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Cutting foam sheets... with a needle!

I'm getting closer to actually cutting some foam-core. The machine moves and the BLDC motor spins. The 'wheelie' motor mount by CapnBry doesn't quite work with the 2212 I have because the shaft is too long. Some redesign required. I want to try using some bearings I have with a 3mm ID but they might end up being too heavy? Or is it just a matter of enough counter weight?

IMG_4339.jpg IMG_4338.jpg

When I was trying to get the RC servo moving up and down, I thought I could power it from the ESC's BEC output. That kinda worked but was weird when I started running the machine - M3 Sxx commands would move the servo from 0 when the machine was stationary no worries, but as soon as the machine was running any other G-code the servo would just return back to 0 straight away. I solved it by feeding the 5V supply from the CNC shield.

I'm using a branch of GRBL which includes the RC servo code changes but is based on GRBL 1.1h. I had to modify the M3 Sxx commands to much greater values than used by the Timsav gcode. Also some tweaks to the config.h for the servo PWM signal range to be more in line with what my servo was expecting. It works well otherwise.

Here's a time lapse of one of the FliteTest model G-code running without actually cutting anything.

 

dkj4linux

Well-known member
I'm getting closer to actually cutting some foam-core. The machine moves and the BLDC motor spins. The 'wheelie' motor mount by CapnBry doesn't quite work with the 2212 I have because the shaft is too long. Some redesign required. I want to try using some bearings I have with a 3mm ID but they might end up being too heavy? Or is it just a matter of enough counter weight?

View attachment 180993 View attachment 180994

When I was trying to get the RC servo moving up and down, I thought I could power it from the ESC's BEC output. That kinda worked but was weird when I started running the machine - M3 Sxx commands would move the servo from 0 when the machine was stationary no worries, but as soon as the machine was running any other G-code the servo would just return back to 0 straight away. I solved it by feeding the 5V supply from the CNC shield.

I'm using a branch of GRBL which includes the RC servo code changes but is based on GRBL 1.1h. I had to modify the M3 Sxx commands to much greater values than used by the Timsav gcode. Also some tweaks to the config.h for the servo PWM signal range to be more in line with what my servo was expecting. It works well otherwise.

Here's a time lapse of one of the FliteTest model G-code running without actually cutting anything.

I must have been dozing when you introduced that CNC machine. I love it! Seems to be a "minimalist" conduit design... initially I thought ZenXY but obviously not. Never heard of IKEA Kvartal (I don't get out much... :oops:)... can you tell us more about it this really interesting design? Are STL's available for the printed parts?

Fantastic work! Looks like you are getting really close to cranking out planes... :)

-- David
 
Thanks David.

It was a thought experiment that started off a few months ago when I was looking at making a pen plotter. The "IKEA Kvartal" refers to a range of affordable curtain rails that I had spare. I was considering using them in a CoreXY design for the pen plotter using some 28BYJ-48 5V stepper motors. At the time, I only had the ULN2003 drivers. To keep things simple I was just going to use the curtain system's own glides/sliders.

The torque didn't look great, the power setup I had wasn't gonna keep up, and the play in the sliders was huge. At a similar time I missed out on the TimSav kit. Shipping from China was $2.50 for most things in the TimSav BoM. So I've effectively merged the projects.

The Kvartal rail has a channel on both sides. One side was narrow enough to support some standard shower screen rollers while the other side is slightly too wide.
IMG_4340.jpg

So my Y axis looks the part but is really only relying on gravity to keep things running on the track. The roller on the bottom isn't gripping the curtain rail much at all.
IMG_4344.jpg IMG_4345.jpg

For the gantry, gravity wasn't going to do, so I placed two of the rails back to back with the narrow channel facing out. This allowed me to adapt the "TimSav wheelie" design with an eccentric nut on the lower side holding a shower screen roller. I didn't modify the wheelie's STL's though - a 7mm drill through it did the job!
IMG_4347.jpg

The ends of the curtain rails are supported by some 3D printed brackets. I have a newer design that incorporates the slots for the GT2 belt but for now I'm just clamping the belt in place.
IMG_4341.jpg IMG_4343.jpg

Once the bones of the machine were together it was a matter of adding NEMA 17 steppers, an Arduino + CNC shield + DRV8825 drivers kit, GT2 gears and idlers, GRBL, Universal Gcode Sender (and a bunch of fasteners) and wire it all up (messy!). Plus the 2212 motor and servo of course.
IMG_4346.jpg

Everything seems fine and runs nicely in the dry-runs. I expect to have challenges when I add the fly wheel and needle. CapnBry was using a Volcano printer nozzle, while I only have a standard 'v6' style one. I will 'suck it and see' as my grandfather used to say.

