Speed stated as 35 Inches per Second..what % speed setting is that?

[Larry Bratton]

I see some vendors state the speed for engraving in terms of "inches per second". I'm not sure I know what my Epilog's speed in those terms is..seems I read somewhere it is stated as 120 in/sec. Is that correct? If so, 35 in/sec would translate to about 30% speed...right?

[Dan Hintz]

Epilog and ULS systems are in the 75ips range... Trotec has one (or more) that's more like 120ips.

[Michael Hunter]

The "%" speed of Epilogs is not linear*, so it is very difficult to compare with other systems.
In your example, the 35in/sec would translate to more like 15-20% speed, but this is just a guess and you would need to experiment.

* The speed change between 91 and 100% is barely noticeable, but the change between 1 and 10% is very obvious.

[Gary Hair]

* The speed change between 91 and 100% is barely noticeable, but the change between 1 and 10% is very obvious.

That's because 1% to 10% is 1000% or 10x, 91% and 100% is 10%, that's a substantial difference.

[Larry Bratton]

Well, all that being said ..Epilog tech support says an EXT is 70 in/sec. So, I guess if I were experimenting, 50% speed would be a good starting point.

[Dan Hintz]

The "%" speed of Epilogs is not linear*, so it is very difficult to compare with other systems.
In your example, the 35in/sec would translate to more like 15-20% speed, but this is just a guess and you would need to experiment.

* The speed change between 91 and 100% is barely noticeable, but the change between 1 and 10% is very obvious.

In raster mode, 100% should be around 70ips, 10% should be around 7ips, 1% should be around 0.7ips... I would be surprised if it wasn't linear as that would make certain calculations a PITA. Not saying with absolute certainty Epilog is linear, but I would be surprised if it wasn't...

[Michael Hunter]

Gary

I agree with your maths - bad example on my part.
On the other hand, "50%" speed on my Epilog is much faster than half its maximum speed.

I read somewhere (maybe the manual or maybe in a forum post by Peck) that Epilog deliberately made both speed and power non-linear as this helps to arrive at a good setting for any material. I haven't used any other system, so I don't know if the "help" is real or imaginary.

[Gary Hair]

One thing that has to be considered is the ramp up and down time that affects the actual speed. It's true that 50% speed on a 70ips machine should be 35ips and "in theory" that job should run twice as fast a the same job at 25% speed, but in reality it rarely works out that way. It's not because the speed isn't linear, it's because of the way the laser works, and physics. If you ran a vector line all the way across your laser bed and ran it at 100%, 50% and 25% speed, you would likely see results that are close to what you would expect. If you ran a job with a 1" line at the same speeds, you would not likely see much difference. The laser can't instantly get up to the speed, it has to ramp up - same thing with stopping and reversing direction, it can't do it all at once. In the scenario of a 1" line, it may never reach full speed. If you run the test in the x axis vs the y axis, you'll get two different speeds as well, it takes much more time to get the gantry moving compared to just the optics.

There is more to this than just a simple calculation of % of max speed. That is why there aren't really any estimation programs out there, too many variables. The driver should be able to estimate since it is sending the signals to the motors, but if you don't have that proprietary knowledge then you are not going to be able to estimate accurately.

Gary

[Dan Hintz]

Gary,

But this wasn't a discussion about total run time, it was how to compare basic power values between machines. Without fine details, halving power for a machine that runs at double the speed is accurate enough for horseshoes and hand grenades.

Lead in/out should be taken care of by the driver in one of two possible ways: 1) By the time the laser starts firing the carriage is up to speed, or 2) The laser increases in power proportionally as the carriage ramps up to speed. It's also assumed the max speed is (in raster mode) for the X-direction as that's the lightest component (carriage) and therefore the fastest. Vector mode is a whole 'nother beast, and each company seems to have their own take on the process (at the moment, I'm not a fan of how ULS has chosen to implement it, though I cannot say if they're worse/better than any other manufacturer right now).

[Michael Hunter]

Gary

I wasn't taking about job-time (with turnround time etc.). I was talking about the speed of the carriage across the x-axis.

Here is a snip from one of Peck Sidara's posts (sorry, I don't know how to link to the post) -

"Most of the acceleration of speed occurs from the 1-20% range, there is a difference between say 30% and 90%speed but due to the many variables (length of nodes, shape and contour of nodes), you may not see a noticable difference in time. Additional variables include acceleration, deceleration and how our laser handles/translates the vector data."


PS Just got out the manual to see if it explains it better - unfortunately not! :

"The speed setting scale of 1% to 100% is not linear - i.e. 100% speed will not be twice as fast as 50% speed. This non-linear scale is very useful in compendsating for the different factors that affect engraving time, but using speed to predict a jobs engraving time is not practical."

It goes on to say that the powere settings ARE linear, so I got that wrong!

[Gary Hair]

Gary

I wasn't taking about job-time (with turnround time etc.). I was talking about the speed of the carriage across the x-axis.

Here is a snip from one of Peck Sidara's posts (sorry, I don't know how to link to the post) -

"Most of the acceleration of speed occurs from the 1-20% range, there is a difference between say 30% and 90%speed but due to the many variables (length of nodes, shape and contour of nodes), you may not see a noticable difference in time. Additional variables include acceleration, deceleration and how our laser handles/translates the vector data."

That's exactly what I was trying to get at. The ramp up/down and the distance of travel all have an affect on the actual speed vs the speed setting. The actual speed will be much slower when you have lots of little lines as compared to a few long lines, even if the total distance traveled is the same. This difference will be more noticable on slower speed settings because the laser is actually hitting those speeds. At higher speed settings it is never hitting full speed so it "seems" to be only marginally faster.

So even though you weren't talking about total job time, this discussion is still valid for the speed across the x axis. If your x axis was 100' long then you would likely see that the time to travel that distance at 10% speed is 1/10 of the time to travel at 100% speed.

Gary

[Gary Hair]

But this wasn't a discussion about total run time, it was how to compare basic power values between machines. Without fine details, halving power for a machine that runs at double the speed is accurate enough for horseshoes and hand grenades.

Dan,
It wasn't about power at all, at least not in the original post, it was about speed only. If you want to throw power into the mix then you are talking about a completely different beast altogether.

Gary

[Michael Hunter]

Gary - please re-read my previous post - with the PS

If Epilog says their speed settings are non-linear, then I ***AM*** prepared to believe them!

[Rodne Gold]

It's kinda amazing that you can actually get a straight vertical line at 100+ inches per second on a bidirectional scan

[Larry Bratton]

That's easy for all you techies to say but..if someone says to me..run your Epilog at 35 in/sec in raster mode and I know that it is capable of 70 in/sec max- what is my setting in terms of %? I understand about linear and non linear but what's the answer? 50% is not it huh?