Time to actually make the extruder. This is probably the easier part in my opinion. If you haven't gotten all of your materials and tools together now is the time to do it. Please refer to the previous step if you are unsure as to what exactly you will need. Or if you are the adventurous type read on. This is a guide and not exactly down to the micron instructions on how to build a Hot Glue Gun (Hot Melt Adhesive or HMA) based Extruder for most CNC XYZ machines.
The first thing you probably will want to do is get your glue stick. The 4" x 0.28" one. You will need this pretty much for every step when adding things to make sure it still is a tight fit. The drawing of the extruder was done in Inkscape (another great open source software package - once you get past the GUI learning curve). It is pretty much to scale and can be used a reference for how I built my extruder. Yours will invariably be different in some way.
Another tip is if this is your first time doing anything like this, get a piece of cardboard 4"x6" and prototype it on that. Just leave the stepper off. This way you can get the feel of how everything is laid out before hacking up your plywood.
Before you start you will want to wire up your motor and make sure it works. I have based projects on a particular motor and then found out it didn't work when I finished. It is also handy to use for testing at various stages.A
I started with the main 100 tooth gear. I made the glue stick path to the left of the extruder and the motor fits on the right. You may feel like you have to center the glue stick but in the end it really does not matter as long as it works. Mount it by drilling a hole with a 9/64" drill bit. You will need to use a screw driver to insert the #8 1.5" bolt from the back (motor mount) side of the plywood. If your gear has a bigger or smaller hole than a #8 bolt. Find a bolt, washers, and nut to fit it and don't forget to find a drill bit (don't drill a hole that the bolt fits loosley into ... you want it tight... like a tiger). Now put 2 washers onto the bolt, then the gear, then 2 more washers followed by a nut. Tighten down the nut so it is snug but still allows free movement of the gear. Now add another nut on top. Snug it tightly against the first nut. This should lock the first nut in place. Check the gears movement again.B
Now is a good time to add the motor. You can add this later but I am going to do it now. The hard part is lining it up so that the gears mesh correctly and then drilling the hole in the correct spot. I basically places the stepper with gear on the shaft in the spot I wanted it. Traced around it with a marker or pencil. Then drilled the hole out to around 0.75" in order to leave room for adjustments. I used the step drill to drill this hole as the only other drill bit I have that is big enough is a paddle bit and it tends to tear up the plywood as it exits the other side. The step drill makes a nice smooth hole. Next place the motor on the motor side of the plywood with the gear in the correct spot with the gears meshed together. Mark your stepper mounting holes (my motor had a mounting bracket attached which made this step easier) and then mount the motor with bolts or screws. I used #6 0.5" Screws. Make sure your screws or bolts do NOT interfere with the main gear. Once you are done make sure your motor can turn your main gear without trouble.C
Now that the main gear is in place it is time to attach the bearings that press the glue stick against the main gear. The bearings are 0.6" apart and on my extruder are nearly touching (the drawing I think has them a bit wider). Place a hot glue stick vertically next to the main gear. Next place the bearing snuggly next to the glue stick so that the stick is pressed firmly up against the main gear. Mark the center of the bearing with a marker or pencil. Drill a hole where the marks are with the 9/64" drill bit for the #8 1.5" bolts. Screw the #8 bolts in all the way with a screw driver. These should have a tight fit. Next place a washer, bearing, washer, and then nut onto the bolt. Now time to adjust and tighten the bearings down. Push each bearing up against the hot glue stick (it is still there right?) so that the hot glue stick begins to bend slightly around the main gear. Then tighten the nut that holds the bearing down. Repeat this step for the 2nd bearing. You should now have 2 bearings pressing a glue stick against the main gear. The glue stick should curve a little bit around the main gear. See the picture of the built extruder for detail on this. The bolts are too small for the bearing holes on purpose. This allows some adjustment before tightening the nuts.D
Next it is time to attach the Hot Glue Gun internals. First remove the insides from the hot glue gun. There should be 5 screws to remove and then the plastic shell should come apart. See the picture of the hot glue gun insides (this one is a little different looking than the one on the extruder I used in the pictures, however it is nearly the same in every dimension). You will need just the part that gets hot that the glue sticks go into (the one with the cord attached). The rest of the parts are not needed. Maybe you can make a toy? gun
or something for your kids with it.
