CoreXZ Build

CoreXZ Build

Postby cdsteinkuehler » Tue Feb 17, 2015 7:07 pm

I'm gathering the remaining bits I need for a CoreXZ build, and I have a few questions:

Are the pulley spacers intended to be 3D printed and is their thickness critical? I may just cut them from some thinner flat stock (I'm having way too much fun playing with the laser cutter!).

There are 3D parts for the extruder in the CoreXZ assembly. Are these the actual files you used (ie: should I export STL and print these as-is) or should I be looking elsewhere? The design looks really elegant, but almost too simple!

Any comments on assembly order and potential "gotchas", or just caveat emptor? ;-)
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Re: CoreXZ Build

Postby Nicholas Seward » Wed Feb 18, 2015 5:17 am

The 625vvs all have to be coplanar so the thickness is very important. Washers and laser cut shims should be sufficient. For me, the weight of washers actually started to add up so I opted for light 3D printed spacers.

The extruder is pretty decent. I used a 625vv to keep the filament inline but I don't know if that is necessary. I would like a stronger spring. It is quite easy for the filament to get stripped. I am not sure what I would do to improve that. The rocker arm needs a bigger ID for its pivot from my experience.
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Re: CoreXZ Build

Postby cdsteinkuehler » Wed Feb 18, 2015 11:12 pm

I'm going through the build steps (thanks for the pics!) and it looks like this is pretty easy vs. any of the other machines I've put together. Of course the first thing I need is the pulley spacers so I may just have to print them.

Anyway, a few questions if you can spare the time:

* Where did you source the bed heater and (boro?) glass? I haven't found anything that matches the sizes in the Inventor files...to get going I'll just use unheated plate glass but I'd like to get a heated bed at some point.

* The extruder looks setup for 1.75mm filament on the input side, but the output side is 4mm dia. Did you add some ptfe tubing or similar that isn't in the Inventor assembly?

* I may need a close-up of the effector string termination, but I think I can figure it out (or find something in one of your videos).
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Re: CoreXZ Build

Postby Nicholas Seward » Wed Feb 18, 2015 11:53 pm

Pulley spaces thickness will need to be experimentally verified. Kerf of the laser cutter among other things will make this impossible to know before hand.

I used a QUBD heater but any 200x200ish heater will work. You will have to modify the cutout to match what you pick. http://www.robotdigg.com/product/99/MK2 ... er-Heatbed

I would use some fiberglass to insulate and press the board against the glass.

I used boro glass from McMaster Carr. http://www.mcmaster.com/#8476K21 10"x10"

I use 2mm ID x 4mm OD PTFE tubing as an insert. The e3Dv5 will come with it.

The stringing on the effector is important. I will have to get you a picture. However, the newest design should have places to bolt the gantry and effector in place so stringing can be done with everything in the absolute middle. (Edit: the previous sentence is false for the files you have.) Meaning... install the spools with the two string ends coming off the middle of the spool. One tuning peg will pull both strings in. (the tensioner) One tuning peg will transfer string from one spool to the other. (the leveler)

tensioner: Both string tie off and then wrap a few times around in the CW direction.
leveler: Both strings tie off and one wraps a few times in the CW direction and the other wraps in the CCW direction.

The retainer.ipt is used to redirect the string to the tuning pegs.

Note: I just looked at the files online and I am not sure what version it is exactly so I may have told you a few incorrect things. For instance, the design online doesn't use an LM8LUUs but still uses the double LM8UU arrangement. I also notice that it is missing a printed part for redirecting the string to the the tuning pegs on the effector so the string stays straight. The good news is that I have verified this design. Let me review the design and see what I need to get you.
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Re: CoreXZ Build

Postby cdsteinkuehler » Thu Feb 19, 2015 1:49 am

Thanks for the reminder, I forgot about the QUBD folks. Heater and glass ordered.

I'm probably going to stick with the dual bearings, as I don't have the LM8LUU's on-hand. If this turns out well we might make several more CoreXZ machines in a class for the Maker space, so I'd switch to the long bearings for that.

I'll have to put enough of the frame together I can measure for the pulley spacer thickness. It will give me something to do until the actual pulleys arrive. :)
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Re: CoreXZ Build

Postby cdsteinkuehler » Fri Feb 20, 2015 1:55 am

First CoreXZ build tip:

1) Buy the proper length 8mm rails. I got apx. 15" rods since they were the cheapest available from VXB (they cost less than the 13" rods!?) and I couldn't find anything pre-cut to 290mm, but they are a pain to cut to length. Of course, if you're looking for an excuse to throw together a home-brew EDM... :)
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Re: CoreXZ Build

Postby cdsteinkuehler » Tue Feb 24, 2015 3:11 am

I got the bearings today, so I could start putting things together.

First step is assembling the gantry and attaching it to the backplate so I could figure out the required pulley spacers. Mounting the pulleys went OK, but when I tried to mount the LM8UU's I discovered my 8" zip ties don't quite fit. A quick trip to Lowes and that's fixed (the 8" Utilitech Nylon zip ties _just_ fit!).

With the zip tie issue resolved, I continued merrily along until I realized I installed the rods on the wrong side of the backplate (I even have the sides painted different colors, you'd think it wouldn't be that easy to mess up!). I fixed that and noticed the zip tie holes were getting kind of shredded. Yep, I forgot the reinforcement block that strengthens this area. After killing several innocent zip-ties, I finally managed to get it put together correctly (I think...no guarantees until it starts printing!).

The good news is I'm taking pictures and notes as I go along, which I'll write up into somewhat of an instruction manual so you don't have to make the same mistakes I did! :)

Oh...be careful when buying zip ties, not all of them are nylon. Most of the zip ties at Home Depot and Menards are some unnamed plastic (the word "Nylon" should be on the package somewhere) and are only rated for operation down to 32 degrees and they're pretty brittle. Real nylon zip ties are rated to -40 deg. (it usually says this somewhere on the packaging as well) and are virtually indestructible.
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Re: CoreXZ Build

Postby sandstone2 » Tue Feb 24, 2015 4:30 pm

This is great information, looking forward to seeing your pictures and notes! Specially looking forward to pictures of the stringing of the effector as I like the idea of using one tuning peg for tensioning and the other for leveling but can't quite figure this out from the movies, pictures and inventor files.
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Re: CoreXZ Build

Postby macmarty » Fri Jun 26, 2015 2:09 am

Hello, @cdsteinkuehler (and everbody else, for that matter)

I am working on a CoreXZ, (frame is complete,) and I would very much like to see any photos or notes that you may have compiled. They say it's smart to make "only new mistakes", I would very much like to hear your experiences in building your printer. Oh, and YOU TOO, Mr. Seward. :) Documents, notes, random photos on flckr, whatever you've got would be VERY much appreciated. We can learn only so much from that walkaround video.
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Re: CoreXZ Build

Postby Nicholas Seward » Fri Jun 26, 2015 2:38 am

https://goo.gl/photos/vCgg7Hsm3egN6P7Y7

Good news! Here are some photos. Bad news! This is 2 version old from what I am building now. It is the version that is in my github.

I wish I had time to give this more time. I haven't been rushing to document this laser cut version because it isn't as friendly as a hand tool version. The laser cut version was more for me to crank out kits for my students.
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