[BobMorside]

Hello all,

I have a new syil america x2 that I took delivery of a few weeks ago. I've gone over the machine and tightened up all of the loose screws and wires I found. I've also tweaked the mach3 configuration to be in the ballpark of where I think it should be for this machine.

The problem I am having at this time is one of accuracy. Specifically, I want to cut a pocket 1" from the edge of my fixture. After setting up the machine and cutting the pocket I find that the pocket position is off by .015" (actual position 1.015") so it is moving further than it should.

I initially was using a mechanical edge finder. After seeing some of the threads here on probing I set that up but ended up with the same results.

I've checked my motor settings, backlash settings, G code, cutter diameter, gib adjustment, etc and can't find anything out of whack. The computer is running xp and was purpose built for this application, it is stripped of all extraneous applications.

I've also replaced the original mechanical limit switches with prox switches in hopes of eliminating any home switch repeatability issues.

Not sure what to check next.
Thanks for any input

Bob

[der_fisherman]

I would cut a scale say at least 12 inches long, longer if your CNC can do it. Start at 0 and mark (cut) at every inch. Do it first on the Y axis, then on the X.....measure the cuts carefully.......
Its what I do in CAD programs before I start to use them.
I hope this helps you to find the error.

[ataxy]

if you did check everything motor tuning, screw and all i would say that the problem might be electronic

[Crevice Reamer]

Cut a 4 inch line on both axes. Measure to be sure that the cutter MOVES 4 inches. If cut is different length than called for then you may need to tweak your steps per inch up or down a little.

CR.

[philbur]

Have you checked the leadscrew nut for backlash?

Have you checked the leadscrew thrust bearing for backlash?

Have you checked the leadscrew coupling for backlash?

Phil

Hello all,

I have a new syil america x2 that I took delivery of a few weeks ago. I've gone over the machine and tightened up all of the loose screws and wires I found. I've also tweaked the mach3 configuration to be in the ballpark of where I think it should be for this machine.

The problem I am having at this time is one of accuracy. Specifically, I want to cut a pocket 1" from the edge of my fixture. After setting up the machine and cutting the pocket I find that the pocket position is off by .015" (actual position 1.015") so it is moving further than it should.

I initially was using a mechanical edge finder. After seeing some of the threads here on probing I set that up but ended up with the same results.

I've checked my motor settings, backlash settings, G code, cutter diameter, gib adjustment, etc and can't find anything out of whack. The computer is running xp and was purpose built for this application, it is stripped of all extraneous applications.

I've also replaced the original mechanical limit switches with prox switches in hopes of eliminating any home switch repeatability issues.

Not sure what to check next.
Thanks for any input

Bob

[BobMorside]

Thanks to everyone for the input.
I'm currently traveling and won't have a chance to get back on this till the coming weekend. (12-20-2008)
Most of these items I have checked but I think i'm going to have to start back at the beginning and systematically verify things.

[BobMorside]

Ok, I've had some time to play with this a bit more and I have come to realize that this is actually a problem with turbocad.

My unit testing of the various mechanical and electrical systems causing the failure all passed. But when I tried cutting the pocket again, it still came out undersized. So I started looking at the Gcode and realized that the code was wrong. Further examination reveled that even though the dimensions in turbocad were correct, when I increased the number of decimal points, the drawing was not actually the correct size. I'm not really sure how this happened but I am new to turbocad so I'm sure it is something I did somewhere along the way.

Bob

[neilw20]

the world of other peoples errors or shortcomings.

That's why I write my own code, and code generating programs.
My PCB editor (32 layer SMD - 20 years young.), My PCB Gcode from editor..
When you make a living from it it MUST be right.:withstupi

[Khalid]

I don't think the TurboCad may be wrong in Gcode..u are not the first who use it...IMO, u must have to check the backlashes, your tool runout and correct diameter, Steps/unit i.e. motor tunining...

P.S: neilw20 can u show us the snapshot of ur program.

[der_fisherman]

What he wrote was that increasing the decimal points (I assume he means the number of places after the decimal point) seems to have caused the errors.......
Maybe nobody else has done that for example......which is maybe why the problem has not been seen or reported before......
Remember that no program is completely "Bug-Free"! The question is always, can one live with the Bugs or not?
Just a thought from
Der Fisherman

[BobMorside]

What I meant to say was that even though the dimensions in turbocad appeared correct, when I increased the level of precision I found my dimensions were actually off by several thou.

I'm not really sure how this happened. I was only drawing with two digits beyond the decimal point, however, my desired dimensions only required that level of precision (2.5" X 1.61")

Increasing the level of precision did not cause the problem, it reveled the problem with the drawing.

Thanks,
Bob

[der_fisherman]

So your actual dimensions were incorrectly keyed in in the first place, your error not the programs...
Thanks for the clarity
der fisherman

[neilw20]

CNC stuff is usually accurate but there are or can be a few gotchas with rounding.

Often internally, like calculating the actual center of a circle, precision is required, so that end points don't go wonky.

I have discovered a few simple rules that work for me.

When drawing use at least one more decimal place than the accuracy of the machine.
ie. Machine OK at 0.001", draw like in autocad, to 0.0001" you will soon see rounding errors you did not expect.

In metric, do similarly with an extra decimal place.
Although your task may not need the precision, you can't input garbage into the machine, like an vertical line that is not.
3.1 is not equal to 3.0009 as far as an internal calculation is concerned, just proves 3.1 is not equal to 3.1 and now the machine tries to faithfully do what it is told but does something skewed, where you wanted it vertical.

Graphically creating drawings all with a mouse (read: Random Input Device) does not help.

Always try to enter parameters with the keyboards. 3.1 can = 3.1 sometimes.
Careful work at the modeling stage pays dividends, even with budget software.
GARBAGE IN, GARBAGE OUT.(nuts)
Until I persisted with using the extra decimal, I always had problems with arcs and circles. When you print a drawing so you can input data into a system for g-code, the precision in the drawing will probably drive the inspector nuts.
2 different print setups, for the end user seems to solve this. They have different needs.

Expensive CAD/CAM software can make these issues invisible to the end users but most of us don't have that luxury.:withstupi
At least some of us are not asking the government for handouts to keep our luxury systems going!