By afarrag

March 6, 2024, 9:14 pm

Tormach PCNC 440 / lower horsepower machine best practices for building CAM using Fusion360 and HSMAdvisor

Hello Eldar,

I was demoing the software and I purchased a license earlier this week since my demo lapsed to continue working with it...

I have built out a bunch of parts in Fusion and am working my way through building CAM for each and machining them out of 6061-T6 but am not having the success that I had hoped. I fully understand that this machine is going to be limited in it's capabilities but I am having trouble reconciling why with this software to help me calculate feeds/speeds that I can't come up with some recipes that work without the spindle bogging down despite HSMAdvisor indicating that they _should_ work and they don't exceed the machine's capabilities.

I will fully admit that I am not a seasoned/experienced machinist but I learn quickly and am familiar with this sort of variable optimization process from other activities and feel like I've reached a plateau where I'm not making any constructive progress with my various experiements with the tools and knowledge that I'm applying.

As the subject says, the mill is a low horsepower machine (Tormach PCNC 440) that I'm working with and I use Fusion360 for both CAD and CAM. I am utilizing the Tormach Aluminum endmill kit (I have charts which list RPMS and feeds in inches for side and slotting for these endmills). I enter those numbers in HSMAdvisor as starting values to get the chipload. The first modifications to the manufacturer's F&S that I make is to raise the RPMS to a higher range (7-9.5k) from 5.6k, where it should be in the power-band of the spindle on the high belt, at least according to HSMAdvisor's curve for this machine. I re-work the numbers to maintain the same chipload from the original numbers. I will adjust WOC and DOC (and then readjust speed and feed) to maintain that same chipload and evaluate that the power/torque is within acceptable limits.

1) Tormach doesn't publish a power or torque curve (only the peak power of the spindle motor) for this machine, however, you (admin) appear to have constructed the one that HSMAdvisor makes available. I was wondering how you came up with those curves / what assumptions are behind them. Did you locate the curves from another source or are these best guesses based upon...?

2) The main issue I'm scratching my head is that I get cuts that are "green" but still bog the machine down, hence wondering if the curves are not accurate...the idea being that within some calculated spindle load percentage, I should be able to model a cut ahead of time and have it run successfully without bogging the spindle down. That is what I would undertand the purpose of this software is...to not have to do significant experimentation with actual materials or to at least limit the experimentation to slight feed/speed adjustments while running...

3) I've watched several of the various tutorial videos you've recorded over the years (wish they would be updated since the interface has changed over the years) and read through what I thought were some relevant threads on this forum but overall, #2 is still where I am at in terms of success of using the software to maximize feed/speed/MRR...far from what I imagine is the ideal use case...or am I being very optimistic about that?

One thing I have tried in the past day was to take some stock and do just a straight pass with manual G-code at the specified feed/speed/DOC/WOC. Some of the calculated feeds and speeds seem to work but I have run across some that bogged down. The major hurdle is trying to use recipes in Fusion360 to clear out a pocket or do anything adaptive. For instance, the helix entry into an adaptive 2D pocket will machine without bogging down but then as soon as it starts to to clear the slot...that's where it bogs down...reducing the feed to 1/4 or 1/10th of the original programmed feed in the operator console is how far I have to go for the spindle to not bog down in some case...

Any tips/hints on what my proocess should be? Feel free to start this process with a list of relevant links/videos that I should absorbed 100% before we dive into further troubleshooting...


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March 6, 2024, 9:42 pm

I just ran an adaptive pocket clearing and it does run on parameters that seem to be "green" but the spindle struggles. A lot. Usually it has been the case where if I don't feedhold, it will completely bog down and stop.

Another question/thought I had is if there is a suggested CAM toolpath where I could run parameters against to potentially "correct" the existing HP/torque curve or determine what adjustment factor in terms of the existing curve of a "do not exceed" this HP/torque or the spindle will bog down...


Eldar Gerfanov (Admin)

March 13, 2024, 7:05 pm


Sorry for the late reply. Somehow I didn't get notified about your request.

Can you please provide an example where HSMAdvisor is not accurately predicting the spindle load.

Please include a screenshot of HSMAdvisor screen and the exact machine specs. Also include whether you are using a hi/log belt configuration (if any) and whether you are using 240 or 120V power. Because apparently the same machine will not work as well if running on 120V



March 13, 2024, 11:05 pm

Thanks for replying! Hopefully with more data, we can figure out what is going on...

Machine: Tormach PCNC 440, USA 120V, High Belt (0-10000 RPM)

Workholding: Tormach 4" vise/parallels

Material: 6061-T6

Stock: 5" x 1.5" x 0.5" rectangular being held 5" X, 1.5" Y, 0.5" Z

Tool: Tormach (made by AB Tools) Mini Shear 0.75" (Tormach part #38803) held in Short Metric 10mm TTS (Tormach part #31813)

Toolpath: Tormach PathPilot conversational rectangular spiral (to keep things simple/eliminate potential issues from Fusion Adaptive)

Feed/speed 1: 0.2" DOC, 0.2" WOC, 10000 RPMS, 55 IPM (HSMAdvisor calculated 90% spindle load)

Cut starts fine, which initially agrees with the software's calculation but the spindle begins to stall about 45 seconds into the cut to the point if I don't feed hold, it will stop spinning completely and crash.

Feed/speed 2: 0.2" DOC, 0.2" WOC, 10000 RPMS, 40 IPM (HSMAdvisor calculated 66% spindle load)

Running the same parameters but at 75% of that feed rate (40 IPM) the spindle doesn't completely stall but is bogged down for the whole cut, starting about 30-45 seconds into the cut.


The above tests suggest that I have to be even more conservative with cutting parameers than your curve?

A similar version of this cutter has been shown to cut with an MRR of 2.25 in^3/min on this exact same machine (US version)...which is what I was targetting with cut parameters #1.

55 IPR Screenshot (1).png 40 IPR Screenshot (2).png

Eldar Gerfanov (Admin)

March 14, 2024, 12:23 am
Updated by: Eldar Gerfanov (Admin)April 16, 2024, 12:10 pm


I am away from my computer and I can't double check your numbers right now but everything seems fine.

I think the issue is the 120V power supply. The drive is struggling to provide the required amps for a long period of time. I recall other people complaining about similar issue.

I know for sure you are supposed to remove at least 3in^3 of aluminum on those machines.

You should not be struggling with 2.2 in^3.

Did you try to use a smaller endmill?

You may have to resort to simply de-rating the spindle power by setting "Warning at" on the mahine profile to 70%

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