Discussion in 'OpenBeam Kossel Reprap and OpenBeam Kossel Pro' started by Chris Gilroy, Jul 22, 2014.
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Hello everyone on the OpenBeam Kossel Pro team!
Are there any sneak peak videos available to show the printer in action?
We are hopefully going to be shooting some videos this weekend. It's been a pretty crazy and hectic time, with Mike's little sister getting married this weekend (so it'll just be me holding down the fort for the next few days). Right now, our focus is on the kitting instructions, so that we can get started on kitting the subassemblies that are part complete, to get kits out to our backers earlier.
What about the defected plastic part molds? Have new parts been made yet?
It would be nice to get another update please. It has been about 10 days.
@Jackal: Defective parts have not been made yet. We are trying to get the mold change package out to Western Tools this weekend.
@KDog: Update posted.
On the Project Update #16 the image that you have of the Work Instructions has the numbers represented in the second part of the image are not consistent with the numbers in the list above. It looks like the number of items are correct, but if someone uses the image of the package to load the package they will be putting in the wrong number of items.
What is the max safe operating temperature of the hot end? Have you tested extruding polycarbonate filament? The polycarbonate filament on the matterhackers site recommends a 270 deg C extrusion temperature.
I am interested in testing a heated build chamber. Have you guys experimented with this at all? Do you think any of the components would fail if heated to around 50 deg C?
@Don Williams: That's exactly why they go through the build right after they've done the kitting, to ensure the instructions are right. I know that that particular sheet has already been corrected
@jasonmiles: I can't speak to the polycarb yet as I haven't tested that myself. I do know that I've set the printer to 270°c before and that seemed to trigger a safety shutoff, but I would think that's more firmware than hardware.
As for the heated build chamber, it hasn't been tested yet but definitely been discussed. When you say components, I'm assuming you're just concerned about whats in the build chamber (end effector, FSRs, etc)?
I think the easiest way to build a heated build chamber would be to use insulation to simply wall in the three vertical sides, the top, and the bottom. This would heat everything including the electronics. Which is probably a pretty bad idea.
I'm not sure how I would go about building a the heated build chamber, but yes I would be most concerned with the parts you mentioned.
The design we've looked at here would enclose the chamber, but not the electronics. Because of the angle & curve in the corners, it definitely makes it a bit more tricky to close, but not impossible. We're currently looking at a couple of ways to seal it up while being cost effective, as well as something that can be used for both the mini and full size units. Weight also plays a factor, not only in the mobility of the printer but also the shipping weight out to customers as well.
As for the components themselves, everything that would be a potential issue within the chamber is rated for more than 50°c+. The FSRs have been tested to run up to 60-70°c along side the heated build platform without any issue. Unfortunately while those temperatures will work well with PLA, the FSRs can't handle what ABS needs for a temperature and so thats when the touch probe comes into play.
Seconded. I have a PC-ABS filament that requires 260-280 °C.
Would it be possible to "double stack" the corner vertices to hold a sheet of Lexan or Duraplex along the three sides of the printer? Alternatively, I suppose an offset sheet of material could be mounted to the existing horizontal extrusions used on the current setup and then sealed at each of the three vertices behind the vertical members for the linear recirculating ball rails.
Also, glad to see some good activity in the forum!
I will add it to the list of filaments to investigate.
We've looked at bolting to the existing horizontal frame, however this proves to be problematic for the design since reaching the edge of the print volume would cause the head to crash into the wall. We could add a software limit to keep it from crashing, but that also reduces the build volume quite a bit (best guess just from looking would be 30-50mm).
However, as I sit and look at the design, how would you guys feel about something similar to the vertices that you could print on your own?
To be more specific, I pledged for the Proto-Pasta Kickstarter: High Temperature PLA, Carbon Fiber PLA, Polycarbonate-ABS. www.proto-pasta.com
I think printing our own vertices would work well.
