[dyode]

Thought I would post some various THC options here; maybe somebody has tried one or more of them:

RobotT3 system:
THC3T 03 Stand Alone Plasma Torch Height Controller | eBay
Manufacturer's site: Mechanized cutting

Proma:
Compact THC 150 Proma ELEKTRONIKA Plasma Torch Height Control | eBay

MiniTHC:
Minithc Torch Height Controller THC | eBay

A compare list of the THC systems that CandCNC offers:
http://www.candcnc.com/THCSelect.html

THC300 series:
http://www.randyray.com/TexMicro/TMCTHC.htm


The THC301d and CandCNC DTHCIV systems both offer anti-dive features built in (and are, coincidentally, the most expensive systems).
The other systems just use a basic bias voltage comparison to control torch height; ok for following contours, but subject to the previously mentioned "dive" problem when crossing previously made cuts or changing direction.
I am thinking that any of these setups could be made to work with Mach 4; it's just that it is a new piece of software and people are lagging behind a little in making their systems work with it.

I have used PID controllers in other projects; I wonder how difficult it would be to add some kind of PID logic to the low cost THC systems? This could certainly be tuned to minimize or eliminate the torch dive problem.

I don't have experience with PID, but I wonder if routing the Z axis motor controls through MACH4 (not stand alone THC) and setting a soft limit minimum on the Z axis would be almost as good as an anti dive feature when cutting reasonably flat steel to overcome diving into previous cuts.

[modelaratrod]

Have you looked at flashcut ? I'm really happy with the repeatability of my flashcut / torchmate setup. It uses applied motion products stepper drivers.

[xjdubber]

dont think he wants to change from mach . However i second you on flashcut, extremely well built system made to last. Have one that i service that has been running for 15 years with very little problems.

[sewerzuk]

Have you looked at flashcut ? I'm really happy with the repeatability of my flashcut / torchmate setup. It uses applied motion products stepper drivers.

No, I haven't. I did just look at their website; looks like an "all-in-one" CAD/CAM system? They don't have prices listed...I'll give them a call.
I have purchased a license for sheetcam, but have held off on the Mach4 license until I decide what I'm doing for THC. The evaluation copy works fine for everything that I'm doing right now; no complex parts or large quantities.

My new Gecko drives showed up yesterday; I'll be installing them this morning.

[xjdubber]

you'll be happy with the gecko drives, did you think about changing the power supply to optimize motor speed?

[sewerzuk]

did you think about changing the power supply to optimize motor speed?

No; I hadn't considered it yet.
My current power supply is a fairly large transformer and rectifier (not sure of the specs on it; haven't looked at it in detail but based on the size I'm guessing it is capable of at least 10 amps) with a capacitor to smooth out the ripple. No regulation circuitry. It runs about 40v unloaded. I haven't watched the voltage during motor movement.
I kind of assumed that, as long as I wasn't topping out the current adjustment on my motor drives and that nothing was generating excess heat, that the power supply was sufficient. What should I be considering with regards to my power supply? I presume that additional motor current yields faster acceleration and more torque, but it wouldn't really change the top speed, correct? And since the motor current is an adjustment in the motor drives, adding additional voltage/current capacity in my power supply really wouldn't change much?
Since this isn't a production type machine, I'm not really interested in achieving really fast speeds. I'm more interested in good resolution and smooth cuts. I'm hoping that the Geckos will remove the slow speed buzz/jitter/skip that I'm getting right now, but if they don't I'll start looking at additional gear reduction.

[xjdubber]

I would say the gecko's would solve your low speed issues probably, Gecko has some documentation on their website for determining the best voltage for your stepper motors based on their specs. Speed is an extremely important factor of cnc plasma cutting, specially on thin gauge material the faster you can travel and accelerate the cleaner your cuts will be.

[LeeWay]

Yep. That is true. I cut thin gage aluminum at 220 IPM. Some material require's even faster cuts. That may not sound fast, but these are all very small curvy parts. It zips right around them in no time at all.

[sewerzuk]

specially on thin gauge material the faster you can travel and accelerate the cleaner your cuts will be.

I hadn't thought about needing to go faster on thin material for clean cuts; its just something I do naturally with the hand torch. I was more concerned with not being able to go slow enough without excessive "jitter" but I obviously need to consider being able to go fast enough for cutting thin material.

