Thursday, 29 September 2011

Printing Surfaces

So there was a little discussion on #reprap the other night about what is the best surface to print onto.
I have tried a few different surfaces and have come to the conclusion glass seems to be the best, its easy to clean, but hard to work with when making your printer.. as you (should be)  printing more than assembling the difficulties in working with the glass should not really be an obstacle.

I have tried several surface materials with ABS (haven't tried PLA yet), l will list them for you..

MDF (plastic doesn't stick well, i suspect it sucks too much heat from the plastic for it to stick)
MDF with kapton tape (plastic sticks ok but will warp up once it cools.)
White masking tape ( sticks ok but my settings were not right and i was applying too much plastic so the nozzle knocked the cube free before it finished.
Bare Aluminium works well but can scratch up really easy.
Glass Unheated. Plastic does not stick!!!
Glass Heated plastic only sticks when its hot enough. ABS110'c. this works like a charm.
Glass Heated with sandblasting surface finish. (0.5 welders slag for sandblasting grit) plastic sticks to this like turd to a blanket.. and is just as hard to clean... when you scrape the top clean there is a little bit of plastic crud that is left behind and cannot be removes by scraping. need to soak in a chemical (acetone for ABS) this level of cleaning (IMHO) is not really required unless you have some real contaminant on the glass bed (eg lard used on crappy nylon bushes on your x axis.) then you may need to really remove the excess plastic that may be harboring some grease or something that will stop the plastic from sticking. there is a caveat to the sandblasted glass, it will efffect the finish on the bottom layer of the object being printed, you will get a surface texture that is the same as the sandblasted surface.
 you can by all means get smaller grits for sandblasting but the 0.5mm grit was what was at hand.

here are some pics of the bottoms of objects that i have printed..

 the two pictures above are of things i printed on a high gloss piece of glass

the above three pictures are objects that i printed on the same piece of glass as above but after the surface was sandblasted with 0.5mm welders slag. this finish is not too bad if you ask me.. i kind of like it better than the full gloss finish. the result of the sandblasting was the plastic stuck really really well at one point i thought i was not going to be able to get the objects off..

for my new printer i am considering sand blasting one side of the sheet of glass that way i have the option to turn it over if i do or don't like one...

there was discussion of getting the glass chemically frosted, as well as frosted with a laser. the chemical treatment would probably work, but from what i learned about how the laser is used i am doubtful that this will have an effect. the laser treatment is performed by submerging the glass object in mineral oil and then directing a laser at the area to frost. the frosting (as i believe the process goes) is a result of the heat of the laser liquifying the glass (maybe to the point of plasticity ) and inducing boiling bubbles in the middle of the glass not the surface. I think the surface will still be flat and smooth. this is only an aesthetic change not a surface treatment. we need the surface to be flat and grippy.  if you look at the pictures of my first printer you will see the glass that i was printing on, there is two pieces one is sandblasted the other is not. they were scrap pieces of glass from some old kiosks at my work.

Sunday, 25 September 2011

Progress Update 5

Today I really really want this printer to do something other than take up space, And after the other nights efforts of Nuking a few stepper controller chips I have decided to install the old crappy Gen3 electronics set.

Oh the Gen3 is a Ugly ass creation, effective to some degree but its a mess!

In my travels today I latched onto some lubricant, Its a can of Spray lithium grease, it smells a little,but no where near as bad as the marine bearing grease that I had used on the old printers axis'
 and @ $10 a can its a bargain, this will make a thick layer on what ever it is sprayed onto, this will be great if i every have to park up the printer and store it for a bit while not being used this will prevent the steel from going rusty.

here is a picture of the printer as it stands, apart from the extruder the beast is wired up.

While i was attaching the endstops someone on IRC #reprap had asked the question about an easy way to square up the print bed, having seen this question pop up a few times previously i thought about it for a moment and devised a simple Z probe for my printer. this is what i have come up with.

 here you can't really see it through the glue holding the cable into place, but i have a tiny micro switch with a lever that hooks into a bit of brass tube that the bolt pushes up, there is a little slot that the lever fits into, this allows me to adjust the height with out it interfering with the amount of travel.
here you can me pressing the bolt head up to illuminate the indicator LED. now i am not 100% sure if this will work, or if its useful so i have also made a traditional micro switch endstop for the Z axis Min, just in case. I am thinking of putting in a switch that will allow me to choose between the two options. MIN or Z probe. the firmware will be fun.

