Plasma cam machines

[Dynatorch_Greg]

Hello All,

It is very disappointing in a debate rebuttal when the person you are debating with throws words like ignorant around so carelessly. To me that is the mark of a weaker argument. In my profound ignorance, allow me to list a few items which are incontravertable.



1. Software like Wincnc, Mach3, and Flashcut were never designed specifically for plasma cutting and must be adapted.Dynatorch was designed specifically for this field and I defy any of those brands to match the features we offer shown clearly on the features area of our website.


2. Mr. Caudle likes to refer to our system as " closed architechture" when in truth the system, when stripped down to its bare bones, without any of the extra bells and whistles is quite simply COMPLETE architechture. The software, mechanical and electrical aspects of the Dynatorch product are designed to work together in complete concert. Our customers need to come to only one vendor should they have an issue with our product. They do not need to be responsible for making separate sub-assemblies from different vendors work properly in a plasma cutting environment.


3. Since each item was designed to work together properly, we do not require any external gadgetry or workarounds. This makes the automated plasma cutting process effortless for our customers.


4. We do not use stepper motors. We use servos for satisfactory operation. Anybody that would imply that a stepper motor could provide equal service when compared to the service provided by a servo motor is not being completely honest. Quite simply, steppers lose torque and power as rpm increases. This means you have less power for the plasma cutting process, less power for rapid traverse moves, and less power for rapid directional changes.This power loss is amplified when stepper motor micro stepping technology is employed. A review of servo vs. stepper technology is posted on our website with appropriate footnotes and bibliographical source notes from very prestigious technological reference sites. Stepper motors are utilized because they are cheap, and produce max profitability for the seller.Customers can go to competitive vendors such as Lockformer, Multicam, and many many other very expensive systems and inquire as to how many of these high end suppliers use steppers to drive their systems.

5. Mr. Caudle implies that utilizing encoders on steppers somehow makes them equivellent to encoder based servos on a closed loop system. For the reasons cited in item four putting an encoder on a stepper system is like putting a racing saddle on a mule......in the end you still have a mule.


Mr. Caudle, in the most real of realities it is our respective customers that will make the choice as to whether your architechture or ours is superior. To date we have been very sucessful, and we intend to maintain that success with ongoing new and exciting technology. We at Dynatorch do hope you can stick around, as we absolutely enjoy the competition.
Greg

[Torchhead]

Ignorance: Lack of knowledge. There are a lot of things I am ignorant of and will admit to but I know how to fix it.

You listen too much to your internal engineers. There appears to be the classic NIH syndrome.

You don't know much about MACH or it's capabilities. I agree about WINCNC and Flashcut (since I have sold retrofits to customers that own both those systems). They were just never crafted with plasma in mind.

MACH3 HAS THC FUNCTIONS BUILT INTO THE CORE ENGINE. If you would like I will direct you to the MACH3 Manual section on THC. Also the entire front of our 46 page manual covers MACH3 and THC operation.

I won't argue the technicalities of stepper VS servos. It would take a small book and on other lists it has been gone over many times. I have years of experience with both. It never was the source of rancor anyway. You made the statement that MACH only worked with steppers and I corrected you on that mis-statement.

So for the record. Is your servo loop closed in the software (where positional errors are sensed and corrected) rather than the driver electronics, and if so how in heck do you get loop response of multiple motors on a serial link?

I have been involved in Electronics (EE since 1973) and spent time in power design and power control (including motor drives and switching power supplies) and then software design and later systems integration and IT. I fixed CNC controls back when they used paper tape. I have been doing CNC plasma cutting since 2001 (when my dot-com job left me "available".)

You need to go back and read more closely about what I said about closed loop. I agree that encoders on steppers using conventional loop gain feedback techniques is lame but it can (and has) been done correctly.

You are spouting marketing stuff and it has little basis in reality. If you really want to get in a feature VS cost debate then let's do it. Your machine running your THC and software VS the MACH3/SheetCAM/Mp1000 combo.

List every feature you can think of and the cost of your solution and I can respond in kind. I know...let's do a comparison chart. If you want I'll even construct the chart.

Forgive me for not responding to the growth rate, and other red herring arguments. They have little to do with the core issues. I'm not a business rookie either but this is not the venue to discuss business 101.

[Apples]

Nice read.

Where is this comparison chart thing?

[Torchhead]

Apples, you trying to start a cat fight?

Okay: here is my start at a chart:

http://www.CandCNC.com/THCCompareChart.htm

[diarmaid]

This was facinating. Had forgotten about this thread!

I dont have a clue about core engines and servo loops, but it looks to me like if (when) I eventually reach the point of a plasma CNC machine, it will be between DYNATorch (Do you sell parts/software for a diy machine, or only the entire setup?) and Mach3/SheetCAM. Please keep this friendly discussion going. Im learning a lot.

Does anyone have a link to a comprehensive thread or source for the pros/cons of steppers vs servos in use on a plasma system please?

[Torchhead]

Pros: Steppers are cheaper and have good torque at lower RPM. They work well when run with bipolar microstepping drives (actually behave like brushless AC motors). You can get 34 frame 640 OZ-IN steppers (new) for about $150.00 each. Much less for used or older types. They can be connected direct to rack and pinion but a 3:1 belt reduction is recommended. They don't have brushes and you don't have to worry about PID loops and tuning and noise on your encoder lines. They also will not self-destruct if they get stalled (like hitting the end of the rack).

