SoCal RS-CNC32 Initial Build Summary

[Zepp3001]

(Edited to add Thingiverse Links)

Hello from Southern California!

RS-CNC32.jpg

I recently completed my initial RS-CNC32 build (started in December, 2020). Key features of the build include:
• Use of the AliExpress kit for most electronics, aluminum extrusions (20 mm X 100 mm) and hardware
• Use of MDF inside all aluminum extrusions to add stability and vibration damping
• The addition of 1 1/4" (31.75 mm) square SS tube with 0.12" (3 mm) wall thickness to replace the 30 mm square tubes
• Addition of custom thickened 3D printed frame parts derived from HTheatre's "Reinforced (thickened)" parts. (Note that HTheatre's parts are based on 18 mm X 100 mm extrusions, and 30 mm square steel tube.)
• Addition of GT2 20T smooth pulleys, per HTheatre
• Addition of custom belt holder parts to account for interferences induced by the larger steel tubes and smaller pulleys
• Addition of hall effect sensors to replace the mechanical limit switches (To be covered in a future post)
• Addition of switched UART serial comms to allow internal or external control of the machine without requiring USB. (I've found that using an external G-Code sender over USB has been unreliable for my machine.) (To be covered in a future post)

Many thanks to Romaker, mstrens, and HTheatre for the excellent hardware and software design of the RS-CNC32. The project has been very enjoyable. The modifications I've made are largely brought on by my quest to use the larger stainless steel tubes, and the desire to beef up the machine a bit using HTheatre's thickened part concept. I did not initially anticipate that these changes would propagate to issues with the X dolly and belt geometries. Nonetheless, it's been a great excuse to spend some time designing parts!

All modified parts are now available on Thingiverse:
RS-CNC32 Reinforced Thickened Parts for 20 x 100 Extrusions and 1 1/4" Square Tubes (https://www.thingiverse.com/thing:4821729)
RS-CNC32 Alternative Belt Holders and Tensioners for 1 1/4" Tube Build (https://www.thingiverse.com/thing:4821928)
RS-CNC32 Drag Chain parts for 1 1/4" Tube Build (https://www.thingiverse.com/thing:4821931)

A few comments:
• I'm extremely pleased with the RS-CNC32 design. The machine is very solid, accurate, precise (repeatable), and has a healthy working area for "meaty" projects. I plan to use the machine for woodworking, PC board fabrication, acrylic parts (Plexiglass), and some metallics (e.g. aluminum and brass).
• The AliExpress kit arrived in very good shape. The hardware was generally of very good quality. That said, between a few mismatched parts and my own mods, I made quite a few online purchases from McMaster Carr, Grainger, Digi-Key, Amazon, and my local hardware stores to complete the build. As a newbie to CNC, it was useful to have the Ali kit as a starting point.
• A major use case for me is to use an external G-Code sender (specifically Universal G-Code Sender or bCNC running on a Raspberry Pi). That said, the TFT front end HW/SW combination developed by the RS-CNC32 team is great, and I use that functionality all the time. Switching between the two at will is great for a flexible workflow. Unfortunately, using an external G-Code sender over USB proved to be unreliable for my system. I spent many hours troubleshooting this, and as mentioned above, plan to post more on the topic soon (including what appears to be a very robust alternative approach).

A test part (Catalina Island, off the California coast):

Catalina Topo Map.jpg

Internal layout:

Internal layout (top view).jpg

Thanks for looking!
John

[HTheatre]

Hi John,

Wow ! You built a splendid RS-CNC32. I love as you took care to arrange the wiring path.
I understand you encountered some difficulties to adapt the reinforced parts to the aluminum profiles of 20x100mm section, because when I had tried myself, Autodesk Inventor had reported me collisions between the fasteners. It needed to modify the bolts' holes positions.