Things left to do.

Need to go an purchase a piece of glass that is 2mm 470mm square, the framing shop quoted me $25 cut to size.
Will need to weld up the frame that will support the glass, heat spreader, element and heat shield. this will be place onto springs and held down with some screws to provide adjustment to get the bed nice and square to the extruder . ahh that reminds me i think i will get the glass cut with some 20mm 45' cuts on each corner to allow for the adjusting screws, getting the corners cut off is much much cheaper than getting holes drilled into the sheet glass.. not as pretty but who is going for looks, i want functionality.
Then all that is left is the Extruder...

but for now i am going to go and play with some firmware to see if i can get it to listen to the endstops. i was playing with Teacup firmware by Triffid_Hunter. but the version i had doesn't explain the endstops really well, so i have no idea if i am configured correctly.
So now i will try Sprinter by Kliment and see how that goes.

Ok Sprinter seems to be working  great, i managed to map all the pins to my setup and i can exercise all the axis' My X and Y axis' move upto 1700mm/min (283mm/second). this is GREAT its about 27 times faster than my previous printer, but the accuracy has been reduced i get 4 steps/mm (ie 0.25mm steps) i will be getting some new 10T pulleys and some new stepper driver chips that will allow better micro stepping option. this will give me 64 steps/mm :) 0.015625mm/step..  i could go even further and use a 8tooth pulley but the belts do not like going around those. the radius is too tight, and would require an idle roller to over come that, that sounds like too much trouble and will only give me an extra 16 steps/mm not sure if i need that level of accuracy.

so far i have tested all three axis' they all work fine except for Z it seems to bind in the upper 30mm of travel, not too sure where the problem is but i dont care about that. this limits my print area to 470Wx470Lx175H on the small bed. ahh things never work out how you plan.. :)

Saturday, 24 September 2011

Not happy!! :(

Just blew up two stepper controllers.. not happy.... have to update/create a separate  page for parts i have blown up, or broken during this whole fiasco..

I Never have any luck with stepper drivers, the only time i get to actually use them is when they come in a kit like the gen3 :( now i am waiting for a RAMPS pcb to arrive in the mail, will start collecting the parts for that, will need to get a arduino mega 1280 to ensure its a hassle free operation.

its not been a good week, the post man took three days to deliver my parts that i just blew up in 30seconds, this hobby doesn't really make ecconomical sense in any way shape or form, but Meh neither does drinking, and we all keep doing that....

have to order up some more steppers, i needed to order another two for the extruder, but now i need another two, and i probably should get a few spares, hmm think i am going to need to get just the IC's and gets the hot air gun out or it will be noodles for me real quick...

Friday, 23 September 2011

Progress Update 4

Last night i was at my mates workshop to build something to connect the belts to the tension springs without the belts wearing. these were really simple they are made from 3mm aluminuim, with a hole for the spring and a slot that the belt can go through. the belt is then bent back and ties off with some cable ties. 

I Also  made some brackets for the X carriage to hold the springs and anchor the belts, these are now installed and ready to go.

I had to add a spacer between the angle and the anchor to raise it above the bearing bolts.

I just visited jaycar and left with lots of goodies, i bought some multi core cable to extend the stepper motor wires, and a whole stack of various connectors and heat shrink, I have been tossing up on weather to upgrade my electronics or not, so i thought i will do some thinking and see what i need from my electronics.

so i want to have 3 nozzles, this will require 6 pins 3 analog inputs and 3 pwm outputs, i will need to control the heated bed this will take another analog input and 1 digital output, could be pwm but it doesn't need to be. i need 1 digital pin for the fan. 12-15 pins for 5 stepper controllers. and 6 pins for the endstops.

6   +    Heater + Sensors
2   +    Heated Bed + Sensor
1   +    Fan
15 +    Steppers ( S,D,E x 5)
6         Endstops

that be a total of 30 pins, that's just what the ATMega644 has exposed on the Gen3 motherboard, yes i will have to use a USB - TTL converter but that's easy. I made one from a pic18f14K50 chip and crystal, used the sample firmware provided by microchip (there is a cdc emulator that is perfect for this no mods needed).

 X carriage you can see  the belts anchored on the left and attached to springs on the right, this keeps the belts nice and tight, the anchors for the belts should help prevent them wearing, if they fail i will get the corrugated plates made for anchors.

