Shed plasma build

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14 Aug 2020 13:10 #178181 by Mud
Shed plasma build was created by Mud
Some pictures of my work-in-progress build - I'm at the niggly stage where it seems close to usable but nothing is progressing! I'm waiting on daft things like a small bit of angle steel and a relay. It is not my first machine build but my first plasma, and the only linuxcnc machine I've done previously was a simple parallel port job on a router (I added tool length measurement and sensor debouncing only). This one uses a 7i96, THCAD-10, and a GYS 40FV plasma cutter. Lots of the design decisions are based on getting a decent quality machine whilst minimising cost and construction effort, e.g. the aluminium profile was free (best score of my life!), and the aluminium is up to 25mm thick in places since it is offcuts...so there's plenty on there I would change for a do-over (and I may go back in to add lightness). I designed it to accept a 1,000x1,000mm sheet since this appears to be a standard size (travel more like 1200mm in x). The huge cabinet is unfortunately GFRP but cost me £20...so I hope my blow-back start gives me a head start on the EMI...

x and y rails are hiwin 20mm clones
z rails are genuine hiwin 15mm with a THK 1204 ballscrew (seems wasteful but had these sitting around)
float and scribe rails are genuine THK - ~£20/each off ebay!
NEMA24 hybrid steppers on x/y (geared for ~15mm/motor rev using rack and pinion)
NEMA24 on z
the tank is luxurious 1.5mm 316!

I intend to be able to use a pen or a diamond drag tool in the scribe, and it is capable of firing into the work quite forcefully, so possibly a centre punch too. It accepts anything up to 1/2" since it takes ER20 collets.

A note on the hybrid steppers - they were chosen only because they appear relatively high performance - the encoders are a mere 5V though, so may end up causing problems (I'm using 5m extensions on y and x2, and a 3m extension on x1). The encoders use VGA connectors, and I have found higher quality VGA extenders to be acceptable (at least just jogging the machine around with no torch). You can use the standard VGA panel mount connectors with screw breakouts with a minor modification as one pin isn't a standard VGA one. Just cutting off the connector at the motor and using shielded cable might have been a better idea. Will see if these bite me later.
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14 Aug 2020 15:21 #178192 by tommylight
Replied by tommylight on topic Shed plasma build
Very nice.
A magnetic holder for the torch would be very advisable.

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14 Aug 2020 15:32 - 14 Aug 2020 15:35 #178193 by Mud
Replied by Mud on topic Shed plasma build

Very nice.
A magnetic holder for the torch would be very advisable.


It was on my mind, but I may have to scare myself to commit to making one as a priority. I'm unlikely to leave the machine unattended ever, but with no plasma experience I don't know if that's adequate remedy. I don't want to dunk the torch!

edit to add - the torch is currently a nice friction fit in the holder (much time with the boring head!) - not sure if you could rely on a bit of upward force to pop it up and out. I could whack a microswitch on there as a presence sensor.
Last edit: 14 Aug 2020 15:35 by Mud.

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14 Aug 2020 16:33 #178196 by tommylight
Replied by tommylight on topic Shed plasma build
There is no substitute for a light and sensitive floating head/switch combo, the latest ones i have built require about 2KG of 4lbs of upward force to trigger and stop the machine. Left it intentionally doing that for over a week every day all day, never fails to stop the machine ! :)

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14 Aug 2020 16:43 #178198 by Mud
Replied by Mud on topic Shed plasma build

There is no substitute for a light and sensitive floating head/switch combo, the latest ones i have built require about 2KG of 4lbs of upward force to trigger and stop the machine. Left it intentionally doing that for over a week every day all day, never fails to stop the machine ! :)


The float activates on a small throw (proximity sensor acting off that small L bracket) with lots of room for over-travel, and currently just acting under self weight (I would guess similar to your 2kg figure). I can add springs to add/remove force (why I made it a funny shape). I hadn't much considered the touch off needs to be a lighter touch than a breakaway though!

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14 Aug 2020 17:52 #178201 by tommylight
Replied by tommylight on topic Shed plasma build
They both have it's uses and combining both will save a lot of money and headache changing torches.

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14 Aug 2020 18:33 #178202 by Mud
Replied by Mud on topic Shed plasma build

They both have it's uses and combining both will save a lot of money and headache changing torches.


I've ordered bits to make a miniaturised version of this - seeing it catch the torch was enough to sway me...not sure why that wasn't an obvious option to me! B)
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16 Aug 2020 00:35 - 16 Aug 2020 00:55 #178340 by thefabricator03
Replied by thefabricator03 on topic Shed plasma build
I like how the control cabinet is so big it makes the components inside look tiny! Good Job.

Also with the closed loop steppers, I use them on my large industrial machine and the longest cable run is just under 15 meters. I have not had any issues with encoder noise. But I am using Leadshine motors, drives and cables.
Last edit: 16 Aug 2020 00:55 by thefabricator03.

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16 Aug 2020 08:32 #178368 by rodw
Replied by rodw on topic Shed plasma build

They both have it's uses and combining both will save a lot of money and headache changing torches.


I've ordered bits to make a miniaturised version of this - seeing it catch the torch was enough to sway me...not sure why that wasn't an obvious option to me! B)


Use 3 ball bearings, not 4 as its much easier to get it to fit. There is a good plasma cut design on the plasmaspider forum by a user SeanP

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16 Aug 2020 13:39 - 16 Aug 2020 13:43 #178405 by Mud
Replied by Mud on topic Shed plasma build

I like how the control cabinet is so big it makes the components inside look tiny! Good Job.

Also with the closed loop steppers, I use them on my large industrial machine and the longest cable run is just under 15 meters. I have not had any issues with encoder noise. But I am using Leadshine motors, drives and cables.


Amazing how the space disappears! I thought I'd fit controls for two machines in there...

They both have it's uses and combining both will save a lot of money and headache changing torches.


I've ordered bits to make a miniaturised version of this - seeing it catch the torch was enough to sway me...not sure why that wasn't an obvious option to me! B)


Use 3 ball bearings, not 4 as its much easier to get it to fit. There is a good plasma cut design on the plasmaspider forum by a user SeanP


I'll try to modify the torch holder I've made - I was also thinking 3 balls (less over-determined). I'll look up SeanP's for further inspiration.

I made the last target required, so now it homes: link
Last edit: 16 Aug 2020 13:43 by Mud.
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