New Own Design Printer 'Cherry Pi'

Vreihen, that effector/mount looks good. I would have to redesign it a little for my 43mm rod spacing and magnetic attachment but if I ever feel he need to a) auto bed level and b) regain my full print height it's a great way to achieve both. As far as PLA goes, take a look at my Thingiverse page (http://www.thingiverse.com/thing:210028) I've posted some images of prints I have done. The sculpture of the female torso was done with the E3D.

Andy

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TheTechnicalNoob
So you managed to store the bed leveling data in the eeprom which eliminated the need for recalibration at every print?
I was trying to find a way to do this but failed to find one. Mind sharing on how its done?

I see, you want to use the matrix based autoleveling from Johann. The original version was not able to store the leveling data into EEPROM. I think I read that someone implemented the storing to EEPROM. But I do not recall where it was. I forgot people use Johann's autoleveling a lot.

I do not use it. The point is that when you callibrate your printer right and have a flat bed (a mirror or glass will do) then you do not need Johann's autoleveling. Getting a flat bed is easy. Compensating for pritner calibration errors is not good if you want your final parts to have precise X/Y dimensions too. That is the reason I did not even consider it as an option.

Properly callibrated printer will move in a plane without Johann's autoleveling. If you are good at (secondary school) math you can try to calibrate it based on this (that is what I did): [github.com]

Otherwise you can try this: [groups.google.com]
It may work or not. I did not try it. I'm sure there is a class of tower postion errors which cannot be fixed by this firmware. But maybe your printer does not have such an error.

Andy,

I've been lucky enough to print out your design on my work's SLS printer. I've built up the frame and its starting to look good! I really like the design, it so simple and quick to put together.

I thought you'd get a kick out of seeing your printer in the wild (see attached)

Thanks again for answering my questions so far - i imagine there will be a few more before the build is done.

Cheers,
Charlie



Edited 1 time(s). Last edit at 02/19/2014 03:06AM by strelly.

Hi Charlie

That's looking great. Well done. You're right about getting a kick from seeing my design being built by someone else. I sort of understand now why the whole open source movement is so popular. A couple of things to watch out for. The original printed guides for the top idler bearing failed after a couple of spools worth of printing. I swapped them out for a new version that does away with the side walls. I'll get them uploaded over the weekend so you can use them if you like. I also added a prusa mk2 pub heat bed. I'll take a few photos for you. Good luck with the rest of the build. Can't wait to see the obligatory first print video!

Andy

It's up and running! Lots of calibration left to do but i couldn't resist printings out a few objects.

Seriously impressed by this design - very simple and easy to work with. Even with simple calibration this blows my old printer out of the water!!

First print video:
[www.youtube.com]

Thanks for all the help too Andy - you are a true open source reprapper!

Well done. I looks awesome. Hope you are as pleased with it as I was.

I've just added auto bed levelling to mine using Rich Cattell's Marlin fork. I've amended a design I found on Thingiverse for the effector with built in Z probe. It use the same 43mm delta rod spacing and 10mm magnets. You just need to mill six extra SHCS cups. I will post the .stl on Thingiverse tomorrow. It works really well BTW.

Andy

I've been looking at auto leveling and its great you've incorporated it into the cherry pi. I'm printing out the new z-probe end effector as i type this!

I guess i need the clamp from this design? [www.thingiverse.com]

Thanks,
Charlie

Hi Charlie

Yes that's the one I 'Cherry picked'

But I've now found this one [www.thingiverse.com] that does away with the probe in favour of using the actual hotend. Seems like a more efficient idea. I'm currently reworking the attach points for the rods.

Andy

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AndyCart
But I've now found this one [www.thingiverse.com] that does away with the probe in favour of using the actual hotend. Seems like a more efficient idea. I'm currently reworking the attach points for the rods.

Mine just finished printing. I can't wait to get rid of the popsicle sticks and multi-function oscillating tool triangular sanding head that I have been using for an effector plate in my RepStrapped Delta.

