For a list of Prusa i3 Rework parts we used the RepRap.org list of build materials for this model.
As we said the components used when building a FDM 3D printer are roughly the same. Essentially there is a plastic extruder and a build platform. Either the extruder, the build platform or a combination of both are moved along an x,y & z axis (left & right, forward & back, up & down). The extruder and build platform are moved along linear shafts driven either by a belt or a threaded rod coupled to a motor. The linear shafts are guide rails. The whole thing is housed in some structure to add rigidity and it is controlled by a motherboard, an electronic pcb board. So when building a 3D printer we need structural components, the axes drive system, an extruder and some electronics. Most of these parts you will have to buy, these are sometimes referred to as the vitamins, the rest it is possible to print. If you haven’t got a 3D printer or don’t know anybody with one then you will also need to purchase the printed parts as well. We are building it with all purchased parts, we haven’t printed any ourselves, as we want to model the experience of building a 3D printer from scratch.
Please remember we are not going to reveal our sources but we will include prices. We are going to break down the components into:
At the end of this article you should get an idea of how much it costs to build a 3D printer. Granted it’s not probably the most cost effective way to build a 3D printer but we wanted to look at all the different parts needed and how easy it was to source them along with the considerations when buying them. We wanted to source the best quality parts we could get without resorting to paying manufacturing grade prices. Some of the components used in 3D printers are also used in building production grade machinery, as a result, for top quality materials, the price can be very high.
1. Buying your 3D printers printed parts (£21.00)
As we said, and as the title suggests, it is possible to print these parts yourself if you have access to a 3D printer. We bought ours. To put it mildly buying these components is a bit of a leap of faith. They are not available from mainstream stores as a rule so you are relying on individuals printing them out and selling them on ebay and the likes. One thing that you will learn is that 3D printing can produce variable results depending on the setup and the proficiency of the user so its possible to end up with a load of rubbish. Ignoring this variable the two things you have to think about are: 1. You need the correct printed parts for your model and version of printer; 2. What material do you want it printed in?
We are building the Prusa i3 rework, printed parts for earlier versions of the Prusa will not work well, the diameter of the threaded rods used has changed for one so buying printed parts for earlier versions will mean problems when putting it together, either extra finishing or it just won’t work. If in doubt ask. Alternatively visit a forum or 3D printing service and pay for them to print your printer parts. This way you can also specify materials as well and be confident that they are printing the parts you want.
As to materials, really you are talking about whether to use PLA or ABS. The material qualities of these materials are slightly different. ABS has greater heat resistance but is more flexible. The best course of action is to use PLA for most printed parts to do with the structure as it is more rigid and then to have the extruder parts that house the hotend part of the extruder (the bit that heats up and melts the plastic filament) in ABS due to its higher temperature resistance. This was our plan, in the end though we failed as we could not find any printed part sets with this kind of set up so we decided to go for PLA printed parts with a view to upgrading the printed parts at a later date when its up and running.
We bought our parts on ebay at a price of approximately £22.00. They are Blue PLA. Generally they all seem OK, we are expecting some post processing during the fitting process but we think they will work. The seller kindly included some duplicate parts where they obviously felt that some could be improved upon.
2. Buying structural parts for your 3D printer (£103.00)
Threaded rods are easily available. The main concern is the precision ground nature of the thread and whether the rods run true. In the Prusa i3 rework the straightness of the rods and it’s impact on the printer where addressed in two ways. Firstly, M8 threaded rods where originally used for the x-y frame that forms the base of the printer and these where upgraded to M10 to make them less prone to bending. Secondly the threaded rods that move the extruder along the z-axis had their diameter reduced to M5. The reason for this is that being less strong than the M8 linear shafts that guide the z-axis movement, any wobble in them would be removed as the extruder is more greatly influenced by the Z linear shaft/smooth rod.
As to buying threaded rods, these can be bought from your local DIY store but you will have to be very careful choosing straight rods. They will also need to be cut to the right length and the ends chamfered to allow a nut to be screwed on. Rods can be cut with a small angle grinder or, if you have one with a large enough throat, a bandsaw. The ends can then be chamfered with a metal file.
