Shop OBEX P1 Docs P2 Docs Learn Events
MakerBot Build Log + Prop Control Discussion - Page 2 — Parallax Forums

MakerBot Build Log + Prop Control Discussion

24567

Comments

  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-17 00:19
    There should be some washers with those tiny screws. I am sure that the wood would break before the screws do.

    When my nozzle is touching the build platform, zero threads of the leadscrew break the plane of the top surface of the plywood. Even if the hole were enlarged and the nut pushed through, it would not engage the leadscrew.

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-17 10:47
    W9GFO wrote:
    Even if the hole were enlarged and the nut pushed through, it would not engage the leadscrew.
    Oh, that would not be good. Okay, I fixed it. But I replaced the washers with a laser-cut fiberglass flange to distribute the weight over the wood a little better:

    attachment.php?attachmentid=83061&d=1310924137

    My biggest concern right now is stress cracks in the acrylic. 'Came in this morning to find a bunch of them in the filament drive platform and in the drive sandwich itself. I don't think I tightened the screws more than was recommended. Now I'm afraid this platform is not going to last and that I may need to rebuild it from another material. Here's a photo of one of the cracks:

    attachment.php?attachmentid=83062&d=1310924137

    I'm really not as stressed about this as the acrylic is. :) I do think that longer screws with nylon washers would have alleviated the problem topside. Dunno how it could have been circumvented where the nuts go. Radiused inside corners would probably help. If I have to make the parts out of something else, I can; but which material to use? Fiberglass or Micarta come to mind. Anyway, it's probably good that it happened now, rather than after everything got put together.

    The hardware store did not have any acrylic cement, but they did have a Super Glue designed for plastics. It came with a liquid activator which you pre-apply and let dry before applying the glue. The glue in the tube had almost dried up, though, so I've got to return it to the hardware store. Maybe they've also got some Goop. But this may all be moot if I have to rebuild the platform.

    -Phil
    354 x 322 - 22K
    353 x 293 - 24K
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-17 14:15
    I wouldn't let the little crack slow you down. When you glue the feet on the stress will be spread over a large area that includes the arches and the cross piece. You could also remove, glue and reinstall the piece that is affected by the crack for extra security.

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-17 14:30
    I'm going ahead with the build. I took the Super Glue back to the hardware store and got some epoxy from West Marine that's formulated for plastics. I'm trying it on one of the feet. It's taking awhile to set up, though, probably due to the cool weather.

    -Phil
  • Ken GraceyKen Gracey Posts: 7,386
    edited 2011-07-17 15:55
    I'm going ahead with the build. I took the Super Glue back to the hardware store and got some epoxy from West Marine that's formulated for plastics. I'm trying it on one of the feet. It's taking awhile to set up, though, probably due to the cool weather.

    -Phil

    Cool to have a West Marine in the 'hood, not to mention those marine plywood suppliers. Erco and I could take a vacation to your local shipbuilding suppliers, I'm sure. The only plywood we can get around here isn't plywood at all - MDF, ACX and other common tract home building "woods" are common.

    I don't think anybody has asked yet, so I'll take the bait and throw out the question: are you going to control this with a Propeller? I am sure their current system does perfectly well and there's little gain to doing so if the objective is to start making SLA models. They've expressed an interest in having a Propeller-controlled version.
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-17 16:43
    I'm really hoping that after Phil experiences the limitations of the current controller that he will feel compelled to use a Propeller. Using a Propeller to read the G code and control the steppers would allow some significant improvements in the usability of this machine.

    One Propeller based board could replace the Arduino Mega, MakerBot motherboard, Extruder controller and the Interface kit.

    Here are some simple features that should be implemented.

    1, adjust feedrate, reversal, flow etc., on the fly. There are many parameters to adjust for the best print. If they could be adjusted during the print it would be oh so much easier to fine tune.
    2, using an LCD, select files stored on SD card and run. Currently, even though there is an SD card slot, you still have to select the file and run it from your computer - unless of course you buy yet another controller.
    3, Pause, jog and resume. It would be extremely useful to be able to pause the print and move the toolhead. Then resume the job. Being able to rewind the gcode would be great as well.
    4, More sensors. There are many things that can cause a print to fail. Most can be corrected if caught right away. If the machine would sense the problem and pause the print so that it can be fixed then many hours, and lots of plastic, could be saved.

