Pretty much as the topic says, I picked up a 3hp dc brushed treadmill motor and I'm just wondering without knowing much about the magical world of electrons whether it is a decent substitute for a VFD / 3 phase induction motor setup.
I saw Hoss using one as a servo, I'd like to learn more down the track and pursue this option if they are indeed good for milling machines.
Thanks.
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CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
My experience is they do not hold up well under load and at high speeds. I would not expect to get any where near the same performance from a treadmill motor as you would from a 3 phase induction motor. It does depend on application though. For a mill spindle I found it was a waste of time, money and effort.
That is not exactly true, it all depends on the nature of the drive, some either use simple SCR controllers or cheap (ebay) PWM, some of the treadmill controllers have very good performance in this area, especially the ones with RPM monitoring.
I have found that the Johnson T.M. motors are well made with hi number of poles.
The majority of T.M.'s use DC brushed motors because they can be controlled at a set rpm and are stable with a varying load.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
My comment is more towards the lower end more readily available motors that most people use. I went down the whole rabbit hole of a treadmill motor following hoss on the G0704 and regret it. One thing to point out to those following his build is that he no longer uses any of those motors on his mill. Yes the higher end treadmill motors are good, especially precor or any of the industrial gym quality machines but yo also pay a premium for them and at their price point you may as well stick with a 3 phase motor. This is especially true if you already have the VFD/controller for that motor. A lot of them use 3 phase motors now though. And more specific to the OP's question was if a treadmill motor was a good replacement for a 3 phase motor. I think it would be hard to argue that any treadmill motor would be a good replacement for any 3 phase motor.
You have to compare two motors with the same True torque rating, compare the torque curve on a DC motor compared to an equal size 3ph AC motor, there is no comparison, the DC is fairly flat from max torque at 0rpm with very slight taper off at the rated RPM max speed.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
I wouldn't recommend a treadmill motor for spindle use on a mill if the drive that one is going to use is also from a treadmill (or similar). Why do I say that?.....
Ryobi DP100 Treadmill motor conversion Photo Gallery by Eldata at pbase.com
Last edited by eldata; 12-13-2017 at 03:27 PM.
Yes!Am I missing something?
https://en.wikipedia.org/wiki/A_pict...thousand_words
Your pictures show using a treadmill motor and an treadmill controller which implies that it works. Yet you say you would not recommend it. That is a contradiction that you need to explain if your post is to make any sense. Stop with the 1000 words BS, how about you use say 10 words and say why you don't recommend it.
eldata, your picture says a thousand words.
Unfortunately those words are not answering the question being asked in this thread. Perhaps we need a thousand and ten words in this case.
Or just the ten words that are relevant.
Treadmill drives are a POS if realizing near full power capacity of the motor, over long periods of time, is a requirement. They're great for treadmills from a cost effective perspective (no surprises there), okay for something like a simple drill press. But don't waste time and money on using one for a mill unless all you'll be doing is drilling or your pulley ratio setup provides ample mechanical advantage (torque multiplication) at lower spindle RPM. This is something people tend to overlook. In terms of available torque at lower RPM, spindle RPM reduction that also includes pulley ratio change capability can often run rings around a fixed pulley ratio setup using only electronic variable speed and a much higher power motor.
Amen.
Have just AVR smashed a 1.5hp treadmill motor for a 2x72” grinder and it’s utter ball grease (the rancid, ageing hippy type) rubbish.for torque under 1500rpm.
Great for a cheap heavy spindle with massive overkill drivers if you can bash some roadkill together to spin something. But if your lexicon includes the concept of “performant” then there’s an infinity of better ways of doing this.
What about one of these Chinese servos as a spindle? - https://www.aliexpress.com/store/pro...476053db4A23UL
That ones $600 delivered to me, about twice the cost of a VFD around here. Additional benefits include being lighter and other fancy things ppl probably know about.
I suspect many people don't realize that the treadmill drive/controller is also responsible for DC power. Not only for the DC motor but also for its own drive electronics. In the case of the MC-70, there are only two 680MFD capacitors for smoothening after full wave rectification of the mains. This is suitable for the 24VDC required by the relay and lower DC voltage electronics. But what that means is that the motor will never see a 100% duty cycle DC voltage. Instead the highest current capability will occur at 120Hz (assuming 120VAC, 60Hz here in the US) intervals when peak voltage is 168V. It's the DC power shortcomings and relatively poor speed regulation under load (compared to say what happens in a BDC servo drive setup) that makes these drives/controllers a POS in high power variable speed scenarios. The motor itself is innocent but has to be judged by the company it's forced to keep.
The truth about DC Treadmill motors, run away as fast as possible unless your favorite pass time is pissing money away. You can grab a 2hp 3ph general purpose motor for $150 new from automation direct along with a drive off eBay and you will have a setup that is reliable for ages and will outperform a dc treadmill motor in every way imaginable. Anyone who suggests a dc treadmill motor has no clue what they are talking about or has never used one on a spindle and if they are using one, it's certainly not in a production manner and they run their mills like beginner hobbiest at baby feeds and speeds. They chew through brushes, Arc at higher rpms and I have seen them sieze and catch fire on mills with little to no warning. For anyone suggesting they are a suitable motor to be used, show us one you've used daily for years without incident in a mill Spindle application or move along to pedal bad advise somewhere else. I have 3 burnt up useless motors here as proof and I was using a quality kbb speed controller. I tried treadmill motors, sick replacement motors, DC brushes servo motors and finally switched to a 3phase ac motor which has happily chewed parts out daily for a few years without a hiccup. Anything else will be wasted money along the way to the best option!!
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I burned up a couple treadmill motors after I completed my conversion. After the second one I bought a 1100W DC motor commonly used on the PM25 mill and 11x26 lathes. I've been using that motor for 4 years without any issues. Most of the time I run it at full RPM (4500) and push the MRR to around 1 cu in/minute in 6061.
That may be the only motor I never tried on my G0704..lol. What is your limiting factor for MRR being set at 1in³ per minute? I run a 2hp general purpose 3ph AC motor and below is my safe no issue cut recipe for day in and day out milling without tool pullout.. I can push it a bit harder with supervision, but if I'm working on other items while it's cutting I use this recipe and it's a non issue to let cut on its own.
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Honestly, I cut G10 and aircraft plywood with diamond cut router bits much more often than aluminum these days.
I can push my machine harder (~1.4 cu in/min) but at this MRR I don't feel the need to babysit it. I don't do big production runs (10-20 pieces max). I also don't do many jobs where I need to remove a lot of metal.
Here's my recipe for 6061:
YGT 2F .375" HSS Aluminum cutting mill (~$10 each)
.625 DOC
.035 WOC
4500 RPM
45IPM