Hello,
How do we go about decreasing the spindle speed to 2000RPM? I tried to disable the Avid configuration, but it did not work.
Do we need to change any code?
Any suggestions are welcome.
Thank you,
Antony.
Depending on the spindle power can drop off a fair amount at RPMs that low.
If you’re drilling wood have you considered peck drilling at a fast moving rate instead?
As Eric said, the power will drop off linearly with rpm (because the torque curve for most spindles is relatively flat over rpm), but for simple drilling in wood thats usually not a problem.
I have had good luck with peck drilling at low and higher speed. If you want to go lower speed, you have to change the settings in Mach4 AND in the VFD settings.
I have done it typically at around 2k rpm.
@jjneeb Would you mind sharing what feed/speeds/stepdown you run for your high rpm peck drilling?
Almost all of my drilling has been between about 1/8" and 1/4 inch diameter holes for things like cribbage boards and other kinds of peg games. Usually its into hardwood plywood and I’m going for quality (i.e. not chiping up the top layer veneer), so I’m prioritizing quality over speed. You have to use upcute bits to clear the chips.
These holes are also always under 3/4" deep (not that you can’t do deeper, I just haven’t needed to that much).
So with these kinds of holes, I’ll just use an endmill and run them at the normal speed I’d use them at the speed I’d normally use them for milling in that material. So thats usually around 16k rpm for 1/4", and around 20k rpm for 1/8".
I usually plunge at about 50 ipm.
The peck depth depends on the depth of the flutes. If its a bit like a typical 1/4" mil that has 1/2" or more of flute, then I’ll just peck about 0.25" deep per peck. If its one of those custom diameter mills thats made for drilling, sometimes they don’t have much cutting area, so I may shorten the peck depth. The main thing is you don’t want the flutes to fill up with chips because then things get hot real fast.
The slow speed drilling I’ve done is when I need to use a regular twist bit either because I need to drill a lot deeper, or I don’t happen to have a mill drill of the right diameter. and don’t want to wait to order one. Those I run at around 2k rpm, and I won’t peck deeper than 1/2" just to try to keep things cool. The thing to watch out for with regular twist bits is they can wander a bit on the small diameter ones if its a rough surface and so you want to make sure you don’t plunge too fast on that initial touchdown so the bit can find the center in the wood.
I have never done this with metal. I’m sure you can, but I’m sure the plunge rate vs. the rpm is a lot more important with metal.
Hello Eric,
We are drilling onto 2mm MS sheets using a twist bit.
My spindle is rated at 9KW, we will have to at least 2000RPM to prevent the drill from overheating and getting blunt.
As we are drilling sheet metal there is no option of going faster or peck drilling.
I have tried a sample with the vfd manually dialled down to 2500 RPM and it works.
My problem is that the spindle speed at the Mach 4 screen will not go below 6000RPM, any option to bypass the same?
Antony.
Hello JJ,
We are drilling 6mm holes on a 2mm thick MS door panels.
Yesterday I did test some holes @ 2500RPM and 60mm/min feed rate.
We could improve the speeds with a few tweaks.
Antony.
You may have to set the min rpm in the Mach4 config:
and you may also have to set this parameter to your min speed in the Machine.ini file:
@jjneeb Thanks so much!
I have been going 18k and 20ipm on .2" pecks, making .25 wide x.5" deep holes for my double-op alignment dowel pins.
My square 1/4 endmills are cutting way cleaner than my new 1/4" drill bit, probably getting the wander that you mentioned as the holes are coming out oversized.
Ya, I find the endmills cut a lot cleaner w/o tearout too. The pointed bits are meant to be used in a handheld drill, and to hit a center spot. However, when they cut the leading edge pushed material out radially and causes a lot of tearout. You could probably use a bradpoint bit to cut a lot cleaner, but with a CNC you don’t need the center point anyway so a mill is fine.
You can usually find a close enough diameter mill for most projects where you want a lot of holes.
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