Dropping in to say hi here
Chris is correct that the FSR sensors will degrade at ABS temperature. Everything inside the chamber should survive at elevated temperatures (until we actually tested one, everything is theoretical).
The material used in all the injection molded plastics is Grivory EVX-5H, data sheet can be found here:
The numbers you should look at is the melting temp as well as the heat deflecting temp. Here's a good explanation of heat deflection temp:
and compare that against the best FDM part, in ABS from a Stratasys machine:
This isn't surprising, because Grivory and similar glass-fiber reinforced nylon (Grivory that we use is 47% glass!) is often used in under-the-hood automotive applications.
That being said, there is another factor to consider - the J-Head that we are using contains a PTFE barrier that can start breaking down at the PC/ABS temperatures. To date, we have tested PET+ in the JHead with great results. I have some Formlay and Gelform (PVA / TPE compounded filament for testing) and Chris's team just got in some of the more rare ABSes (such as conductive ABS for printing ESD safe nest fixtures). As we build more test printers, we'll be running some of these filaments through our test printers.
To run higher temp materials, we'll need to replace the end effector assembly. The fastest way to do this would be to print the reprap version of the end effector and mount a E3D hotend to it. But unless you can print the parts out of Ultem (there are RP shops that can do this for you), the printed part will not survive well in an enclosed chamber above 80 deg C. I'm hoping that someone will release after market machined parts for end effector retrofit after they get their hands on the printer - I know of at least one machine shop that's a kickstarter backer.
Simple out-of-the-box question:
Will this arrive as a raw kit of parts or will it be partially assembled at all? Do you have a "part number count" and "estimated time from sealed box to printing" for new users?
Thanks for the info. Grivory seems like an awesome material.
Another option for high temperature resistant part replacement is sintered stainless steel 3D printing. I have had good luck with parts from both iMaterialise and Shapeways. iMaterialise quotes out the standard Kossel end effector at under $60. This part could probably be further optimized to reduce weight and costs.
@thoughtfix: We are still working on instructions, etc. (And my house looks like a war zone - my wife's been extremely understanding, to put it mildly). So I've never actually sat down with all the parts pulled and in one box to time myself building one. I am estimating, based on subassembly part count, that it will take a skilled tech about 4-6 hours from opening the box to first print. I would double this number to form the basis of an estimate for how long it'd take someone to assemble the printer from scratch, having to read through the documentation, etc. It should definitely be able to go from "open box" to "w00t, first print" in a weekend.
We will ship the hotend as a partially assembled unit (You will still need to install the heater cartridge in it, but the thermistor will be terminated and potted in, and the entire thing assembled). Aside from that we are planning on shipping a kit of parts, but we've been putting a LOT of effort into laying out a clean kit. Please see our most recent kickstarter update for details:
From initial BOM roll up, there were over 1000 parts on this printer, but most of that is in screws, nuts and bolts (350 M3 nuts alone...). For future expansion we have our users load extra fasteners into the rails so that future accessories can just be bolted on. There are 30 unique and custom parts, but we reuse a lot of the same parts (for example, 48 ball bearings, 24 bearing housings and 12 ball bearing mounts for the ball joint system). This being a delta robot, multiples of 3 are very common (3 of this, 6 of that, 24 of this, 48 of that, etc).
@Jason: That's an awesome suggestion, Jason. I didn't think SLS stainless would be that affordable.
That being said, I am not sure if that is a compatible end effector. The OpenBeam Kossel reprap branch is here: https://github.com/ttstam and that's where I've been putting the parts I'm designing that are subassembly level compatible with the Kossel Pro.
Thanks for the detailed response. This will be my second 3D printer from a kit, but my 3rd build. I'll volunteer to do photos, video, and torture tests of my build and submit documentation clarifications (I do that well) but I will have to re-learn a lot of my tricks (Slic3r hacks, bed adjustments, extruder mods) to cope with the transition from cartesian to delta.
@jasonmiles and @Terence Tam Hey now, what about that no 3D printed parts on 3D printer philosophy? That's not a bad option considering the price!
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