That helped a lot. that explains the second article I linked. If he were to test torque of say 1/32nd step instead of at the full step mark it would be less. Awesome thank you.
I will spend my efforts on testing the z axis and probably ship them at a different step rate now.
I think the x and y could use a little accel tuning as well.
Thank you for the lesson and motivation.
You were very right I was hitting the marlin speed limit. I changed the z to 1/16th and not I can move it much faster. It would stutter or stop in 32nd and with to 16th, smooth as butter.
These screen shots were z max on my better machine, I have another that is kinda tight so I want to try this on that one as well.
I’m finding for me a big limit on speed seems to be rigidity of the middle component. If I try going much faster through material the DW660 actually starts getting pushed from it’s intended path. It’s not the X/Y steppers though, it’s definitely twisting on the middle part. Sometimes I wonder - what if I took one of those $20 makerslide things and used it just for the middle? A mount that puts the X steppers slightly higher than where the Y steppers are now, then the belt goes across the middle pulling the middle mount along the makerslide.
Although I’ll probably end up trying that wooden middle remix I’ve seen on Thingiverse (thanks to your work I have the machine to cut that wood now) before going the Makerslide route. I am however definitely going to try that $14 4 start leadscrew on Amazon. From my understanding at 2mm pitch, 4 starts, every 1 rotation of the motor SHOULD move it 8mm up or down. That’s a pretty huge difference from the 1.44mm per rotation of the all thread, and at 1/8 microstepping I still get a resolution of 0.000625mm per step which is accurate enough. If I wasn’t trying to keep the cost down to the cheapest stuff I’d just go ahead and get one of those stepping motors that has the lead screw built in for $36 from Robotdigg and get rid of the coupler. $14 vs $36 though - eh, I know I’m going to go the cheaper route. If I didn’t already have the stepper though it seems like it’d be a great deal to get stepper and lead screw all in one, and eliminate the need for the coupler at that price.
The machine can already do some really amazing things - I just want it to go faster now.
The biggest effect on the center rigidity is distance of the tool tip from the bottom of the gantry. Half the distance, twice the rigidity.
When you say you are having a speed limitation how fast are you going now, through what material, how far from the gantry is your tool tip, and how fast would expect a machine under $10k to be able to go?
I mill aluminum with the tool as high as possible, I actually have a new mount for the dw660 that should make things even more rigid but At the moment requires modifications to the z rails.
No comment on the rail, at that point you are making a different machine.
Why switch to a lead screw? Plunge rate through most materials is really slow, seems like a waste to change all that just to speed up your z rapids.
I like the 3D carving projects the best, but when doing a 3D Roughing if I set a pass depth of .06mm it will go along the contours of the 3D model in the wood, back and forth (I can select either X or Y axis) and where it needs to cut deeper it cuts up to .06mm there. The problem is with 3D the Z is constantly moving up and down, so the fastest you can go is the speed of your Z axis. For 3D to come out good I like to use thicker material that gives more depth. Imagine 3D printing something 13 inches by 9 inches by .75 to 1 inch thick and it is going at .06 layer height and limited to 5-10mm print speed. Most of the time it isn’t even cutting (just following the contours of the 3D model where it has already cut down enough). A 17 hour project would only take 8.5 hours if I could double the speed of the Z (and most of the time it is not plunging down into material). If I had a more rigid middle and was able to cut .1 inch per pass that might even come down to about 4 hours.
Your middle should be rigid enough to cut much deeper than .1mm in wood per pass. My machine can’t handle a plunge rate of 14mm/s because of tool strength not just machine speed.
How far is your material from the gantry?
I cut that Brazilian walnut at 4mm (my full tool depth) in a single pass at 20mm/s, at 4" from the gantry and easily had room to do much more much faster. That wood is super dense so if you are doing pine or something soft you should be able to go much more per pass. Try roughing using a waterline pass much faster with very few z moves and high step over and only use the contour cut for the final pass with a low step over.
You haven’t given any information to determine if your gantry is loose or you are just trying to cut beyond the machines capabilities. Axis speed is not the only way to get a final product faster more efficient tool paths, larger roughing tools and smaller finishing tools help.
The posts that just say it isn’t fast enough or it needs to be more rigid is bad press, so I do my best to help those people out. But not rigid enough for what material, what gantry distance, What spindle, what spindle speed, what cutting bit, what step over, what depth of cut? Your settings might just be off a bit and the problem would be solved or maybe you just expect too much.
Hmm, it is soft material, not hardwood. I know I can manually push on the Dewalt (with it off) and make it rotate a little around the middle. I calibrated for size, and all the bearings are making contact, but I kept having my PLA crack on me so I switched to polycarbonate. Is it possible polycarbonate is just too flexible? Dewalt DW660, spindle speed would be approximately 12-32k with a MCLS speed controller (setting of 3 to 10), Inventables sample end mill kit with 1/8 inch 2 flute straight, 1/8 inch ball nose, and 1/8 inch 1 flute upcut (also has some fishtail bits, but being 1/32 in size I really didn’t try to push depth per pass with those). 45% step over, 0.06 inch seems ok, but at .1 inch the Dewalt starts getting slightly pushed out of the way and no longer is cutting in a straight line. Sorry, just noticed I wrote 0.06mm earlier - I meant 0.06 inch.
The 1/32 is probably moving more than the dewalt, that is a tiny bit, you should start with an 1/8". Pushing on it by hand doesn’t mean much.
How far is your work material from your gantry?
How long are your axis?
How fast are you moving when the bit strays off course?
From the wasteboard to the X axis it is 7 inches. The axis are 30 inches. 25-35mm/s feedrate.
My all thread seems to have rougher spots where it doesn’t want to turn as well, if I make the gantry shorter it seems to run into one of those rough spots. That was another reason I was considering a lead screw - my first all thread came in the kit and I didn’t notice anything wrong with it when building everything, while the all threads at my local Home Depot visible aren’t perfectly straight across their length.
7 inches is nuts, a lot of other small cnc’s only have a 3 inch Z. You should really bring that down to 3 or under. Your bit only has .5-1.5" cutting ability anyway, you should always put your material to be cut as high as possible. If you are only cutting 4mm deep only leave 6-7mm room. Cleaner more precise cuts. Half the distance twice the speed. Think of it this way, most 3D printers only have a 8 inch z and you are slamming around a 4lb spindle+the drag from its cord.
If your allthread has a rough spot take, it out and chuck it in a drill, lube up the rod and run it back and forth a few times until you feel the rough spot go away.
I feel 25-35 is pretty fast, sure faster is possible, but I don’t think I have made any videos faster than 20mm/s, I go slow and just very the depth to keep cuts real nice with minimal finishing work.
You machine sounds good your expectations just seem a little high. I can make the machine do more but, I am focused on making it easy to use for everyone, not just bleeding edge fast for perfectly adjusted machines.
I’m going to do your suggestions on the all thread and the drill, cut smaller legs, and see how my rigidity is then. I also replaced a middle end today that had apparently developed some kind of wear (it used to have all 3 bearings firmly touching the pipe, but one of the 3 were just barely touching now - maybe it could also have to do with the temperature being in the 90s when I put it together but now in the 50s)
“I actually have a new mount for the dw660 that should make things even more rigid but At the moment requires modifications to the z rails.”
How extensive are the modifications? Is it just drilling some new holes or is it ‘take the middle assembly apart’?
I wouldn’t reprint it. You might just want to loosen it up the whole middle assembly and then tighten it back down while it is on the pipes. Starting to find out that is a better way to build them.
The new mount is just a bit bigger, it pulls the router up 20mm higher. just the 4 screws to change it out.