It's really not a very rigid machine and flexes up and down slightly as the gantry gets to the middle of the Y axis travel. In the X direction those same rails flex sideways under load. But probably good enough for a needle cutter? If not I have a couple of ideas how to make it more rigid.

I've put the STLs on Thingiverse, although when I view the thing the print details etc aren't as I set. My guess is that it's the CDN they use not replicating to me locally.

Cheers,
Graham
 

dkj4linux

Well-known member
Thanks, Graham. for the walk-through. It's those "thought experiments" that I find most fascinating and fun. :D

And yeah, you can probably get away with a bit of flex for a needle-cutter or pen-plotter :unsure:

-- David
 
First cut! I eventually had time to get the spinner printed and assembled. I used the minimal spinner in CapnBry's TimSav Wheelie design, tweaked the parameters for the bearings that I have - just a small update to the OpenSCAD design. As I showed above, these little bearings have a V-slot which is perfect for wrapping a needle around and no worries about it coming off. The bearing doesn't get hot at all.

I took the following photo for this post and noticed that unfortunately the minimal spinner design is coming apart already. Perhaps I can glue it back together... :eek: But I probably should go for something more robust like the 'standard' flywheel design rather than having M3 bolts flying around the room.

IMG_4394.jpg


The 'V6' 3D printer nozzle is glued in with wood glue. So far so good, but it does get hot. My gantry, consisting of two extrusions back to back, seems to be allowing a fair amount of movement in the Z carriage. It seems not too terrible for the needle cutter.

For some reason everything just stopped half way through. I blame the dodgy Arduino Uno clone that came with the CNC shield. I've had a devil of a time getting it to hold on to the GRBL sketch, and I'm having to re-flash it regularly.


Anyway, Happy Hallowe'en! I found this Ghost SVG (with a CC0 license) and processed it with Inkscape and the extension as found in the ERC TimSav thigiverse page. Easy!

Cheers,
Graham

IMG_4395.jpg
 

dkj4linux

Well-known member
Thank you for your kind words. That's a fantastic looking machine... and I wish you *tons of fun* cutting planes.

I haven't posted here in a while as the thread has slowed to a crawl... but I'm literally in the middle of moving back to my place in rural East Texas; i.e. we packed the truck this evening and are headed out tomorrow. This will be my last post for a while and then I'll power down my laptop and stick it in a box for the move. Unfortunately, I'll be saddled once again with pretty poor internet in my new old rural residence. But hopefully I'll be able to get back online in a few days and once again be able to interact with my internet friends.

Have fun, stay safe, and... Happy Thanksgiving!

-- David
 
Hey guys... need some direction.. I printed this needle cutter frame, but am confused on which mount I am suppose to use on my Z-axis to attach it to. it references hicwic's universal mount.. .but not sure which one I should print.
 

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Hey guys... need some direction.. I printed this needle cutter frame, but am confused on which mount I am suppose to use on my Z-axis to attach it to. it references hicwic's universal mount.. .but not sure which one I should print.
This mount was used on https://www.thingiverse.com/thing:724999/files. Back when I modified/printed it attached to the part called “C-ToolMount.stl.” Now I see the current revisions have two different versions of the tool mount file, so I am unsure which to recommend. See my post 1424, https://forum.flitetest.com/index.php?threads/cutting-foam-sheets-with-a-needle.24251/post-360287, for what tool mount it was modified to attach to.
 
This mount was used on https://www.thingiverse.com/thing:724999/files. Back when I modified/printed it attached to the part called “C-ToolMount.stl.” Now I see the current revisions have two different versions of the tool mount file, so I am unsure which to recommend. See my post 1424, https://forum.flitetest.com/index.php?threads/cutting-foam-sheets-with-a-needle.24251/post-360287, for what tool mount it was modified to attach to.
Thanks Michael - I'm happy to see you still on the forum.

With your guidance, I was able to determine that the Z-axis and the mount spacing for the Primo and the Burly line up correctly, which means that v1engineering did not change the Z-axis layout or spacing. The mount Tool_Mount_C_4mm.STL lines up exactly.

Thanks for getting me pointed in the right direction.