My only hesitation for using this design was deforming the tip of the nozzle by intentionally pushing it into the print bed repeatedly. Seeing Johann now doing it with a hard fixed hotend mount and measuring with pressure sensors where the minimum range is 0.1kg, I think that rocking the hot end on a switch with a rubber band as a spring will be more gentle on the nozzle......

Quote
AndyCart
But I've now found this one [www.thingiverse.com] that does away with the probe in favour of using the actual hotend. Seems like a more efficient idea. I'm currently reworking the attach points for the rods.

Andy

Now that's an awesome idea. Does away with Johann's latest approach (the three pressure pads under the bed) and keeps the ability to use the nozzle.

I did see that one too but it relies too much on the nozzle tip being completely clean prior to calibration. I guess a simple wipe script would solve that problem.

I'm going to hold off auto bed leveling until i've got my print quality a bit better. One thing at a time!!

The great thing about this printer is how easy it is to modify. I had to take the hot end off yesterday (on my old printer that was a big problem) and it took minutes! Just simply pull the end effector off the magnets and you're half way there!

If the printer's already up to temperature it should be fairly ok I'd have thought.

The alternative is have the printer do retraction at the end of a print, then again before attempting to level. That combined with pre-heating should make it ok in most instances I'd have thought.

Hi Guys

I've not had any issues with a 'dirty' hotend since I swapped out the Jhead for the E3D. As soon as I have the new hotend probe up and running I'll post a report and some pictures. As far as swapping effectors/hotends goes I do it all the time. I have come up with a plug and socket arrangement for the heater, thermistor, part cooling fan, E3D cooling fan, LED ring and now the Z probe microswitch. I'm beginning to wonder if there is anything else I can hang on there!!! I invested a while ago in a set of molex crimps (£25 off ebay) they allow me to just crimp connectors on. I currently have 3, 3 pin connectors for all of the above. The biggest issue with changing an effector is heating up the hotend to be able to pull the bowden tube out and not burning my fingers in the process . I'm fairly sure if I looked closely at the Rumba schematics I could get the cable count down by sharing gnd connections but so far I having had a problem as I put a few spare cores in when I built the machine.

As far as print quality goes it's like all other machines, speed and temperature. I currently run 80mm/s on both PLA and ABS and 190 for PLA, 230 for ABS. Since I added the Mk2 heated bed I run that at 70 and 110 respectively. The borosilicate glass (£5 for a 200mm square 3mm thick from ebay - china, and included postage, how do they do it???) things are a lot easier as all i do is unclip the glass at the end of the print and parts just pop off when it cools. PLA doesn't need anything but bare, clean glass. ABS, I use a Pritt stick. so far so good and print quality is better than my Huxley at 30mm/s. The E3D nozzle is 0.4 and I normally print at 0.2 layer height.

I also have started using Cura. It's great as there's not much that you get tempted to fiddle with and it slices in a flash. Still use Repetier Host if I want to 'talk' to the machine as I much prefer it's interface.

One issue that's cropped up this week is that the rotary switch on my RRD smart controller is playing up. It feels different and to get a click takes two or three goes and I normally have to pull up a bit before I push down. Anyone know if you can get a replacement?


Regards

Andy

Edited 1 time(s). Last edit at 03/03/2014 11:58AM by AndyCart.

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AndyCart
The biggest issue with changing an effector is heating up the hotend to be able to pull the bowden tube out and not burning my fingers in the process .

For the sake of your fingers, buy a length of PTFE tubing for each of your hotends and detach them at the cold extruder end.

I'm thinking about putting a mounting plate next to the cold extruder motor with the plugs for the hotend secured to it. That way, the cable umbilical follows the same general path as the bowden tube, and the weight of the connectors are "sprung weight" (to borrow a term from race car suspension design) attached to the printer frame and not the moving effector plate. Any mass that is removed from the effector plate for reducing momentum is a good thing, IMO.....

