My Denford currently has a 1.5 HP DC Motor controller with the original Sprint 1200 controller. The RPM on this is 4000 rpm which then runs via a belt at a set of gears at a 1:1 ratio and in turn runs the spindle at 4000 RPM.
Based on some calculations (FSWizard) and similar, I should be able to cut the type of speeds and feeds that I require in Aluminium with relative ease. My biggest drawback at the moment is the low RPM. On that basis, I have to feed slower.
Something that concerns me is that I have stalled the spindle before. I am using flood coolant most of the time and I tend not to be aggressive on speeds / feeds and WOC / DOC. For example, if using something like a 6mm 2 flute carbide with no coating, I will cut no more than 2mm deep when doing profiling. I am still experimenting with different options for plunging and ramping down based on all the options in Fusion 360 (which is excellent btw).
I have also blown the 10Amp fuse that feeds the board numerous times when the spindle stalls, not good but I keep the fuses in bulk for when it happens.
So, question time.
How 'strong' is this DC setup? If FSWizard indicates I only need 0.5 HP (For example), surely the DC spindle should be able to manage? Could there be a setup problem with the DC drive (ie, just not setup correctly)? The fact that it is blowing 10A fuses implies its taking full power. On Saturday I had the spindle start to act odd, I need to see why but it runs and blows the fuse now when I power my mill (even before I ask for a spindle run).
So, options ....
Do I replace the Sprint controller with a modern isolated version for £170ish excluding VAT?
Do I spend £470 on a 4KW liquid cooled Chinese spindle with suitable VFD? Are they really able to deliver 4KW? From what I can see, I can probably cut a new plate (if I can get my spindle working properly) and get a 10 tooth gear onto the motor. The current gearing is 18 / 18 tooth. So this will take me to a max speed of 13300 RPM which will be good however I dont know if the system will have enough torque.
What does the torque / speed curves look like on them?
I would also likely need to replace the bearings on the spindle, additional cost.
If I now run at 10:18 gearing, the slowest speed is probably around 3000 rpm, but can it actually cut anything at that slow speed (lack of torque)?
Back Charl so I'll answer here rather than email.!
check out the controller setup and wiring first if blowing fuses. Often blowing fuses for no obvious reason is a sign somethings on it's way out.!!
Also you have to bare in mind the Spindle bearings and there speed rating. If Max speed was 4000rpm then I very much doubt the Spindle bearings will be rated for 13000rpm.!!
I'd look to replace the DC motor with AC asyncronous Motor like this one but the correct size for your needs which is the correct tool for the job.!
Ironically, the top bearing is rated 11K and 13K RPM (oil / grease) but I dont know the number on the lower bearings (they are different). The top bearing is a Nachi 6007ZE (I took the spindle out to measure up a replacement plate but have not yet dropped the spindle out.
Ill take a look at that option. There is a guy on utoob that has converted his Triac to a 2,2 KW Chinese spindle and seems happy with it. Trying to get some further information from him.
At present too on the non isolated version I have, speed control is manual via a pot. Not ideal, will be nice to go 'auto'.
If you want to try this I can lend you a 2.2Kw spindle and VFD. Thou it would be a lot work to find out it's not much good.!!
This lowers the speed to almost half and should therefore provide almost double the torque. Its a pity that the removed Servo motors are a bit small, else they would be ideal, specifically with closed loop control. They also do 8K RPM, worth a look at all?
Servo will offer more torque across the speed range.! . . . . You can get some largish and Cheap Servo drives from ali-express so may be worth a look and it will make a proper job of it.!
i also have a denford triac with the standard sem servo motor, owned the machine for 3 years. ive never once managed to stall the spindle.
i do 1mm deep cuts in ally with a 20mm end mill no problem, i also do 2mm deep cuts with an 8mm end mill no problem. the motor has plenty of torque.
but i do agree it is pretty slow on the rpm front and i have also been looking at other options for new motors. although i can take 2mm of ally off at once with a good finish, due to the low rpm feed rate is pretty slow at about 250mm/m.
the current sem servo motor in the traic is £1200 new and brand new replacement with more speed is going to cost even more. the thing to bare in mind when looking at the high speed chinese spindles is the atc and bt35 tool holders are only rate to about 8-10k rpm.
It looks like my controller has died. Ill probably just get a newer version of the controller and then look at the high speed spindle options later. My brushes still look OK, perhaps a bit worn, looking to find some replacement ones to be sure.
Is your machine the same as mine? BT30 or 35? Mine is BT30. A good rpm speed is around 8K I think. So take the 24K Chinese spindle and gear it down by a factor of 3. I think that will give a good balance for speed / torque.
yeah i regulary use a 20mm end mill just to get lots of meterial away at once then switch to a smaller cutter for final finish. i had a massive problem with my sem motor, smoke the lot. the rpm keep jumping up and down by like 500rpm when running. ive installed sinplde feedback into mach.
so i recently sent the motor away for repair, cost me £500 but it has been working very good since the repair. the brushes on mine looked fine but there was clealy another issue.
mine is bt35
8k with some decent torque would be ace. things like this pop up on ebay regulary, but its trying to find out the exact spec of the motor thats the difficult part -
ive also been working on a 10 station atc for my triac, it currently only has a 6 station
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