 The Y Axis belt attaching to the springs. i bent the belt back again just to keep the excess from interfering when the carriage goes all the way to the end, the excess would jam the pulley.

 just a couple of shots showing me the measurements so i could make the brackets the right size.

 I have started to layout the track board RAMPS type carrier for my nice new shiny stepper motor controllers they are pololus without the 5 volt regulator. that's no problem i will add one its easy.

i am planning on soldering the gen3 motherboard to the track board and run wires to the bit on the under side, this will be much neater than the previous setup. as you can see there is 4 pololu stepper controllers there, these are fro X Y and 2 for Z, I could use one driver for Z but my motors are Larger Nema23's so i will use one for each. i will then reuse 2 of my MB2.3 stepper controllers to drive the two stepper motors on the extruder. one is for selecting the filament and the other feeds the selected filament. i am thinking of re-designing the extruder, and i may change the filament selection stepper for a smaller one with a much much higher gear ratio, the camshaft doesn't need to go really fast so i can use a smaller one and save weight, i might even switch to a smaller stepper driver to suit. I have a stack of PM14 and PM20 stepper motors and some 1amp driver chips to suit, i have drawn up a control board for them, yet to get them etched, i will one day soon, if anyone wants to look let me know and i will post the schematic and pcb files, i have used a pic to convert the SDE signals to grey code that the stepper driver wants, the pcb is really small, i have drawn the board up to take 5 of these but can be separated. the plan is for a micro printer one day, will be slow but very very accurate, a friend of a friend is a jewellery setter and  can drill me some micro nozzles, this micro printer would have a 50mm^3 print area designed for wax casting.

Sunday, 18 September 2011

Progress Update 3

It's been a productive few days, the plan changed slightly, only the threaded rods for Z axis comes off the main frame, all smooth rods are welded into place and bearings cannot be changed, Meh...

So at the moment i have all the motors mounted, with their pulleys attached and their respective idle pulleys. The Z axis is all bolted up and the lead screws and motors all turn very easily by hand, i have attached a few spare gears from the old setup to the tops of the motors to allow easy adjustment.

The Y axis bed frame is welded and bolted to the bearings, The same for the X axis, all the axis run really nice and smooth they don't free run when you push them but they all move with a single finger.

Next i have to attach the belts 2 for  each X and Z axis. this will hopefully this will keep the carriages nice and square and allow them to roll nice.

I will have to stop at the hardware and get some screw in rubber feet for the base of the frame to keep the Y axis from hitting the motor i have had to mount it about 10mm lower then the bottom of the frame, so at the moment that end of the frame is resting on the motor mount, this will be resolved with some standoff feet. They will also help keep the noise from the table vibrating.

 Under Shot of the X carriage.
 Top Shot of the X carriage plate.
 Shot showing the lead screws coupling to the Z motors.
 Y Axis motor with T5 20teeth pulleys.
 X Axis Motor with pulley, same as Y axis.

 Where X meet Z axis. and X axis idle pulleys.
 Another overall shot you can just see in the top of this picture the gears i have mounted to the Z axis to allow easy adjustments. I have also placed the old Glass bed that the previous printer used as a print bed. this new printer is has a bed that's twice the size of the old bed, but will be able to take another bed that's twice this size. this frame is square with 478mm sides and  677mm diagonals. the longer bed will be 800mm+ long with the same width.

The Z axis was an absolute bitch to install, even though the entire printer was welded pretty much in situ we moved the bearings so the TIG welding didn't cook the goodness out of them, this allowed things to move. It was almost like they were welded under tension, but i know this was not the case. So i persevered, I had to file 1mm clearance extra around the vertical smooth rods as the X frame seemed to have gotten a little wider, this solved half the problem, next i had to bend the bracket that holds the captive nut for Z so the threaded rod would run that little bit smother. Then everything went together really nice, rather annoyed at myself for leaving the belt at my mates work shop. My boss probably thinks its a good thing as i will get a good night sleep instead of working on the printer until i get movement :) so i will go to the workshop tomorrow buy a few mice and feed the snake while i am at it, he is really hungry and then see about attaching the belts, that reminds me i also left the tension springs there too.

Now that i have this much done i am questioning the design of the Triple extruder that i have been planing to use from the old printer, it seems like it going to be rather difficult to install with out it interfering or limiting my print size too much, every way i look at it, it doesn't seem to fit, That was a prototype, and never was intended for long time service, there are too many little things i am not happy with on it, so i may take this opportunity to start the Triple extruder MK2. a lower profile version that may even be print able. to get to use all of the current print bed i am going to have to cut some arches out of the X carriage plate to clear the lead screws and bearings on the Z axis.  

