Prusa i3 3D printer

[tekkydave]

Ordered some sheets of acrylic to make a fume enclosure for the Prusa. I realised I needed to make the x-axis narrower as the idler end overhangs the base. I'm currently reworking the idler in Sketchup so the bearing is to the inside of the z-axis threaded rod. A bit fiddly as I dont have the original Sketchup files, just STLs provided by the kit seller. Incidentally the kit seller, Semi-Utilitronics has now dropped out of the 3D printer market.

[tekkydave]

Managed to redesign the x-axis idler part. The right-hand end now stops at the end of the smooth rods. I need to build some kind of belt tensioner into it before printing it.

Original kit part

Redesigned part

 

[tekkydave]

 

One thing I have noticed while looking at other x-carriage configuration & parts on Thingiverse is that my Prusa is different. All the others have the horizontal x-axis smooth rods between the vertical z-axis rods and the frame. Mine has them in front. Must be a quirk of the kit designer. It's not an issue really just curious. It could be easily rearranged if I use different printed parts but I would need to move the y-carriage backwards wrt the frame to allow the front edge of the print bed to be reached by the print head.

I am toying with the idea of replacing the z-axis M5 threaded rods with proper leadscrews. There is a nice set of printed parts to use on Thingiverse that I came across yesterday.

 

[Gina]

I toyed with the idea of using those "proper leadscrews" on my printers but ended up with string, pulleys and drums as you probably remember.

[tekkydave]

I haven't made any further progress today as I have been out painting the pergola green.

It's a bit like painting the town red but less hedonistic  

 

[John78]

On 10/20/2016 at 09:07, tekkydave said:

 

One thing I have noticed while looking at other x-carriage configuration & parts on Thingiverse is that my Prusa is different. All the others have the horizontal x-axis smooth rods between the vertical z-axis rods and the frame. Mine has them in front. Must be a quirk of the kit designer. It's not an issue really just curious. It could be easily rearranged if I use different printed parts but I would need to move the y-carriage backwards wrt the frame to allow the front edge of the print bed to be reached by the print head.

I am toying with the idea of replacing the z-axis M5 threaded rods with proper leadscrews. There is a nice set of printed parts to use on Thingiverse that I came across yesterday.

 

Thats a mighty fast screw he used!  I've got the rods and home made antibacklash delrin nuts for mine, I've just got to fit it - autobed levelling is tomorrows upgrade though.

 

TR10 - 2 taps are cheap on ebay and the screws aren't too bad...  I use ebay seller marchantdice

http://www.ebay.co.uk/sch/marchantdice/m.html?_nkw=&_armrs=1&_ipg=&_from=

This set looks quite good value...  You'll need access to a lathe to make the nuts though.

http://www.ebay.co.uk/itm/Custom-Set-TR10x2D-Trapezoidal-Spindle-Tap-Delrin-4pcs-Flange-Housing-3d-Printer-/311335037367?hash=item487d03a9b7:g:uaEAAOSw7aBVJnzZ

[tekkydave]

Added a mechanism to the x-axis idler to allow for belt tension adjustment.

I initially printed it after slicing with the usual Slic3r setup I have been using since I built the printer. I had real trouble removing all the support pieces so decided to try Cura for slicing instead. It is reputed to produce support that is easier to remove. Well I can report that it's true. The support just pulls off with a bit of twisting & pulling. Here are the results. 

The M4 nut was inserted into the slider with some heat from a soldering iron to get a good tight fit. The M4 bolt through the rear of the body moves the slider in & out so tensioning the belt. There will be a couple of 624ZZ bearings on an M3 bolt between the 2 holes at the front of the slider. 

Overall this knocks about 30mm off the overall width of my printer so it should now be possible to build the enclosure.

 

[tekkydave]

Got round to fitting the new x-idler today. Here is the old one I removed first. It includes the very ugly clip-in adjustable tensioner I designed a while back (the white bits). The extra width this added to the printer is what is causing the current issue.

I then assembled the new tensioner with the adjustment at the front.

Finally this was fitted to the printer x-axis.

Before and after shots:

This actually reduces the overall width of the printer by 52mm. It now sits within the dimensions of the base enabling a fume enclosure to be constructed. I have 5 sheets of 3mm acrylic 500mm x 500mm but I haven't come up with a satisfactory design yet. It needs to be pretty airtight but also be able to be removed easily for maintenance. I would like to be able to disassemble the enclosure so it takes up minimal space when not in use. It probably needs to use a slotted or foldable design so I need to get my thinking head on.

