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Re: New Build - CNC Plasma Table

Posted: Wed Aug 31, 2022 1:33 pm
by landmark573
I'm warming up to the idea. Maybe I will start by welding up the frame. I have rolled it in and out of the garage hundreds of times with it just being tacked together :lol:

Re: New Build - CNC Plasma Table

Posted: Wed Aug 31, 2022 4:22 pm
by ShawnM
That would be a great start, a good, solid, heavy machine bed is always better.

Re: New Build - CNC Plasma Table

Posted: Wed Aug 31, 2022 7:17 pm
by landmark573
This gear motor looks interesting. It has a 12mm keyed output shaft.

https://www.ebay.com/itm/333582829153?m ... media=COPY

Re: New Build - CNC Plasma Table

Posted: Wed Aug 31, 2022 9:55 pm
by ShawnM
landmark573 wrote: Wed Aug 31, 2022 7:17 pm This gear motor looks interesting. It has a 12mm keyed output shaft.

https://www.ebay.com/itm/333582829153?m ... media=COPY
Stepperonline has a bunch of great products. Have a look at their website. Many forum members have purchased from them. Just make sure you can get the proper pinion gear for a specified motor shaft BEFORE you buy it. They also sell real good stepper drives that are rather inexpensive as well.

Re: New Build - CNC Plasma Table

Posted: Thu Sep 01, 2022 7:10 am
by repauli1
Have you looked at the 3:1 avid cnc belt reducers, they work great.

Re: New Build - CNC Plasma Table

Posted: Thu Sep 01, 2022 10:08 am
by landmark573
repauli1 wrote: Thu Sep 01, 2022 7:10 am Have you looked at the 3:1 avid cnc belt reducers, they work great.
Thanks for the suggestion. I have looked at the avid belt reducers. Unfortunately, I would have to replace my racks and carriages to use them. I was hoping to just add gearboxes to my existing motors. But I'm having trouble finding parts that will fit.

I just looked at your build thread. Your table looks great. In one of your videos cutting the "hook" demo part it looks like the feed rate was accelerating going into the curves just like what I'm seeing with mine. Have you had an issue with that?

Re: New Build - CNC Plasma Table

Posted: Thu Sep 08, 2022 2:06 pm
by landmark573
I found a 5:1 gearbox that will fit my existing nema 23 motors. It says the no load backlash is <= 15 arcmin. Most other gearboxes I’ve looked at are rated at .8 degree. If I understand arcmin’s correctly then 15 arcmin would be much better at .25 degrees. That sounds like an acceptable amount of backlash, right?

https://www.omc-stepperonline.com/ple-s ... le23-g5-d6

Re: New Build - CNC Plasma Table

Posted: Thu Sep 08, 2022 6:40 pm
by ShawnM
It is what it is, you cant change it so why worry. Those are nice gearboxes, a local guy near me has those same gearboxes. Just make sure your machine and frame is solid and everything is bolted tight and critical hardware has Loctite on everything. Once all that is done and you have the mechanical backlash to a bare minimum you can take out the rest of the backlash in the software, that is if it's very minimal. Backlash compensation will not help you if you have a poorly constructed machine but will help with the minimal backlash in the gearboxes. Build the best, solid machine you can to start with.

Re: New Build - CNC Plasma Table

Posted: Fri Oct 21, 2022 12:54 am
by landmark573
I haven’t posted any updates for a while now but I have been busy working on the table. My cut quality hasn’t been great but I can make useable parts. The biggest upgrades have been building the controller cabinet and installing 5:1 gear reduction units on the X and Y axises. I did have direct drive rack and pinion motors with an OTR of 0.423841. With the addition of the gearboxes the OTR is now 1.59155 putting me in the sweet spot. I’ve updated my photo album and will add some videos hopefully showing improved cut quality.

https://photos.app.goo.gl/kNqNsR1g1UCafaFBA

Re: New Build - CNC Plasma Table

Posted: Fri Oct 21, 2022 3:15 pm
by landmark573
First cut after adding gearboxes. Material is 1/8” a36. Cutting at 35 amps, 100 ipm, and smoothing turned on. I wasn’t able to use smoothing without the gearboxes. One thing I’ve noticed without smoothing is the feed rate for circles and curves slows way down and speeds up to the profile rate on straight cuts. With smoothing on it looks like the speed rate may actually increase on circles and curves.

https://photos.app.goo.gl/Zk3wgBmVnnhcmPDq6

I will post a report after running some more test.