Thursday, 8 September 2011

Not much going on..

So not much progress on the printer we are waiting for the weekend so we have some space in my mates workshop, All we have to do is drill some 10mm holes for the dowels to be welded into.

So i thought i might describe my plans on how i am going to drive my axis'. The Z axis has two motors on it, these are rather large  KL-23-251-24-8B Nema 23 motors that have ~0.6Nm they will have no issues picking up a few kilograms between them with the 1/2inch threaded rods and linear bearings. I have also used the same motors for my X & Y axis but these are being driven by 24Volts (Z axis is 12volts) hopefully the extra voltage will result in more Speed!!

To help try and make things runs smooth i will be using two belts on each axis. The motors i bought have the axles 25mm out each end, i have purchased 8 T5 15tooth pulleys and 5meters of belt, i think i am going to be short on belt and have to order some more. The main reason i want to use two belts is to ensure that the bed is pulled evenly and not jam the linear bearings, as X is a little narrower i don't need to use two belts but it makes things easier if i do. It allows me to mount the motor sort of centered.

Currently when I have been playing with the axis' if i try and move them by holding the ends of the aluminum bars the bearings jam, but if i apply the pressure in the middle a single finger can roll them back and forward, I think I should be fine with two belt, this also keeps the center of the X plate clear for the extruder to live.

Friday, 2 September 2011

Progress Update 2

So my nights have been long and cold working away in my mates workshop we have made quite a bit of progress and only one or two stuff ups to the tune of $10, when i purchased a 1.5m length of 10mm bright bar for the X Carriage to run on and cut it into two i noticed i had about 200mm left over that i thought sweet i could use that to make the axles that the T5 pulleys spin on, so i measured those and cut them first. then i cut the remainder in half for the X axis this was BAD and resulted in me not having enough steel to make the distance between the end plates that bolt the Z axis bearings, which i had to spin around to allow me to move the leadscrews to just inside the A frame.

Now i have all the parts for the X Y Z carriages and frames tack welded into place, the motor mounts are all done as is all the smooth rods all that i need to do before everything gets a final weld is to make some mounts for bearings at the bottom of the lead screws to keep them true as they spin and i should be good to go, this will require me to remake the lead screws so they are a little longer and have a smooth section that the 1608 bearings will run, and to install 10mm dowels into all the sections that are removable this will remove any chances of them going back together in a different place and thus keeps everything nice and square and maybe a little serviceable.

 I am a little worried that once everything is tacked and then i try and pull it apart that i may not be able to take the Z axis smooth rods off, if this happens with the current setup i will not be able to take anything else off if i need to, if i find this is the case i will have to cut the peaks of the A Frame off to allow me to take the Z motors off..

Hmmmmm Bearings 10mm & 16mm linear bearings i bought off ebay :)

Upside Down upside down.. here is an action shot of the frame being TIG welded by a master of the Art, that's not Me...

The Bare Frame Completed, 25mm box tube 3mm walls and not a bit of flex in it :)

 The Motor mounting plates, made from a section of 55x75x3mm ROHS box tube cut firstly into L sections then cut the center holes in each then the mounting holes were drilled then tapped, i plan to screw the motors down from above the motor.
 The Z Axis 16mm Linear bearing with X axis 10mm smooth rods that were just a little too short and had to be replaced Doh!
A different angle of the end plates.

Z Axis smooth rods with the bearings mounted, yes all the bearings will be welded onto the smooth rods and will not be replaceable, i had planned on getting split style bearings but when i was ordering i could not justify triple the cost, for these purposes i doubt they will wear out too fast not much load on them.

 here you can see the mounts for the Y carriage as well as the other axis, the two 50x3mm flat aluminum bar will be taken off and four pieces of 20x15x3mm Angle will be attached to make a frame that the glass bed will seat into, the glass bed will have a smaller 10x10x2mm angle frame that supports the glass the heater and a sheet of 2mm aluminum that will act as a heat spreader and give me a way to mount the heater tight against the sheet to couple the heat better, below this i may add a second sheet on the lower side of the heater to reflect as much heat upwards as possible and stop my desk from bursting into flames.

 here you can see me aligning the axles of the motors up with the axle for the idle pulleys, making sure the belt does not hit the bearings or the bed or anything.

another angle of the alignment process.