About the smooth pulleys I suppose you have noted they are not enough large : the opened belts rub a few on the X_belt_tensioners and the Y_belt_hold. I apologize because I didn't found the time to share the information on Thingiverse, but using 25T ones (without teeth) is much better. STL, STEP and IPT (Inventor part extension) files are available here if one day you decide to replace them, but pay attention that the parts are still designed to match with aluminum profiles of 18x100mm section. The pulleys I used are these ones (model: bore 5mm no teeth). I also used the modified X_belt_tensioners designed by loadinglevelone.The files are available here. For more information, you can take a look to our discussion on this topic.

See ya,

[Zepp3001]

Hello Gilles,

Thank you for your kind words! Yes, I took great care with the wiring to avoid problems (more on that later..).

Yes, I had seen your posts and discussion about GT2 25T smooth pulleys. I tried to source these, but was faced with ordering direct from China, and I was frankly impatient to continue with my build . I was able to find GT2 20T smooth pulleys from Amazon with rapid (and cheap) shipping. Regardless, the larger 1 1/4" tubes do create some additional geometry challenges, which the 25T pulleys will not fully address. For example, here's what happens with the X dollies:

X Dolly Clash.jpg

And here is the same dolly with my alternative X belt and tensioners (note the drop at each end of the holder to provide room for the M8 nuts). Yes, you can still get a hex driver in to adjust the tension!:

X Tensioners and Holder.jpg

And finally, here is the Y dolly with my alternative "Y belt" and Y belt hold" (I went for an in-line design providing gobs of clearance):

Y Belt and Tensioners Installed.jpg

By the way, I have published all the parts (after fighting for hours with Thingiverse). I placed a note in the "Alternative Belt Holders and Tensioners" thing regarding 25T pulleys. Here are links to the parts, which I will also add to my original post:

RS-CNC32 Reinforced Thickened Parts for 20 x 100 Extrusions and 1 1/4" Square Tubes (https://www.thingiverse.com/thing:4821729)
RS-CNC32 Alternative Belt Holders and Tensioners for 1 1/4" Tube Build (https://www.thingiverse.com/thing:4821928)
RS-CNC32 Drag Chain parts for 1 1/4" Tube Build (https://www.thingiverse.com/thing:4821931)

Thanks again,
John

[DaveDolsonUSA]

Great presentation and a beautiful machine.
I’m about 50% done with my full AliExpress kit.
Both of your mods are great concepts. And thanks for the easy to follow instruction document.
My ANet A6 printer had some bad problems when I tried printing the modified x motor drive. But I got printed today, installing tomorrow.

Some design questions: what about the use of a nut pocket in place of the easily damageable tab for the dolly z rail mounts.it will allow for much easier setup and adjustment of the dolly roller plates jam nuts.
I had to print the gantry rail brackets, used the thickened model. Looking forward to completeing the assembly. I also have the thicken belt idler and adjustable x belt holder.
I painted the provided predrilled waste board with green plastic paint on all surfaces. With that I’ll be able hookup water flow the future.
If there was an easily created precise toleranced pan for the bottom along with the holes in the wasteboard we’d have a fabulous clean air cooling dust collection box with a rear mounted (back or sides) vacumn port and a frame alignment fixture.
The demensions need are already in the instructions. Just cut the corners the same.
Could even be created with finger hold to allow access to the electronics. If using legs attach it like the top is done with the 90 degree rails and screws.
Think I might build a plywood plate one. And add the electrics to it until I get my control center cabinet built.

[Zepp3001]

Hello Dave,

Thanks!

Regarding the X/Z dolly tabs for the Z linear guidway rails:
I used HTheatre's "reinforced" dolly parts for my X/Z dolly, as it sounds like you have chosen to do. To address the first part of your question, I found the tabs to be more than adequately stout. Upon assembly (especially with an aluminum Z-plate installed) the dolly is very strong and stiff.

