TechPaladin Printing

MendelMax build: extruder

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.

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Categorised as: 3D printing, Hardware, MendelMax