess filament. I've tried increasing the retraction to 1.5mm at 30mm/s but it hasn't made much difference, any ideas?

Try slower retract, 30mm/s is too fast in my experience. I don't know why it is the default unless it is for a direct drive extruder.

---

[www.hydraraptor.blogspot.com]

Ok thanks, I'll give that a go. I did think the cogs were turning too fast to make any difference.

I've noticed that servicing the extruder is not an easy task because the entire thing needs to be dismantled to remove the nozzle, for example. Is there a better design that will accomodate for the J-head and allow the nozzle to be removed with ease? I'm going to print a large cog with holes in to make it easier to remove the motor too.

Edited 2 time(s). Last edit at 06/19/2012 05:56AM by remondo.

The normal way of attaching a nozzle is to put two long screws all the way though from the non-motor side. You can then remove the nozzle by just unscrewing those.

I must admit I could never see how a groove mount would work without wobble and is seems that it doesn't. It has to be said though that the plastic body is not designed for groove mount. Perhaps if the hole in the body was slightly shorter than the bit of the insulator above the plate then it would be trapped more securely.

A problem with that sort of mount is that the considerable force required to push the plastic is now transferred via the screw holes that are distant from the line of force. That puts a lot more strain on the plastic and I have had it fail. I had to put large washers on the screws to spread the load.

Perhaps somebody that uses groove mount could explain how it is supposed to hold the nozzle securely. The slightest wobble at the top of the hot end will cause a major error at the tip. The hot end normally goes 10mm into the bracket and is secured by screws that are tapped into the insulator and hold it tight.

---

[www.hydraraptor.blogspot.com]

I've got my ABSPrusa fully built now, and all the elctronics fitted. The two things I am very dissapointed by are:

1) James from thereprapkitstore NEVER replies to email....I wont be buying anything else from there.
2) The instructions are not complete

How do I calibrate my electronics, end stops, extruder, etc? Any help anyone could provide would be most appreciated.

Regards,

Keukpa

WRT James and his communication skills, that is now a matter of record!

WRT the slot mount for the head, I still use the aluminium plate in the slot. I've justed added the shim on the cog side and the screws on the other side to support the top. The full extrusion force should be taken by the plate. I don't know if this works yet as I'm waiting for a new thermistor.

Does anyone know what solvent I could use for clearing the PLA off of the head?

As far as instructions are concerned, they are all in the wiki or referenced by the wiki. They're just not all in one place.

I don't know why James doesn't respond to email from customers. I suspect they get caught in a spam trap or something.

The force is between the drive mechanism and the hot end, so with the metal plate all the force goes through the extruder mounting screws and stresses the plastic base of the extruder. When the hot end is screwed to the block there is no force through the mounting points, only through the strong part of the bearing block.

I don't know any solvents for PLA other than caustic soda. If you heat it to 60C though it should become rubbery and easy to pull off.

The kit is basically a Prusa so it shouldn't really need instructions for things like firmware, electronics and calibration as they are not specific to that machine.

---

[www.hydraraptor.blogspot.com]

Keukpa I used the wiki pages mainly, I did ask James to finish the instructions in several of my emails but no reply. I am using Pronterface which has Slic3r built in and I edited and re-uploaded the Sprinter firmware (which you can download in my post above) using Arduino 0023. I suggest you use the RepRap IRC channel if you are in need of immediate help but if you'd like me to go through my method of getting my machine up and running I'd be happy to guide you via a Skype chat or something. I can't guarantee my method but it seems to work, I just have a little more calibrating to do. Read through the rest of this thread and I'm sure you will get answers to most of your questions.

Nophead, I think the aluminium plate James has used to secure the nozzle is too thin, there is a lot of play between the groove in the nozzle and the aluminium, perhaps thicker aluminium would wedge the nozzle in. A short term solution is just to use the screws as initially intended. I suspect that if the top of the nozzle sat flush with the base of the extruder housing it would not wobble. I doubt emails are getting caught in a spam filter because it took a paypal dispute for James to eventually respond regarding missing parts despite multiple emails which he recieved fine previously, it just seems James selectively replies to emails. I'm happy with my kit now but I would not recommend James' service.

The product page for the kit says it comes with a 0.4mm nozzle but most people I've come across with that head have a 0.35mm nozzle. My calipers are not precise enough to measure such a small hole so I'm just reluctantly relying on James' product description to be correct.

Edited 3 time(s). Last edit at 06/19/2012 11:17AM by remondo.

They are available with 0.35, 0.4mm and 0.5mm nozzles so I have no reason to doubt it is 0.4mm if James said it was.

---

[www.hydraraptor.blogspot.com]

Ok fair enough, I hadn't seen any mention of 0.4 or 0.5mm nozzles. I was concerned because there is a forum post in which people were having issues with prints only to find that their 0.4mm nozzle as advertised was in fact 0.35mm.

Can anyone shed some light on how I'm supposed to level the bed along the Y-axis? There is about 1-2mm difference from one end to the other but the Hex pillars don't allow for any adjustment. The only possibility I can see is to tighten or loosen the bar clamps holding the Y-axis smooth rods, other than that the bed should be level.

Edited 1 time(s). Last edit at 06/19/2012 11:20AM by remondo.

I am not sure, but if the pillars are screwed into tapped holes you can do it the same way I do on Mendel90: [hydraraptor.blogspot.co.uk]

I.e. raise the hex pillars by unscrewing them from the Y-carriage a little. 2mm seems a long way out though.

---

[www.hydraraptor.blogspot.com]

Ah yes of course, yes they are tapped holes IIRC. I'll give that a go when I get home thanks.

Hi Remondo, thanks for your offer...I might take you up on some advice at some point! I think I've got most of it sorted now. Just configuring the Sprinter config for my endstop positions, etc.

Could someone post a picture of where they have put their screws to prevent the extruder head from wobbling. That would be cool!

I just need to get my headbed working, and I'm good to test. When I use pronterface to turn on the heatbed nothing happens....I've measured the pins and no voltage out. Does anyone know what pin it should be in the pins.h for an Atmega644P?

Many thanks,

Keukpa

Did you press 'Set' in Pronterface next to the heatbed temp dropdown? I had the same problem and this was what I was doing wrong.

Regarding the nozzle screws, just have a look at the side extruder housing on the side where the motor is mounted and you'll see 2 holes towards the bottom below the hobbed bolt hole, level with the top of the nozzle.

If it's advice you're after Nophead is your man, or try the IRC, they're a really helpful bunch of guys on there.