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-17 16:51
    Ken Gracey wrote:
    Erco and I could take a vacation to your local shipbuilding suppliers, I'm sure.
    You're always welcome! Be sure to bring a truck (and plenty of cash). You won't be able to leave EdenSaw without a truckload of exotic wood!
    Ken Gracey wrote:
    ...are you going to control this with a Propeller?
    Initially, I just want to see it make stuff; so I'll have to hold my nose, let the Arduino do it's thing, then seek penance for my sin. However, if there's sufficient demand for a Propeller controller -- especially if it adds perceptible value -- I'd certainly consider tackling the job.

    -Phil
  • ercoerco Posts: 20,244
    edited 2011-07-17 22:41
    Ken Gracey wrote: »
    Erco and I could take a vacation to your local shipbuilding suppliers, I'm sure. The only plywood we can get around here isn't plywood at all - MDF, ACX and other common tract home building "woods" are common.

    Au contraire, Ken. I live in the nexus of materialism: Los Angeles. I have my pick of two West Marines nearby, and a plethora, a plenitude, a serfit, nay a gallimaufry of hardware, surplus and electronics stores. I can get the good stuff for cheap. Seinfeld's Newman once said "it's the wood that makes it good", and the same can be said of my town!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-18 23:01
    Tonight I finished the "Step-struder." Most of last night and today was spent waiting for epoxy to cure. I really should add some reinforcing to this. The acrylic supports continue to fracture right and left -- all the way through in some places -- and I'm afraid it's just going to fall apart if I don't do something.

    Anyway, assembling the heat chamber where the plastic gets melted was fussy but otherwise straightforward. An extra pair of hands to help tape the ceramic insulation in place would've been nice.

    I did a little extra prep where the thermocouple gets bolted on. The instructions just say to clamp it under a washer on one side. Well, I knew that it would eventually work its way out of there like a slow-motion tiddlywink. So I put a kink in one side of the washer and filed it flat, then bent a smaller lip just opposite the flat part. This creates a more horizontal "roof" under which the thermocouple can lie, and the lip provides extra security against it slipping out when tightened down:

    attachment.php?attachmentid=83098&d=1311055228

    After the heater is wrapped, you're supposed to poke holes in the wrapping where the threaded holes are. But where are the holes? I used the holes in the aluminum plate as a template and a Sharpie pen to mark their locations, so I didn't have to go probing like a student nurse looking for a vein.

    Here's the "finished" stepstruder, cracks and all:

    attachment.php?attachmentid=83099&d=1311055230

    I don't like it one bit. I just know it's going to crumble. What I might do is laser cut out some 1/32" fiberglass sheet that I've got and laminate it against the sides to strengthen it -- kinda like a crown on a cracked tooth. It'll look like hell compared to that sexy clear acrylic; but then, there's nothing sexy about cracked clear acrylic.

    One thing I don't quite understand -- but maybe the logic will manifest itself later -- is this: the ball bearing is uncovered, and there's nothing to hold it in the hole that surrounds the extruder shaft. Moreover there are no wood or acrylic parts that fit this spot, even though there are unused nuts buried in the sandwich, as if waiting for some sort of cover.

    -Phil
    407 x 337 - 27K
    648 x 486 - 65K
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-18 23:50
    If you were to fashion a small strut that goes from underneath the back of the stepper to the rear floor of the Z stage then the acrylic will be under very little strain.

    The bearing gets half pressed in. I put a bit of superglue on it to hold in place - until I printed out a new extruder.

    Rich H
  • ajwardajward Posts: 1,120
    edited 2011-07-19 07:01
    Ken Gracey wrote: »
    Cool to have a West Marine in the 'hood, not to mention those marine plywood suppliers. Erco and I could take a vacation to your local shipbuilding suppliers, I'm sure. The only plywood we can get around here isn't plywood at all - MDF, ACX and other common tract home building "woods" are common.

