The Shop > Composites & Plastics
3D Printing. How to (And not to)
ParCan:
Hi Bill
The tapes give a good surface for the print plastic to stick to and also be removed.
The warmth keeps the plastic just below it's transition temp so that it won't warp as it cools and also aids the sticking process.
If you wish to make a cylinder printer you have a few things that I see to consider.
You can use the existing Y Motor and mountings to drive the cylinder with the Y belt.
Attaching the cylinder is going to be interesting with current machine designs.
The the cylinder must be accurately calibrated to give the correct revolution. That is going to be easy to do using the Y axis calibration in Firmware.
The real fun will be to extrude more as the Dia of the print increases.
I'm not aware that any of our software can handle this at the moment.
We control the extrusion rate in the Slicer software we use to take a 3D object and cut it in to layers for printing.
I'll talk more about the software toolchains in a later post.
I missed the 2nd part of your Q thismorning. It was rather early !
The extruder drives solid filament which is then fead into a heated chamber to melt it.
If you use a screw you get air bubbles in it.
Alex.
ParCan:
Part 4
Electronics and Software.
Once you have your hardware together you can start to make it move and do stuff.
The Reprap printers are Belt driven from stepper motors (X & Y) and a pair of lead screws for Z.
T5 Belts have been superceeded by T2.5 belts.
We use NEMA 17 Motors. Must have Good Holding torque.
Something like SY42STH47-1684B from Zapp Automation in the UK are ideal.
DO NOT scrimp on the X, Y and Extruder stepper motors. You can howeve use lower power motors for the Z.
The RepRap Community (and others) have developed their own electronics and it is a minefiled out there.
Most RepRap stuff is based around the AT Mega chips and Arduino boards. i'll try and summerise the options here.
Gen3: Obsolite and will not work with current firmware.
Gen3+: Obsolite but will (with some work) Work with current firmware.
All the Gen 3 Series requires separate Motor Drives and End Stop Boards.
Gen 4 and 5 never took off.
Gen 6: developed by Mendel-parts.com is a really nice attempt at a 1 board solution.
It's stepper drives will only do 1/8 stepping. This makes your printer noisy as hell.
It has no Heated Bed support.
Current Firmware will run with some work.
I have one of these boards gathering dust, it's simply far far to noisy.
Gen7: A well respected low cost and full featured DIY solution. Well worth looking at but still being developed.
RAMPS: The most popular current electronics. It's a shield that plugs into an Arduino Mega board.
Works with all current software and Firmware.
Uses 4 separate 1/16 stepping Polulu Drivers
Has support for 3 end stops, 2 Heaters (Nozzle + Bed) and 1 fan.
A very good choice.
Sanguinolulu: My Preferred Choice.
Missing the Fan controller that RAMPS Has. That's about all.
It's a stand alone 1 board solution.
Easy PTH Soldering (except for the FTDI chip).
Image attached from my Reprap mendel.
There are Other Electronics solutions out there that may or may not perfom well. I have not seen used or tested anyning not in this list so am unable to pass comment.
You then need 3 End stops for X, Y and Z.
Many People use Micro switches. They are low cost and easy to buy.
I prefer Opto End stops. They seem to be more repeatable than the switches, especially for Z.
Nozzle Heater:
Aim for 22 - 30 W of power.
@ 12 volts that's between 5 and 7 ohms
I use 6.8 Ohm 3 watt wire wound resistors.
Bed Plate Heater: Aim for 100 - 150 watts.
@ 12 Volts that about 1 Ohm.
Power Supply.
Minimum 300 watts @ 12 volts.
You can hack about an old PC Supply but put a load on the 5V rail or the 12 V supply will drop causing Brown outs.
Without a Heated bed 100 W will happily run the printer.
Software tool Chain.
To drive a reprap you need 3 things.
Firmware to:
Tell the motors what to do.
Control the Temps of you Bed Plate and Nozzle.
Look after end stops etc.
Look after Calibration (Steps per mm)
There are 2 Current Firmware tool chains, Marlin and Sprinter, that are worth looking at.
I prefer Sprinter myself. Config / Calibration is quick and easy and I get some really nice prints from it.
Marlin is also very popular but i have not used it myself.
The firmware is uploaded to your board using the arduino software from www.arduino.cc
Slicer:
The Slicer software eats your .stl Object files and converts them to g-code files that your Firmware can convert to movement and Filament feed
Again several choices here.
Slic3r is considered to be the best around at the moment but I have not used this myself.
I Use SFACT, which is no longer being developped.
It works just fine for everything that I have ever wanted to print.
Repsnapper is great but very limited. I suggest you avoid it.
Control Interface.
This one is easy. Pronterface is by far the leader here.