On another note, I installed the new Gecko G213V drives tonight. Pretty simple affair; it took me about 10 minutes to wire them up. WOW!! Such a huge difference; the motors run nearly silent now. No more jitters at slow speed, smoother accel/decel, no motor heating during hold, more torque, greater step resolution, etc. I should have done this earlier. The old motor drives are going in the scrap electronics pile. Money was well spent on those things...
At this point I do not think that I need additional gear reduction. I'm able to move both axis at extremely slow speeds with good motor torque and smooth operation.

Next step: THC

[LeeWay]

Heh heh. I remember thinking the exact same thing after my first Gecko drive install.

[sewerzuk]

Threw together a quick video of the table in operation with the new drives (inclduing a clip with one old drive and one new drive for comparison):

https://youtu.be/TrQcLBWscjQ

[sewerzuk]

I elected to start off cheap/simple for my Z-axis and bought the DC gearmotor Z axis off of Ebay. It arrived last night; actually seems to be a reasonably well-built piece considering the cost. Operation appears to be smooth and construction looks good. The linear axis has a spring loaded limit switch built in for setting initial torch height.
I don't have any way to drive the DC gearmotor; my 2 basic options:
1. Get some kind of DC motor controller that can take a 5v input signal from my ESS. Something like this could work: Electromen :: EM-243 DC-MOTOR CONTROLLER 12-24V 50A
2. Take the DC gearmotor off and install a stepper motor, and get another Gecko G213V to drive it

Option 1 is less expensive, but I'm thinking that option 2 might be the better way to go.
Any input from you guys?

Attachment 295448

[sewerzuk]

I haven't put any effort into THC yet; but I have been working the table for an hour or two each week.
I have burned out several smaller pieces of artwork, letters, etc. I made up link brackets, shock towers, and spring buckets for a 4x4 project I am working on. Most recently, I got a job rebuilding a bunch of electric Rollac shutters on a house; the house is beachfront and the owner asked me to replace steel parts with stainless. So, I bought some sheets of 18GA T304 and have been cutting parts out of that. I have the machine dialed in pretty well, and have learned quite a bit about creating accurate cuts with minimal cleanup.

The stainless work has highlighted the need for THC; that thin material warps quite a bit during the cutting process and I have to sit there with a welding hood and constantly babysit the torch. So, I'm moving ahead with the THC mod.
I already have the Z axis (see previous post). I have been stalling on purchasing a THC control system; I had my eye on some of the cheaper ebay systems, but never had the urge to put the work into making one of these work.
Yesterday, I managed to pick up an "almost new" open box/unused CandCNC LCTHC system off of ebay for cheap. I realize that I may have to do some tinkering and customizing to make it work with Mach 4, but I'm reasonably confident that I can put together a working system. I have some DB25 and DB9 cables, breakout boards, 5v relay assemblies, a current transformer, some project boxes, and shielded cable on the way. I'll be doing some late night tinkering for the next few months

[dyode]

I haven't put any effort into THC yet; but I have been working the table for an hour or two each week.
I have burned out several smaller pieces of artwork, letters, etc. I made up link brackets, shock towers, and spring buckets for a 4x4 project I am working on. Most recently, I got a job rebuilding a bunch of electric Rollac shutters on a house; the house is beachfront and the owner asked me to replace steel parts with stainless. So, I bought some sheets of 18GA T304 and have been cutting parts out of that. I have the machine dialed in pretty well, and have learned quite a bit about creating accurate cuts with minimal cleanup.

The stainless work has highlighted the need for THC; that thin material warps quite a bit during the cutting process and I have to sit there with a welding hood and constantly babysit the torch. So, I'm moving ahead with the THC mod.
I already have the Z axis (see previous post). I have been stalling on purchasing a THC control system; I had my eye on some of the cheaper ebay systems, but never had the urge to put the work into making one of these work.
Yesterday, I managed to pick up an "almost new" open box/unused CandCNC LCTHC system off of ebay for cheap. I realize that I may have to do some tinkering and customizing to make it work with Mach 4, but I'm reasonably confident that I can put together a working system. I have some DB25 and DB9 cables, breakout boards, 5v relay assemblies, a current transformer, some project boxes, and shielded cable on the way. I'll be doing some late night tinkering for the next few months

I'm in similar position with THC,I was thinking of a scratch design so I can modify/playwith the Z movement time constant for antidive function. I would be interested in what THC you settled on. See video of my1st cut at:
https://www.facebook.com/ddyedesignsblacksmith/videos/450348928503014/?video_source=pages_finch_main_video