    Ken, if you're willing to take a small road trip, we have three West Marine locations in the Bay Area... Alameda, Oakland and San Francisco.
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-20 14:13
    I have another tip for you. The connector that supplies power to the heated build platform has failed on mine. On the red wire, the little metal blade inside the connector, is a bit thin and has heated up enough to melt the plastic of the connector so that the spring tension of the blade has pushed it through. And I am sure the springiness is not was it used to be due to the heating. In order to get up and running again quickly I cut the connector into two parts so that red wire is exposed and soldered the red wire (the blade) onto the pin of the HBP. Printing has resumed.

    I'll try to remember to put up some pictures.

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-20 15:03
    Thanks, Rich. My build is stalled, ATM. A piece of acrylic fell off the extruder support. I'm looking at ways to rebuild it with stronger materials.

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-20 18:23
    Here's a pic, and there are many more in my SmugMug MakerBot gallery.

    5959772052_ab53e132fd.jpg

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-20 19:14
    Rich,

    Impressive gallery! Thanks for the photo and link!

    I notice that your extruder support exhibits no cracks at all. Maybe I'm just tightening things too much. (A good friend has, more than once, called me "Dr. Goodwrench" -- perhaps for good reason.) Anyway, I'm considering extruded aluminum vertical supports with a horizontal platform of graphite laminate. (I'll have to machine the graphite, since the laser cutter won't touch it.) Anyway, I should have more progress tomorrow, since my other itch (FIR filter) has now been scratched.

    -Phil
  • VonSzarvasVonSzarvas Posts: 3,273
    edited 2011-07-21 13:09
    W9GFO wrote: »
    Here's a pic, and there are many more in my SmugMug MakerBot gallery.
    Rich H

    OK SmugMug, I am sold! Christmas list torn up and replaced with one item!

    Triple WOW with red extruded plastic on top!

    :)
  • $WMc%$WMc% Posts: 1,884
    edited 2011-07-21 16:27
    Maxwin wrote: »
    OK SmugMug, I am sold! Christmas list torn up and replaced with one item!
    '
    :)
    '
    Me too!!!. This printer is awsome.
  • max72max72 Posts: 1,155
    edited 2011-07-25 13:54
    Phil,
    I decided to go with a Rapman, being cheaper in my case.
    Anyway in the forum there is a huge warning about loctite and acrylic. It shows a behavior similar to the one you experienced:
    http://www.bitsfrombytes.com/forum/post/re-caution-loctite-cracks-acrylic-new-replacement-parts

    Massimo
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-25 14:06
    max72 wrote:
    Anyway in the forum there is a huge warning about loctite and acrylic. ...
    Oh no kidding! So it wasn't my gorilla-torque screw tightening that did it after all!

    Well, that changes things a bit. I got some Lexan and have been modifying the DXF files so I could cut the replacement parts on my CNC mill. (Lexan doesn't laser neatly.) Maybe I'll just use the files as-is instead and laser cut some more acrylic.

    Thanks for the heads-up!

    -Phil
  • max72max72 Posts: 1,155
    edited 2011-07-25 14:17
    The Rapman user was able to print ABS replacement parts before the acrylic failed. The nice thing is on the wiki there is a full set o 3D models available to make ABS printed spares.. I think they will be my test parts.
    Massimo
  • W9GFOW9GFO Posts: 4,010
    edited 2011-07-25 14:37
    Hmm, I used loctite on mine. Maybe the difference is I apply a small amount to the threads before assembling. I've seen others paint it on after it is together...

    Oh, I also use the paste version which comes packaged like those glue sticks (not hot glue) that children use.

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-25 16:59
    I used the liquid version. It's pretty hard to control the "dosage", especially on such small screws.

    -Phil
  • $WMc%$WMc% Posts: 1,884
    edited 2011-08-02 17:23
    Is Phil Pi stuck to his printer?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-02 18:44
    The kit's material quality has me a bit bummed, so I've been concentrating on a more rewarding endeavor, while I mull over my next step:

    Besides, the weather in the Gray Pacific NorthWET is rather nice now, so outdoor activities beckon. Nonetheless, today I reached a "semicolon" with that other project (on an up-note) and should be able to resume my attention here. 'More to come...