Now comes the hard part. You are going to need to carve out about 1/4" deep space for your hot glue gun internals into your plywood. The dark brown area on the drawing. I used a dremel tool with a 1/4" router bit and a router attachment so I could slide it around and carve out a nice space. You can just use a dremel tool with a bit that eats wood or just a plain chisel and hammer. It doesn't need to be perfect or really flat ... just 1/4" deep and big enough to fit the Hot Glue Gun internals into. You may have to make it deeper than 1/4". The idea is to keep the glue stick almost flat against the wood. You can test fit this by putting a glue stick in your glue gun insides and press it into the hole with your fingers. If the glue stick looks like it is even with the main gear then you are good. If it is not even (sticking up above it) then you will need to make your trough a little deeper. Take your time otherwise you will have to start over. 3/8" plywood is not very thick. I had to use a popsicle stick to raise the metal part of the glue gun up a little bit because there is a silicone (or some sort of rubbery heat resistant material) tube on the inlet to the metal part. This is a bit bigger in height than the metal part. So in order to lay flat I put a popsicle stick under the metal part. It is underneath the hot glue gun bracket in the drawing however if you move the bracket in Inkscape you will see the stick.
Next you secure the hot glue gun internals by drilling 2 holes. One on each side of the metal part (see lower part of drawing) using a 1/8" drill bit. Screw in a #6 1.5" bolt. Then put the 2" hold down bracket on top of the Hot Glue gun internals. Secure with a washer, lock washer, then nut. Make sure it is tight and the glue gun stuff does not wiggle. There will be lots of force applied by the glue stick when this thing is working. Be careful as this bracket gets HOT too!
Now is a good time to drill the holes for the zip ties that hold down the AC wires for the Hot Glue gun. I used a drill bit big enough so that the zip ties loop around and hold the wires to the board. See the black holes below in the drawing. Secure your wires with the zip ties now. This is so they don't break off and have to buy another $3 hot glue gun.E
Next we need to add some items that prevent the hot glue stick that is being forced into the hot glue gun from bending and going wacky tacky on us. This consists of 2 bearings to straighten out the hot glue stick (just below the main gear) and 2 bolts that hold the silicone tube that is attached to the metal part of the hot glue gun. This tube needs to be straight otherwise your pressure and extrusion quality may vary.
To do this put a glue stick about 2/3 of the way through the main gear pinch section. The glue stick should want to bend towards the motor side of the board. Place one bearing on the right of the glue stick to straighten it up. Mark your hole and drill using a 9/64" drill bit for the #8 1.5" bolt. Screw the bolt in place. Then place a washer, bearing, washer, nut on the bolt. Adjust the bearing to make the glue stick straight so it points directly into the hot glue gun silicone tube and then tighten down the nut. Make sure the bearing rotates.
Next attach another bearing on the left of the glue stick. This keeps it from going to the left and missing the silicone tube. Use the method in the above steps to secure the bearing to the extruder board. Make sure it rotates too.
Now time to place the bolts on the sides of the silicone tube. I simply just drilled 1/8" holes on the right and left (about 2/3" up from the bottom of the tube). Then I screwed in 2 #6 1.5" bolts. This holds the tube in place and does not allow it to bend much from side to side (which it wants to to do...).F
Take the 3/8" x 4" long straw tube thing (I got mine from some household door seal kit ... it held screws.. you could probably find something similar in the plumbing section at your favorite hardware store ... Like Ace Hardware, they have everything especially a super duper great selection of nuts and bolts). Anything will do just as long as a glue stick slides effortlessly through it using just gravity alone. To mount it I used Hot Glue! Test place it on your extruder in the position shown in the drawing. Drop a glue stick in it. If it slides without getting stuck into the waiting jaws of the main gear and spinning the main gear grabs the glue stick then mark its position and glue it down with a bead down the back and a couple of spots on the sides. Careful not to melt it with the glue gun tip.Z
Lastly we are going to attach the L shaped bracket to the wood. This bracket allow you to attach the extruder board at a right angle onto your CNC machine's Z Axis. I used a 1/4-20 bolt and nut just as my router uses to attach to the Z Axis. I am sure this part is going to be somewhat custom so play around with it and do what is best for your setup. Look at the pictures in this instrutable and at the drawing to get some ideas on how I did it.
Congratulations, you now have a contraption that looks neat!
Next we move on to testing the extruder.