You wanted it, so you got it; a load of GT2 belts and pulleys are on the trucks now, and I should have them in stock within a week or so. I know that GT2 belts and pulleys are tough to source outside of the USA, so international customers should be pleased to hear that I ship anywhere in the world, and for very low rates with small packages such as the kinds that belts and pulleys can fit into. GT2 belts are nice because their rounded tooth profile almost entirely eliminates backlash. If you need your GT2 fix, check back soon!
Finally, the included extruder now comes with mounting holes for Makergear, Budaschnozzle, and J-head hot ends all built-in, so your hot end choice isn’t final anymore. Pick up a set today!
A bunch of the sintered bronze bushings that are becoming popular in the RepRap community arrived recently. These bushings are really nice since they’re as precise as LM8UU bearings, but they’re smaller, cheaper, don’t rust, and tolerate up to 5 degrees of rod mis-alignment.
I have ones with 8 mm and 10 mm interior diameters, and the nice thing is that both have the same exterior diameter so you can easily upgrade to 10 mm rods later without replacing any of your bushing holder parts!
I’ve released updated versions of my X-ends and X-carriage that can fit these bushings. You can use the bushings with the following parts:
We’re nearing the end of the mechanical parts! I’ll be using the popular Greg’s Hinged Accessible Extruder in this guide. This section may differ for you if you’re using an alternate extruder such as the venerable Wade’s, but they’re all broadly similar.
Let’s start with the idler. You’ll need to put a 608 bearing onto a 20 mm segment of M8 rod, and then insert that into the idler body:
I’ve used a threaded rod here, but a smooth rod should be perfect as well; it really makes no difference. You also need to insert an M3 nut into the nut trap in the idler’s hinge. That’s what keeps the hinge screw from falling out. I know, right? It’s pretty clever!
Clean up the extruder body before putting the idler on. This basically entails drilling the holes that were used as bridges. Then stick the idler onto the extruder body and fasten it with an M3 screw. A 25mm long screw is perfect; any longer and it’ll interfere with the large gear. A washer is optional since this screw isn’t really load-bearing, but I think it looks nice. You should wind up with this:
Stick two 608 bearings in the 608 bearing-shaped cutouts on either side of the extruder body. Now it’s time to insert your hobbed bolt and attach fasten it to the large gear. Depending on the positioning of the hobbling, the bolt’s head may be on the gear or the other side. Test its positioning and add M8 washers on the appropriate side if the hobbling doesn’t align perfectly. Make sure there’s an M8 washer between the 608 bearing and the large gear. Once you’re satisfied with the bolt’s positioning, it’s time to screw everything down. If the gear winds up with an M8 nut connecting it to the hobbed bolt, lock that nut against another one to prevent it from rotating independently from the bolt.
Next, you want to fasten the idler to the body. Assuming you use a strong enough spring, you only really need one screw. I found that a 45 mm long M3 screw was the perfect length. Put a washer on the end of the screw and stick a spring up against it, then put another washer on the other side of the spring. Drop an M3 nut into one of the nut traps, put the assembled screw-and-spring through one of the holes in the idler, and screw it into the embedded nut. You should wind up with this:
Time for the motor. Take the small gear and stick an M3 nut into the nut trap, then screw in an M3 set screw:
Stick the gear on the motor shaft with its now-embedded set screw pointing at the shaft’s flat part (if it has one), but don’t tighten down the set screw just yet. You may need to adjust the gear’s position up or down the shaft a bit to ensure that its teeth match up with those of the big gear.
Now you want to mount the motor to the extruder body. Use 12 mm M3 screws and washers, and adjust the positioning so that the gears’ teeth mesh snugly. When you have the motor fastened down, tighten the small gear’s set screw to make sure it doesn’t go anywhere!
Now mount the hot end. How you do this depends on your choice of hot end, but most of them will use a wooden, acrylic, or printed bracket to connect to the extruder. The J-head I know is simply stuck right into the hole in the bottom and fastened with screws, which is even easier.
I’m using a MakerGear extruder with the wooden mounting pieces. Now, unfortunately my wooden pieces didn’t come with the holes drilled in quite the right places, so I had to open them up with a dremel tool a bit. Yours might not suffer from this issue; YMMV. In any event, attach your hot end to the mounting piece and then stick the mounting piece onto the extruder, if your hot end so requires.