In keeping with our model of assuming that not everybody has an extensive range of tools we bought ours online, again from an online auction site for ~£18.00. That’s quite expensive in comparison to buying it in 1m lengths and doing it yourself which will be under £10.00.
The alternative to using standard threaded rods is to buy leadscrews or ballscrews. This is especially popular for replacing the z-axis threaded rod but can also be done on the x-y axes. Lead screws are precision ground with low tolerances for the thread, i.e the distance that one rotation of the thread moves is very repeatable along the length of the rod. Because if this they are considerably more expensive, this is where we travel into the world of precision engineered components. We plan to look at using leadscrews at a later date, a possible upgrade of the Prusa i3 rework. However, there are also issues with using leadscrews, backlash and also the greater influence of any wobble in the lead screw on the precision of your printing.
Linear shafts or smooth rods
The extruder or build plate move back and forward along x-y-z axes. This movement is powered by stepper motors, the rotational force of the stepper motors moves the extruder/build plate either by moving a threaded rod or by moving a pulley and so subsequently a timing built attached to the pulley. What determines the direction of movement are linear shafts or the smooth rods. The extruder and build plate glide along on these linear rods, attached to them by bearings or LM8UU bearings to be precise driven by either a belt or a threaded rod.
So what are the main qualities of a linear shaft? They need to be very straight, very smooth and have a hard surface that is not prone to wear or abrasion. Obviously they need to be straight in order that what it is guiding moves in the correct direction in a straight, and so predictable, straight line. The smoothness and hardness are important as what ever is running along it needs to run easily and smoothly without resistance. The smoother it is the less resistance the bearings will encounter and the less impact on your 3D print. If your bearings aren’t running smoothly you can get anomalies in your print where the bed or extruder is sticking as it is trying to move. The harder the surface metal, the better the rod will be in retaining that smoothness.
One of the important things to think about when selecting a smooth rods is the metal that it is made from. It would be possible to buy some steel or stainless steel from the local DIY shop. This is going to be your cheapest option. The problem is going to be that they are unlikely to be straight and their surface is not going to be very smooth. How ever, assuming that they are straight we have heard of people wet sanding their linear shafts with paper as fine as 1000 and then polishing them with metal polish. This may in fact work for a while but due to the soft nature of the surface they will quickly wear and scratch and so will require a higher level of maintenance than hardened steels.The main issue with standard steel (302, 304 or 316 grades of stainless steel) is that if used as linear shaft with ball bearings under load the bearings will start to leave tracks, reducing the lifetime of both bearing and shaft. The best option is something like CF53 hardened steel. Cf53 has a higher carbon content to the standard mild steels you get in the DIY shop (~50%+ Carbon). If you really want to go for it you can invest in X90CrMOV18 that is even harder, it has ~90% carbon with about ~18% chromium, but this is obviously more expensive. Basically the higher the carbon content the harder the steel, the addition of metals like chromium aid hardening and increase corrosion resistance.
Linear shafts can be quite expensive, we where quoted by a specialist supplier of linear shafts to industry ~£60 for a set of Cf53-56 steel or ~£134 for a set in X90CrMoV18 steel and that’s not including delivery. In the end we got a set of pre-cut Cf53 steel linear shafts for ~£35. They look good and clean but it is obviously more expensive than buying some at the DIY store and polishing them up (~£10.00 + hard labour).
The frame adds rigidity to your 3D printer, you don’t want it to be moving about as the extruder/bed is moving about and also you want it to be true, remember a 3D printer needs to be printing in a clearly defined xyz space, if that space is not quite square due to, perhaps a bent frame, then the extruder is not going to be laying down plastic where its supposed to be, there is going to be a fixed amount of error in your print as a result of that warped frame.