It's full featured and well put together.
This is where you start your print jobs from and do things like Home it and set Temperatures.
Again, theer are other Software and Firmware packages available. No doubt some are very very good but i'm writing this from my own personal experiences.
All the Soft / firm ware will run on Mac, PC or Linux.
Full Details of all the products can be found on the Reprap Wiki at http://www.reprap.org
Alex.
ParCan:
Part 5
Exrtruding the Plastic.
The hardest bit to get right is extruding the plastic.
There are 2 extruders worth looking at, both very similar in design.
Wade and Gregs extruders use an M8 Bolt with a Hobb cut in to it with a tap.
I have attached an image of a Hobbed Bolt.
The bolt is held in 608 skate bearings.
A 3rd 608 skate bearing is used to force (with springs) the Plastic Filament against the hob.
The Large cog drives the 13mm hex head of the bolt.
This arrangement is low cost and works extremely well.
The next part is the Thermal Insulator or heat shield.
This prevents the heat from the Nozzle form melting your extruder drive.
PEEK, a high performace plastic is used as the heat shield in most modern hot end designes.
PTFE can also be used but it is not suitable as a structural part of the Hot end and must be supported.
ABS and PLA stick rather to well to PEEK, so the heat shield must be lined with PTFE or your filament will jam up.
Most modern hot end designes use PTFE Tube.
The PTFE Tube also needs to be fixed in place to stop it form moving when you retract your filament.
The next part is the heat chamber and Nozzle.
Most hot ends have an intergral nozzle.
Some do have an interchangable nozzle but the additional thermal Junction can cause issues.
The melt chamber does exactly what it says on the tin.
It Melts the filament before being extruded through the nozzle.
Nozzles are available in a range of sizes from 0.25mm up to 0.75 mm.
Start with a 0.5mm Nozzle.
A 0.5 mm nozzle is a great compromise betewwn print speed, detail and surface finish.
Most modern heaters use a block of Brass or Aluminium drilled and tapped to fit the nozzle.
The heater is a 3W 5.6 or 6.8 ohm Wire Wound resistor.
The Sensor is a 100K glass bead thermistor.
These Hot ends are well respected within the Reprap community.
Arcol: http://shop.arcol.hu/
Budaschnozzle: http://www.lulzbot.com/en/5-hot-ends
J-Head: http://hotends.com/ & http://www.emakershop.com/Seller=784
Makergear: http://www.makergear.com/products/operators-pack
Parcan: http://www.emakershop.com/Seller=59
Which one is the best one ?
That is cause for much debate amongst the community. None of those listed abouve are bad and would be a vrey good choice.
You will also notice my name in the list.
I make and sell RepRap Hot end kits, Hobbed Bolts and other related items.
That is also how come I have a Lathe.....
That's all for now.
I have 1 more tutorial to add to this, and may do it as a Video.
It's the actual printing process.
Alex.
ChrisC:
Hi I've been lurking here for a while, so I thought it was about time I made a post! I built a Prusa Mendel about a year ago and have been using it quite a bit. In general I'd say it works surprisingly well. I have found that the design of the extruder and hot end nozzle makes a big difference to the quality of the print you produce. I initially used the simple hot end from the Reprap site, similar to the one shown by ParCan in an earlier post. I currently use a slightly simplified version of the Budaschnozzle, which I find works very much better and has greatly improved the quality of my prints. I use a Wade extruder but have found that knurling the M8 bolt seems to work just as well as the hobbed bolt, and is much easier to make. You need to turn off a few thou in the area to be knurled, so that the completed knurled bolt will fit through the bearings. I used a medium diamond knurl which seems to grip the fibre very well. Some commercial machines use rubber coated rollers rather than knurling or hobbing.
I agree with ParCan's summary of the electronics. I have been using a Gen 6 board, but as he says it is noisy and also has a couple design problems. The thermal management of the stepper driver chips is poor, I've added tiny heatsinks to the chips, but it is not ideal. The thermistor input circuit for the hot end is also wrong on my version of the board, it results in a poor calibration and a very noisy signal. I'm building a Sanginololu at the moment.
I found a Reprap machine was very handy when I was doing my CNC conversion of a Sieg X3. I used it to make opto limit switch brackets and flags (use black PLA for the flags, other colours are too transparent for the opto switch to work!). Numerous brackets for holding cable chains and covers were made, entirely suitable and much quicker than machining.
I'm in the process of building up a couple of other designs of Reprap machines to try out a few design ideas... I'll post photos and results as I progress if people are interested.
Chris
tumutbound:
Has anyone built a printer utilising and existing CNC device i.e.a CNC router?
All you should need, hardware wise, would be the hotplate and the extruder head.
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