CNC Sewing machine question

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05 Aug 2019 23:37 #141463 by SPH
Replied by SPH on topic CNC Sewing machine question
You've seen this guys video yeah?

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06 Aug 2019 13:15 #141524 by rjd1234
Replied by rjd1234 on topic CNC Sewing machine question
I agree SPH. Right now my strategy is to have the needle stepper running constantly, but have the x/y moves take place when the needle position is between 160 and 360 degrees. The needle is down between 0 and 160 degrees.

The piece I am missing is:
- how do I measure the stepper position while it is in spindle mode?

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06 Aug 2019 13:16 #141525 by rjd1234
Replied by rjd1234 on topic CNC Sewing machine question
Yes, I have seen that video. That is basically how mine is running now.

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12 Aug 2019 20:37 #142000 by andypugh
I think that the way to do this is to use adaptive-feed to halt the fabric when the needle is down.

How do you know the needle position? The stepgen outputs a position. If you add homing for the spindle then you can use a custom HAL component to output the adaptive-feed ratio.

But how to home a spindle? Currently that's not built-in behaviour. But it could be part of your custom hal component

Have you seen the commercial sewing machine servos? They are surprisingly cheap, and have a rudimentary encoder:
www.ebay.co.uk/itm/392335513626
as an example, Cheaper ones exist, and more expensive more powerful ones too.

I think I would be looking to use one of those, and then try to work out the adaptive feed from the needle-up signal and some cleverness in a HAL component.

The stepper should work, but the dedicated motors are a lot more powerful.

Tell us which way you want to go, and I think we can come up with something.

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08 Jan 2020 12:16 #154303 by ahmetbm
Replied by ahmetbm on topic CNC Sewing machine question
Hi,
I am sorry if here is not the right place to ask this question.
I am developing a cnc sewing and cutting machine.
I am using 2 different motors to move hook and needle seperately as an axis(Z and A) and 2 other motors for x-y movement.
However i have a problem, what should i do when thread is broken?
Thanks.

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08 Jan 2020 12:45 #154305 by andypugh
You could trigger a program-pause.

halui.program-pause

linuxcnc.org/docs/2.7/html/man/man1/halui.1.html

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08 Jan 2020 13:59 #154308 by ahmetbm
Replied by ahmetbm on topic CNC Sewing machine question

andypugh wrote: You could trigger a program-pause.

halui.program-pause

linuxcnc.org/docs/2.7/html/man/man1/halui.1.html

Thank you.
How can i be sure the needle is at top position?
In other words how can i pause when needle and hook motors are complated revolution?

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08 Jan 2020 14:33 #154310 by andypugh
How are you controlling the machine? Is the needle slaved to XY?

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08 Jan 2020 17:03 #154319 by ahmetbm
Replied by ahmetbm on topic CNC Sewing machine question
I added needle and hook as 3rd and 4th rotary axes and they are not slave to xy. X and Y are linear.

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08 Jan 2020 17:13 #154323 by andypugh
By "hook" do you mean "foot"?

If the needle is a rotary axis then you can just make sure you only stop at specific positions?

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