Cons: Steppers lose torque with RPM. If they are run outside their limits or encounter a motion problem they will loose steps and you won't know about it in subtle conditions. Steppers are normally run close to their limits (RPM and torque) and because of the inverse torque curve have little or no reserve to tap if the conditon calls for it.

For plasma you need speed for cutting and there are no cutting forces involved so ususally the need for more torque is not an issue. Torque is handy on quick direction changes but typically that is done at lower speeds so stepper torque is greater when it is needed. Hundreds (if not thousands) of designs use steppers and they are still being used today. They are no older technology than DC motors (Servos) and the current drives (see thread on new Gecko 203 drives) are the latest technology.

You will get faster, smoother motion out of a Servo system and it will compensate for lost position within the lock range. They will lose position if the encoder signals are compomised, they will "run away" (go screaming off at full speed in one direction) if an encoder wire comes off ; the resulting crash will be impressive and expensive. Typical servo designs need to be geared down (especially on rack and pinion) since the RPM of a servo can be 3000 and full speed direct connected moves end up being close to the escape velocity of the earth! (e.g a 1" dia pinion moves 3.14" per rev. At 3000 REV/min that is 9424 IPM (157 inches per second).

There have been endless discussions on the CNC technical boards about servo VS stepper. IF you want an earfull post the question on either the CADCAMEDMDRO (CCED) Group or the DIY-CNC group.

[mog5858]

we have a 5x 10 table at work. if u don't wont to d any kind of mance at all just use i would go with timing betls with V rollers ( i think that what there called). but when u stat pushing the flex really bad any think over 125ipm in fine work dose not work but on big stuff works grat but i think if we did it agin i would get soild drive e.g ballscews/ rack and pion.
p.s get hight control it really time consuming to sit there and move the toch up and down cus your plate is woraping cus of the heat.

[massajamesb]

Attachment 25506
Sorry, didn't quite catch that last part.
Tom, I thought you brought up some good arguments. Although it was getting pretty deep in here.
I think that you have raised some excellent points as far as the proprietary systems, and I am quite interested to see what Dynatorch or Plasmacam have to say about it, at least beyond the arguments they have presented. A quick fill out of your chart would be informative and helpful to everyone.

[diarmaid]

LOL . I was thinking the same thing. Sounds like me at the end of a good night out!

[massajamesb]

LOL . I was thinking the same thing. Sounds like me at the end of a good night out!

Attachment 25507 + keyboard = Diarmaid ??
Careful with those 220 circuits J/K

Attachment 25508

[Torchhead]

I hate to wax so technical but sometimes there is no way to avoid it. I just got my beautiful, full color, illustrated catalog from PlasmaCAM. I have to take my hat off to their marketing. WOW. I KNOW about their short comings and even then it gets me excited; then you realize they are selling a "vision" rather than a machine. Of the 24 full color pages there is a small panel OF "Specifications" with 10 items including Power required, Weight and Dimensions. Absolutely no information of any value about their "Digital Height Control" and there appears to be no controls related to that. No real info on their magic software that they claim "automatically prepares complex drawings for cutting". There is page after page of beautifully photographed stuff you can make with their machine.

There are a lot of aspects about cutting metal with plasma that just get ignored. It is only after the machine is paid for and delivered do you find out things like pierce height, Arc Good, lead-ins, THC and other technical aspects make the difference between making parts and making scrap.

The concept you can import a photo, hit a button and cut it out is like saying all you have to do to fly a helicopter is crank up the motor and pull up on the stickey thingy.

When you are standing in the empty, dimly lit shop filled with plasma smoke and dust that marketing guy is sitting at home watching TV and eating Ding-Dongs.

I spend hours a day talking and e-mailing Hobby CNC guys and I know that electronics and techno-speak make them go numb. I try my best to explain things in terms we can all understand.

I can't tell you how many guys (and a couple of ladies) I have talked to that are stunned about how difficult it is to start turning out production.

The first thing that gets them is that the sellers of the equipment "assume" that since you can spell CNC and can write a healthy check then you are a CNC expert and understand all of the aspects of the type cutting you are going to do. Over 70% of plasma issues are plasma/operator based (what size tip, what is the best feedrate, how much slag should I get, etc).

The next thing is that the development of a toolpath (turning an idea into a piece of cut metal) is not as slam dunk as you would expect. Just the fact that you better be pretty good with a computer and graphics is glossed over. I call it the "what do I do now" syndrome. You have the table, you have your plasma cutter you have things setup as best you can determine....now what?

It makes me tired to see marketing hype thrown out as technical specs. If you say the same thing often enough it will start to resemble fact.

Sorry, about the ramble. Just finished my third cup of coffee. My in-laws are in for the weekend so my mood is less than chipper!

"220, 221, whatever it takes"

[Scratch]

I hear ya on the marketing skillz of Plasmacam. I got that DVD and after a couple minutes watching it, my wife happened to sit down too. By the end of the DVD, even she was ready to write the check!

Luckly, I found this forum and decided not to buy from them.

Although I've since then met a local high school teacher that has one in his class and they use the crap out it! and he loves it! He's even planning to buy it from the school once he retires. And he claims he's never done any modifications to it. He did have some issues in the first few months though, but they were handled good according to him.