Weakest link?

[jzarski1]

Just a random question. What is the weak link in my Prt standard I have the gecko 203v drivers? Why will it only do 9-10 IPS rapids? Is it the SB software, motors or the v bearings that limit the speed?

John

[jerry_stanek]

10 IPS is pretty fast that is 600 inches a minute

[jzarski1]

That's my point. What is limiting me from doing 10ips. If I try now the machine falls on its face. Missing steps or skipping gears, not sure what it is. I can get away with 8.5ips. But I am just curious what is holding the machine back from doing the 10ips?

John

[zeykr]

There's always a trade off between speed and accuracy. I expect you can change your gear ratio (new pinions) to get a higher speed if that's your need.

[Brian Harnett]

The weakest link is my router it would die at those speeds.

The question is what do you need those speeds for? Its a shopbot not a million dollar cnc rig.

[jzarski1]

The weakest link is my router it would die at those speeds.

The question is what do you need those speeds for? Its a shopbot not a million dollar cnc rig.

I agree with you 100% I was just curious what falls short on the Shopbot for it not to be able to handle those speeds. I really have no reason to rapid that fast. Like I said in the first post I am not talking about cut speeds I am talking about rapids or I guess there called jog speeds on SB3. Still trying to get away from Mach3 life. Not an easy task :confused: . If I where to put linear slides on my machine would I gain anything? If I ran it with Mach3 would I gain anything? What about putting different motors? Just curious what seperates the Shopbot from that 150K machine. Besides weight and giant foot print. This is just weekend conversation. Nothing really important just curiosity.

John

[mryan]

That's my point. What is limiting me from doing 10ips. If I try now the machine falls on its face. Missing steps or skipping gears, not sure what it is. I can get away with 8.5ips. But I am just curious what is holding the machine back from doing the 10ips?

John
I think what you are experiencing Is the same as I did just a few weeks ago. What I sounded like gears skipping turned out I beleive to be stepper motors not getting data fast enough. It has been explained wel here in the past so do some searching on USB ports for more clarification.
Mryan

[Bob Eustace]

John, suggest you add all the costs up beautifully detailed at the end of this 30 minute video. If goes to Mach3, changes just about everything but the steppers etc. what it doesnt show is if it was all worthwhile performance wise.

http://www.youtube.com/watch?v=4WQ8KcTSKyQ&feature=youtube_gdata_player

Bob

[jzarski1]

John, suggest you add all the costs up beautifully detailed at the end of this 30 minute video. If goes to Mach3, changes just about everything but the steppers etc. what it doesnt show is if it was all worthwhile performance wise.

http://www.youtube.com/watch?v=4WQ8KcTSKyQ&feature=youtube_gdata_player

Bob

I have watch the video already. When I first purchased my used Shopbot I was going to convert it to Mach3. That is what I used for years on my other machines. I decided not to do it and I am still not of the mind set to convert. Just want to know if that is what is limiting the speeds on the bot? Is it the actual machine itself? Again this is just conversation :D my machine runs nonstop six days a week so not problem there. Just really curious?

John

[bleeth]

The principle thing limiting speeds faster than that on a PRT Standard running on Geckos is the decreasing torque in the motors as the speed increases.

[adrianm]

Not an expert on it but I doubt it's a limitation of the software as the current alpha can move faster than that.

[Brady Watson]

A few things can limit the speed of your Standard:

1) Low COM speed - The higher the efficiency, the faster the tool will go. The very first 4G board (I was there when Ted cobbled it together from some 202 Geckos and a hacked Alpha board) - jogged 22+ IPS on a laptop with Quatech PCMCIA to USB card @ 93% transmission efficiency.

2) Low voltage power supply to steppers. The higher the PS voltage, the higher up in the RPM range the stepper will lose torque. My 100% factory spec BT48S could easily jog 17 IPS via laptop @ 89% efficiency. Geckos top out at 80v max. Alphas run somewhere around 170v(!), which is one thing that gives them fantastic performance.

3) The model Gecko you use matters. Earlier 201,202 models did not use internal 'morphing' like the newer 203 'vampire' drives. This morphing occurs at faster speeds, which essentially turns off microstepping, and morphs to full stepping, theoretically reducing the communication and step pulse requirement by a factor of 10. So you may find that 203 drivers will offer you more performance (if you don't already have them in your box...they are red), over the older 202 (black/yellow) drives.

On a side note, my Alpha can jog up to 30 IPS. The gearboxes are really only rated for 22 IPS, and I set my JS to 15 on the XY. It really isn't necessary to jog over maybe 8 or 10 IPS on a smaller tool anyway, because the time savings is next to nil. I've got a 5X16' machine to get around on...and 15 IPS is plenty fast. Plus, lower speeds save pinions and bearings.

-B

[garyc]

John...
To oversimplify an answer; your checkbook. More dollars always equals more speed. As in the ShopBot Alpha Controller System. The Alpha system offers 1 1/2 times the resolution, triple the speed and around 4 times the torque. And in many cases these features are not as important as the closed loop feedback.

The Standard is not designed to rapid any faster than 500 IPM or 8.333 IPS. The posted specs for the Standard are shown below. Those specs are based on the abilities of the drivers, motors and data stream to the controller card, and are pretty accurate. They are also based on supplying current to the motors and drivers that will ensure reliability over time.

My in the field experience shows that: 65% of all Standards perform well at the published specs. 10% perform higher. 25% perform lower. It is my opinion that in most cases, the control computer is responsible for both the higher and lower performing machines.

[gerryv]

Reading the info on the latest Beta SB control software, it appears that we may all be in for a "free" performance boost from Shopbot, or am I interpreting this incorrectly?

If this is true, would it be correct to assume that the increase/improvement would be dependent on such limiting factors as power supply voltage, which Geckos (or more recently OM drivers) are installed and what SB board version is in the controller. i.e. A fella with a machine that's a year or two old would likely see a bigger improvement opportunity than a fella with a PRT/4g and so on down to little or no improvement opportunity for a PR with no controller upgrades?

[garyc]

Gerry....
There are a number of enhancements coming in the future. There is a good chance that communication from the computer to the controller will be improved.

I believe that it is more likely to help the under performing machines get up to par with the specs than to raise the specs. Software can seldom increase the abilities of hardware.

Don't read anything into the new SB3 information. It cannot add power or speed to an existing motor/driver combination. It is unlikely that if you have a machine that is performing up to the published specs, an increase in performance will be noticeable. Features and ease of use, yes. Performance, no.

[erniek]

I've got the same machine, PRT standard 48 x 98.

I do run it at 10 inches per second but only when I'm surfacing the spoil board.

Normally I'm cutting a 4.5 to 5 IPS and jogging at 7.5

I have had it go faster in the past but it's not worth the risk for losing steps.

[curtiss]

"The Alpha system offers 1 1/2 times the resolution, triple the speed and around 4 times the torque..."

That means 4 times the stepper torque over the PRT stepper motors correct ??

As one moves from a PC to a spindle, in general, how does that improve cutting speed or resolution ?

Is not the xyz speed basically related to the chip load of a given material ??

[gerryv]

Thanks much for the clarification Gary. The enhanced communications elements look promising. I guess this means you're going to have to add a warning to the final release notes stating "No, you still can't use a 72' USB cable!"

[jzarski1]

So with my 4g board and red 203v gecko drives, I should have the proper setup? Not sure how big my PS is but what size should I have?

John