Rascal CNC

[flyingavocado]

I found these W2-ZZ bearings on AliExpress this evening which according to the spec sheet are an RM2-RS bearing replacement.

The ones in the spreadsheet currently sell on Amazon for $49.95 for a pack of 16, and these currently sell for $1.31/ea plus S&H, which put this at $33.23 for all 16 with S&H to the Los Angeles area. Granted, the estimated delivery date is a month away... so clearly Amazon wins out there... but I am waiting ordering stuff from AliExpress for the build which I have to wait for anyway. For ~$18 less it's worth a shot to me.

Just thought I would share this finding in the thread.

 

[TB RC]

While I am waiting for hardware and parts and to arrive... I am curious if anyone has added end stop switches to their Rascal? It seems like it would be an easy thing to add, and openbuilds has a Micro Limit Switch Kit which they claim fits in the C-Beam.

I did add end stop switches similar to the ones you linked to. They are pretty straight forward to install and super helpful and even make the machine safer to use. The wiring is the only hard part. Here’s a link to the setup. https://github.com/gnea/grbl/wiki/Wiring-Limit-Switches I used the normally-closed switch circuit without any of the noise reducing circuit. There is too much noise to use hard limits but they work great for homing and soft limits. Hope this helps.

 

[flyingavocado]

@TB RC Thanks, the link is super helpful!

I ended up getting switches for the x and y axis -- but skipped the z axis. My thinking is that the range of motion for that axis is going to be pretty limited, and is relative to the thickness of the material being cut plus the spoil-board anyway. I figure it's a cheap thing to add if I later realize it would be a good idea.

 

[flyingavocado]

I received my C-Beam the other day and I am wondering if OpenBuilds has improved the quality control on the cutting of the product. I just checked the ends against my square and to my surprise, with exception to one corner being about .25mm high an another corner on a different 1000mm piece even less than that, they were are all fairly true.

I quickly hit the high spots with some 120 grit sandpaper using my multitool and now it looks to be about .1mm. Without milling the ends I don't think I can get much better. Overall, I am pretty happy with the factory cuts I received. I was worried that would be more of a pain in the butt then it turned out to be.

 

[Fidget]

@flyingavocado, mine were pretty square also. I didn't sand them much at all.
Finally getting back to my build where I left off last fall.

 

[nerdnic]

That would be great if their cuts are more square now.

 

[flyingavocado]

I finally got the GT2 belt and timing teeth/pulleys -- the one thing I noticed is that the the pulleys seem to have a 7MM ID rather than a 6MM, giving it a full 1mm of play on the sides of the belt. I am not sure if this is normal or not though.

 

[JohanK]

Rascal Short Kits now Available

I just finished cutting out my first Rascal kit on the Rascal CNC. If anyone wants one just contact me through the forum.

$40 + shipping for the unsanded kit
$60 + shipping for the sanded, finished and painted kit
View attachment 136948
(BTW I did correct the all-right-leg problem you see in the image)
View attachment 138770
(painted version)

Can you tell me what the all in prise (including shipping to the Netherland is) for the sanded, finished and painted kit ?

 

[JohanK]

I tiled and printed out the plans at 100% as sugested in the podcast and then cut them out of some old scrap wood with a scroll saw and drill press. Now that I have the machine running I can cut out a nicer set and rebuild.

Wher can i find the plans to print them?

 

[TB RC]

Wher can i find the plans to print them?

They are posted on the first page of this forum. Here is the dxf file.

 

[nerdnic]

I finally got the GT2 belt and timing teeth/pulleys -- the one thing I noticed is that the the pulleys seem to have a 7MM ID rather than a 6MM, giving it a full 1mm of play on the sides of the belt. I am not sure if this is normal or not though.

It's normal. Mine are the same and it doesn't cause any issues.

 

[flyingavocado]

I am working assembly right now, and I realized the linked part for the M5x30MM bolts in the parts list is incorrect.