Not all 3D printers have a frame, for example the original Mendal was built using threaded rods and smooth rods. The Prusa i3 is either built as a single frame, this is what we are building, or a box frame. The most common material used for making the frame is acrylic, most of the cheap kits you will find use acrylic. It’s also possible to make the frame from wood, aluminium and steel. Metal is generally better as its less flexible and so provides a stronger support for the whole printer, generally acrylic frames don’t have a very good reputation. We have seen that it is possible to get an all in one frame called a P3 Steel. These look very strong and would add a lot of support for the printer. We decided not to go down this route though as we thought, rightly or wrongly, that any warping in these frames would be very difficult to get around.
When buying or making the frame you will also be making the print bed at the same time (the bit in the middle of the photo). You can make the frames your self and the.dxf files that give the frame specifications are readily available. We bought ours, the single frame and print bed made from adonised, laser cut aluminium came to ~£50.00.
3. Buying your 3D printers mechanical parts (£150.00)
The Prusa i3 requires 3 types of bearing. It turns out that bearings can also be very expensive, especially the LM8UU that are used in conjunction with the linear shafts, some of these were offered for as much as £30.00 each. So what do you need to look for when buying a bearing?
Firstly, all the types used in this build use ball bearings and yes there are other types of bearing (roller bearings, needle roller bearings etc..). Both the 608 and 624 bearings are deep groove bearings designed for use in situations where the inner ring rotates. These bearings have ratings and they principally come with either a rubber seal or a metal seal. they will come as either, using the 608s as an example: 608 2RS – with 2 rubber seals; 608 RS – one rubber seal the other side open; 608 2Z or ZZ – with two metal seals; 608 Z – with one metal seal and one open sided. You will need either the 608/624 2RS or the 608/624 ZZ/2Z. The seals are to prevent the entry of dirt. We went for metal seals, believing these to be more robust. In the end we paid ~£0.60p for our 624 2Z and ~£2.50 for our 4 608 2Z. The 624 is for use in Wades extruder whilst the 608s are for use in in the belt drive set up for the x and y axes.
LM8UU linear bearings are used on the linear shafts, i.e. the print bed is attached to LM8UU bearings by ties and that allows the bed to move freely backwards and forwards along the linear shafts / smooth rods. The smooth running of all 3 axes are highly dependent upon the smooth running of your LM8UU bearings. We needed 11 for the Prusa i3 build. It seems quite common for people to have problems with cheap linear bearings, generally this is to do with very poor rolling ability due to the poor running around the four tracks of bearings that the LM8UU house and bearings can also fall out. Sometime this can be solved by a drop of oil but generally this is down to build quality, there has to be a difference in quality between spending £0.80 per bearing and £30.00 per bearing.
Initially we went for the low end and bought 12 for ~£10.00. This turned out to be a mistake, the bearings lost their balls very easily, they would just drop out and they would not run smoothly on their linear shafts, some even grinding as they moved actually damaging the smooth rods. We tried to resolve these issues by taking out the ball retainer and repacking them but this did not resolve the issue, essentially the retainers appeared to be of a low grade soft plastic that had been poorly moulded. In the end, knowing the importance of these parts we sent them back. The next step up for us was £7.20 a bearing, we bought 11 for £79.20. These KG LM8UU bearings were very different, they all ran smoothly and it made a big difference to the quality of our stage movement. We were so impressed with the difference that we are now selling these KG LM8UU bearings from the store. We know it’s a big jump in price but you get what you pay for and the cheaper bearings were going to ruin our linear shafts, give us poor quality prints and cost us money as we would have had to replace them.
A belt drive system is common for moving bed or extruder along one of the axis in 3D printers. The belts have teeth which are designed to fit snugly into a toothed pulley, the pulley is then attached to the spindle of a stepper motor. As the stepper motor moves so does the pulley and therefore that moves the belt around. The belt is not in a closed loop but is secured at the ends to a bracket of some sort that is attached to the stage that the belt system drives, for example to the bottom of the print bed so that when the belt moves it is pulling the stage along.
