[Firebass]

Hi All,
I am new to this forum and see that there's a good wealth of information here. I purchased a Dynatorch Retro Kit recently and I am building my unit now. For me this is a crazy project since I am new to the CNC scene. I own a small machine/fab manufacturing company and thought I'd just make the plunge. So far I've fabricated the table and learned to convert dwg's into G code. I've run the software in simulate mode and read manual about 3 times. It's starting to make sense but I'm sure glad I found this forum. I'm running the dual X drive system and was wondering if anyone knows off-hand what size pinion gear is used on the rack gears? I'm trying to keep it as stock as possible. I'm building the 5 x10 table. All input is greatly appreciated

Thanks
Firebass

[cstroke]

wow i dont have a clue

if all else fails call down and talk to the guys at dynatorch
good luck with your project

[Firebass]

Not much responce on my project Anyone ever made a gantry like this?

Firebass

[millman52]

I didn't resopnd simply because I'm not familiar with a dynatorch (other than reading on their site & others posts here). Does your machine have the rack gears installed? If so you need to determine what pitch they are. After that you should be able to use a matching pitch pinion of whar ever diameter will work. Use the same diameter (# of teeth) on both X & Y axis. I am only assuming you can do this with Dynatorch controls. Because the machine controller I use will allow for just about any combination you could imagine.

[Firebass]

No, I haven't mounted them yet. I'm at that point now where I'm ready to purchase the rack and pinions. I hooked up the bare system tonight and ran a few dry run cuts with the software, just to watch the servos dance. After my first attempt all the motors did they're job of making me smile. Man! do those servos run smooth. Now I'm starting to wonder if the Vee wheels will be accurate enough for my gantry?? How small of holes can one expect to cut in 3/16", 1/4" and 3/8" Mild Steel?

I also have a Thermodynamics Cutmaster 75 that I'm told it will not work with my torch hieght controler. Anyone have any options before I buy a new Plasma unit?
Thanks
Firebass

[millman52]

No, I haven't mounted them yet. I'm at that point now where I'm ready to purchase the rack and pinions. I hooked up the bare system tonight and ran a few dry run cuts with the software, just to watch the servos dance. After my first attempt all the motors did they're job of making me smile. Man! do those servos run smooth. Now I'm starting to wonder if the Vee wheels will be accurate enough for my gantry?? How small of holes can one expect to cut in 3/16", 1/4" and 3/8" Mild Steel?

Thanks
Firebass

Right now I am using Ox/fuel. Even with that I can cut accurate 1/2" holes in 1/4 thru 1/2. I would imagine smaller with plasma.

Looking at your drawings The V wheel idea will work. I think you'll find it hard to get the spacing between the angle close enough to keep the carrage from being tight in spots then loose in spots. I think also it will be very hard to keep in parallel alignment to keep the carrage from wobbling.

Have you thought of using a length of cold rolled square key similar to pic below? Depending on length of gantry it might get a bit heavy. Probably need to be 1 1/4-1 1/2" square.

If money isn't a big issue I recomend precision liner rail for your gantry. I was able to find a couple 34" lengths of 15MM on Ebay with bearings. I didn't have trouble with butt joining them. If I were buying new I'd probably get 20MM or 25MM but the 15MM is working fine.

[millman52]

before I bought the R&P I'd check with the Dynatorch folks tech help department to be sure I could adjust the software to match randomly selected rack pitch & pinion diameters.

[millman52]

I also have a Thermodynamics Cutmaster 75 that I'm told it will not work with my torch hieght controler. Anyone have any options before I buy a new Plasma unit?
Thanks
Firebass

I couldn't advise you there either. Is the Cutmaster 75 a high frequency start machine? If so it's not to friendly with anyones controls. HF start units will cause lots of RF noise which can bleed over into your control circuits especially on a servo system. I have read of people making it work with very careful cable routing & good shielding all your control cables. But best to stay away from HF start plasma outfits.

[Firebass]

Right now I am using Ox/fuel. Even with that I can cut accurate 1/2" holes in 1/4 thru 1/2. I would imagine smaller with plasma.

Looking at your drawings The V wheel idea will work. I think you'll find it hard to get the spacing between the angle close enough to keep the carriage from being tight in spots then loose in spots. I think also it will be very hard to keep in parallel alignment to keep the carriage from wobbling.

Have you thought of using a length of cold rolled square key similar to pic below? Depending on length of gantry it might get a bit heavy. Probably need to be 1 1/4-1 1/2" square.

If money isn't a big issue I recomend precision liner rail for your gantry. I was able to find a couple 34" lengths of 15MM on Ebay with bearings. I didn't have trouble with butt joining them. If I were buying new I'd probably get 20MM or 25MM but the 15MM is working fine.

Yes I considered what you described with CR But I thought by the time I added The gear rack and 72" of solid bar it would get too heavy???
I have the exact same concerns about the angle getting tight spots and line-up. I could possibly machine a slight groove for the angle to set in and use screws to anchor it in place might even have to machine the whole thing. It would most likely end up in a barrel when I'm done... Just thought I throw it out there. I like the Idea of larger wheels on the carriage but how much do I want to fight inventing the wheel. I really don't think much of cam followers... I do like the precision rail ...except the cost...Decisions Decisions....
Thanks for the input.

[millman52]

I just searched Thermadyne's website for a "cutmaster 75" & couldn't find anything listed in their literature. Are you certain of that modle #?

[millman52]

I researched the hardened & ground V rails & bearings, Round linear rail(s) cam followers, etc, etc. To me the v rails required fairly exact machining (drilling/tapping 2 parallel lines of holes) doable but being precise a must. Round linear rails bulky & weight would get up there especially with 2 pieces 72". Cam followers, also bulky with all the brackets & then adjustments out the wazooooo.

The price a bit less on most of those methods but also much more labor intensive.

I personally think the best inexpensive method is a piece of CR strap for the rail. 9 sealed ball bearings (3 with cam adjusters) or 6 bearings & 3 cam followers.

I am not an artist but I attached a quick sketch to give you the general idea.

[cstroke]

something to think about, from what i've read small holes with plasma are not very accurate
though someone posted about just using the pierce and punching with an ironworker..

[Firebass]

I just searched Thermadyne's website for a "cutmaster 75" & couldn't find anything listed in their literature. Are you certain of that modle #?

Yes it's about at-least 5 years old maybe older like 7 years old. I bought it new and it's paid for itself about 50 times. I think it has High Frequency Start. Basically it can cut up to 1/2" good and it will penetrate thru 3/4" but never do I use it for such thick mat. Today Leon at DT told me that some are successfully using HF systems but it's really hard on computer equipment. And you have to make a few components. Anyone successfully tackled such a feat?... I'm leaning towards a new machine at this point but then again... Decisions Decisions...

Again, thanks for the input