The issue with these tap bolts is they do not have a socket head as shown in the build video. This is not critical if the end plates are bored slightly wider to allow a socket wrench to fit inside. However, the spec design does not provide enough clearance between the sidewalls and the bolt head to fit a socket flush to the side plates.

Since McMaster Carr is 15 minutes away from me, I just replaced them with this part https://www.mcmaster.com/91290A194/ -- alternatively, I could probably just have drilled them wider... but in my case drilling and respraying would have taken longer than ordering and picking up from will-call. There probably is a part on Albany County Fasteners which is the same and likely cheaper. McMaster Carr tends to be a bit pricey.

 

[flyingavocado]

I just started working on the electronics and decided to check the version of GRBL on my controller and discovered sometime last year there was a new Auto Square feature added to the 1.1h version. I know limit switches aren't part of the default BOM for the Rascal, but I am nevertheless curious if anyone has tried using this feature on the Rascal at all to fine tune the alignment of the gantry.

 

[Horseman3381]

I just started working on the electronics and decided to check the version of GRBL on my controller and discovered sometime last year there was a new Auto Square feature added to the 1.1h version. I know limit switches aren't part of the default BOM for the Rascal, but I am nevertheless curious if anyone has tried using this feature on the Rascal at all to fine tune the alignment of the gantry.

I installed Limit Stitches on mine to use as a sort of "O Crap" back up in case I screwed something up in setting up the file and the parts were bigger than the machine cut area. I have never used them to fine tune the alignment, or define a start point for the machine as I bough far to cheap of limit switches to be able to do that.

 

[flyingavocado]

I've got everything up and cutting! I made some big changes to the machine from the original design, but it works nicely. I am having issues with the 0.8mm burr bits tearing the DTFB paper. I am cutting at 120IPM and 8000 too ~8200 RPM. Does anyone have a recommendation for an specific end mills for this purpose which are less likely to tear the foam? Side note, I have found the latest batch of DTFB to be ~4.2mm and just slightly different than the stuff from a year ago for some odd reason.

I also have been breaking a LOT of these 0.8mm and 1.0mm burr mills. I suspect I need to tram by spoilboard once more time since I changed out the spindle mount, and also should add a sacrificial layer of DTFB underneath. Any suggestions one might have would be appreciated!

 

[AIRFORGE]

I've got everything up and cutting! I made some big changes to the machine from the original design, but it works nicely. I am having issues with the 0.8mm burr bits tearing the DTFB paper. I am cutting at 120IPM and 8000 too ~8200 RPM. Does anyone have a recommendation for an specific end mills for this purpose which are less likely to tear the foam? Side note, I have found the latest batch of DTFB to be ~4.2mm and just slightly different than the stuff from a year ago for some odd reason.

I also have been breaking a LOT of these 0.8mm and 1.0mm burr mills. I suspect I need to tram by spoilboard once more time since I changed out the spindle mount, and also should add a sacrificial layer of DTFB underneath. Any suggestions one might have would be appreciated!

I cut with .8 mm, and 1/32" upcut bits at 2000 mm to 3000 mm feed. I have cut at over 4000 mm feed, but there's no need to cut that fast. You'll get better cuts if you go slower.
I always use another foam board as a waste board under the FB I'm cutting, and I remove the paper on both sides, too. That way there's no stray paper getting snagged by the bit. It can be reused many times.
The biggest detail to pay attention to is the cutting depth/length of the bit. I has to be longer than your foam board, or your bit will rub, and snag the paper on the top of the board you're cutting. Look for ~5mm - 6 mm cutting length.

 

[flyingavocado]

I cut with .8 mm, and 1/32" upcut bits at 2000 mm to 3000 mm feed.

Thanks, this is excellent help. To clarify, it sounds you are using square upcut end mills -- not burr grinding bits, yes?