One of the issues with belts is backlash. If the teeth do not fit well with the teeth of the pulley then as the belt starts to move and stops there is movement so that the print bed or extruder stage may be slightly out of sink. With this in mind the RepRap world has focused on using GT2 belt drive systems that are designed for linear motion drive. The other problem with belt drive is slippage, pull on the belt causing the belt to move with the teeth of the belt slipping over those of the pulley (the pulley moves but the belt doesn’t). Having more teeth on the pulley engaged with the belt at any one time helps reduce this, to this end GT2 pulleys with 20 teeth are generally used.
So how to select GT2 pulleys and belts? There was not a lot of variation that we could find. GT2 pulley system for the Prusa i3 uses a 6mm wide belt with 2mm pitch (the distance between the centres of two adjacent teeth on a belt). Again there was the choice to go to an industry supplier and pay more for what you would perceive to be a higher spec. belt and pulley, presumably quality here is measure in the consistency of the fit between belt and pulley and how tightly they fit together as well as the material used. We did encounter suggestions that for the pulley it was a good idea to have rounded flanges so as to reduce wear on the belt from abrasion against the pulley.
In the end we paid ~£13.00 for 2x 20 teeth GT2 pulleys and 2m of rubber, fibreglass reinforced, belt from one of the online 3D printer component suppliers. We won’t know if we have any problems until they are installed and in use. Once again though, because of the importance of the accuracy required, they are quite important and a source of error for our printing quality. If anybody has some experience of the different belt materials and there effects on performance we would be interested to hear.
We have been making enquiries as to people experience of the different composite types of GT2 belts which has ranged from untried NinjaFlex 3d printed belts and belts printed in Nylon to Steel reinforced belts. The jury seemed to suggest that, if you can get them, steel reinforced belts are better as they have less stretch. We haven’t tried them ourselves yet but it seems to be the preferred option.
A stepper motor is used to power the movement of the bed and extruder chassis along the linear shafts as well as the gears to move the filament through the extruder. As the name suggests the motor moves in steps. There is a shaft attached to the motor, the shaft turns in steps, generally a step of 1.8 degrees or 200 steps per revolution. The turning motion of the shaft powers the pulleys and also the threaded rod of the Z axis. The stepper motors are then controlled by Stepper Motor drivers. The stepper drivers can be used to add finer control to the steps that the motor takes, generally speaking your can set it to full-step, half-step, quarter-step, eighth-step, and sixteenth-step. Additionally the stepper motor driver has adjustable current control. There are two things to think about when selecting a stepper motor, the current and the voltage. The amount of current determines the holding torque of the motor whilst the voltage determines how quickly it steps. When stepping it is the inductance of the windings that has the greatest impact. The higher the inductance the higher the voltage required to make a step in the same time or the slower the step. The listed voltage is that which produces the stated current given the winding resistance (in Ohms). Therefore if you have a current of 1.68A and the winding resistance is 1.65 Ohms that gives you V = Amps x Winding resistance = 2.772 V. Generally though you may want to run it at higher voltages as this will increase the speed of the revolutions, otherwise it can become to slow, but run it at too high a voltage and the movement may become jerky with each step snapping in to position.
Stepper motors is again one of those components that you can spend a lot (~£100) or a little (~£50.00) and there are a lot of choices out there. RepRap.org has a nice page on the models that you can choose and good guidance in that you are going to want to look for a NEMA 17 stepper motor or one with similar physical dimensions that is rated at 1.5A to 1.8A or less at 1-4 volts with approximately 44mNm (4.5kg.cm) or more of holding torque and 1.8 or 0.9 degrees per step (200/400 steps/rev respectively). For the Prusa i3 build we are looking at 42mm Nema 17 with >= 44mNM holding torque and 1.8° degrees per step with a low Amps rating. The Prusa i3 requires 5 Stepper motors and the standard RAMPS board has a 5A rated circuit to power the stepper motors and board. Therefore if you get Stepper motors >1A you will need to down rate them, which you can do via your stepper motor drivers. It is possible to use 5 x Stepper motors at rated at 2A and adjust their draw via the stepper drivers variable resistor. The other advantage of running them lower is that the motors don’t get so hot. So when selecting the stepper motor you want low winding inductance as this will increase the effciency of the motor. Lastly you should check the physical dimensions of the stepper motor. As a rule of thunmb holding torque increase with the length of the motor so if you get a more powerful motor you may have to adjust the stepper motor brackets. The Prusa i3 rework takes motors of 42 x 42mm in width and depth and up to 48mm in length.
