Reply with QuoteSpeeding up the spindle with stock bearings *could* pay for itself many times over if your producing parts that actually create income and have the demand to make shorter bearing life worth it.
It's all in how you use your machine.
My take on the issue is as follows:
Bearing preload is needed for spindle rigidity - the higher the preload the more rigid the spindle and, the higher the spindle rpm for a given preload the shorter the bearing life.
So if you up the spindle rpm you have to give up either some rigidity or some bearing life, or both. For a given set of bearings, and all other things being equal, there is no practical way round this. So when somebody impliments a big increase in rpm you need to ask what the trade off is with respect to spindle rigidity and/or the bearing life.
Phil
Speeding up the spindle with stock bearings *could* pay for itself many times over if your producing parts that actually create income and have the demand to make shorter bearing life worth it.
It's all in how you use your machine.
Of course that's one possible outcome, but it's not the only one.
Trouble is if a person can't reasonably predict the bearing life then they can't estimate if its going to give them a commercially improvement for their particular way of using their machine. It's becomes a bit of a leap in the dark, you make an investment of time and effort without being sure of the outcome.
Phil
For reference, my bearings are about $50 total, rated at 8.5-10K RPM and take under an hour to swap out now that I know the process.
PM-45 CNC conversion built/run/sold.
Yeah, I don't get all the concern about bearing life. Unless you WAY overload them, they'll last a long time. Even if, worst case, you have to replace them once a year, it's not a lot of time or money to do it.
Regards,
Ray L.
Originally Posted by BAMCNC.COM
I'm fairly certain the bearing life could be estimated quite accurately by running the spindle at max speed and seeing where the temperature stabilizes. Especially if you had numbers to compare to from before the swap.Of course that's one possible outcome, but it's not the only one.
Trouble is if a person can't reasonably predict the bearing life then they can't estimate if its going to give them a commercially improvement for their particular way of using their machine. It's becomes a bit of a leap in the dark, you make an investment of time and effort without being sure of the outcome.
Phil
Trouble is if you are going to estimate if the commercial advantage is sufficient then you need to assess the bearing life before you do the modification, not after.
Phil
Is that 8.5 to 10k rpm rating with a positive preload typical for a machine tool spindle.
I thought we were talking about Tormach spindles, which have match pairs of AC bearings top and bottom and come in at a bit more than $50.
Phil
How much are they Phil?
Phil,Of course that's one possible outcome, but it's not the only one.
Trouble is if a person can't reasonably predict the bearing life then they can't estimate if its going to give them a commercially improvement for their particular way of using their machine. It's becomes a bit of a leap in the dark, you make an investment of time and effort without being sure of the outcome.
Phil
While that is a true statement, the thing that is the back of my mind is that:
1) I can change a set of Tormach 1100 bearing in 2 hours and they cost $170USD.
2) I am fortunate to have a spare 1100 spindle loaded with new bearings in the base of the machine which changes in 10 minutes.
I have changed two sets of bearings in the 1100 spindles to date and it is a bit of work but falls into the actual risk verses the potential reward arguement. My machine currently pays between $62 and $128 USD depending upon which part we are running on our standing orders. If we can pick up a few hours a month it certainly starts to look attractive and makes a bearing change affordable.
In my mind the balance or rather lack of rotational balance is the biggest huddle to be overcome in speeding up the 1100 spindle. I also agree that if the spindle is pushed in speed and load the bearing life is shortened, sometimes significantly. This could translate to a spindle life of 5 months verse 5 years or 10 years - who knows, but if the bearings heat (first indication) or get noisy the world hasn't ended and it is not terrifically expensive to recover.
Additionally, if you desire truely higher speeds, the water cooled spindles look like the best way to go. 3HP - 24,000RPM = $1000 including the inverter and when it takes a dump get another. I know that is steep for a hobby machine BUT if the machine is making parts and time is truely an issue rather than "I want to go fast!" the cost of the spindle has to be looked at a part of the cost used to price the job. If we can hold the price and reduce the time there is more margin made to afford things like bearings and high speed spindles, etc.