Insert M4 nuts into the nut traps at the bottom of the extruder:
Now attach the extruder to the carriage with M4 screws, inserted up through the bottom of the X-carriage. Some carriages—including the standard Prusa carriage—may need the holes drilled out to M4 size since they’re for M3 screws by default. If your hot end has a mounting bracket, the M4 screw should go through the mounting bracket as well. Here’s my completed extruder on its X-carriage:
It’s time to attach the completed extruder carriage to the belts. First, we’ll need to set up the X-axis idler and motor. Let’s start with the idler. Take a 40 mm long threaded rod and attach to it 608 bearings, washers, and nuts so it looks like this:
The large fender washer can be safely omitted if you don’t have one. I just like to put it there as extra assurance that the idler won’t eventually bow inwards. Just like with the Y axis, the dual bearings ensure that they won’t wobble and dump the belt off! That’s why you don’t even need a fender washer on the outside.
Now put the remaining pulley on your remaining motor and tighten it down as close as possible to the motor body. With large diameter pulleys like mine, it can be tough to get the belt in once the motor is attached, so loop the belt around the pulley before you attach it if that’s the case for you. Then screw the motor to the motor X-end with three 12 mm M3 screws:
At this point you can attach the loose ends of the belt to the carriage. I recommend mounting the belt clamps first and then loosening them a bit to accommodate the belt ends. The carriage has built-in nut traps, so it should be very easy to mount them with some 16 mm M3 screws and washers. Slide the carriage all the way toward the idler or motor when you’re getting ready to clamp the belt end closest to it so you can be sure the clamped end is lined up with the motor pulley or idler.
Then slide the carriage over to the other side and do the same with the other end, making sure to pull it taut before fastening the belt clamp down. Here’s the fully belted carriage:
And that’s it for the mechanical components on your MendelMax printer! Bask in the sheer badassery of your beast of a machine before you move onto the electronics.
Time to move onto the Y-table. A huge X-Y build area is one of the big advantages of the MendelMax, so this is a fun process.
Before you do anything, insert your bushings into their holders. This will depend on your bushings and your holders, but I’m using Igus bushings and my Igus bushing holders.
Now stick these bushings-in-their-holders onto their Y-rods (two per rod). Fasten the rods to the sides of the Y-rod holders using printed clamps secured with M5 screws, screwing them into M5 nuts in the built-in nut holders. I found that screws longer than 10 mm helped here, so I pulled out some 16 mm long M5 screws that work perfectly.
The actual Y-table itself will really vary from machine to machine. Heated build platform choices, bushing choices, basic structure, etc. I’m going to go with a fairly conventional approach of a bottom plate of MDF that the bushing holders and belts are attached to, which itself is attached to an MDF print bed. I’m not using a heated build platform, but this setup gives me the flexibility to add one in the future by simply attaching it to the print bed.
I cut a 290 mm x 290 mm square of MDF to serve as the print bed and a 290 mm x 100 mm rectangle to serve as the bottom sheet. Now, my MendelMax is 40 mm wider than the “standard” size so all the lengths here reflect that. If you’re building a standard-sized machine, the print bed should be more like 250 x 290 and the bottom sheet should be 250 x 100. Measure your machine to make sure the dimensions make sense.
Now you need to drill holes in the bottom sheet to attach the bushing holders. Take the bushing holders you already attached to the rods and press them against the bottom sheet, moving the sheet until you have it positioned right. Then use a pencil and blacken the MDF visible through the screw holes in the bushing holders. Then go off and drill those holes to accommodate M3 screws.
Attach this drilled bottom sheet to your bushing holders and tighten the holders down:
Slide the carriage along the rods and push it sharply and see if its momentum continues the movement for a bit. If it doesn’t, then the bushings are binding somewhere and you’ll need to slightly reposition the holders. I found that enlarging or extending the drilled holes using a dremel tool allowed enough wiggle room that I could position the holders in such a way that there was no binding. Once you have this done, tighten the holders down in their new positions. Again make sure the carriage slides smoothly and keeps moving a bit after you stop pushing. If not, then continue this process of slightly repositioning the bushing holders until you get it perfect. You really want the Y-table to be as close to frictionless as you can manage.
