kbob and Impulse, the Rostock MAX

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Re: kbob and Impulse, the Rostock MAX

Postby kbob » Fri Jul 19, 2013 7:04 am

I am lousy at keeping these build logs updated. I finished building the Rostock MAX on June 11th and took it to Eugene Maker Faire on June 15th. It was very poorly dialed in, and I was running it at 30mm/sec because I didn't know it could go faster. But it still generated intense interest, and my booth was mobbed all day. It's easy to forget that 3D printers are still alien technology to most people.

I've printed a few vases from Thingiverse -- if printed with a single perimeter and no infill, they print quickly and fairly reliably. I've also designed and printed some other trinkets and a few useful things. My tallest and widest print so far is a PrettyTron 9000 vase scaled to 200%. That made it 245 mm tall by about 200 mm wide (9.5 inches by 8 inches).

The RAMBo board that came with the printer did not have an Arduino bootloader. I eventually found out how to install a bootloader through the ICSP pins, so now I can reflash the firmware.

Here are the issues I am still working through, in roughly the order I want to address them.

The physical dimensions in the firmware do not quite match my printer's dimensions. These dimensions are used to translate desired X, Y, Z motions of the print head into vertical motions of the carriages. Because the dimensions are off, the firmware's idea of a flat X-Y plane is warped. I can print on roughly a 120mm (5 inch) patch in the middle of the bed, but beyond that, the nozzle is too far from the bed for plastic to adhere. I've been on a quest to accurately measure all the dimensions and correct the firmware. Here's what I wrote about it this morning over on my other build log (which I've updated more frequently). http://forum.seemecnc.com/viewtopic.php ... 167#p16124

I printed an alignment jig to get the three delta towers exactly equidistant. Photos here. But I haven't actually done that alignment yet.

I have compared my thermistor's temperature readings to a thermocouple, and I know what the thermistor's error is. I need to figure out how to change the constant in Repetier to compensate. (Anyone know of a good tutorial on setting that?)

I have two more colors of ABS that I haven't tried to print in yet. (neon purple and black, to complement the neon green and neon orange I've already tried. The green is much less finicky than the orange.)

The stock hot end has a fairly long melt zone. That, in conjunction with the Bowden tube, makes it hard to control retraction. I get little "coral stalks" whenever the nozzle moves between two different objects. As the print head moves away from an object, plastic keeps oozing out, and it gets wiped on whatever it passes over. I've done what I can. Many Rostock MAX users are recommending a different hot end with a shorter melt zone to reduce the oozing.

I really want to make a set of magnetic arms a la BerryBot3D. They just seem cool. Doing so will require a new effector platform (the part that moves in 3D and holds the hot end) and new mounting mechanism on the carriages. I've bought the parts for the arms. I would print new carriages and effector platform.

I have a redesign of the carriages in mind that will reduce the moving mass by a lot.
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

Re: kbob and Impulse, the Rostock MAX

Postby kbob » Mon Jul 14, 2014 2:42 am

It has been a year since my last report. (The whole site seems quieter lately.)

One of my friends has five 3D printers. He often says, "I wanted a tool, not a hobby." He is lying, of course. He's always got a project underway to build, upgrade, redesign or repair one of his printers. OTOH, with five printers, he almost always has one that's working. (-:

I try to keep my printer a tool, not a hobby. Sometimes I succeed.

About last October, my hot end broke. The PEEK tube got brittle from heat and snapped in two. I used that as an excuse to upgrade to an E3D v5 hot end.

After that, I was plagued with wobbly prints. I upgraded the delta arms to Trick Laser's carbon fiber arms around February. That definitely helped. http://www.tricklaser.com/Carbon-Fiber- ... M-CFTX.htm The Trick Laser arms are actually heavier than the nylon arms that came with my printer, but they're much stiffer, and the bearings have both less friction and less free play.

But the wobbles came back. About a month ago, I realized that the mount I was using can't keep the print head from tilting in the -Y direction. So I upgraded it by printing a second copy of the top half and supporting the E3D in three layers instead of two. (see below) Now it seems to be good.

Here is the mount I was using. http://www.thingiverse.com/thing:137140 It has two pieces. The upper piece constrains the hot end in the X and Y directions, and the lower piece constrains it in X and Z. It has very poor mechanical advantage constraining it in Y.

I duplicated the top piece, and now the head is held in a sandwich of upper - lower - upper. The Y movement is better constrained in that configuration, and the wobbles seem to be gone. I usually run with 3600 mm/sec/sec acceleration, so the hot end mount is working hard.

I would still like to get a metal mount some day for even better precision.

Aside from those things, there've been the usual maintenance activities: re-surfacing the bed (I use white glue), re-leveling the bed, tightening things, cleaning things, tweaking the Slic3r settings.

My software stack has not changed much. Since it's "not a hobby", I'm still running the same version of Repetier Host and Slic3r I started with. I've recompiled my firmware a few times with tweaked settings, but it's still the same Repetier-MAX release. I've added NetFabb to my workflow. I've dabbled with Sketchup and FreeCAD, but I keep coming back to OpenSCAD when I want to get something done.

I've used ABS exclusively to this point, though I have some Taulman 618 and some NinjaFlex waiting for me to get experimenting.

Right now I'm printing some pieces for my laser cutter. If it comes out okay, look for an update over there next.

viewtopic.php?f=16&t=1505
Bob
"If you didn't code it, it will never own you." (-:
kbob
 
Posts: 151
Joined: Mon Jul 09, 2012 6:39 am
Location: Eugene, OR, US

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