Hello. I’m planning on having an MPCNC, and right now I need to figure out what kind of spindle I need to use. I live in Russia, and so I can’t get DW660 or RT0701C that are most often mentioned (but 3709 is available).
I want to mill PCBs, wood and aluminum.
My budget for a spindle is 100$ and the options I seem to have are:
A Makita 3709 router: 530 watts, 30k RPM. Also M3700 is available, 35k RPM. They both have 6mm collets.
Should I get one of these routers, or should I go with an engraver/grinder route? A number of them are available, like Dremel engravers (3000: 130 watts, 10k-33k RPM, 3.2 mm collet; 4000: 175 watts, 5k-35k RPM, 0.8 / 1.6 / 2.4 / 3.2 mm collets), or Makita grinders (0600, 0602, 0603).
Or should I go with a dedicated spindle, unless decent spindles are out of my price range. And I don’t know what spindles are decent, and my only spindle sourcing option would be AliExpress?..
I don’t know what would work best in this context. And I don’t know exactly what goes into choosing a good tool. But, from what I managed to find, too much RPM is rather problematic.
My intuition tells me that I should go with Makita 3709 or Dremel 4000. The latter also have a speed control and supports several collet sizes. What bugs me is the fact that routers are the tools that are designed to work with a load coming from the side. Or are engravers too?
So, what works best: a router, a dremel or a spindle?
I hope MPCNC users will enlight me on this matter. I’d be grateful for your feedback.
I don’t know. But I do know Ryan’s first cnc had a dremel on it, and it had too much deflection or runout and quickly ran out of power.
The dw660 is 600W and it is like a trim router. The dw611, on the low rider, also is considered a “trim router”.
I would look at the weight, at the diameter, and the power and try to find something within 30-50%. I would also try to find something that is a router for regular contractors or home enthusiasts. If they can survive being dragged to a job site, used for hours, and put away wet, then they will be fine living the life in a CNC machine. Unless someone can chime in with knowledge of what they used in Russia, I doubt you will get closer than that.
But, at the end of the day, don’t worry too much. It needs to fit, and any router is going to be making dust in no time. If you can’t find the perfect one, the good one will still get you a working CNC machine.
I would stay away from these low RPM spindles if you want to mill aluminum. I’ve seen most of these being listed at 12000 rpm or below.
Theory
Chip behavior depends on the surface speed the cutter moves at. In a nutshell at lower speeds, there is more plastic deformation that requires more force to overcome while at higher speeds the behavior is more like a brittle break. Cutting forces and temperatures tend to raise steadily before that threshold is reached, then fall off once the chip behavior changes. This happens with most metals, however with soft aluminum alloys the drop is especially sharp. There is a diagram from a study done long time ago in this article. Later research confirmed that using badass methods such as shooting workpieces at cutting edges and filming the behavior.
Why this matters? Because cutter surface speed (sfm) is directly dependent on the RPM and the diameter of the cutter SFM = .262 * D * RPM
Thanks for your input. I ended up buying… well, it turned out that that Makita RT0701C is available in Russia, it’s just that in this region it has a different last digit in the model number. So that’s what I went with. It provides 10k-30k rpm and has a speed control, which is very good to have. The only drawback is that it uses its own proprietary collet type, and if I want to use 1/8’’ end mills I need to buy a 1/8’’ collet that’s more expensive than I’d like it to be. Or I suppose it counts as a standard price for a decent collet regardless of format. Oops, and I’ve missed the discount for this specific size.
By the way, given two end mills with the same cutter diameter and specs but different shank diameters (e.g. 1/4 and 1/8), should one choose a thicker one (supposedly more rigid? but more expensive) or it doesn’t really matter?
Ryan sells the ones from Elairecorp. I bought one of them before Ryan stocked them, they are great.
I don’t think the bigger one is more rigid, since they tend to break at the smallest part, which is the cutting area. I am not an expert though.
I think this is more opinion than fact. This is my opinion:
1/8" is a good balance between strength and speed. A 1/4" bit has twice the load on the cnc. So it will need to go half speed or half depth. This is OK for pockets, because you need half as many passes. But on a cutout, the 1/4" is removing twice the material than you need and it will take longer on the whole.
I also think there is a good reason table saws and miter saws use about a 1/8" kerf. I think it is strong enough to not break under force, but small enough to not waste a ton of energy turning waste boards into sawdust.
A good bit is important though. If you can only find good bits in 1/4" then that will be better than a poor bit or a bit that is meant for a different job.
Starting out I broke or ruined my share of bits. It is a lot cheaper to break 1/8" shank bits than 1/4" shank bits. Plus there are a wider variety of bit types with 1/8" shanks. I doubt there is much functional difference during cutting with the same cutting diameter but different shank sizes.
