[SPEEDRE]

Has anyone tried to scratch build an extruder ?. How difficult could it get ?. How bad could it get ?. Too technical for amateurs ?

[fritzgutten]

I've built an extruder of my own design. It was time consuming. By far the most tedious parts are drilling a .5 mm hole and making my own heater coil. Luckily there are ways around both. There are simpler designs available using off the shelf components. Definately doable with a bit of effort

[jolafson]

Hey SPEEDRE, John here. We sell just the hot-ends from our machines, if you're interested. Also, we sell the nozzles and resistors/thermistors seperately too. Our nozzles come in .020" dia. hole size, 5/16-24 threads if you wanted to make your own heater block and use our nozzle. SeeMeCNC is our website.

Ok, done with the advertising now. Don't be afraid to try it. It's not that hard at all. If you have a CNC, you've learned more than most starting out in the 3D printer world! The only big thing to consider is:

1.75mm or 3mm filament

They are both semi-easily sourced. The reprap crowd uses both extensively. 1.75 is easier to use they say. It takes less force to extrude, and the smaller diameter is easier to control extrusion rate.

Other than that, the next big challenge is driving it down into the hot nozzle. We use a teflon tube inside a PEEK plastic barrel, dual drive rollers that have a light knurl, an aluminum upper heater block, for fast thermal transfer, a steel lower clamp section for heat retention at the nozzle, two 6.8 Ohm resistors that actually do the heating, a 100K Ohm thermistor for measuring the temps, and a $10 relay board that takes the signal from the thermistor and sends the current to the resistors. It works great.

Here's some pics and links to take a look at what we do
Jpeg of our entire extruder

Top view of ours

Looking inside the extruder This one shows the PEEK tube, but inside that yellowish tube is where the teflon "liner" goes.

Hot-End This is a good shot of our hot-end. From bottom to top, the brass nozzle, steel clamp, aluminum body, PEEK barrel, PEEK barrel mount, then the rest is the mounting for our x axis carriage.



Take a look at those, and give it a shot.

Also, as we are an open source project, you're free to download the .stl cad files and build one from our prints too! But, for $38.00, we'll ship you one tomorrow! (Ok, last shameless advertising, I promise)


Have a good one
John Oly

[SPEEDRE]

I don't understand something. Does the extruder on the site include, the heater for the filament, and a connection for the temperature regulator. It may be clear I am not up to speed on the terms used in 3d building, but am I right to say all I have to do is add a stepper motor to have a fully functioning extruder head.

[jolafson]

SPEEDRE

The extruder kit comes with the two heating resistors and the thermistor used to heat and monitor the heats. You can add a stepper motor for $25 more to it, so you get that too. The only thing you will have to do is provide the stepper control for the motor, and heating circuit control. We use inexpensive velleman MK138 thermostat kits. If you use that kit, all you need to do is swap the resistor #5 for a 10-20K Ohm resistor, and the thermistor included in our kit will allow the velleman kit to control the temps up to about 450-475 F range. The heater is "standalone" meaning you turn it on, wait for it to get hot, and when it's hot, run your Gcode!

Hope that helps clear it up,

Thanks again,
John

[EL34]

Hi John,
I am assembling an extruder from scratch to mount on and test on my CNC machine
If I like the test results I will built a stand alone printer.

Glad I found your post because I was wondering how to control the temperature without spending big bucks on one of the fancy temp control boards that have a display. Display would be nice, but not needed for my test rig.

velleman MK138 thermostat kits - I googled this and found the web site. thanks for that info.

I noticed you change out the thermistor to change the temp range
Are you using a 100K thermistor?

thanks for any help

[Fastest1]

I have built, combined and or changed the parts from 3-4 designs on the market. Presently I am running a stainless tube from a Makerbot or Makergear product of some kind (it was laying in my parts bin) I bored a piece of PTFE rod as the liner to assist the feed. I use no PEEK. I removed the finned barrel of the Arcol's V4 and screwed the stainless tube directly into the heater block. It is much more rigid, not near as delicate. Has less parts and extrudes beautifully. I can put my hand on the stepper at anytime in a multi hour print and temps are reasonable. I can leave my hand on it. Also the way the SS tube clamps to my stepper, the aluminum piece is never warm. I have a fan on there to cool the tube but have had to redirect the flow because it gives the heating block difficulty in achieving higher temps. Btw, insulate the heater block itself if at all possible, just the block. If you can cool above and below it, your printing will be great.

I went ahead and showed the parts of the Arcol's on the last picture. I ended up only using the stainless tube screwed directly into the nozzle (same thread) then screwed that assembly into the heater block.
In the picture with the hot end having the insulated tube around the barrel. This set up had the most stable heat production and I will likely use a liquid insulation product to coat the heat block only. I have seen the product on Nopheads site somewhere. When running the Arcol's, I had used the SS tube to mount it to my stepper. The multiple junctions created too many issues in feeding. Arcol's didn't intend it to be used that way and his design would have fed well most likely had I not modded it. It was an accidental realization that I could eliminate most of the parts. I have run 230C with no issues for hours now. When I ran anything with PEEK, it would get flimsy at temp. I hated that. I still can't figure out why anyone used it. The SS works great.

[Fastest1]

The last picture as you can see has 4 parts, though they are partially assembled. I only used 2 of those 4. Also Arcol's used a jet of some kind to hold the small PTFE liner he had right at the entry. Nice design, I just had a different idea and mount.

[Fastest1]

I shot a little video to show the results.
RepStrap hot end temperature isolation - YouTube

[EL34]

Nice vid, thanks

Just got my spool of 1.75mm PLA and now I have to figure out the tube situation down to the nozzle

Are you running 1.75mm ABS?
I am guessing you are not running PLA cause you have a heater bed?