Now we need to drill holes at the corners of this bottom sheet where it will connect to the actual print bed. I like to remove the bottom sheet, duct tape it to the print bed, and drill both at the same time so I can be sure the holes will line up:
Now’s the time to mark on your bottom sheet where to drill holes for the belt clamps. You want the belt clamps to be directly in front of the motor and idler pulleys when the carriage is slid all the day up or down the rods. I like to place the actual clamps in place and use a pencil to blacken the MDF visible through their holes. It’s not a disaster if they’re not perfectly centered since you can simply slide the motor and idler mounts along their extrusions to center them with wherever you put the belt clamps.
After drilling the holes, attach the belt clamps and their nut holders on the other side with washers and M3 screws that are at least 20 mm long:
Now you want to attach the bottom sheet to the print bed. There are several schools of thought on the best way to accomplish this, but I’m going with the tried-and-true screws-and-springs method. The upside to this method is that leveling the bed is incredibly easy, but the downside is that if you have weak springs, the bed can wobble and vibrate as the bottom sheet slides along the rods at high speed. To alleviate this, and to work around the fact that I didn’t have any super-powerful springs in my big box ‘o springs, I used three of them for each 45mm long M3 screw:
Fasten the bottom sheet to the print bed with M3 nuts and washers. Don’t worry about tightening them all the way down or leveling it yet; we’ll do that later. Once you do, with all those springs, there’s so much tension that the print bed will be rock solid! Here’s what your completed bed should look like:
Now let’s deal with the Y-axis motor and idler mounts. I used a spare M8 bolt I had lying around for the idler, but you could easily use a 50 mm length of M8 threaded rod. Put two 608 bearings on your rod with washers on either side and tighten it down with M8 nuts. The dual 608 bearings are important because they prevent each other from wobbling. A single 608 bearing will eventually wobble and make the belt collide with the side of the idler mount.
Center the idler mechanism so that the bearings are right in front of the carriage’s belt clamp and tighten down the M5 nuts holding it to the extrusions. Note: this is the older-style idler mount; your idler may be the newer improvement made by AlephObjects, in which case it will function exactly the same way but look like this:
Time for the motor mount. Attach the motor with M3 screws that are 10-12 mm long and two washers. Then attach your motor pulley; I’m using metal ones from Misumi which are pricy but nice. Like with the idler, move the mount to center the motor pulley at the belt clamp on the bottom sheet and then tighten it down.
Almost done! Now comes the final step: attaching the belt. This part is a little tricky without access to the underside of the machine, so I balanced it on two kitchen table chairs to allow me to work from below.
You’ll want to take one end of your belt (I’m using 2mm GT2 belts) and fasten it to the idler-side belt clamp by loosening the clamp, inserting the belt, and tightening it back up again. Then thread the belt around the idler:
Now do the same on the motor side. Take the loose end of the belt, loop it around the motor pulley, attach it to the clamp on the other side. Pull it as tight as you can! You can cut off the loose ends to prevent the rest of the belt from flopping around. Here’s what it looks like on the bottom:
And from the top:
Slide the table around and let your imagination go wild as you think of all the 280 mm long objects you’ll soon be able to print! Next up: the extruder.
Wow! I’ve been completely bowled over by the demand for MendelMax parts! I’m printing these parts as fast as I can, but the queue that’s built up has forced me to close the listing for now while I catch up with the demand. If you’ve ordered a set, rest assured that I’m working as fast as I can to get all your parts printed! Feel free to drop me a line at nate@techpaladin.com if you’d like a status update.
I’m now selling high-quality aluminum motor couplers you can use to connect your motors to leadscrews or M8 threaded rods. These couplers are a really nice upgrade from the standard printed couplers since they’re guaranteed to hold the rods centered, and they’re slightly flexible so they tolerate minor misalignments. All of this improves your layer consistency. These aren’t the couplers I originally tried for my MendelMax; they hug the rods rather than digging into them with set screws. I like these much better. Pick up a pair today!
Note: Due to overwhelming demand, this product listing is temporarily closed while I print everyone’s orders!
I’m now selling printed parts sets for the MendelMax printer. I love the MendelMax design and I’m eager to see it take off, so I think this is a pretty exciting development. Here’s one of my kits:
A lot of people have asked me recently how I make extremely high-detail prints, such as this little gnome house:
Using a better firmware (Marlin) and a gcode generator that creates more sensible paths (Slic3r) are the first two things you absolutely must do. Without using both Slic3r and Marlin, you’ll struggle to print your perimeters at more than about 25 mm/sec without seeing severe blobbing on corners and arcs. Let’s assume you’ve followed my advice in Getting all the pieces to fit together and you’re using Marlin and Slic3r. Excellent! Let’s get started.
