Indexing head

[Johno1958]

This is my first ever project I have built.
Thank you to cfellows and rodw ,works like a charm.
Cheers
John

 

[gabby]

congrats that's a very tidy wee unit
Gabby

 

[Herbiev]

Well done. Looks great.

 

[Johno1958]

Thanks very much.
I did have a little trouble with the TB6560 driver I used but at 10 dollars and a little bit of fiddling it doesn't miss a beat.
Cheers
John

 

[rodw]

Very nice. Did you adopt an existing sketch or change it to suit yourself?

 

[Johno1958]

Thanks Guys
Rod I"m using your sketch which is slightly modified in the parameters.
Micro steps 16.This is the only way I can get it to run sweetly without it groaning and missing steps.
Ratio 6 .The head is only temp. until I can afford a table.
Max Frequency 8000
Timer Delay 70
I'm using a 24 volt 5amp wall wart type power supply with a 100uf cap to filter it a little more.The stepper motor is quite powerful 1.8 amp 333oz inch motor and holds very well using a spanner to test. Er25 collet.
Accuracy using a protractor is spot on and i can run it back and forth for an hour using all functions, hit the home button and straight back to where I set it.
The TB6560 is rated at 3 amps stepper . 30volts. All inputs are earthed except
Enable.
I have to thank you again for the effort you put into that program.
Cheers
John

 

[rodw]

Johno, thanks for the wrap, I'm glad you got value out of my sketch. One of these days I will move my temp setup into a box. I got a bit distracted after I started to build a plasma table with the left over stepper controllers.

8,000 Hz sounds about right. I have to say since I have been playing with LinuxCNC, my Arduino stepgen algorithm could be improved. I made a deliberate decision that the step pulses for on and off would be the same length to simplify the code. LCNC has a more sophisticated stepgen algorithim. When I tested it, LCNC can run at almost double the stepgen frequency I got out of the Arduino using the same stepper controller.

Having said that, my algorithim was no better or worse than the other Arduino stepper motor sketches out there. So my Mesa card with its inbuilt stepgen lets me do something like 55,000 Hz as I am using 25x microstepping. This equates to about 700 rpm vs the 400 rpm I could get out of the Arduino.

 

[Johno1958]

Just had a look at your plasma table thread and WOW you don't do any things by half measures . Its all over my head but but all I can say is WOW lol.
Cheers
John

 

[rodw]

Just had a look at your plasma table thread and WOW you don't do any things by half measures . Its all over my head but but all I can say is WOW lol.
Cheers
John

Yeh, it kinda got out of hand. I just hope it all works once I join it all up. It all started becasue I had some spare stepper controllers...

 

[Herbiev]

Just wondering where you got your TB6560 from. I have bought two so far and each time they blew up after only a very short period.

 

[Johno1958]

Hi
Got the TB6560 from ebay for 10.27 dollars free postage.
http://www.ebay.com.au/itm/CNC-Rout...ivers-TB6560-3A-driver-board-GO-/371474309278

Sainsmart sell them although a little more expensive. They all look to made by the same company.
Cheers
John

 

[MachineTom]

How do you intent to lock the spindle when machining the work. A brake of some sort?

 

[Johno1958]

Yes I was thinking that I may have to lock it down some how but for small parts If you check out cfellows thread
http://www.homemodelenginemachinist.com/showthread.php?t=17896
I may not have to do this but I haven't tried it out yet. I really made this for a rotary table which won't be that far down the track.
Got me thinking now .
Cheers
John

 

[rodw]

I'd wait until you try it, you might be surprised how much holding torque your stepper motor has.

 

[MachineTom]

Having worked with RT's, DH's and simple indexers, When you try to square the end of a .625 round to .500. you will find out what kind of forces are put into the work from the cutting tool. Both my DH, and RT's have spindle locks, even though they have worm gearing. 40:1, and 90:1. These can't backfeed torque, but any backlash in the gearing shows in the work. A toothed belt is not a good choice as applied here.

 

[Johno1958]

I'll have to give it a go on the weekend and see how much chatter going to happen.
Cheers
John

 

[John S]

Having worked with RT's, DH's and simple indexers, When you try to square the end of a .625 round to .500. you will find out what kind of forces are put into the work from the cutting tool. Both my DH, and RT's have spindle locks, even though they have worm gearing. 40:1, and 90:1. These can't backfeed torque, but any backlash in the gearing shows in the work. A toothed belt is not a good choice as applied here.

First one I built had a massive type 42 motor on it and quite a low belt drive reduction. First job I did was a set of splines and after two splines the job was scrap as they were traveling in a spiral due to cutting forces.

That went into the scrap bin and got replaced by a stepper driven dividing head at 40:1 ratio and never looked back.

These belt driven ones seem to come from China as positioning for laser cutters where it's all non contact but now, because they are easy to make they have gotten very popular but I question how many actually get used ?

 

[Johno1958]

Sorry for taking so long.
I haven't tried it out yet but I have given it some thought. If I need to I will
fit a clamping collar to the front of it. I have 15mm of shaft protruding out the back .
Cheers
John

 

[Johno1958]

I have just upgraded my little indexing head to a 6" vetex rotary table 90:1 ratio. I also upgraded to tb6050 stepper driver to a cheap Leadshine
closed loop driver knock off and a 36 volt 9 amp power supply. It appears to be working very well. You may notice two leads coming from the stepper , one
is an encoder. Suppose to be accurate and will bring up an error code ( flashes out a code on a red led ) if some thing goes wrong like missing steps or over shoot
or under voltage ect.
John

 

[rodw]

Be careful Johnno, You will get the CNC bug with your first upgrade behind you now! ooops, I just purchased a 120 amp plasma cutter to go on my table. Pierces 16mm thick mild steel and edge starts 25mm! Very nice upgrade of yours though!