[tekkydave]

Forging ahead with my plan to relocate the Ramps & Raspberry Pi to a fixed enclosure on the printer. I originally put them in a separate enclosure connected by 37-way DSub connectors. This has worked very well but I now want to enclose the printer for fume control. This will be easier if everything is self-contained - fewer leads and cable entry/exits to worry about. I found this enclosure for Ramps and RPi B+ on Thingiverse which I am currently printing. I printed the top & bottom shell parts over the last few days. They each took about 8 hrs as I did it at a slow speed (40mm/s max) to reduce vibration. These tall prints can become detached from the bed if they get too much shaking. I am printing the end panels today - Pics to follow later.

Once the electronics are integrated I plan to do some other enhancements such as adding temperature control for the extruder fan. There is an advanced option in Marlin that allows the extruder fan speed to be connected to the extruder temperature. This means the fan will only come on when the extruder is a above a certain preset temperature (e.g. 50C). At the moment mine is on all the time, powered from the 5VSB supply and a 5V to 12V buck converter. It can be annoying as it is quite loud & doesn't need to be on unless the machine is actually printing. This will need extra electronics & a Mosfet circuit to control the fan via a spare pin on the Ramps board. Usually one of the spare servo pins is used. I could use the spare D9 Mosfet output but that is used by Marlin as the printed part fan control which I also want to add at some point.

Another enhancement could be separate Z-motor drivers. I have a spare stepper driver position on my Ramps which is normally used for a second extruder. Another advanced option in Marlin allows this to be re-defined to drive one of the Z-steppers. This allows each motor to have its own driver allowing faster Z movement and the possibility, with 2 separate z-axis end-stops for auto-levelling of the x-carriage. At the moment both of the Z-steppers on my prusa are controlled by a single Pololu driver. It works but the z-carriage speed is limited to about 3mm/s otherwise it stalls, even if the Pololu current limiting is at maximum.

[tekkydave]

Pics of the new enclosure:

The two halves of the shell

The end panel that houses the 80mm fan

Trial fitting of the first 3 parts

I will print the other end panel this pm.

I have some M3 threaded brass inserts and M3 thumbscrews on order to make panel fitting and removal easy. I'm always fiddling with the electronics and normal screws into plastic holes soon wear out after a few insertions & removals.

  

[tekkydave]

Printed the other end panel. This provides the access to the Ramps/Mega and Raspberry Pi connectors.

I may well end up redesigning this depending on how I need to route the cables to/from the printer components.

 

[tekkydave]

These are the threaded inserts I have on order. The outside dia. is about 5mm. If you drill out the hole to 3 or 4mm you can push them in with a hot soldering iron. They melt into the plastic and stay put. I'll fit these in the ends for the panel thumbscrews. Hopefully this will make it easy to remove one half of the shell for access without needing access with a screwdriver which would be awkward. I intend to fix the Ramps half of the shell to the Prusa and have the RPi half removable.

[Gina]

I'm rather surprised your extruder fan is noisy Dave - mine is barely audible even on the full 12v.  This is one on Amazon though I got mine from ebay for about £8.  The fan is 30mm square and nice and quiet.  Beware that some of these fans are 5v not 12v.

All Metal J-Head E3D V6 Extruder Feeder Hot End 12V DC with Cooling Fan 0.4mm Nozzle for RepRap 3D Printer 1.75mm Filament

My cooling fan for the electronics is a 60mm square computer fan rated at 12v which I run on 5v from the ATX PSU normal +5v rail.

Also, I wondered why you have your extruder fan run from the +5V-SB supply.  I run mine from the ATX PSU +12v rail.  It switches on when the print is started and off about 3 minutes after printing has finished allowing the filament to solidify before cooling is turned off.  Currently, I'm using timing but could use hotend temperature I think (not sure).  I just control the PSU power from the PS-ON connection on the RAMPS.  The Arduino Mega is powered continuously from the USB.

[tekkydave]

It's more annoying than noisy really. It is the 30mm fan that came with the kit and it's definitely 12V. I have the 5VSB stepped up to 12V by the buck converter to run the extruder fan so it is always on. I didn't want to risk damaging the extruder printed parts like I did when I was first building & testing the printer.

The cooling fan for the electronics is the 120mm fan that came with the PSU case the whole lot is currently housed in. That is on the ATX PSU 12V supply so only runs when the 12V supply is on following an M80.

If you look at the Configuration_adv.h file in Marlin it has instructions for how to implement each of the advanced features, including temperature control of the extruder fan.

[Gina]

I could leave mine on, in fact I could leave the whole lot on as I can't hear anything running if I'm more than a couple of feet away from it.  On the settee, the computer fan nearer me drowns out the printer when there's no TV or radio on.  But I have this idea of saving a few watts of power when it isn't needed

My Pilot printer started off as the Velleman kit but there's very little of that left - just the frame and the Y carriage and rails.  Oh and some of the stepper motors I think.

