First machine build

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Aaron3309
Posts: 3
Joined: Wed Nov 27, 2019 9:45 am

First machine build

Post by Aaron3309 » Fri Nov 29, 2019 4:26 pm

Looking to build my first machine, right now my experience is limited to a shapeoko router but I’ve been researching plasma tables for several months. I’m a mechanic and welder by trade so I’m reasonably handy.
I have so far decided on a 4x4 water table design, 20mm linear rails and direct drive rack and pinion from nema 23 or 34 steppers.
For electronics I am thinking Uc400eth controller, Gecko g540 driver and neuron lite thc using Uccnc.
Is anyone using this hardware setup, we any problems or have any suggestions?

Rodw
Posts: 284
Joined: Sun Aug 21, 2016 1:49 am

Re: First machine build

Post by Rodw » Sat Nov 30, 2019 2:44 am

I would not recommend a direct drive rack and pinion. You need a 3:1 to 5:1 reduction drive. If you are accurate, there is no need for a spring loaded pinion. You need about 25mm travel per motor revolution and you will be up over 90mm per revolution. Motion will be very jerky.

There is a Plasma primer document as part of linuxcnc which you may find helpful regardless of your chosen platform. http://linuxcnc.org/docs/devel/html/pla ... rimer.html
Full disclosure: I wrote it

By the sound of it, coming from Grbl, you are not really wedded to the Windows platform. Before you make a decision on hardware, have a look at the Plasmac config which is now part of the Linuxcnc distribution for V 2.8 and up. http://linuxcnc.org/docs/devel/html/pla ... guide.html
It is vastly superior than any external THC can ever hope to be becasue torch height is being managed right inside the motion controller resulting in a superior design. Should you go this way, I'd suggest that you look at the ethernet Mesa 7i96 ($119) and a Mesa THCAD card ($69). The high performance THC is managed within the LinuxCNC PC itself.

Because you will not be using a parallel port breakout board, the Gecko 540 is not a good choice. So using Leadshine or Longs Motor drives will be the ticket.

I get excellent performance from Longs Motor DM542a drives off eBay driving NEMA 23 and small NEMA 34's up to 21 metres per minute using Mesa hardware running Linuxcnc and Plasmac.

Aaron3309
Posts: 3
Joined: Wed Nov 27, 2019 9:45 am

Re: First machine build

Post by Aaron3309 » Sun Dec 01, 2019 10:10 am

Wow glad I joined the forum, I knew i would be able to get the info I needed here. So I have just a few follow up questions if you don’t mind I really appreciate the help.

What method of gear reduction do you suggest? Gear or belt or?

Do you have any power supply you recommend?

Would there be much of a difference between interfacing with an everlast or a hypertherm plasma, I may start with everlast and upgrade later depending on budget.

Thanks again.

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acourtjester
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Joined: Sat Jun 02, 2012 6:04 pm
Location: Pensacola, Fla

Re: First machine build

Post by acourtjester » Sun Dec 01, 2019 11:32 am

The are many excellent ways to built a table that will give years of service, do your research a settle on a design you like. Different drive, electronics and controller are some of the differences. There is member who have built their own table and have post construction details. Rodw is correct with no direct drive but ones that had reduction built in. Attached is the way I do the reduction for a rack and gear drive a belt drive is used from the motor to a secondary shaft with the gear mounted. I do use direct drive for a lead screw on the Z axis, with a 10 turn per inch lead screw.
The connection to the plasma unit is made with a plug on the back of the unit, if you Everlast are fairly new it should have one and the manual will show it. You should be using one that has “Blowback” type start for the plasma sequence, Hi Freq of Hi Voltage are not good for CNC work.
I have built 8 table and buy a kit with the Motors (1 nema 34 and 2 nema 23, 2 power supplies, and the drivers for those motors).
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Rodw
Posts: 284
Joined: Sun Aug 21, 2016 1:49 am

Re: First machine build

Post by Rodw » Sun Dec 01, 2019 3:06 pm

I use belt drive reductions on gear racks. Power supply is a 10 amp meanwell 48v for motors and you would need a 2amp 24v power supply for a mesa card plus a 5 volt one if you choose the 7i96. Plus another 24v for ohmic sensing. The everlast will work for you but Hypertherm or thermal dynamics is much better. There are some traps with the everlast voltage divider I documented on this forum.

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