Aluminium Extrusion Router Build

[NFryer]

Hi everyone, just a quick question regarding the design of the linear power supply for the stepper motors. I'm going with a transformer power supply and know to take into account the mains power supply variations to calculate the DC output but what margin should you leave for the voltage rise caused by the motors back EMF. Also I'm using quite a large toroidal transformer as I've got 4 motors to power, does anybody use inrush current limiting, as there are some nice looking 16A Sedlbauer current limiters on eBay at the moment for £30. Thanks in advance for any help.


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[Clive S]

What size toroidal, what motors and what drives are you using? Too many varables

[NFryer]

What size toroidal, what motors and what drives are you using? Too many varables

Hi Clive,

The drives and motors I'm using are the Leadshine Hybrid Stepper ones, HBS86 drive and 60HBM30-1000 NEMA24 motor. The drive has a maximum voltage rating of 80VDC. The toroidal transformer which I haven't got yet will probably be a 45VAC+45VAC 1000VA one from Airlink transformers. I did the following calculations to arrive at this, and if you see any obvious errors can you tell me.

The motors are 2 phase with a current of 5A per phase so 10A per motor. The motors have 4 power leads which means that they will probably be series wound so I think that the motors will pull approximately a third of the maximum, so about 3.3A per motor. I'm using 4 motors so the total current draw should be about 13A.

For the voltage I took the mains voltage +10% as a worst case so

45VAC + 10% = 49.5VAC
49.5VAC + 4% for transformer regulation = 51.5VAC
51.5 multiplied by 1.414 = 72VDC
72VDC - 2.2V for the bridge rectifier drop gives roughly 70VDC output.

Hopefully this is alright and I haven't made any obvious errors.

[Clive S]

OK You might have been better with 8 wire motors wired in parallel as you would get more speed out of them I take it these are for a router. Although having said that I have no experience with the motors and drive you have.

I have 4 motors on my router running from a 500Va tx at about 70V with no problems. I doubt they would pull more than 8-9 A

Good luck with the build.

[wiremonkey]

Woohoo! That is one stout build and very clean work, particularly for not having a mill. Seriously, great stuff. I missed the type of linear rails you're using and do you like them? Also, do you have a supplier. I'm in the USA.
Thanks

[A_Camera]

Hi everyone, just a quick question regarding the design of the linear power supply for the stepper motors. I'm going with a transformer power supply and know to take into account the mains power supply variations to calculate the DC output but what margin should you leave for the voltage rise caused by the motors back EMF. Also I'm using quite a large toroidal transformer as I've got 4 motors to power, does anybody use inrush current limiting, as there are some nice looking 16A Sedlbauer current limiters on eBay at the moment for £30. Thanks in advance for any help.


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I am using inrush current limiter, I think it's a MUST have with toroidal transformers. If you have a mains fuse of 16A then you can use that one, but if your mains fuse is smaller then you should use a smaller one.

[NFryer]

Hi everyone, I've managed to get a bit more done on the router build, and have finished the 4 end plates which connect the 2 X axis aluminium extrusions, the corner legs and support the X axis ballscrews. I had to slightly alter the design as the ball screw on the fixed bearing end protruded through the end plate a bit more than anticipated. I had to make a simple rectangular cutout for the motor and a separate plate for the motor adjustment to tension the belt. To make the rectangular cutout I made a series of holes to get rid of most of the material and then used a end mill in the router and a template to neaten it up.

[Nickhofen]

Nice work!

[NFryer]

The second part of the update is the making of the motor mounting plates which were done in a similar way to the end plates. The 4 bolt slots were first drilled and then tidied up using the router and a end mill. This time I didn't use a template, just a side fence and 2 stops at the front and back. The centre slot was then made bigger then necessary to allow for larger pulleys to be used and because the motor face was not flat and had a raised centre part.

[routercnc]

Wonderful work. Anyone looking to build their first CNC machine without access to a mill should bookmark this thread as a great example of bootstrapping your way in.