Once you have a 3D printer you can make another with improved spec.  The "RepRap" principle, of course.  I guess I cheated and bought a ready made machine (the little UP Plus 2) as the Velleman kit never performed well enough to make parts for 3D printers of much else actually.  Of course, I have spend an enormous amount of time getting these printers working and if my time were to be evaluated they would cost the earth   But it's all good fun if rather frustrating at times (like astronomy!).

[tekkydave]

Bit the bullet today and started disassembling the existing control box. The area on the printer where I want to put the new enclosure is currently carrying lots of cables so had to unclip all those first and remove the cable clips.

The remnants of the sticky pads came off with some sticky remover and meths.

The Ramps and RPi fitted into their respective halves of the shell. Had to do a bit of filing to allow the connectors to fit in the end panel.

I may move the RPi slightly to the right so the power connector is fully inside the case. That will mean printing a new end panel so will have to wait until I get everything reconnected.

 

[Gina]

Might be easier to build a new printer

[tekkydave]

I wish I had the money and the space

 

[tekkydave]

Spent most of the weekend rewiring the printer.

First fitted the Ramps half of the case to the printer frame. I was planning to keep the hardwired power and bed cables but decided they were pretty ugly. I removed them but the pcb copper is so thin it was too damaged to fit new connectors in the 11A holes. I managed to fit screw terminals on the 5A input and tie the two inputs together at the fuse inputs. Not ideal but ok for testing. I have ordered a new Ramps board - should be here tomorrow.

Fitted the 80mm cooling fan to the end panel.

The end of the 37-way D Connectors.

All the leads with new headers fitted and connected to the Ramps for testing. I had to extend some of the leads to reach the new case. I have wired the two z-axis motors separately back to the Ramps. There is a dual header next to the Z driver. Eventually I want to drive the motors with separate drivers - there is a spare position for a Pololu driver in the E1 slot. At the moment the single driver is at the limit of its capabilities driving two motors.

 

 

I want to fit the new Ramps before completing the 12V wiring but I gave it a brief test. All the motors, end-stops, and thermistors work fine. The z-probe servo is ok and I can home all axes and execute an ABL.

 

[Gina]

I guess the screw type Z drive produces a lot of friction.  No doubt simpler than lots of pulleys and cord but the only resistance to mine is the (single) stepper motor) - just enough to hold the weight of the Z carriages, X rail and carriage plus extruder from descending by gravity.  I think mine are probably lighter than yours though Dave.

[tekkydave]

Yes I think its a definite weakness in the Prusa design. The X carriage is quite heavy so the screws really should have a driver each. Marlin is easily reconfigured to handle it if you have a single extruder. Some people have ditched the threaded rods and substituted lead screws which I may look at doing myself. It would mean reprinting quite a few parts as it changes the distances between the screws and the rods. Another thing would be to switch to a bowden extruder to reduce the weight of the X carriage, although I dont think it works too well with 3mm filament. If I was building a printer from scratch I would probably go down the pulley route.

[Gina]

I find the Bowden filament feed works well with 3mm filament - I have it on my Titan printer and also on the Pilot before I went over to the new 1.75mm direct feed extruder.  I'm planning to work on my Titan printer today.  I've learned quite a lot from the recent work on my Pilot printer   The Bowden filament feeder was one of my successes on the Titan.  You're welcome to copy my design if you like

[tekkydave]

That's interesting. I was under the impression that 3mm wasn't flexible enough for bowden, especially PLA which is what I use exclusively at the moment. If I go that way I would definitely be interested in your design.

[Gina]

I have used PLA in the Titan and no problem with flexibility - though it doesn't go round tight corners.  The bending required for a Bowden feed is nowhere near as tight as it is wound on a spool.  The main problem I've found with either type of filament (ABS and PLA) is getting enough traction from the hobbed pulley.  Why PLA exclusively?  Have you tried ABS?  I find it works well with a glass bed - sticks with a bed temperature of 100C and releases at about 50C.  I use an extrusion temperature of 260C.

I shall be trying PLA in the Titan once I have it working well with ABS - I have plenty of both types in 3mm size.  I'll be starting with the 0.8mm nozzle but trying a 0.4mm too.  I have downloaded and installed the latest Repetier Host with Cura engine on my Win 7 desktop and set them up.  I may try the Linux version later but one advantage of using the Win 7 machine is that I have SketchUp on it so no need to transfer the STL files between machines.  I'll start off with the currently installed Marlin but will probably update to the latest version before long.

[tekkydave]

I want to use ABS but not until I have an effective fume enclosure. The printer is in an office (upstairs bedroom) so the smell would be an issue at the moment. Unless there is an odour-free ABS I can buy.