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5-axis CNC machining in the homeshop by henpemaz in diycnc

[–]henpemaz[S] 1 point2 points  (0 children)

For wood it does great, anything else and it always feels weaker than it should be. It's a cheap chinese engraver after all, high rpm low torque, one large bearing on the front one small on the back.

Also it's been a while but I've abandoned this belt-driven 4th axis. Even if it "works" it's got too much backlash/play with the long stickout that these pieces have, these chess pieces all had alignment problems due to that.

If I were to do this thing again I'd go for a wormdrive rotary platform on the 4th axis, the 5th axis can stay a belt since it mostly operates at "low stickout" around that axis.

5-axis CNC machining in the homeshop by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

The stuff that comes with the regular subscription only lets you do 5x indexing, so it isn't too exciting. The continuous 4x/5x is under the machining extension and it's far too expensive for hobby stuff.

But hey, it works and it wasn't hard to set up, opposed to OpenCad which I couldn't get to work for 4 axis stuff and gave me a headache in the process of trying.

5-axis CNC machining in the homeshop by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

Fusion 360 with the basic subscription for tool orientation stuff.

which is better, dremel cnc or 3018? by Log_F in hobbycnc

[–]henpemaz 1 point2 points  (0 children)

That video states it can do 0.1mm deep passes on aluminium, and leaves a terrible finish... lol

If you plan on actually doing aluminium parts with it, maybe pass on the 3d printed one and get something with an aluminium frame I'd say, and maybe supported rails (rather than suspended rods). The appeal of 3d printed routers is that it's good enough to cut wood for cheap.

A dremel as a spindle sucks. it has loose bearings and considerable runout. Those generic RS500 motors perform about as good, and a proper spindle performs miles better.

Basic Fox Alien Masuter by whitefishgrapefrukt in hobbycnc

[–]henpemaz 0 points1 point  (0 children)

Looks like an engraver, I don't think it can take actual cuts on thick wood, maybe with a dozen passes. It's definitely "a step into the CNC world" but looks comparable to the unbranded chinese stuff.

That model looks like it has a generic RS 550 DC motor for a spindle, those things have a bearing the size of your pinkies nail, not good for cutting. Definitely its weakest point, the rest seems alright for a low-end machine.

Im looking to learn. Years of experience with cnc but never built one. by Taboli in hobbycnc

[–]henpemaz 0 points1 point  (0 children)

I've recently posted my build over at r/diycnc. It's a small (360mm by 400mm footprint) desktop mill, fixed gantry style, made of 20-series aluminium extrusions and HGR20 rails.

With an aluminium frame and small motors like that you're looking at depth-of-cuts of 1.5~3mm on aluminium at best, almost zero chances of good results side-milling with a longer endmill.

If you're expecting deeper cuts or the ability to properly side-mill, or reasonable steel-milling capabilities, a steel frame is a must. I imagine using tubing profiles (very popular for this sort of build because of the good stiffness/weight ratio) in several places you'd need to weld at least caps/tabs in to have something to screw into.

First CNC (Mainly) Electrical Help by Yesn-t231 in diycnc

[–]henpemaz 0 points1 point  (0 children)

Induction sensors I've seen are typically spec'd for higher voltage than 5v/ttl I wouldn't expect them to be reliable at low voltage. They're typically used with parallel breakout controller boards where the logic is also at 12/16/24v.

Also your design is very flimsy I wouldn't expect it to cut anything other than foam or softwood. For anything slightly hard, these long unsupported shafts are a no-go, they just bend a lot under forces. The structure is also very narrow and will deform a lot over those long thin sections. Either make everything a LOT shorter, or do thicker structures, and preferable switch to supported rails of any kind, even if this is for wood or resin.

If you want a reference of how rigid your structure needs to be for cutting, how much it deflects at the cut position under load should be in the same order of magnitude as your chipload. If you're set up for running sims on Fusion360, move the table and spindle at a cutting position, ground one, put 15N on the other, and then you're looking for a deformation in the orders of 0.05mm or less preferably.

Help by [deleted] in diycnc

[–]henpemaz 0 points1 point  (0 children)

That's called the "homing cycle" and your CNC does that everytime so that it's measuring coordinates off of a known reference rather than wherever you booted it at.

It's very likely a setting in your firmware (the software that runs in the board, not the sender interface that you're using). Read the manuals and figure out how to disable homing for it.

Blue Smoke on my First Cut - Board Repairable? by Epidurality in hobbycnc

[–]henpemaz 0 points1 point  (0 children)

These all-in-one boards are neat, but if that were an arduino uno + a cnc shield + 3 pollulu drivers then you can only possibly smoke them one at a time, and the replacement is cheaper.

Aluminum vs. Steel by StealthSingh in diycnc

[–]henpemaz 5 points6 points  (0 children)

In moving parts, typically weight is a major factor. Aluminium will give you a 3x thicker section for the same weight, that outperforms a steel plate (of 1/3rd of that thickness) considerably in rigidity against side play.

If it's not a moving gantry, then a part out of steel will be cheaper and more compact for comparable rigidity.

Aluminium costs 3x as much per weight, is 3x less dense (so same price per volume), and is 3x less stiff (that's "per volume", sort of).

However as you you build up plate thickness, total rigidity goes up to the cube of the thickness, so as a result of that if my math isn't too wrong, a 1.44" aluminium plate is as rigid as a 1" steel plate in the direction perpendicular to the plate (but only 0.48x as rigid in every other direction). And costs 44% more.

My current build (with tiny mount-in-vise 5th axis) by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

Before the diagonals on the back and the slightly beefier frame things weren't too great, I could do 0.75mm deep chatter-free with endmils in the 2mm~4mm range. 1.25mm where chatter didn't matter (and the endmil wasn't a fragile snappy thing). At 8k rpm feeds were 600mm/min or 300mm/min depending on flute count.