Stepper motor problems are generally that they burn out, which is usually a problem with the driver, or that the bearings wear out. You can check that the windings/coils are good with an ohmmeter to check the resistance. On a bipolar the resistance for both windings should be the same in both directions.
In the end we decided to buy ours from a supplier via an auction website. We paid ~£50 for all five and bought 2.8v 2.0A with a holding torque of 59mNM with 1.8 degree steps (200 steps per revolution). The idea being that less voltage is required to produce the required current as the windings resistance is 1.4ohms. Inductance is 3.0mH so a higher voltage may be required in order to have steps made at a good speed. We will have to see how well they perform later which we will go into when we talk about the calibration of a 3D printer.
The motor couplers, two in our Prusa i3 build, attach the shaft the stepper motor to a threaded rod, the threaded rod being used to move the extruder stage along a particular axis. For our build it moves the extruder stage along the z-axis. The role of the motor coupler is two fold, firstly to transfer torque from the motor to the shaft and secondly to accommodate any shaft misalignment, between the threaded rod and the stepper motor. Broadly speaking one can get two types of motor coupler, rigid and flexible. Rigid couplers are used where the alignment between shafts are good in precision engineered roles, for us and for hobbyist 3D printers the flexible motor coupler is used. There are also pivoted/sliding couplers which are more flexible but these are not required. The more flexible the coupler the greater the loss of torque but of course the greater the dampening effect on shaft misalignment, good for protecting our print from shaft wobbles.
You can spend a fortune on motor couplers as with all these components. The type of coupling that we purchased and seem to be used in most machines is a flexible aluminium single beam coupling. What does that mean? Well it’s made of aluminium, they can be made of steel giving a longer life expectancy but they are obviously more expensive. The “single beam” specification refers to the helical cut around the beam coupler that adds the flexibility. You can get multibeam couplers that have a couple of helical cuts made that gives greater compensation for misalignment, although with apparently greater wear on the motor. In the end we paid £7.20 for two, we went for a slightly more expensive version that had one side threaded (m5) to increase torque transfer. Normal ones simply have a hole, of the correct diameter for the shafts with a grub screw.
Make sure you check what size holes they have at each end. The shaft diameter is 5mm on our stepper motors and the threaded rod we used is m5, check your printers requirements before you order a coupler.
4. Buying your 3D printers Nuts, Bolts and Springs (£30.00)
Nuts, Bolts & Washers
There is a huge list of nuts and bolts required for this type of 3D printer build, plus with the Wade extruder we need a Hobbed bolt (pushes the filament into the hotend) and two springs (apply pressure between the filament and the hobbed bolt). If you add the heated bed you will also require some extra springs.
The first thing that might spring to mind is a visit to your local DIY shop, our suggestion is don’t. Buying from a DIY store is likely to be very expensive and you will probably have problems finding all the sizes that you need. The other option is to look for a printer specific collection of nuts and bolts on ebay or on a 3D printer related website. This may be your cheapest option but you will need to ensure that it is a kit for your 3D printer model and version. We found some on ebay for ~£20. Again quality can be an issue here although nuts and bolts can be quite cheap if bought in bulk.
In the end we bought our nuts, bolts and washers from an online store specialising in nuts and bolts for a cost of £21.00, but this does not include the springs and the hobbed bolt. We went for pozi pan head machine screws made from A2 stainless steel. Using pozi pan head bolts rather than Hex headed bolts should make it a bit easier to assemble and disassemble and we were also able to get all the sizes that we required for the bolts.
Buying springs was an interesting venture into the world of spring specification.We found this a bit opaque at first. Springs are needed for the print bed so that you can level it. More importantly two springs are used in the Wade extruder. They are placed on two 60mm bolts that compress a bearing on one side of the extruder against the hobbed bolt with the filament feed in between. Therefore spring tension impacts the pressure placed on the filament as it’s fed through. So the question is what type of springs does the Wade extruder require. All we found was a recommendation for between 25-35N of loaded force and ~20mm in length (unloaded). So given this information we went about finding some springs.