    -Phil
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-10 19:56
    It's been awhile. 'Been working on other stuff while I ponder my next course of action. Meanwhile, the acrylic pieces continue to crack and crumble. The extruder assembly has been reduced to ruins. Whether it's from the LockTite or from my Dr. Goodwrench overtorquing seems immaterial at this point. I've considered other materials and have samples in hand, including ABS, paper/phenolic, carbon fiber, better plywood, more acrylic, and Delrin.
    • The ABS seemed attractive at first, since it's both transparent and tough. But it doesn't cut well in the laser cutter and I would have had to mill it. This would have required a significant redesign of the pieces to accommodate the cutter radius.

    • It turns out that the laser cutter won't touch carbon fiber or thick pieces of paper/phenolic, so those are out for the same reasons as the ABS.

    • The 5mm plywood I can get here is only marginally better than what came with the kit, and I wanted something substantially better to replace the acrylic parts.

    • I don't know where MakerBot got their 5mm acrylic; but, in any event, I couldn't find any and wasn't too keen on repeating the past.

    I've settled on a home-built laminate, consisting of 1/8" Delrin (acetal polymer) clad in 0.045" Formica (paper/phenolic), using double-stick tape as the adhesive. The overall thickness comes to 0.225" -- 0.025" more than the 5mm acrylic supplied with the kit. This laminate has several advantages:
    1. The interior layer of Delrin is very tough. It will not crack. But it's not very stiff.

    2. The Formica is very stiff and provides a nice decorative finish to the structure.

    3. By using three layers, I can provide pockets that don't go all the way through, leaving a cleaner-looking face.

    4. The laser cutter can form threads in the Delrin for sheet metal screws, obviating the need for those pesky nuts.

    I did a small test assembly to try out the idea. Here's a photo of an unclad Delrin piece, with a #4-24 sheet metal screw inserted:

    attachment.php?attachmentid=83936&d=1313030138

    Here are the two finished pieces, looking down into the screw hole and the post pockets:

    attachment.php?attachmentid=83934&d=1313030136

    Finally, the assembled pieces:

    attachment.php?attachmentid=83935&d=1313030136

    I've ordered some black screws from http://www.microfasteners.com and will use those instead of the zinc-plated version. Meanwhile, I can begin cutting parts. The laminate weighs more than the acrylic, so I will probably cut some lightening holes in the interior Delrin core.

    The double-stick tape is pretty unforgiving, alignment-wise, and the photos betray my lack of care in trying to align the pieces by hand. But I realize now that I can use the cavities in the piece the Delrin parts were cut from as alignment jigs by placing the Formica piece in the cavity sticky-side-up and pressing the Delrin piece in place on top of it.

    -Phil
    691 x 489 - 38K
    457 x 451 - 26K
    645 x 589 - 57K
  • W9GFOW9GFO Posts: 4,010
    edited 2011-08-10 22:20
    That looks nice, interesting idea.

    Have you tried cast acrylic? The stuff I have is more flexible than the extruded, almost like polycarbonate.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-10 22:32
    Rich,

    I've got some 1/8" cast acrylic that I use for other things. Do you think the acrylic provided with the MakerBot is the extruded kind? I don't know how to tell the difference just by looking.

    I also need to replace the acrylic in the step-truder. Is there any advantage to the front piece being transparent? If so, I may have to resort to another piece of acrylic or else machine it out of Lexan.

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2011-08-10 23:01
    I don't know for sure but since extruded is cheaper, it seems likely that they chose to use it. It probably helps to be able to see the part that puts pressure on the filament but I think the printed extruder is far superior.

    I'd be happy to print one for you if you like.

    MakerBot-063-S.jpg

    Rich H
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-10 23:23
    Rich,

    That printed extruder looks much more robustly engineered! Did you design it? I will gladly accept your offer and be happy to pay you for it. This is the missing piece that I wasn't sure yet how I'd replace. I assume it fits the same slots as the stock extruder, right? Where did you get the pinch-wheel idler bearing?

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2011-08-10 23:54
    No, I did not design this one. I do like the design, so far the two of them have worked flawlessly.

    It does fit in the same slots.

    I have plenty of bearings, I think I can spare one. :) No payment necessary, just PM or email me your address.

    Rich H
Sign In or Register to comment.