I am currently working on the X axis for Heavy Metal and was wondering a few things. If I run dual drives on the X axis using the X32 Blackbox can I reassign the outputs for the X and Y in software to take advantage of the extra Y driver circuit? Do I really need a dual drive? I am using a 2:1 gear set to drive a 4mm pitch ball screw. Do the advantages outweigh the dis-advantages? Right now I have everything set up for dual motors Any thoughts?
Yes, there is a compile option for dual X, I have found compiling GRBLhal to be a bit of a fiddle so maybe Peter will be kind enough to compile this for you. Seems to me to be something that should be done anyway since some people like to rotate the bed and use the gantry as Y and the 2 bed rails as X. In fact that would suite my old Ox which normally sits sideways on the desk so it does not overlap the edge.
On a machine this rigid I'm not sure you do. If the rails are strong enough and the carriages are spaced out sufficiently, the table itself is rigid enough, and a single drive motor has enough power, you shouldn't need to add complexity to avoid racking.
I think the 12mm rail is plenty strong for a single motor. I am running 5A Bi-Polar steppers that will be wired in series for torque. The bed is a solid piece of 6x18 3/4" aluminum plate which will also have a machinist vice mounted for metal work or a 300 x 300 slotted aluminum bed and a spoil board for wood and acrylic. I expect the table assembly alone will be app 10Kg. I would expect that the largest pieces I would work on would add up to 10 more so an extra motor to keep acceleration at an acceptable rate doesn't sound too extreme. My main concern with the dual motor config is binding between the screws if they get unsynced.
What if you put both motors on each end of the same screw? You'd get the acceleration/inertial matching benefits with the heavy system, but without the possibility of mechanical failure- and limiting the consequences of electrical failure. If it were me, I'd put a big 8Nm closed-loop NEMA 34 on the back of it and call it good. My X-Y on the mill (still on dovetail ways, so no inertial problems but needs hefty acceleration) have 4.5Nm NEMA 34s. The table weighs around 15kg by itself, I'd guess, without the SMW fixture plate, X motor, or parts/workholding. The Z has a 12Nm (because motor weight is irrelevant, the head is heavy and it was cheaper). I just got the cables from Igus for M4, so maybe we'll be finding out how much those motors can sling around on 20mm linear profile rails using 1610 ball screws before too much longer. I doubt they'd become unsynced, realistically. Many, many other people operate XYYZ machines with zero issues every day. If it were me though, I'd be using HGR15 rail, a single DFU2005 screw, and I'm confident it would be absolutely fine. You could always run the calculations to be sure.
A motor on each end is an interesting thought but I don't think the ball screws I have will accommodate it. Lol Rob "The Tool Man" Taylor. No such thing as too much power! If only my budget was as big as my eyes Hope to see some video of your rig in action I think I will keep the twin motors as a starting point and consider single screw options if it becomes a problem. Chances are good that upgrades will be upcomng after the initial build is done. My goal is to eventually get to 5 axis and the ability to cut my own turbines
I'm at a loss for which axis you're calling the X axis. The only place I see 2 screws is under the bed and that's the Y axis (for which you already have 2 outputs).
Yeah usually you'd have to get them double-end machined direct from the factory. Most will accommodate, but it has to be a decision ahead of time. Ha! With too much power, you can dial it back. Not enough power can't be overcome, and will usually manifest as poor surface finish or terrible efficiency. The price drops in the maker space are absurd- even with pandemic pricing, it's cheaper to buy industrial components than hobby parts most of the time. Probably the most sensible plan. If you do go single screw, a larger size will help buffer the table inertia during deceleration (at the cost of overall acceleration, of course). But I have an SFU1204 on the mill's X and it's been fine. Happens every time. Recently upgraded to C5 ground from C7 rolled on that 1204. I didn't think it was gonna be that big a deal, but it's magical. I have a C5 1605 coming for the Y now. Leaving the C7 DFU1605 on the Z though- the column flex is way more than I can gain from a screw upgrade. I still have eventual (hobby-level- if I can ever justify/pay for a Speedio, I'll just buy one) 5-axis plans as well. It's the dream, right?!
The bed is the axis I am referring to. And yes you are right that is normally the Y axis and I am turned around.
Not sure I can definitely answer this but one of my machines is kind of similar and I use one screw. So maybe this will provide some perspective. this is what it looks like I have a single belt driven 1605 on both x and y and they are 1:1. the motors are open builds high torque motors and the control is a BBx32. I know I would be better if I had geared them the way you plan to and maybe in the future I might try. I am able to make the parts I want and happy with the results. The bed is MDF on a 20"x15.5"x3/8" slab of mic-6 and some times I attach a low profile vice. So my guess is your on the right track for as heavy as your bed and vice will be. Hope this helps.
With the aspect ratio of your plate, I would say it's probably a good idea especially if you plan to cut metal.