Low layer height
Layer height is the primary setting that determines the surface detail of your print. The lower the layer height, the greater the “resolution” of the print. A 0.3 mm layer height will display visible layers, while at 0.2 mm layer height, the layers will begin to appear smooth with certain filament colors. The gnome house above was printed at 0.2 mm layer height in silver PLA, which is very forgiving of surface blemishes. Black PLA is similar, and translucent blue PLA is even more forgiving, but white PLA needs lower layers and perfect layer alignment before they need to disappear; 0.15 mm layer heights and below, usually.
As for your nozzle diameter, the truth is, the relationship between your nozzle diameter and your layer height is a very loose one. A bigger nozzle lets you print with a slightly higher layer height, but doesn’t really constrain you that much when you want to decrease it. This is because the nozzle diameter merely determines the width of the extrusion that comes out of it. Even a fairly wide extrusion should react fine to being smooshed down on top of the previous layer. To sum up:
Larger nozzle (0.5 and above):
Taller (and more visible) layers possible
Greater maximum speed is possible
Smaller nozzle (0.35 to 0.4)
Shorter layers (< 0.1 mm ) possible
More contour on extremely short layers possible
One thing I’ll mention is that I do not recommend a 0.25 mm nozzle. That small of an opening makes it a real challenge to print quickly, and can lead to jams. I really like a 0.35 mm nozzle. I can get great high-detail prints, but I’m also able to print infill at 120 mm/sec without the extrusion getting too sparse. If I go much faster than that, though, I can see it start to string out. A 0.4 or even 0.5 mm nozzle would be better for higher speeds than that, but my focus is maximizing speed given a certain quality I want to achieve, so I’m more than happy to sacrifice a bit of potential infill speed so I can get the benefits of a lower potential layer height. Perimeters, of course, are printed much slower than 120 mm/sec to ensure good surface detail and layer alignment. Which leads me to…
Only maximize speed for the desired quality
In the beginning, I was so excited about pushing my printer faster than I sacrificed quality to ramp up the speed, going as fast as 65 mm/sec for the perimeters on this building. Now I know better. It’s far more sensible to pick a desired quality level and then maximize the speed without diminishing the quality.
Once you have a desired quality (say, 0.15 mm layers), you can set about increasing the speed until you start to see diminished surface quality. The exact speed you can achieve for your target quality will vary from machine to machine, so you’ll need to do some experimentation. Here are some tips:
Print hollow if you can. This really saves time and filament, and more models than you think can be printed without any infill at all. The real challenge is for models with flat tops; those flats need good bridges. But that’s not too hard if you make sure to keep your number of solid layers at 3 or more.
Print infill faster than perimeters. After all, nobody sees the infill! If you can’t print hollow, you can increase the infill speed all the way until the extrusion get stringy and begins to lose its structural integrity. For me, with PLA and a 0.35 mm nozzle, this is about 120 mm/sec.
Don’t print infill for every layer. Again, if you can’t print hollow, this is another good alternative. Skeinforge calls this “Skin”, but Slic3r uses the “Print infill every n layers” setting. Make this 2 or even 3 if your layer height is really low or you have a big nozzle.
For PLA, use a fan. PLA needs more time to cool than ABS, so the faster you go and the hotter your nozzle, the more imperative it is that you use a fan to cool the extrusion after it hits the previous layer.
Increase your first layer speed by moving the nozzle closer to the build platform. The only reason you need to go slow for the first layer is to ensure good adhesion. You can also get this by moving the nozzle closer to the platform, ensuring that the extrusion is really smooshed down. But don’t go too close or it can be tough to get the print off the platform!
Once you’ve got good prints with all that, there’s an additional piece of the puzzle that lets you increase the speed even more: a rigid frame. No matter how you slice it, the Prusa Mendel isn’t an especially rigid machine along its X axis. The faster I go, the more I can see the frame triangles wobbling back and forth. That won’t do! There are band-aids such as this brace but a better design is really needed. That design is the MendelMax. I’ve finished my MendelMax’s frame and axes, and the thing is rock solid. Even at very high speeds, I just don’t see it bending or wobbling at all. So get yourself a MendelMax!