So your stainless tube has a teflon sleeve inside, is that correct?
Do you know the OD and ID of the tube?

All the tubes I have been looking at are combinations of teflon and what not and it seemed to me it could be done more simply like yours

[Fastest1]

I am running 3mm ABS, 230C, .5mm nozzle diameter, .2mm layer heights at the moment. I took a piece of PTFE rod and drilled out the center to accomodate the filament. Then I turned the outside down to fit in the SS tube, I left a small collar (OD) at the nozzle end that is clamped between the nozzle and the tube when they are screwed together that eliminates the PTFE moving. Simple and a total of 4 parts. The tube, PTFE insert, nozzle and heater block. If I would turn it off I could disassemble it easy enough to show you but I am having too much fun.

[EL34]

I have access to all that stuff to make the delivery tube and a lathe but I don't quite have a clear picture of your internal pfte tube yet

So it fits inside the SS tube and you have a hole down the center that is 3MM or maybe a tad larger than 3mm so it does not bind easily?

Then where the pfte tube meets the nozzle you have a flange

Is is like what I have drawn here?
thanks for your help

[Fastest1]

Exactly like your drawing. The flange is just thick enough to be pinched in that joint. I haven't had any leakage and every thing has been running rock solid.

[EL34]

That flange makes perfect sense as a seal
Thanks

I also have to make a heater block once my 40 watt heater cartridge arrives and I can get an accuracte diameter of the heater cartridge

I'll pick up a cylinder of pfte at mcmaster carr unless someone has a better source

The hole through the pfte tube
I am wondering how much play to leave for 1.75mm PLA
It varies up to 1.79 mm so the hole size should not be too close to 1.75mmm or it will pinch or have too much drag

Maybe the hole should be 2mm?

[Fastest1]

I just stuck it in the lathe, put the chuck in the tail stock and drilled it with the next larger bit than the filament measured. Hasn't been a problem. The seal has been of benefit as every other hot end has spewed plastic from the joint of the barrel and nozzle even when using Teflon tape. I still use the tape, mostly to ease removal when that time should come.

[Fastest1]

That 40watt cartridge is most likely a hair over .25". I have one around here somwhere.

[EL34]

Any reason to have a stainless tube?

I was thinking I could use some other material for the tube like aluminum, brass or copper.
I can machine and thread those materials way easier.
It's just a container tube that hods the pfte, so material should not matter
Something that sheds heat fast like aluminum sounds like a better choice

As long as your heater can keep the block up to temp as you extrude

At one time I had an idea that the joint between the tube and the nozzle could be a flared tube and a flared fitting.
Like used for pluming or propane gas???
Flared joints are really tight since the copper seats itself against the brass joint

The nozzle would be a drilled out end cap
They make these fitting for 1/4" tubing.
1/4" fittings would not be all that bulky like 3/8" and larger fittings
These fittings can be machined on a lather to customize the shape if needed
You could even solder some of the joints for a perfect seal

[Dean448]

Here are a few points I learned when it comes to the lower end of an extruder.
First if something is available on the market for a relitively low cost then its better to buy the build. The SS tube, PTFE liner and high quality nozzles are all avalilable from makerbot. You can build or buy the hot chamber connecting the tube to the nozzle.
I found it best to run the PTFE tube from the very bottom of the inside of the nozzle to the top of the stainless tube. No breaks in the liner where material can force its way out Also no place for the material to touch anthing else then the liner until at the opening of the nozzle.
Since the liner is not held in place vertically, it will float up from material that gets forced between the nozzle and the end of the liner. So you must contain the liner at the top of the SS tube. The liner must be held in all directions.

[Fastest1]

It turns out the SS doesn't transfer heat very well at all. This is a benefit as you would really like the heat on only a very small area (the tip itself). An aluminum tube would dissipate the heat of the block faster than the resistor could generate it. Plus it turns out a fan is necessary to blow directly on the print as it is being extruded. I used it because it was in my parts bin (I keep saying it is a Makergear part, but I don't remember where I got it) and it fit. I do like the design overall but if I were building from scratch I would do it just a little differently.
I would keep the feature of the SS tube screwing directly into the nozzle. Not the heater core. The nozzle has a female and male threads. The tube only has male threads. This allows the assembly to be removed easier and the seal seems to be maintained much better than other systems I have tried. Most ooze at this joint. Though the joint is tight, threads are well cut and Teflon tape is used.
The parts I would change is to have the nozzle protrude thru the block 1/8-1/4" more because I want to insulate the heater block itself with a brush on or dippable liquid ceramic or silicone insulation of some kind. Maybe change the profile of the tip itself to tbe more tubular and smaller in diameter for the very .01" say. This might help minimize the wiping or picking up of erratic strings occasionally. This could also be a temperature issue.
I run Nuri's Gnexlab heat control board. This is a wonderful and independent way to control temperatures but doesn't allow for adjustment on the fly.
Now with my little bit of success I would like to try a hotter temp to begin the print, say 235-240C and the bed at 95-100C. This would allow a better adhesion to the bed (though I have had no adhesion issues unless I turn the bed off). It would also allow the flow to bond with the previous layers/strings extruded possibly creating a tighter seal/fit of the laminates (or an actual 100% fill). My last print yesterday almost looked like an injection mold on the bottom where the first layer is extruded onto the heated build plate (tempered glass in my case). The visible joints between the passes are definitely getting less (they previously were not detectable by feel or fingernail, but proves not to be watertight).

[EL34]

Having a flange at the bottom would solve the problem of the pfte tube moving

I agree that sometimes it's better just to buy pre made stuff but I am a DIY type of guy with a CNC and other machines and so it fun for me to do this sort of stuff