USB Communicator HIbitual Problem

[paco]

Good document for sure but it need more explanations and details to ensure novice understand what they're doing...

some points are obvious optimization while some other may put some people into trouble...

[terryd]

Mike,
Before new control boards, Mach, Gecko's Benchmark Testing and Tech adventures why don't you buy a real computer and see what it does. Pentium III will bearly run ARTCAM software so how do you expect to reach the optmization of your 'bot' which you so obviously desire as per your mariad of post. After all a $10,000 dollar CNC deserves a $300 new computer to allow it to run as designed by SHOPBOT.

Terry

[gerald_d]

I am surprised that ShopBot doesn't sell a "factory-approved" PC as an option. They could make a good profit on it and avoid many service calls. Support only provided for the factory-approved version.

[richards]

Gerald,
Thanks for the document. I was surprised how many of the settings needed changing on my Shopbot computer. Since that computer is ONLY used to run my Alpha, I felt safe in following all of the guidelines except the ACPI setting.

Terry,
It would be interesting to run a test comparing various speed computers. I would believe that the amount of memory in the computer would play as important a role as the speed of the computer because it would allow more lines of code to be cached in memory instead of being read directly from the hard disk. Unless I've misunderstood the role of the computer controlling the Shopbot, it appears that it works more as a 'file server' than as a 'processor'. By that, I mean that it reads in the SBP file and then communicates the lines in the SBP file, one at a time via the USB-Serial port to the actual control card in the Shopbot control box (I'm mainly talking about the Alpha model because I don't have PRT box to look at, at the present). Although the computer has to do some processing, I believe that it is fairly minimal. HOWEVER, I may be completely mistaken. Perhaps someone who knows the inner workings of both the control computer and the controller board could tell us both the minimum configuration needed to keep the Shopbot controller board running at maximum speed and the maximum practical computer speed that could be used before the controller board in the control box becomes the bottleneck. I would think that the minimum speed computer and the maximum speed computer would be about the same. If a computer having less than the minimum speed were used, the controller card would have to wait for instructions. If a computer having more than the maximum speed were used, the computer would have to wait for the controller computer before it could send more instructions.

Years ago, when the Z80 was the king of the computer chips, I built a dual cpu Z80 system. One of the Z80 chips acted as a master computer that read data from a floppy disk and sent it to the slave Z80, which used that data to control a sophisticated - for the time - Kodak photo printer. Since the slave computer could only operate the Kodak machine as fast as the stepper motors, solonoids, air valves, etc. could actuate, the slave computer never had to wait for the master computer. Those computers were only running at 4mhz - thats mega with an m, not giga with a g. Granted, that was long before Windows appeared, back when CPM was the operating system of choice.

It seems to me that putting the King-Of-Computers on the Shopbot would mostly create heat and electrical noise compared to using a more modest computer that had 'just' adequate speed to stay just slightly ahead of the controller board in the control box. On the other hand, I would use all of the computer speed that I could afford on my design workstation that runs AutoCAD LT and PartWizard as well as various compilers needs to generate code. I don't want to ever wait for the design workstation when I'm in the middle of designing parts.

[terryd]

Mike, Having programmed and designed software programs from the early seventies, mostly in assembler, I don't need Windows to function. I use it because it is the standard of the day and what the machine currently uses. Linux would be my first choice as a platform. When I first got into this field I was recruited from college to develop bank accounting programs using a Cyber18 from Control Data Corp having 8k of transistor memory, batch processing, punchcards and sheetfold printouts. The banks were happy and we had a job. When QDos hit the market with the 8080 intel chipsets I knew that my career was fading, finished at 18. Now you didn't have to understand and use scarce resources to perform a computation. Computer illeterates could now buy and run CNC's
To futher answer your post. I would rather have a head to head comparison of the cash I generate from my mundane setup. A 3.2 Ghz processor cost $100 more than a 1.4 Ghz processor. With average revenues of $1000 a day minimum I will buy ten 3.2 Ghz systems and connect them in parallel if the 'bot' needs it. Cash is king the rest is Bull***. For the price of a router bit I want all the pipeline, burst cache and processor speed I can get. Memory is not the issue.

The ultimate limitation on speed in this system is not the USB or the controller or my computer. It is the speed in which electrons can travel in a copper conductor. In the end when Shopbot finally changes to fiber optic data transfer they will take us to a whole new level.Maybe even go to a closed loop design with feedback and all.

As for King o Computer generating more heat and noise. NADA. Increasing data flow in a shielded copper cable (USB) does nothing adverse except increase to flow of data so that the control board never has to pause or look ahead to its next instruction. This is why changing directions like when cutting an circle or arc the computer not the controller has to look ahead and decide what it is going to do next before it has the controller do anything. Hence the need for processor speed. The more instructions loaded into the registers and waiting to be sent by your computer the more consistent the speed and cutting process.

And finally why would want never to wait for your design program which generates most of your unbillable hours yet just want you 'Bot' brain to stay only slightly ahead of the controller. The bot brain is what makes money. Cut time is billable.
This is business and I try to make every hour I work billable. Screwing around testing, benchmarking and competing is something I do with my cars. My shoptools just run neverending at a liveable and profitable pace. It would never dawn on me to enter the bot into a speedcutting contest. My poor beltsander is still whining.
Have a good one.

Terry Doherty

[richards]

Terry,

ALL hours are billable in my business, whether those hours are designing hours or cutting hours.

CNC machines are mechanical, meaning that whether I have one move in the que or one-thousand moves waiting in the que, as long as there is at least one move in the que the controller will never be waiting for the computer AND the machine will still be running at its maximum speed. However, the last time I read Shopbot's programming guide, there was something in there about the amount of memory available and the size of a code block that could be processed before everything hesitated while another code block was loaded into memory.

The ultimate limitation on speed is the mechanical limitation of the slowest device required to complete a move. Example: If I set my xy-axes move speed to 6-ips and my z-axis move speed to 6-ips and then ramp into the cut(s), I'll be cutting much faster than if I have to run the z-axis at 0.75-ips because I'm drilling. Moving electrons, regardless of the vehicle, will always be faster than the mechanical devices involved can use those electrons.

Using the lastest and greatest computer on the market might be good for the ego, but it won't change the laws of physics. Mechanical is still mechanical. If a certain mass has to be moved using the same motor that's being driven by the same driver that receives its pulses from the same controller board, even hooking things up to a cray would make no practical difference.

Whenever I am paid to make someone's process more efficient, my first step is to find the worse bottleneck in that process. In the case of the example above, I would tell the client to change the z-axis speed and then ramp their tabs instead of drilling their tabs and they would have a remarkable increase in production. My consulting fee would be zero or the minimum billable amount. On the other hand, I could easily sell them a faster computer, charge them a fortune for consulting and then quietly change their files to ramp instead of drill - and the net result would be the same. The world's fastest car goes slowly on an icy road. The world's fastest computer goes slowly when held back by mechanical bottlenecks.

Of course, you are perfectly entitled to use whatever computer you feel best meets your needs and to suggest that we all use that computer for best performance.

[gerald_d]

That document is from the Mach Yahoo forum, under the Files section, Utilities.:
http://groups.yahoo.com/group/mach1mach2cnc

[terryd]

Yawn.