Just my $0.02 worth, invoice for consultation will be forwarded via snail mail. (I also enjoy hearing myself talk.)
nitewatchman
Tormach 1100 bearing are more like $170-$180 for the two matched duplex sets and take about two hours to change and reset the preload after running in.
nitewatchman
That's not a solution, nitewatchman. For truly tiny cutters, I have a Proxxon that goes 20krpm, and have worked out a way to simulate TTS (i.e. premeasured tool lengths) with it. I machined some custom leaf springs from .003" half-hard 301 stainless a couple of weeks ago with it for my job. But only the primary spindle accommodates full-size TTS. Not the Proxxon, not the Kress, not the Chinese eBay spindles (not even the Tormach speeder). And an auxiliary spindle means accurately measuring its offset from the primary spindle to mix tools in a job.
I guess I'm in a different category of user. I have a "day job" and only have nights and weekends for my own jobs. As it is, if my spindle was stuck at 4500rpm I could live with it--for 90% of the machining I do I keep it pegged at 4500 and ratio the feed down from what the cutter really wants if it were used at its proper RPM. Doubling my RPM would let me double my feeds, and in many cases let me finish a workpiece in a day rather than leaving the machine on overnight (or several nights, depending on how many other operations I do before the finishing, which for some profiling can take 7-10 hours per side). My machine is a hobby machine and has not made a cent in profit so I can't justify dropping $1400 for a speeder or auxiliary spindle. So it sometimes stays on for days at a time. If the 770 had been available when I bought my 1100, I'd have taken the 770 in a heartbeat.
On the other hand, if I could expend a $50 set of bearings once a year to double the spindle speed on my 1100, I'd do that in a heartbeat, given that there would be some initial setup and tweaking (balancing pulleys etc.) to do up front.
I wonder how many 10krpm spindle cartridge retrofits for an 1100 would sell?
Randy
Why haven't you done it. For sure you can squeeze more rpm out of the spindle, it just depends on what bearing life you are prepared to put up with.
Why not turn it into a business opportunity.
Phil
The RF45 build thread quoted in an earlier post reported 8,000 rpm as smooth, although some intermediate rpms had some vibration. So it looks possible, unless he was just lucky. The builder didn't quote bearing life at 8,000 rpm, or degree of preload.
I guess the essence of my point is: beware of getting something for nothing, invariably it is never that easy, or it would already be that way.
Phil
I think you will find that the expected life of the bearings in a stock 1100 spindle is considerably less than 5 or 10 years if run consistantly at high rpm.
Phil
My knee mill came setup for 5000 RPM. I've run it now for 5+ years at up to 8200 RPM, with zero problems. Many days it's run most of the day at that speed. I think concerns about bearing life, and balance are being way over-blown here. And, again, even they bearings do need replacement every year, if that speed enables more productivity, I'd do it in a heartbeat. If you really run the machine a lot, the electricity savings alone might justify it.
Regards,
Ray L.
Even though I brought up concerns about balance, I suspect you are right. There seems to be plenty of evidence of people running at 10k without any issues.
The same goes for your question about clamping through the bearing. If you have done it without issues, it is obviously OK.
Cheers,
Geo
The point is that most people including myself don't run at high speeds and some hobby machines do not accumulate many hours in 5 to 10 years. On one of our most profitable parts there is 2.6 minutes at 5140RPM out of 20 minutes cutting time.I think you will find that the expected life of the bearings in a stock 1100 spindle is considerably less than 5 or 10 years if run consistantly at high rpm.
Phil
If I cut that in half on 500 parts run since January at $120 sales dollars per hour.
Good point. Then just go for it, sounds like an economic no brainer for your work pattern. I'm sure there are many here who will be interested to hear how things work out, me included.
Phil
Posting Permissions
