4 Steppers on one Driver

Has anyone ever wired 4 steppers from one driver? The RAMPs board has two parallel outputs for the z-axis. I was thinging of wiring two pairs of 36 oz-in steppers in series, then connecting the two pairs in parallel by way of the two z-axis outputs on the RAMPs board. Will this draw too much current for the driver, or lose too much torque. I'm using a 12V regulated power supply. I have both A4988 and DRV225 drivers to try.

Edited 1 time(s). Last edit at 06/04/2015 04:03PM by runninfarmer.

Too much current for one driver

Quote
runninfarmer
I was thinging of wiring two pairs of 36 oz-in steppers in series, then connecting the two pairs in parallel by way of the two z-axis outputs on the RAMPs board.

It's worth trying. Ideally you would increase the voltage beyond 12v. But with typical stepper motors that only drop 2 to 3V at full current, 12V will probably be enough as long as you are not looking to achieve high speeds from those motors.

Quote
Floyd
Too much current for one driver

2 motors in parallel (as implemented on RAMPS) is already too much current for one driver, if you are using typical motors and want to drive them at anything approaching their rated current. It's usually much better to connect the motors in series, as RepRapPro does in their kits.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

How much is torque and speed affected by wiring all four motors in series using 12V? Would I need to go up to 24V with all four in series? I wouldn't need high speed since it's the z-axis.

Edited 1 time(s). Last edit at 06/04/2015 06:57PM by runninfarmer.

12V is probably not enough for 4 motors is series. Can you post the specification of the motors?

I think Marlin can be configured to drive two Z motors connected to separate drivers, using the 5th driver slot on a RAMPS. You could use this arrangement and connect 2 motors to each driver.

If you wire motors in parallel, the maximum torque is reduced unless they are low current motors. Ìf you wire them in series, maximum speed suffers unless you also increase the supply voltage.

Edited 1 time(s). Last edit at 06/05/2015 03:29AM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Keeping four motors synchronized, if you're using them to lift the corners of the print bed or undercarriage, is going to be a real challenge, whether they all connect to one driver or you use separate drivers for each. The electronics to drive multiple motors in sync is the easy part. The mechanical stuff is the hard part. I hope your're using lead screws and not threaded rods. All you need is for one screw to bind a little and miss a few steps and that will cause the whole thing to bind. You're going to spend a lot of time adjusting and readjusting the level position.

Why four screws and not three? Three screws fully constrains motion to a plane. Adding a fourth creates an over-constrained condition. Think about what happens if one screw binds and the motor misses steps. The other three corners are locked to the screws driving them, so the plate has to flex. If the plate is trying to flex, it will increase the load on the other screws which may cause one or more of those to bind. Where does it end? You're going to be spending a lot of time aligning and realigning the plate.

It would be much better to keep the screws synced with a belt driven by a single motor.

I'm using 4 screws because I'm doing an XYZ moving gantry and and wanted overconstraints to prevent X/Y movements from throwing the z-axis off. They are also 8mm 4 start leadscrews