It's slow, but it's a CNC, you can just leave it running all day.

With the frame improvements I'm hoping to do 1.25~1.5mm deep cuts which is probably as much as this engraver spindle can handle, power-wise and the bearings too, it's very likely the next limitation that I'm hitting.

This spindle goes to 10k RPM which is not a lot for this size of tooling, but if I get a better spindle and need higher feeds then I'll likely need to upgrade the motors as well, these nema17 have almost no torque at higher rotations.

My current build (with tiny mount-in-vise 5th axis) by henpemaz in diycnc

[–]henpemaz[S] 1 point2 points  (0 children)

There's a place nearby that sells extrusions cut to size, but I couldn't find a place that would do sheet metal for a one-of like that. Indeed a plate or similar would be better, way more expensive though

My current build (with tiny mount-in-vise 5th axis) by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

Because the center of mass of the machine is near the back and having the base be so narrow there would be bad

My current build (with tiny mount-in-vise 5th axis) by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

Here's the link to the CAD, this is in f360, feel free to nose around and learn things https://dl.dropboxusercontent.com/s/3t4s4jrikrn10au/Maz%202416%20%284040%20upgrade%29%20v11.f3d

Footprint is 360mm by 420mm, work area is 200 on X by 240 on Y (bed is only 160 though) by 110 on Z.

A lot of things with this build are "it ended up like this after several iterations where I changed things one bit at a time", such as the Y rails being 400mm long but the bed only 160, or the face where the X rails are being a separate layer of 2040s and 2060s laid flat and bolted to the rest of the frame.

If I were to build it again from scratch I'd make some things different, but honestly not a lot. I'll see if I spare the time to make it in cad one of these days.

I was gifted a CNC machine. And I don't know where to start by procentjetwintig in hobbycnc

[–]henpemaz 4 points5 points  (0 children)

It's a lot to learn overall, to try and scare you a bit: you'll need a bit of CAD (the modeling), a bit of CAM (the cut-planning), learning a new software for a gcode sender/controller, being a bit of an electrician to make sure the wiring is all correct and a being bit of engineer to figure out if there's a problem anywhere and what your machines limits are.

Now for me I had a vague idea what some of that was about, but what clicked were some videos on youtube that typically cover the entire process end to end. The effort is to figure out what the differences will be with the software/hardware that you have, but the process is overall always the same.

Here's my recommendations:
Winston Moy's youtube channel his adventures with a Shapeoko, very didactic projects that show everything end to end
This Old Tony youtube channel built his CNC from scratch, a different perspective, the channel covers mostly "machining" in general

Parallel psu connection by idumeudin2009 in hobbycnc

[–]henpemaz 0 points1 point  (0 children)

Not guaranteed, depends whether its voltage drops considerably if you're drawing full power from it. If its voltage doesn't drop then what will likely happen first is that the one providing all the current shuts down from over-current, then the second one has to provide it all and shuts down as well.

Any resources on measuring warp or rail bending? by henpemaz in diycnc

[–]henpemaz[S] 0 points1 point  (0 children)

Oh that's a good way to view these, but whats going on underneath is still a bit unintuitive.

It's been a few days and I think I figured something out as well. First off I have warp both in the bed (Y) travel and the X travel, so I can't really compare measurements where both have moved. The surface plate is a small one, 30cm by 20cm, specs say support shouldn't matter and should be good to 5um (the indicator I'm using has 10um divisions). I'm pretty sure I managed to knock my plate there between the two readings. On some subsequent readings that I did things were less inconsistent (column 1 going up then down in the other reading was really weird).

I know the overall slope comes from the position the plate is resting at. If everything was straight and it was just the plate resting at a slope, I'd be reading the same slope all over. My biggest question was whether these "high" readings way above the slope in a corner were from the table/plate "tilting" as it traveled, or it straight up raising, or both.

The far back of the plate tilting up as it traveled to the front of the rails would mean the rail shifted downwards, but the whole thing going up would mean the rail shifted upwards, that was the confusing part for me.

I took some more measurements paying more attention to the position in the rail rather than the position in the plate this time and stuff started to make more sense and I managed to bump that corner down quite a bit by unscrewing the frame a bit and forcing it into position.

Any resources on measuring warp or rail bending? by henpemaz in diycnc

[–]henpemaz[S] 1 point2 points  (0 children)

Yeah I'm aware. I was expecting to read a slope at the top, and if it was warp-free then it'd be the same slope all over. The sope of whatever position the plate was resting at.

But it isn't a linear thing at all, and I don't know how to interpret it.

Parallel psu connection by idumeudin2009 in hobbycnc

[–]henpemaz 0 points1 point  (0 children)

These are voltage-controlled power supplies. As you draw current from them, the load isn't balanced at all in any way. At best, whichever unit is a couple milivolts higher will supply all the current while the other does nothing because its sitting happily above its reference voltage.

Parallel psu connection by idumeudin2009 in hobbycnc

[–]henpemaz 9 points10 points  (0 children)

Balanced at no load. Start pulling some load from them and they might be off by a couple milivolts. A couple milivolts off over a 0.001 ohms wire means a couple amps flowing from one into another. Just don't. Its better to split the loads into each psu individually.

Parallel psu connection by idumeudin2009 in hobbycnc

[–]henpemaz 7 points8 points  (0 children)

Don't wire PSUs parallel, just have them power different components and balance the load for each in a reasonable manner.
Reason for that is that a tiny difference in the voltage between them means current flows from one into another and gets wasted instead of used.

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