Chiming in to muddy the water. I have used two flute downcut bits on 12mm ply a lot . Two passes at 6.25 DOC without tabs. The chips would pack into the cut and hold the parts in place. The time saved was worth any shorter life of the endmill for me.
I find this use case highly intriguing…
It’s what I used when I was selling these: Plant Stands
I didn’t want to trim tabs and was cutting full nested 4x8 sheets of them. It was a real time saver for me.
Well two months later…
Since my last post here I have finished working on the cars, and managed to get a bit of progress on my LR3 build:
- Designed and built a tilt-away/roll-away table base.
It makes a huge difference in being able to move the LR3 out of the way so that I can get the cars in the garage when needed. Link to the thread is here.
- Installed the hardboard struts that I cut back on Jan 07 (post #105 in this thread)
The hardboard has a LOT of flex, so my plan is to cut out some blank struts from 3mm aluminum sheet (salvaged signs) and place them behind the hardboard struts. I also want to paint the struts (probably black on the aluminum and red on the hardboard, to provide a contrast for the lettering), but that can wait for now.
I also put some epoxy on all of the non-captured nuts, so that adding the aluminum backing hopefully won’t be too much of a PITA.
- Installed an Air Mist system for cutting aluminum
I used @DougJoseph’s kinematic tool holder (modified with @jamiek’'s “mountains and valleys” fixed and mobile parts), and Doug’s Air Mist Attachment (Side mount version model B). For more info you can check out this thread.
I still have a few bits and bobs to mount the air hose system to the table (valves, elbows, etc), and I had a couple of hiccups with printing the tool holder (post #200 in the tool holder thread), but overall it works great!
- Designed and printed a “quick release” system for my built in vacuum/dust collection hose.
I had a bit of an issue where the outside of the prints were very close to the design value, but the inside of the print (hole) was about 0.5mm too small. I used post-processing (sandpaper) to make it work, but it looks like I need to go into Cura and play around with the “Hole Horizontal Expansion”" settings.
Coming up - I bought some 9mm aluminum for the YZ plates, and I scrounged a bunch of 6mm aluminum for the XZ plates, and now that I have the air mist system up and running, I’m working on setting up the files in Estlcam to cut those items. I’ll probably do some test cuts with the 3mm aluminum for the strut backing first, but I need to finish removing the vinyl and adhesive from the old signs before I start that.
Whew, that seems like a lot of progress!
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Wow, this is awesome! Thanks for the updates and info!
So a bit more incremental progress to report…
While I’ve been procrastinating (er, umm, I mean researching aluminum cutting feeds and speeds), I decided to do a bit of cleanup on a few items.
First of all I mounted a power bar with a kill switch, and a shutoff valve for the air supply to the mister assembly. I put it near the future Min X Min Y location (I’ll be converting from Portrait to Landscape shortly) so that it will be close by when starting cuts.
From there I ran some air hose and an extension cable to the midpoint of the rear of the table, and made it so that everything can be quickly disconnected.
Next up I installed a “drain wire” inside the section of vacuum hose that connects to the LR3 for static grounding.
Also I designed and printed a bottle holder for the Iso-Propyl Alcohol (IPA) for the mister system.
Coming up, I really have to get off my a$$ and start cutting the aluminum struts, followed by new aluminum XZ and YZ Plates.
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Progress!!
After a lot of procrastination (er, um…I mean research), I think I have sorted out the feeds and speeds for cutting my struts. I used G-Wizard (CNC Kitchen) to come up with the following suggested rates for 2.5mm DOC, Single Flute 1/8" mill, with 0.35mm finishing pass:
Any comments/sanity checks are more than welcome.
After a bit of a misadventure trying to figure out EstlCAM parameter sets, I managed to create and save the g-code for a variety of different speeds. Tomorrow (or at least this weekend) I hope to do some air-cuts to test for excessive vibration and shaking at different speeds, and then hopefully start making some aluminum chips!
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Even at 2250 mm/min, there really doesn’t seem to be any concerns about vibration or shaking, at least with the air cut. I’ll try actual cutting as soon as I get a couple of hours free to devote to the project.
1350 mm/min @ 0:00
1685 mm/min @ 1:12
1965 mm/min @ 2:12
2250 mm/min @ 3:15
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Great progress, then a great setback…
The day started out well, with the first cuts in aluminum. I went with the 20000 RPM settings, because it said that it would only take about 2.5 hours.
(turn down the volume for this video)
The chips looked really good, mostly smaller segments because of the Trochoidal milling, but some good spirals in there as well…
The AIr Mist system worked really well, and blew all of the chips out of the cutting path quite well.
I made it all the way through cutting all of the screw holes, as well as the first strut part, when disaster struck…
I put screws into several of the strut screw holes to secure the material to the spoil board during cutting. I had EstlCAM Clearance Plane set for 3mm.
When the first part was finished, the gcode called for a rapid move to the next part. Unfortunately that path was right over (through) one of the screw holes that had a screw in it, and there was contact. I had used a mix of 1/2" and 1" screws, and fortunately the screw in question was one of the shorter ones, so it pulled out rather than snapping the end mill. However the resulting loss of steps caused the router to start cutting into the just-finished strut part.