Just been playing with some thin walled prints and ive noticed the printer is acting a bit strange. The end effector seems to slow down slightly every couple of seconds which causes a slightly bulged wall.

video
pictures

I've asked on the reprap IRC with no luck. I've spec'd the machine almost identically to Andy's one. Any idea mate?

Thanks,
Charlie

Hi Charlie. Very strange. Doesn't look like stepper driver thermal shutdown. That's normally a complete stop and restart. I can't remember which Arduino board you are using. Maybe you're delta segments per second is too high. Try 160 to minimise the calculations required. I assume this is from an SD card print. I.e not direct from the PC. I have had PC prints do this when the PC couldn't push data down the USB fast enough.

Andy

Cheers for the reply Andy.

I'm using Rumba with DRV8825 drivers at 1/32 microstepping. It's printing from SD card direct from my full graphics LCD.

I've tried reducing the delta segments down to 100 and even 50 and it still does the same thing. I've tried a different SD card with no luck. i've tried dialing down the printing speed on the jog wheel too.

Its strange because when the xyz movement slows down the extruder does too. Its like the printer 'pulses' from normal speed to a lower speed.

Pulling my hair out because i'm not sure if its a slicing issue or firmware issue.

EDIT: do you think its worth reducing my microstepping down to 1/16? would that effectively halve the data being processed?

Edited 1 time(s). Last edit at 03/03/2014 05:17PM by strelly.

Hi Charlie

It's got to be worth a try. It's a bit of a job pulling two jumpers off every driver though. My set up is identical to yours and I run 200 delta segments and 1/32 micro stepping. The only difference is that I have the smart graphics display not the full graphics like you. I have printed loads of spiral vase prints from Slic3r with no issues other than the occasional thermal shutdown from a driver. I've dialled the pots down a bit now and it's cured.

Is it only exhibiting with spiral vase prints?

Good luck

Andy

Hi Charlie

Just a thought. My Rumba came with a spare SD shield. I assume yours did too? Try disabling your graphics controller in firmware and use the SD shield instead. You can initiate the SD print from RH or Pronterface. It would take that aspect out of the chain. The most likely cause is that the Arduino isn't getting data fast enough so the SD data path must be a good place to start diagnosis.

Andy

Hey Andy

I might try going down to 1/16 and run a print as see what happens. The stuttering seems to happen on all prints but its especially obvious on the spiral vases.

Also another point i forgot to mention is that the full graphics display is very unresponsive only when the printer is printing.. there definitely seems to be some sort of bottleneck.

Good point about the SD shield - that would certainly cut out the possible problem associated with the display.

I'll keep tinkering! Thanks for all the help Andy

Charlie

Looking at that video Charlie the stuttering/stopping would likely be those DRV's - I've seen a few videos of the same thing. It's something to do with the board needing to pause to catch up or something (yeah, not the most technical description - sorry!).

Andy - for the SmartLCD if you do need to get another one, I've seen some pretty cheap on eBay and AliExpress. I'd go for the AliExpress ones as if they arrive and the soldering is terrible, you just take a photo and file a dispute and the seller will be forced to provide a refund. It's in their interest to provide high quality goods as they dont get paid until you confirm it's ok.

£11.02 for the standard Smart LCD here: [www.aliexpress.com]

Or if you want the fancy one, it's £24.24 here: [www.aliexpress.com]

Have a look around though as shipping times can be pretty long for some of the sellers.

It might pay to check if its related to the resolution of the prints. If a circle has 20 segments, thats pretty blocky and easy to process, but if a circle has 5000 segments, the arduino is going to stutter as it pauses while it processes all that data while its trying to move in a circle. If its resolution that is the issue then commands like G1 Y100 shouldn't be an issue as it is simply saying go to this coordinate and not overloading the arduino.

