Resolution Settings in DE

[Joe Jones]

DesignEdge allows owners to change the X and Y resolution settings, but I cannot find an explanation ANYWHERE of what these settings do, or what changing the values will do.

It seems pointless to give owners the ability to change these settings without a clear and unambiguous explanation of exactly WHAT you are changing, and how it will affect either the software or the table operation. The answer, "Just leave them at the default values" is not an answer. If we are not supposed to change these values, then WHY are we given that option?

The default setting for the X and Y resolutions is .000471239 Okay So what would a slight change in that value, or a RADICAL change in that value do for me?

Any clear answer will be appreciated!

Joe

[Joe Jones]

This is ALL the video manual says about it...

so the default number is .000471239, but that doesn't tell me ANYTHING about what to set the numbers at if I WERE to change the gear ratios!

[weldguy]

I agree, seems odd they would make the available to end user with no explanation. I expect that people would change the number cause that's what people do and then have problems with scaling and call tech support. For that reason I would think they would hide it. As odd as that is its better than it not being there if you wanted to use the controller for other things requiring different gearing so I suppose just be happy its available to tweak for a specific application.

[Joe Jones]

Okay! I called Zack at PlasmaCam and a two, three (or four?) -way conversation took place. Apparently this had never been asked before. so the "technicians" got onto it, and began to backtrack the math to discover WHY the default setting for X and Y is .000471239

I thanked Zack for his help, and he DID help me by mentioning a little known but not particularly secret formula that is used to derive that number, although I was still a bit puzzled by the reasoning behind using THAT formula.

((((encoder # = 500) x 4) x motor pulley ratio 4) X resolution value for X or Y)

So in the interim, I did some quick math and referred to a .pcm file I created a couple of years ago, wherein I wanted to calculate the true geometry and gear ratios of the PlasmaCam tables. Then the answer came to me! (Insert chorus of angels here)

So I called Zack, and he said they came to the same conclusion almost simultaneously.

I now KNOW why the default number is .000471239 I still cannot understand what possessed the makers of DesignEdge to calculate it this way, but they did. Rather than calculate the full 360 rotation of the gantry shaft in order to achieve 100mm of lateral movement of the gantry tube or carriage, they based the resolution setting on 24 teeth of the pinion gear rolling along the gear rack, WITHOUT returning to the first tooth at the starting point, which would have completed the full 360 degree rotation.

The resolution is NOT calculated on a 100mm movement of the gantry or carriage but rather, a 96mm (rounded up) movement of the carriage or gantry via 24 teeth of the pinion gear, where 25 teeth (24+1) should have been used.

The photo below shows the difference, and I will make a video that explains all of this so that everyone can understand it.

NOW I know what I need to do, to calculate the exact X and Y resolution when using the gantry or carriage motor to drive the belt, which in turn drives something else either larger or smaller in diameter.

Joe

[rdj357]

Interesting. I just reverse engineered it for my rotary calculations and made a spreadsheet to calculate it. Good info!

[Joe Jones]

Interesting. I just reverse engineered it for my rotary calculations and made a spreadsheet to calculate it. Good info!

Right. so supposedly, if you change to a 12 tooth motor pulley, that gives the machine a 5:1 advantage (slower speed, more torque) at 12:60 as opposed to the standard 4:1 (15/60 combination) I guess you then adjust the resolution to a number that gives you that 96mm of travel.

Seems simple enough.

I think this will come in handy for people who want to use a belt to drive something other than the traditional gantry or carriage motor. A lower ratio of 2:1 for example will give the user much more speed, but less force. Can we be far from a Plasmacam GO KART?

I like to play with things like this to see how far out of the lines I can travel!

Joe

[Joe Jones]

I will try to explain this better ...

The gantry and carriage motor encoders have 500 bars or pulses per full rotation (360 degrees).

500 pulses x 4 rotations = 2,000 pulses - The multiple of "4" handles the four (A) motor rotations required to rotate the (B) 60-tooth pulley once. So the 60-tooth pulley's 360 degree rotation is divided into 2,000 encoder PULSES, rather than just 360 DEGREES. This improves the accuracy of the movement because a value of ONE PULSE rotates the 60-tooth pulley AND the 24-tooth pinion gear 1/2000th of a full circle rather than 1/360th of a full circle.

2,000 pulses x 4mm pitch of each gear tooth = 8,000 PULSES to move the (C) 24-tooth pinion gear 95.7558mm along the gear rack - One extra tooth makes it a 100mm travel distance, because the gear rack has a 4mm pitch. (96 + 4 = 100)

The RESOLUTION is the number that 8,000 pulses must be multiplied by, in order to achieve that 95.7558mm distance of travel at .000471239mm PER PULSE or roughly 47/100,000ths of a mm of movement of the carriage or gantry tube PER PULSE. That is where the PlasmaCam gets it's accuracy!

Does that explain it?

[rdj357]

My dial indicator and digital caliper measurement reverse engineering method gave me 8006 pulses so I didn’t miss it by much.

[Joe Jones]

My dial indicator and digital caliper measurement reverse engineering method gave me 8006 pulses so I didn’t miss it by much.

Right. 282/100,000ths of a millimeter isn't anything to worry about!

The encoder has 500 pulses per revolution, but in the math, the other six were probably picked up in extended digits beyond the "..1239" set.

I am going to need to measure out my 510 table for a longer main wiring harness. I have to get rid of that $^%*& BOOM ARM!

Joe