So the next step now is to re-run EstlCAM to produce a new gcode with a 5mm Clearance Plane, use Notepad to remove everything up intil the start of the second strut part, re-home X & Y, reset Z using the touch plate, and try again.
I did notice a couple of issues during the initial cut:
- Every time my compressor kicked in (8-10 minute intervals), the ensuing voltage drop resulted in the router speed decreasing enough that I could hear a change in the cutting. The chips still seemed ok, but it sounded like it was struggling a bit.
- EstlCAM estimated that the whole thing should take 2.5 hours, but cutting the holes and one of six struts took over an hour, so the actual time is more likely going to be closer to 5-6 hours
More updates once they happen
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If I’m not too late for a suggestion I would go higher with your clearance plane. Always better to have too much than not quite enough. I was using screws with 3D printed washers for the V5 parts and I believe I set mine at 10-15mm. Way more than I needed but never once did it get anywhere near a screw lol
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I was going to say the same as I was reading it. I keep mine at 10…for peace of mind
So I made the changes noted above (and increased the Clearance Plane a few more mm as recommended), and restarted the cut. Before doing that I checked the end mill and noticed a bit of aluminum welding to the cutting edge, so I changed out the end mill for a new one. Probably happened when the mill tore into the material and I had to hit the emergency stop.
It all went well for about 90 minutes, and then the mill snapped off. Kinda surprising, because the material was well secured (so no chatter), the air mist (IPA) was keeping the slot free of chip buildup, and the sound of the cutting was consistent with the previous 2.5 hours of cutting.
I may need to pick up a few more end mills before I start up again, and the program ran for a few minutes before I paused it, so I will probably have to figure out where in the gcode the mill broke, and edit to restart a few seconds before that point.
Only mildly annoying, and it is giving me a great opportunity to learn about editing gcode. Also gaining more experience with every hurdle. Pretty soon I might even have a clue about what I am doing! 
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Well where did those last six weeks go? Time seems to accelerate, and progress on the LR3 seems to creep along.
I ordered a few more end mills from V1E, then edited the g-code to resume the cutting where the previous effort left off. I managed to finish the cuts without breaking or welding aluminum to the new end mill, so I have no idea why the earlier one broke where it did.
The LR3 seemed to cut through the 2mm aluminum really easily. I used Trochoidal Milling for most of the cuts, and Regular Milling for the smaller text on one of the struts, and both worked great.
Feeds and Speeds:
Trochoidal: RPM 20000, DOC 2.75mm, FR 2250mm/min, Plunge 500mm/min, Plunge Angle 90, Trochoidal Stepover 7.9%, Trochoidal Width 35%, Finish 0.35mm
Regular: RPM 20000, DOC 2.75mm, FR 475mm/min, Plunge 475mm/min, Plunge Angle 90, Finish 0.35mm
Some video highlights of the non-trochoidal cut:
The 2mm aluminum seemed a little thin, and still had a bit of flex when cut to the 80mm width of the strut. So I cut a total of 6 struts, and doubled them up . Two of the struts had the Lowrider 3 logo cut out for the top layer of the front and back struts:
(The top two aren’t as shiny because I cleaned the others with IPA and a ScotchBrite before taking this picture, but hadn’t done the last two yet)
I painted the lower strut and then laid the upper strut on top, for a very nice contrast (at least IMO).
Next up is cutting of aluminum XZ plates (6mm) and YZ plates (9mm). Stay tuned…
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very nice!
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A couple more notes from the strut cutting:
I’m using an old electric air compressor to supply the Air Mist system, and every time the compressor kicks in and runs (every 4-5 minutes for about 2 minutes) the router speed drops a bit, I bumped up the router speed setting about 1/2 a notch to compensate, and it seems to make pretty good chips at both the full and reduced (compressor loaded) speeds.
I also had a couple of issues with the cuts. As mentioned in post #126, I had cut all of my screw holes and just finished the first strut outline cut when the end mill hit a hold down screw and I had to restart the cut. I homed everything and restarted, but for some reason the following cuts were offset in the Y direction by about 1mm. Because of that, when I went to install the front struts, they were contacting and interfering with the XZ plate on one end, rather than having a bit of clearance. I ended up stacking up the last 5 struts and cutting a few mm from one end with a hacksaw.
The other issue was a bit of a goof on my part. My vacuum hose and air line routing was such that the hose assembly was very close to the core at one point on the travel, and when the cut reached the very last strut, the top bearing on the core got hung up on the hose, and it started skipping steps and jumping up and down. I restarted the cut at that point several times, with the same skipping steps and jumping, before I found out why. A quick reroute of the hose and a tie wrap to keep it in place, and the last cut went smoothly after that.
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Wow! That looks great.
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Re. Bartman's LR3 build thread - A New(bie) Adventure! - #130 by Bartman
You need to enter this in the V1E GO Maker Faire!
Hey, don’t forget to post at least one pic to your new entry, and probably also include the video.
Rather than posting just the link (which does not show pics or video), edit the code text for your earlier post, copy it, and then paste it into the Maker Faire entry post.
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Thanks Doug - entry post has been edited with a re-post of the above
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