Once again, there are many sources of springs which give the size of the spring but none of the springs sold as for the Prusa i3 or Wades extruder gave information on the force of the springs. Again, on popular auction sites we could find springs at ~£8.00 for all 6 springs required, we also found some on another site for ~£4.00 although the postage time for those was very long. They were all advertised as for the Prusa i3. After some research we found some springs which seemed to fit the criteria and that were:
- – Free length: 19mm
- – Wire diameter: 1mm
- – Inner diameter: ~4.3mm
- – Max length fully loaded: 12mm
- – N/mm: 6.62N
- – Max load: ~33N
Now as of writing this we have not tested it out yet but they appear to fit the criteria that would be required. So in order to save some cost we order in bulk and we are selling these extruder springs on the website. The cost of the springs was not an issue but the postage and packaging was.
The hobbed bolt is a very important part of the extruder, this is used to drive the filament through the hot end so if it doesn’t work correctly then your extrusion is going to be poor. So what characteristics does a hobbed bolt require? Well, the grooves that are cut into the hobbed bolt to give it purchase on the filament need to be well made, you don’t want them unduly sharp as they will cut and abrade the filament. Also the placement of the hobbing is critical to a good feed, you need it to be well centred on the filament.
Hobbed bolts can be purchased quite cheaply, for a few pounds, but they can also be relatively easy to make. Guidance for making hobbed bolts can be foound on the RepRap.org website. As with most things we tried to err on the side of caution and found one that looked well machined. Also it was adjustable, i.e. their where nuts on either end, that way we can control the positioning of the hobbing in both directions. Price ~£6.50.
5. Getting the electronic components for your 3D printer
This is going to be slightly different from the proceeding sections in that, unlike the previous items we bought is all as a bundle. The reason why? A big factor was cost but that was only part of the rational, the reason why cost was taken into account with these components, arguably including the most important, was that after lengthy investigation we could find very little difference between sellers given our choice of set up.
So what electronics are required for a 3D printer?
In general you need a control board, a bit like the motherboard of your computer. It’s the brain of the printer that houses the printers firmware (the software used to control the board) which tells the printers components to do their various jobs and how to do the jobs, i.e move to point 2,3,1 in xyz space, tell the hotend to heat up to 210°C. There are a number of different control boards available and new ones being designed all the time. They each have different specifications and you need to check what your 3D printer needs to be able to control in order to pick you board. We had already decided that a heated bed was a must, we have a requirement for two outputs for heating, one for a heated bed that has a greater draw and one for the hotend. Likewise we need to be able to plugin two thermistors (temperature sensors). Additionally you will need the circuitry to add the stepper drivers (plugin control boards to control your stepper motors). We needed four stepper drives to plugin. 1 for the extruder and one for each axis. Although the z-axis of the prusa i3 uses two stepper drivers these are controlled by a single stepper driver. You will also need to be able to plugin endstops, these are sensors that are triggered when the extruder stage or printbed reaches the limit of an axis. Lastly you can get various other goodies, SD card, LCD screen and ethernet. It’s the later extra goodies that can vary a lot between boards. For a good list of electronics available take a look at the RepRap page.
We decided to go for an Arduino Mega 2560 with a Ramps 1.4 3D printer control board purely on the basis that this is the most popular RepRap electronics configuration and so by choosing this set up we would gain a a shared experience with a wider audience. It was this decision that led to us going to the electronics bundle. Arduino are an Italian manufacturer of the well known Arduino boards, used by hobbyist all over the world, they are great for electronic prototyping. A branded board is going to set you back £30.00. There are of course many non Arduino made boards with the same specification of the Mega 2560 but you have to gamble with quality. Although we have always strived to go for quality, and in the first instance we believed that we wanted to reduce the failure risk of the board our decision was swayed when we tried to find RAMPS 1.4 boards. Essentially no matter where we searched they all seamed to be pretty much made by the same few companies of Asian origin therefore we could end up spending money with low risk for the Mega 2560 only to have it destroyed by a low cost RAMPS, so in the end we thought that we should just go for a low cost Mega 2560 and RAMPS.