If I understand your question correctly, yes, in principle nut pockets could be designed directly into the horizontal "slab" of each dolly part, but you'd have to be sure that the holes on the linear rails would align. The existing tab design aligns the holes with those in the rails, and the vertical slots provide (almost) sufficient detolerancing to account for variances in tube sizes (e.g. 30 mm square vs. 1 1/4" square) and the need to precisely vertically space the dolly parts for ideal pressure of the bearings against the steel tubes. I think you'd have less room in the "slab" of the part for adequate vertical detolerancing. The exposed tabs also provide (limited) access to the M3 square nuts during the somewhat finicky rail installation/alignment process. Full disclosure: I had to elongate one pair of slots to get everything aligned for my 1 1/4" tube build (I just used a Dremel tool).

Your part cooling plans are more ambitious than mine! It sounds like if you can keep the water out of the MDF and electronics, you should be fine. The dust-collection concept is also promising. I look forward to seeing what you come up with! So far I've just got a prototype "dust shoe" connected to a shop vac (a remix of a design from Thigiverse). It's not infinitely flexible, but it works great for compatible part/tool/clamping geometries. On my list is replacing my incredibly noisy shop vac with a proper dust collection unit.

Dust Shoe.jpg

Oh, and I also had problems with printing the X motor mount. The unsupported large bearing holes were a bit ugly on my 3D Printer. I also tried printing one with supports, but that was more of a disaster. I ended up just cleaning up the "unsupported" print with a dremel tool, and called it good.

Good luck on your build!
John

[DaveDolsonUSA]

My 20 year old Craftsman vacuum has been place in the back 1/2 of my building and that works great for noise for now. I am adding a cyclone dust collector made from 2 big box store buckets. All off the shelf parts. No printed 3D parts needed. I’ll let you know how that works out. Plans from You Tube I’ll send the link if you want it.
If you have the out side space build a little lean to shed for the motor unit and run a pipe( with a grounding wire for static) and wire the vacumn control into the GRBL board for off on switching to go along with the feed from the ESP32.

I need to figure out the wiring to hook up the VFD I have. I know there are other threads for that.

Here is a pic of the mock up so far.

[HTheatre]

Hi Dave,

I need to figure out the wiring to hook up the VFD I have. I know there are other threads for that.

If you are talking about a VFD unit to control the RPM speed of your spindle, you need to purchase a PWM->0-10V converter like this one, first. It will take place between the PWM pins of the 32bits GRBL board and your VFD unit.

See ya,

[DaveDolsonUSA]

Looking forward to getting stuff together.
Thanks for the board suggestion. Do you happen to have anything in your documentation on this? I’ll be glad to send pics as needed. If you want to add it.

I calibrated the dolly using the side plates and rails before starting the motor assembly, a construction square was used to verify that the assembly would be square at each x rail end when I took the picture. Waiting for a spring scale from Amazon to test the drag on each axis. Then at power up I’ll be checking motor amperage to fine tune motor drag, plus monitor motor heat for binding conditions.
This is all stuff I learn years ago and relearned it when I got my 3D printer.

[Zepp3001]

Dave,

I'll probably end up with a wall-mounted dust unit inside my garage, but the outside unit sounds like a great way to go given the time and space.

In other news I tried my first aluminum parts on the machine (.25" / 6.35 mm thick stock). Fairly successful for a first run, though I pushed my luck with inadequate lubrication, requiring some clean-up/resuscitation of my abused carbide end mill.. The first part also revealed that my machine wasn't quite square, so I took the opportunity to dial it in better. The second part came out nicely square. Very promising!

First part out.jpg

.25 in aluminum stock .jpg

Second square is square.jpg

John

[HTheatre]

Hi Dave,

Looking forward to getting stuff together.
Thanks for the board suggestion. Do you happen to have anything in your documentation on this? I’ll be glad to send pics as needed. If you want to add it.

No, I didn't write any documentation on this, because connections between the PWM->0-10V converter and the VFD unit vary regarding the brand and/or model of VFD unit. Moreover, the VFD unit have to be set to specify the RPM speed of the spindle is externally controlled (by the PWM->0-10V converter).

So... I made a documentation for you . Here it is:



See ya,