Archive for November, 2009

Insulator and copper jacket

Friday, November 27th, 2009

Two successful pieces of progress last night! I redid the PTFE insulator and it came out great, plus I made the copper jacket.

Both of my successes are because of the drill press vice that my Dad lent me yesterday (shown here clamped to my drill press):

This time, I lined the PTFE up in the vice along a vertical notch that let me keep the PTFE rod lined up (despite what the cut end of the rod looked like). This time the end was smoother anyway because I used my table saw to cut the PTFE, rather than a hand saw. I then used a 1/8″ bit to drill all the way through, swapped out the bit with a 3/16″ bit, and drilled that 15mm in.

Since 3/16″ was still too small to screw the barrel in, and since I don’t have any metric tap tool, I tried putting the heater barrel itself in my drill press (cone facing down, lightly gripped) and drilled it into the PTFE. (It was a move of desperation; if the barrel was held tight, I imagine it would strip the PTFE, but if it was loose, it might just dig in and then slip out of the drill’s grip). That’s actually what it did – the barrel was completely pulled into the PTFE and the drill press lost grip with it (which is probably a bad idea; I imagine I’m going to horrify a bunch of people who actually know how to use their tools properly.. :) ). That was actually with my last failed PTFE rod as a test, so I had to unscrew the rod, which wasn’t easy. I actually used duct tape on the rod to get a grip, and was able to unscrew it, and it was thread perfectly (with PTFE jammed everywhere since this wasn’t a proper tapping tool with grooves). I repeated the process with my 2nd PTFE rod attempt, and here was the result:

Perfect! (as you can see above, I also carved out a groove or two on the back the way I’d tried before – putting the barrel in the drill press, spinning the PTFE, and using a triangular file to try cutting a notch or two in at the end (for glue to set into in the future, so I’ve read).

You can even see all the way through:

and here’s that view from the top:

and, of course, video:

So unlike what I said at the end of the video, it’s not quite time for fire cement yet. Next I had to create the copper jacket to fit at the end around most of heater barrel.

Unfortunately the copper pipe I have doesn’t the same as the pipe in the pictures on the Thermoplast Extruder 2.0 doc page. Mine had far thicker walls, and the outer diameter was a bit smaller than the PTFE rod (looking back at my order, it was: Copper Tubing 3/8″ Tube Size, 1/2″ OD, .37″ ID, .065″ Wall, 1′L). I think it’ll be ok, but there won’t be nearly as much space for fire cement between the nicrome wire and the copper jacket as there is in those pictures. I’m half tempted to go to the hardware store and look for a wider diameter (and thinner walled) section of copper pipe, but again it wouldn’t be in metric measurements, so it’d probably be much wider than the PTFE (and I have no idea how that will affect applying the fire cement. Eh, it’s all a learning experience. We’ll see. So here’s what I did with the copper pipe I had..

Here’s the copper pipe with the “tab” still unbent. As you can see, its diameter is definitely smaller than the PTFE (which the docs say is ok, I just don’t know if the wall thickness robs me of too much fire cement insulation):

I was worried that the thicker wall would make the tab more difficult to bend, but it wasn’t too much of a problem.

Here’s the jacket with the notches cut out for the nicrome wire leads and for the thermistor:

And finally here’s what it looks like when I test out placing the jacket over the barrel. Again, I’m worried about how much space there is inside there for the nicrome wire, and for the cement around that wire. We’ll see.

Since the bootlace ferrules are part of the order that’s not arriving until Monday (with the timing belts and the XLR power connectors), I won’t be able to do any more on the extruder until then. If I did get time over the weekend to work on anything else, it’d be soldering the 6 OptoEndstop boards, but I think I’ll be busy.

Progress! Progress is good! :)

Heater Success, Insulator Fail

Wednesday, November 25th, 2009

Well, this evening I had great success re-doing the heater barrel, but then failed at my attempt to create the PTFE insulator.

Whereas my first heater barrel was bent and had an offset nozzle hole, this second attempt was perfect. I used my regular drill press for the whole thing, not touching the Dremmel press thing. (LarryP, I should have taken you up on the smaller drill bits, but I hadn’t planned on redoing the barrel this early). The new barrel:

This time I tapered the nozzle edge first, by putting the entire brass piece in the drill press chuck, spinning it, and filing down the edges.

Here you can see how straight the new barrel is, alone and compared with the old barrel. I made sure not to let the barrel get too hot during any of the drilling:

So that was the success part of the night. Wanting to finish another part, I moved onto the PTFE insulator.

I don’t have metric drill bits, so I drillled a smaller-than-M6 equivalent (I forget what size exactly) in the 15cm, then used the 1/8″ to drill all the way through. When the hole came out the other side, it was waaaaaay off center. :( I figured I’d continue the rest of the steps anyway so I could learn any future lessons on this PTFE scrap, and drilled a new all-the-way-through hole from middle on the other side.

Other than that, it looked nice..

I even carefully put my precious barrel in my drill press chuck and spun the PTFE so I could use a triangular file to create the external notch seen here (I have no idea how anyone fit that in a normal drill chuck unless they mean what I did – put the brass barrel in the chuck):

Still, that wobbled like crazy.

So, I have no idea how I’m supposed to actually do this drill-through correctly. I’d cut the PRFE with a small hand saw, but the other end was perfectly flat, and I’d had that on the bottom. It looked like it was lined up well. I have no idea how to hold it down – all I could come up with was this messy collection of clamps:

I think I want some way to drill a small hole in clamped down wood, mark the center of PTFE on one side, somehow anchor that center to the wood hole (like a very small nail maybe?), then line the top of the rod up with the bit (then obviously stop before I reach the nail), but that sounds crazy. Maybe I should google how people actually use their drill presses. :) I think it’s crazy that I could so precisely hollow out a tiny brass rod, but this huge PTFE piece is causing me trouble. :)

All of my Mendel RepRap parts

Tuesday, November 24th, 2009

Well, I gathered together on one table all of the parts that I’ve ordered and received for my Mendel. I’m still waiting to order 3 Stepper Motor drivers, but everything else is ordered (I have timing belts, bootlace ferrules, and power connectors in the mail due in 6 days). Here’s what I’ve got:

And here’s a bunch of pictures.


In the center you can see my finished heater barrel:

Lots of fasteners:

All of the bar and threaded rod that make up the frame:

The USB to serial board:

More stuff, including stepper motors and boards:

The gear I’m putting on one of the stepper motors for the pinchwheel extruder:

Opto-endstop board parts, nicrome wire, a thermistor:

Another closeup of my finished heater barrel:

Copper pipe and teflon (PTFE) rod:

And of course, fire cement:

Yup.  I certainly have a lot of stuff ready..