With the regards to the foam waste board, how do you get the foam for both the spoil board and foam to cut to be stay flat? I've noticed the DTFB likes to curl away from the surface due to thermal changes between ambient temperature (perhaps moisture too) and the surface temperature.

For what it's worth, I've designed a vacuum pad cut from 1" EPS (or XPS if I so choose) which I hope will solve this issue long term. Unfortunately, I've put the project on hold since COVID is currently in a state of uncontrolled spread here in the US.

 

[AIRFORGE]

Thanks, this is excellent help. To clarify, it sounds you are using square upcut end mills -- not burr grinding bits, yes?

With the regards to the foam waste board, how do you get the foam for both the spoil board and foam to cut to be stay flat? I've noticed the DTFB likes to curl away from the surface due to thermal changes between ambient temperature (perhaps moisture too) and the surface temperature.

For what it's worth, I've designed a vacuum pad cut from 1" EPS (or XPS if I so choose) which I hope will solve this issue long term. Unfortunately, I've put the project on hold since COVID is currently in a state of uncontrolled spread here in the US.

Yes. Using end mill bits. I think a burr bit could possibly melt the foam part of the board.
I have clamps on the edges, and sometimes hold down the fb by hand during the cut, or use a couple of thumb tacks in carefully placed locations. The top of the tacks are below the surface of the fb.
Your vacuum table idea sounds like a winner!

 

[dkj4linux]

A number of us use an easy-to-fab 3-sheet DTFB vacuum pad to hold down our DTFB for cutting. It consists of two slotted sheets (one East-West slots, one North-South slots) and one "holes" sheet (holes at intersections of slotted sheets) stacked to form a vacuum pad. Here's the stack up and a first test (turn down the sound)...

and here it is in action...

A much more instructional and detailed video is here...

This should work equally well with RascalCNC as long as the kerf remains fairly narrow... and it holds the workpiece (sitting on top of the 3-sheet vac pad) nice and flat for making different depth cuts (marking/scoring/through cuts). The two slotted sheets are usually glued together... the holes sheet is sacrificial (though fairly long-lasting) and not normally glued to the stack so it is easily replaced. The 3d-printed vacuum fitting/plenum can be found here.

 

[flyingavocado]

The 3d-printed vacuum fitting/plenum can be found here.

This project is actually where I got the idea, but the 3D-printed plenum was the only reason I opted not to go this route. I don't have a 3D printer and I wanted to something which uses entirely commodity parts. I suspect the cost of 3D printing the plenum from Cloudcraft or some other online provider is probably far more expensive than the design I came up with. Granted my design is going to need a few iterations, but I hope in the end I can give back to the community a design which is more accessible. The 1" insulation is $13 in a 4'x8' sheet and the PVC parts are about $12, so all in around $25 will be able to make four consumable vacuum pads.

The design I have I am going to just use some 1 1/2" PVC instead of a 3D printed part, which I intend to just heat up with my heat gun and pressure fit the vacuum hose into. The pad is a bunch of 1/2" wide by 1/2" deep channels, which I plan to just set the DTFB on top and cut away. I've attached a screenshot of the Fusion 360 drawing. There will be a DTFB cover over one side with the vacuum port. I do have concerns that as it cuts it will lose suction through the cuts, but I am hoping I can just use carefully positioned T-pins to hold the work to the vacuum pad to prevent this from causing to much of an issue.

I am not sure if it's going to work, but I figure it's worth a shot. I am open to critical review too... so if anyone sees this and thinks, "this isn't going to work," please tell me what issues you spot. I am very new to this whole CNC world and have a LOT to learn.

The only other issue I have right now is the CAM planner in Fusion is reeaaallly terrible... it takes a LONG time to generate the cut paths -- when I constricted it to only move the cutter within the dimensions of the stock (Fusion likes to plot movements outside it for whatever reason), it took days and then never finished. I probably should just dump it as a DXF and find something else to plan the cuts.