The z axis is slow, so don’t expect to be cutting any lithophanes. IMHO call it 2.5D+, the plus being v cutting like in lettering. Might have made up the plus designation name (not the actual engraving, which looked great in the posted example)
@Rafi aren’t there specs available for the specific bit you are using?
I would expect some recommended feed speeds and spindle speeds at certain cutting depths.
Manufacturers alway’s like to point to spec sheets when something breaks to show the customer that it’s a matter of RTFM, IYAATFTFM. (if you are able to find TFM) 
So my understanding is that for plywood, we should be striving for 0.011 to 0.013 inch chip loads. With a feed rate of 47 ipm (which I understand is the current limit), a single flute 1/4-inch bit, the required RPM is about 4000, which is too low for the router. If using a 2-flute bit, you need an RPM of 2000… even worse (please correct me if I’m wrong, this is all new to me).
If you switch to a 1/8-inch bit, the desired chip load is .004 to .006 inch chip loads. With the 47 ipm feedrate, single flute 1/8-inch bit, the required RPM is around 10000. This is the low end speed for the R22002 router.
So, again, correct me if I’m wrong. With the current setup, we can achieve the desired chip load using an 1/8-inch bit, however, it will take twice as long using an 1/8-inch bit because you can’t cut as deep in a pass with an 1/8-inch bit as you could with a 1/4-inch bit (this is why I assume everyone is talking about 1/4-inch bits).
Maslow is slow and I’m ok with that. I spent 2.5 hours cutting out a frame for a chair this weekend and honestly would rather spend the money on a new router bit at the end of it than take 5 hours and have a working bit afterwards. However, some of the minecraft-ish things I made over the last week required I drop the feed rate to 10 ipm (otherwise the router overshot the hard turns) I think if I do those again, I’ll switch to the 1/8-inch bit and spend the time reading a book while Maslow does its thing… reminiscence of waiting for a C-64 to load a game off the floppy when I was a kid
A bit of a ramble, but would like confirmation that my analysis is sound…
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The limit is currently 1000mmpm, just under 40ipm.
Sorry… some reason 47 ipm stuck in my head… but it makes the situation worse for 1/4-inch bits, right? With a slower feed rate you need slower RPMs to realize the desired chip load.
great question, i also like to know
and thanks for explaining why and how you got to the question.
Does anyone know how warm a router bit is after an hour of work?
Some of us had to load C64 games from tape, manually adjusting the head while listening to a little speaker .
that really made one appreciate the floppy.
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your thinking is sound, but also keep in mind that an 1.8" bit is going to be
far more fragile as well. It also has far less mass, so will heat up much
faster.
feeds and speeds are calculating the ideal production rate that is cutting as
fast as possible. If you go too much slower, then you start burning things, but
you can go a fair bit slower than ideal before you run into trouble.
I think the 1/4" single flute bit will end up being better than going with an
1/8" bit
David Lang
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Just curious, where are you getting your chipload recommendations from? I’ve been using the Onsrud chipload tables to get my values. I know these are intended for Onsrud’s tooling, so far it has served as a pretty good starting point. According to their tables, 0.011-0.013 is nearing compression bit territory. Up/downshear bits at 1/4" diameter need somewhere between 0.005 - 0.007. This still means that at the Rigid R2200 router’s minimum RPM of 10,000 the Maslow should need 3,000mm/min (118 ipm). If the spindle speed could be reduced to about 3000 rpm, then the Maslow’s maximum feedrate of 900mm/min (35 ipm) would be okay. Last I checked, that was the max feedrate set in the firmware, but it could have changed. Also, all these calculations are for two flute bits. I have yet to get any of my two flute tools to cut without screaming as they go, so I’ve stopped using them for now.
So far the best solution I have come up with for running bits at an optimal feedrate is to use single flute bits. The single flute bit I bought from the Maslow store has lasted me about a month of weekend work. I just noticed it was getting dull last weekend. I dialed the tool into 12000 rpm at 500 mm/min (20 ipm) cutting around 6mm (1/4") with each pass.
We have been going over options to increase the machine’s max feedrate in this thread.
You should be able to touch the bit after any amount of cutting (WITH THE SPINDLE OFF!!!). If it is noticeably hot to the touch, then the feed and speeds are wrong.
While I have not gotten the feed-rate right for my two flute downshear bits, I have not had any trouble with it pushing the sled off the work-surface. I hadn’t seen any comments about downshear bits on this forum so I wasn’t sure if that was something that I should pursue further. I’ll just need to find a supplier for single flute downshears or get more work done on increasing the max feedrate to pursue this futher. I would prefer to cut with downshear where possible, since it gives me much better top edge quality.
