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Upgrading a CNC milling machine Part 1

stuartChilds
13
maker, hacker, doer

Comments

[Comment was deleted]

February 25, 2019 13:29

I realize this is an old thread, but did you happen to keep the original control board? If so would you be willing to sell it?

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March 4, 2019 09:03

@JASONVQUICK we may have and if so, you can have it. Drop me an e-mail andrew HAT abopen DUT com. I can have a rummage next week...

September 16, 2015 10:04

@Shrikant:
Thanks for the comment and well done for spotting our error. You have in fact highlighted two things that we have now fixed.

Firstly, the diagram showed example values from the GeckoDrive website, and in copying the text was changed in error - from 5,882 uF to 5.882 uF - the comma replaced with a full stop!

Secondly, it showed to me that it would be more appropriate to use our actual values, rather than simply example values from the GeckoDrive site. Therefore I have changed the values in the diagram to reflect this.

Note that there are two independent supply rails - each with their own bridge rectifier and smoothing capacitor - shown in the photograph.

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September 16, 2015 04:55

The DC power supply circuit shown contains capacitance value of around 5uf., but I feel the capacitance value must be 14000 uf.
On PCB, mounted capacitance value is showing two 10000uf which works.

My calculation of capacitce is C = Rl / 1000. where C in farads, Rl load resistance I ohms. Rl is calculated by dividing DC voltage / DC Max., Load curret.

Thu Rl = 68/5 = 13.6 Ohms = App. 14 ohms.

C = 14/1000 = 014 farads i.e. 14000uf. ay value more than this Value is suitable.

Thus the calculation shown in circuit diagram is not correct.

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June 23, 2015 14:26

@wellnitzeli no position feedback and just relies on the steppers. Note that parts 2 and 3 are now up.

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May 26, 2015 13:56

I couldn't tell. Does this mill have position feedback or does it just rely on the steppers?

I'm also looking forward to part II.

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May 25, 2015 18:07

@connectable

Usually the rectifier bridges have a hole to attache them to a heatsink, only low power ones do not have holes

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May 25, 2015 15:25

The holes in the bridge rectifiers are for mounting screws. If they pull heavy current, they should be mounted to a heatsink.
Excellent project, btw.

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May 25, 2015 14:22

Sue wrote:

> My experience since then is that whilst a bit more complicated in terms of hardware,
> it is better to have a local controller to drive the steppers, &c. rather than rely
> on the PC (unless it is running an absolutely dedicated control program without
> an Windows OS, e.g. TurboCNC under DOS) .

One of the benefits of the BeagleBone is that, in addition to having an ARM processor which runs Linux, it has a Programmable Realtime Unit (PRU) — a microcontroller that can be used to generate pulses without the overhead of an O/S.

Nice project btw!

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May 25, 2015 13:38

connectable, those holes are intended to mount the rectifiers to a heatsink, they can get quite hot.

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Sue

May 25, 2015 10:18

Hi, excellent piece. I look forward to Part II.

I did something similar to an Emco F1 CNC mill back in 2004, although in that case I interfaced directly to a PC running Mach3.

[attachment=0:1l82trpy]susan-stepper-drive-box-2004-1-1200.jpg[/attachment:1l82trpy]

My experience since then is that whilst a bit more complicated in terms of hardware, it is better to have a local controller to drive the steppers, &c. rather than rely on the PC (unless it is running an absolutely dedicated control program without an Windows OS, e.g. TurboCNC under DOS) .

The biggest challenge was machining sleeve adaptors to convert the new stepper motors' 6.0 mm shafts to match the 1/4" shaft apertures in the timing belt pulleys (of course I could have got 1/4" shaft steppers, but I was using what I had to hand).

[attachment=1:1l82trpy]susan-shaft-adapter-1-1200.jpg[/attachment:1l82trpy]

So now I still use Mach3 but have an 'Ethernet SmoothStepper' controller to twiddle the control lines (no more dropped steps).

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May 25, 2015 09:52

I wonder why the Bridge Rectifiers have holes in them?

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May 20, 2015 15:08

Stuart, thanks for this and I'm really looking forward to the next part. I've been planning something similar for a while now, I was going to use a small PLC for the control so I'm really interested in how you get on with your solution.

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