Just placed an order on Aliexpress. Wow those prices are good. I ordered a replacement LCD and a full set of RAMPS, A4498s,LCD, Mega, steppers, psu, belts and pulleys to build a second Cherry Pi ie everything apart from bearings, extrusion, hotend and a few nuts bolts, tubing, etc and it cost less than £120 including shipping. That should have a complete Cherry Pi up and running for less than £200.

Andy

Edited 1 time(s). Last edit at 03/04/2014 12:29AM by AndyCart.

Nice one I bought my wantai motors via AliExpress - couldn't fault the service. I think my Prusa i3 motors came from there too. I'll be picking up another RAMPS 1.4 and arduino as well, as the one on my Prusa i3 is faulty (cant upload any new firmware). The AliExpress ones are dirt cheap compared to RepRapDiscount (who do also sell on AliExpress).

The only thing I've not been able to find there is borosilicate glass. I'm having an absolute nightmare trying to get a 250mm round piece. The only place that has it is in the US and charges $40 + $30 shipping with no returns (so if it's broken, I'm screwed).

One thing's for sure - the Cherry Pi allows for a very cost efficient build. My biggest expense was the Rumba kit, everything else has been really cheap and easy to source. All I've got left on the list is the glass, and I've got to decide what route to go with the effector with regards to magnetic connections and auto levelling.

Edited 1 time(s). Last edit at 03/04/2014 05:33AM by RickM.

My borosilicate was easy to source as I used a square mk2 heat bed. Round would have looked much better though. At less than £20 for the heater and the glass it was too cheap to ignore and it works great. Maybe round glass and heaters will have dropped in price for my next build!

Andy

I think I may end up having to go for a square piece for now. I pinched an old microwave plate that's the exact size I need. Unfortunately it's got those three annoying bits sticking out the bottom of it to attach to the microwave, and there's a slight dip in the center of the flat surface. Not sure if it'll be any good for heat transfer as there would be a ~1cm gap between the heat bed and the plate.

I'm looking at the possibility of using a slightly modified base for my printer, with a sprung bed. Basically I was planning on either getting an acrylic, or hardboard piece cut that will sit on top of the triangle shaped base, then have a raised surface from there, with some fans positioned under the bed to allow better cooling of the rumba board. Basically the end result will be that the base is fully enclosed, with cooling and the head bed and glass will sit on top of a circular insulated plate.

Theoretically it'll work...in practice I have no idea!

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RickM
The only thing I've not been able to find there is borosilicate glass. I'm having an absolute nightmare trying to get a 250mm round piece. The only place that has it is in the US and charges $40 + $30 shipping with no returns (so if it's broken, I'm screwed).

It doesn't need to be borosilicate. Try a piece of round mirror glass like this: [www.amazon.com] (that's 10 inches diameter, which is 254mm). You should be able to source one in your country pretty easily. Where are you located?

Many people (including me) have used mirror glass like that with much success. The thermal stresses aren't great enough to really risk breaking the glass, and if you do manage to chip or crack it, it's cheap to replace.

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They're expensive, but I'm curious to see advantages/disadvantages of using a pizza stone for the bed.

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NewPerfection

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RickM
The only thing I've not been able to find there is borosilicate glass. I'm having an absolute nightmare trying to get a 250mm round piece. The only place that has it is in the US and charges $40 + $30 shipping with no returns (so if it's broken, I'm screwed).

It doesn't need to be borosilicate. Try a piece of round mirror glass like this: [www.amazon.com] (that's 10 inches diameter, which is 254mm). You should be able to source one in your country pretty easily. Where are you located?

Many people (including me) have used mirror glass like that with much success. The thermal stresses aren't great enough to really risk breaking the glass, and if you do manage to chip or crack it, it's cheap to replace.

I'm in the UK. Sadly all the circular mirrors around here seem to be made of acrylic.

Quote
RickM
I'm in the UK. Sadly all the circular mirrors around here seem to be made of acrylic.

Here you go: [www.amazon.co.uk]

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Help improve the RepRap wiki! Just click "Edit" in the top-right corner of the page and start typing. Anyone can edit the wiki!