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I got my values from https://www.vortextool.com/images/chipLoadChart.pdf that @JaceD posted above. Am I misinterpreting it?
I missed that. You’re reading it right. It’s not too surprising to me to see different numbers coming from different manufacturers. I don’t see any note as to which tool geometries apply to those chip loads… maybe I’m missing something?
My past CNC work was all with 1/8"/3mm or smaller bits at 20K+/- RPM so the rules might be different, but I just figured out feedrate empirically using the guide below. The 25 to 35 ipm rates I found, mostly based on cut quality (less interest in breaking bits than the guys who’d sell replacements) in plywood, are pretty much inline with Maslow speeds. I mostly used surplus solid carbide PCB bits, cheapskate moose…
This was with a 150w Paul Jones spindle.
http://www.precisebits.com/tutorials/calibrating_feeds_n_speeds.htm
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Hope I haven’t steered anyone in the wrong direction by sharing this. The chip load chart I shared is geared towards a production setting where machine feed rates are in the 200-400 ipm range. Vortex makes some nice tools, but as @MeticulousMaynard pointed out, different manufacturers will have different recommendations based on their flute geometry, etc…
I guess the main point I was trying to share is that increasing chip load will result in longer tool life. Single flute bits and lower RPMs are good options for Maslow given the limited feedrate of the machine currently.
I doubt that a 1/4" bit will product enough cutting force to lift the sled, even when it’s dull. I’d just try to use the right tool for the job, personally.
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That’s a valid issue, chip loads are still relevent. I want on the beta list for the 400ipm Maslow V2 but until that happens single flute and smaller ID bits might be the way to go. 3/16" (that’s around 5mm but 4 might be better) might be a compromise between size and a bit more strength.
A random thought, but would a little ducting help a shopvac cool the bit? Just how how hot does carbide get in wood (hot enough to burn, clearly), and how does that compare to the bit’s rating?
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the optimum chipload is based on production usage where they are looking for the
best possible throughput, finding the sweet spot in tool life (cutting slower
doesn’t singificantly improve tool life, cutting faster hurts tool life or runs
the risk of breaking)
if you cut too much slower, you don’t remove enough heat and things overheat,
causing grief.
but what is the window between ‘optimum’ and ‘slow enough to overheat’
it’s common to make finishing cuts that are much lighter than the much cuts, and
therefor have a much smaller chipload.
how can we find the minimum rather than the optimum chiploads?
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Thats a nice question! And probably the best one on this topic.
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It will vary by bit, but should be pretty easy to find experimentally, as long as your Maslow isn’t hanging over an excavated pit. Start off with a light cut and go from there. I’d use the maximum depth of cut to eliminate the step marks.
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I have broken so far only one bit and it flew off by breaking somewhere in the middle… after total of around 18-20 hours of cutting in entire new lifetyme of my maslow, for those in volume think about two entire sheets of 3/4" plywood with several cutting tasks. I always run my ridgid router at its max speed of 23000 revolutions, using 1/4" bit of Ryoby and now Truper brand, those are cheap. I feed rate at 60 ipm and do cuts in 0.16" every step, so in five steps I have cut through the entire 0.8" thickness. I don’t know if its too much or too little, the cuts are nice and edges can be easily cleaned off with a sander using some 150 grit sandpaper.
the maslow is only able to get up to ~48 ipm, and at that rate, running at 23000
rpm is too fast, and the bit is going to get hot.
look up ‘feeds and speeds’ and you can get a lot of guidence as to what settings
to use.
I would set the router to it’s minimum speed, not it’s max, and expect to get
the bits lasting longer.
David Lang
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the easiest way to see if a bit is dull is take the router and cut off the corner piece of the plywood by USING YOUR HANDS, NOT THE CHAINS. You can probably just grab the whole sled as well.
anyone who has some practice with working with hand tools can tell in a few seconds if the bit feels like it is cutting smoothly.
I like using 4mm bits and I have no problem cutting double the diameter, 8mm, in plywood. If I was cutting aluminum the max I would do is half the diameter or 2mm.
Again take the router off the machine and do some test cuts by hand, they will give you a lot more feedback than any computer screen will tell you.
I bought a 500w chinese spindle, which runs at about half the speed as the rigid router. They are also about $100 cheaper (even factoring in the cost of z axis and motor mount). Seems like the more I read these forums, the more and more it seems like a slower spindle makes more sense.
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