Posts made by maukvdlaan

@catalin_ro Thanks for your ideas! I plan to mount the gantry against the wall, so the whole Y-table moves free vertically. Same design, but totally different use.

I do this because i want to have multiple spindles on the gantry as a kind of a cheap toolchanger, so it would become too heavy.

But there are more advantages: it saves floor space, the chips simply fall down, there could be a second gantry, or even spindles that mill from the sides.

As for the Y-nuts: i think that the forces involved in moving the table are comparable to moving the gantry, but the table has two motors and bigger nuts (more threads).

You are right about the way the wheels are used, especially on the gantry. I have to change the gantry anyway to hold more spindles. I would like to rotate the gantry extrusion, maybe make it stronger with steel.

I will have some fun with it, and post some videos when it works.

@catalin_ro I agree with the 40mm/s when milling, because of the forces involved. At that rate (5 rpm) the steppers still have a decent torque. But when not milling, rapid feeds of 100mm/s seem to work fine. But i will keep an eye on the wear of the delrin nuts of course!

This is going to be fixed gantry machine, mounted vertically on a wall, with the Y-axis moving up and down. I choose the workbee design because it speads the load on the Y-axis between 2 motors and nuts.

@dc42 So what caused the different currents? Is there some default mapping for drive 4? It worked after removing the E mapping.

@typqxq I also tried your solution and it works. I was wondering if i could get rid of that unused extruder output, so thanks.

@veti Thanks, that helped. Now the machine moves reliably at 100mm/s.

M569 P0 S1                                  ; Drive 0 goes forwards (X)
M569 P1 S0                                  ; Drive 1 goes forwards (Y-1)
M569 P2 S0                                  ; Drive 2 goes forwards (Z)
M569 P3 S1                                  ; Drive 3 goes forwards (E1)
M569 P4 S0                                  ; Drive 4 goes forwards (Y-2)

M584 X0 Y1:4 Z2                             ; map motor drivers to dual Y

; 16 steps w/interpolation
; 1 rot = 200 steps = 8mm = 25 steps/mm. 
; full-step resolution 0.04mm
; x16 = 400 steps/mm
; max speed 5rpm x 8mm = 40mm/s, 2400mm/min
M350 X16 Y16 Z16 I1                         ; Configure microstepping
M350 E16 I1                                 ; Configure microstepping with interpolation
M92 X400.00 Y400.00 Z400.00 E420.00         ; Set steps per mm

M566 X400.00 Y400.00 Z300.00 E120.00        ; Set maximum instantaneous speed changes (jerk) (mm/min)
M203 X6000.00 Y6000.00 Z6000.00 E1200.00    ; Set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z150.00 E250.00        ; Set accelerations (mm/s^2)
M906 X2000.00 Y2000.00 Z1400.00 E800.00 I40 ; Set motor currents (mA) and motor idle factor (40%)

M84 S15                                     ; Set idle timeout (15S)

@veti M906; Motor current (mA) - X:2000, Y:2000, Z:1400, E:800:800, idle factor 40%

Hi,

I am experiencing problems with my workbee 1000mm CNC. It has two independant motors for the Y-axis.

It all works, but it seems that one motor gets less current then the other. One motor stalls on fast moves. And after the idle timeout, i can rotate one motor by hand while the other is still strong. It seems to me that the second Y motor still has some lower current setting.
If i reverse the cables on the board the other motor becomes weaker, so this eliminates motor, driver or wiring differences. I tried upgrading to 2.02 but no change.

Some data: 24V, 2A current, Y connected to P1 and P4 (M584 X0 Y1:4 Z2).

Any ideas?

Mauk

@catalin_ro Thanks for the replies everyone! I will give it a try with the duet. I will strenghten the x-axis with small steel strips for more rigidity. But i will have to test it of course, i will keep you informed about the results.

@joergs5 I just read about the duet 3... it would be a waste to buy a v2 now, especially since i need an expansion board as well. @duet people: do you need a beta tester? i am a seasoned embedded developer and electronics guy.

@joergs5 Yes that is another approach of course, with less moving mass. And it could even have two x-axis. Are you using duet electronics?

@t3p3tony Thanks. Would switching stepper drivers while the others keep their hold current be possible as well?

About the mass - I plan two 500W's for milling POM and aluminium. The others would be lighter motors for drilling, chamfering and tapping and an edge finder. So i guess 5kg would be a reasonable guess for the total weight.

I have experience with a MiniMill with DRV8825's and it looks strong enough to me. But for this new design i will use heavier steppers and i hope that the trinamics will work out better. Can anyone confirm that?

I also plan to mount this machine vertically on the wall. The weight of the x-axis would be on the Y steppers and the Workbee has two of them, sharing the load. Not only does it take less space that way, but i like it that the chips will just fall on the ground.

@chris Yes nice! But difficult to build i guess. I really like the openbuilds system and i guess it would be easy to adapt.

Hi, i am designing a modified Workbee CNC. It will become a small production machine that requires some form of automatic tool changing.

Since toolchangers are difficult to and expensive, i want to mount six spindles on a wide x-axis plate. Each spindle can move vertically with its own z-axis stepper. So all spindles will move x-y at the same time, but only one is 'down' and actually milling.

The software has to maintain a table of spindles/tools with x-y offsets and tool heights. When it executes a toolchange, it should raise the current spindle to a safe height and lower the new spindle while adjusting to its offsets.

For this machine I could use a duet with expansion board to drive the 10 stepper motors.

Has anyone ever built a CNC like this? And would the firmware support it?