Endstops, as the name suggests, are sensors that are triggered when the extruder stage or the printbed reach the end of an axis, the single from which is used to stop the stepper motors from moving along the axis any firther in that direction. There are two types, mechanical and optical, the later is a light sensor the former a mechanical switch. Normally 3 endstops are required, one for each axis, the stages are prevented from going off the other end by specifying in the firmware that it is an electronic endstop, it cant go past the limits of the length of that axis as specified in your firmware. Usually the origin, 0, is used for this with the upper limit controlled by the endstop.
We didn’t go into too much detail with these as they came with the bundle. One thing that we did encounter though was that the endstops we got did pose some issue with mounting, which although it was easily solved we were slightly perplexed at first. We will go into this in more detail in the next section on actually building the printer.
Stepper drivers are provide the means to control the steps that your Stepper motors move in, allowing you to control movement of the stepper motors in fractional steps, typically upto a resolution of 1/8th of a step to 1/32nd dependent upon the driver. They also allow you to fine tune the current available to the stepper motor via a trim pot that can be altered using a screw driver. You can therefore power up or down the power of your stepper motor. This will be necessary as your board will only be able to provide a certain amount of amps per circuit. The Stepper motors on a Ramps are on a 5 amp circuit so running 5 stepper motors with a 2A draw each is not possible. Adjusting the stepper drivers trim point can therefore regulate this. There is a good article on using stepper drivers on the rep rap pages.
With the PSU you have a couple of options you can use a standard LED strip PSU or a general computer ATX PSU, although alternatives exists like the PSU from an XBox games console. RepRap, as always has a good page on the subject. Not having a spare games console PSU laying around we were going to make a decision between the LED strip PSU and the ATX PSU. For us the decision was base on safety, we where a bit sceptical about A). the provenance of some of these LED strip PSU that are about on auction sites and the like and B). the lack of protection features and regulations C.) open mains wiring. Although, by and large LED PSUs are cheaper we wanted to go for something which was not going to fry our electronics or ourselves.
So on that basis we went for an ATX PSU with their many circuit protection features. You are going to need one with an output on the 12v rail of at least 22A, this should be easily achievable. We found one for approximately £15.00 which appeared to meet our requirements.
The only downside to using an ATX power supply is that you will have to do some reorganisation of the wiring. The details of which can be found on the above RepRap link. Now there are two ways to go about this. You can either take the casing of the ATX PSU and start cutting wires, invalidating your warranty, or you can buy a couple of 6/8 pin and a 24pin female Molex cables. and connect the existing PSU motherboard and graphic card cables to them, strip the molex off the other end and use those wires to connect to your Ramps. We will explain in more detail in our next post on building the 3D printer. The Molex cables are going to cost you a couple of quid each.
In the end, the issue of component quality did rear it’s head again, with respect to the PSU. The First ATX PSU we brought died after being turned on about twice, which was not very impressive. Therefore we sent it back and got a refund (which we were able to do as we didn’t take it apart and cut cables). We then invested in a branded PSU designed for gaming, it is 750w capable of supplying 62A on the 12v rail which is more than enough for our needs. It was a lot more expensive costing close to £50. One could have been found cheaper but we were in patient at the time.
The second issue we had with quality was that the one end of the Molex cable we used to connect the ATX PSU to the 11A heated bed circuit melted. We think this was down to the fact that the original PSU only had 4 pin Molex connectors, so only four wires carrying the heated bed load. With the new PSU we could upgrade to 8 pins.
As you can see we haven’t bought everything yet but we will do in the coming weeks. As always with all our posts please comment, either by making and account on iDig3Dprinting and commenting on the post or by commenting on a connected social media post or even drop us an email. If you could please keep comments specific to the post in hand, in this case the parts and how to choose them. We’ll get to the building and printing phase later.
Happy 3D printing