High speed machining- 200ipm/5000mm or bust

Currently I’m running a stock S3 with aluminum bed, Beaver HDZ, custom linear X support, and Makita rt701c. This configuration has let me push 175ipm adaptive cutting on 6061 without issues or chatter which is amazingly fast for such a tiny cnc.

The current goal is to reach the stock default maximum travel speed while keeping cut quality. Also I need to start seeing how much acceleration values can be tweaked to keep cut speed up. I’ll take some measurements on Z carriage weights from stock to hdz.

I love the simplicity of the belt drive configuration but I think we’ll see it have issues over 200ipm. Just like a race car, go as fast as you can - break things, rebuild it better - go faster. I’ll post up all my findings and results here. Feel free to add anything guys!

Little Hero S3
Metal Storm


Cool, looking forward to your experiences. Keep the updates comin’.


Care to elaborate on what you have in mind with regard to ‘rebuild it better’ ? :smile: I’ve always wanted 20mm rails and a ballscrew on my x axis… surely thats the next weakest link?

Your comments about the belt system reminded me of something I stumbled across on YouTube a few weeks ago. A double belt arrangement might be useful for pushing past 200 ipm. I created a general topic for this because I was curious if anyone else had tried it or contemplated it:


It’s like a little miata, let’s see how far it will go and still be a “street car”.

Ballscrews are super temping but becomes costly. I dont think we are seeing close to the weight they can take. First thought is that you wouldn’t want to do the X and not the Y because of differences in acceleration and tolerances. Maybe it would work well, dunno. I’m thinking we could easily step up to a 15mm belt for additional load capacity

Trying to swing mgn12h rails for the X but that wont be for awhile.

Double belt looks interesting

Unfortunately, all of the wider belts I’m aware of have increased backlash, save for the claimed 10mm wide GT2 profile available from some vendors.

I’ve since changed out the steppers for higher torque ones. I’m still tuning with those, and I’m not convinced it made a difference. The higher weight of the bigger steppers (they’re about 3 times as long as the stock ones) looks to be offsetting their higher torque. They also have 8mm shafts, which made getting the right 21 tooth pulleys a little more difficult than I expected.

Anyway, significantly higher speeds are available if you’re willing to try. It does make a difference in your cutting times by greatly reducing your time in rapid movement. The machine will move around more if it’s not held down well though.


Why is this the current goal?

Got a link to the motors? Still using the stock board and drivers?

Looks like its stock belts then, thank you for that info Will. Honestly i’de rather not mess with the drive system too much anyway.

Mike, those are an interesting option. The weight offsetting is something ive been trying to keep in mind. Looking at the HDZ there is quite a bit of fat we can trim from that as well. I try to use all the fusion cam tricks to reduce rapids already. A little work goes a long way there!

As far as the 200ipm goal goes, it’s a decent step up from where I’m at right now. I need to take some time and calculate actual MRRs. I calculate a few different adaptives each time to find the most efficient ones right now via machining time. Until I test new rails I’m pretty much doc limited and i was under the assumption that I couldn’t run these carbides that fast. More rpm = more feed

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MRR is driven by axial and radial cut dimensions as well as feed rate, why prioritize feed rate if MRR is the ultimate goal?

In my experience on my two builds there is a certain sweet spot for radial and axial cuts depending on setup. Pass that zone with higher axial and lighter radial cut - overall machining time usually increased. But it looked cool…for those that want to do it for the gram lol.

I steadily increased rpm with proper lube/heat mgmt and that let me stay in that sweet spot while increasing chipload. I would also like to point out that most of my shapes are pretty curvy and taking the biggest doc you can isn’t always the fastest way to 3d machine depending on finish quality/runtime/tool-changes.

I’ve read quite a bit but I’m no expert. Just telling and showing what works for me.



Thanks for sharing your experience and insight! Most of the posts that I’ve seen indicate that the S3s MMRs are limited significantly more by machine rigidity (and router speed) than router power - do you agree?

Theoretically, any increase in feed rate would require a proportional decrease in either depth or width of cut to maintain the sweet spot. Does your experience support that?

2018-11-02 - I edited this post to remove “(except yours claiming a MRR of 20 lbs/hr)” because it looks like you were/are claiming only 2 lbs/hr (1/10 the cutting power and force). Sorry, I don’t know how I screwed that up!

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Stock board and drivers. I still want to put a scope on it and see how things look, but it’s functioning fine.

Be warned, you need to use an 8mm 21 tooth gear, which is NOT what is on your stock steppers, you can’t reuse them. You’ll need to put pins on the cables (not a big deal), and they are about 2x as long as the stock steppers.

Those motors have a much higher inductance (17mH) than the stock (I think around 5mH). I’m getting out of my league here, but wouldn’t you need, or ideally use, a much higher drive voltage to get the speed and torque those motors are capable of?

Ideally, I would be using a higher current stepper as well, but this is the only one available at a current I can supply that has any more gumption than the stock ones. Hence why I want to look with the scope. Worst case, I start getting into bigger upgrades and add some higher current stepper drives (TI 66xx), another power supply, bigger steppers… If I go that far, I’ll replace the board with one that doesn’t have built in drivers. Easy to get carried away…

(can be upgraded to 1.1) and 4 of these

For what it is worth according to the Gecko G540’s manual, the ideal voltage supply for a stepper would be:

Sq. Root of the stepper’s inductance in mH x 32

therefore- (√17) x 32 = 132 V.

Not very many drivers will sustain that… well not for long anyhow!

Isn’t a lower current rating better all else being equal?
I know the Carbide board limits what we can do. I’d bet you’d get a lot more out of those steppers if you used a 48v or 60v power supply and capable driver.

Have you measured deflection vs force and slippage with the stock S3 stepper motors?

Well, yeah. But:

  1. I don’t have a bigger supply at hand (which the carbide board could likely actually use…the 8825 can use up to 45v supplies…would have to look into that a bit)
  2. I don’t have a different driver. I want something based on the TI66xx series.
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