Messages

11

General Mach Discussion / Rippled finish only when cutting arcs

« on: December 23, 2015, 01:29:48 AM »

It's arcs, not lines.
I changed the acceleration parameters and the finish is much better, almost perfect. It looks like it will need some further tweaking but it's a software thing.
Thanks!


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12

General Mach Discussion / Rippled finish only when cutting arcs

« on: December 22, 2015, 04:22:12 PM »

Thanks a lot, I'll try some different parameters!


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13

General Mach Discussion / Re: Rippled finish only when cutting arcs

« on: December 22, 2015, 02:31:09 PM »

Thanks, how / where do you tune the servo?

14

General Mach Discussion / Rippled finish only when cutting arcs

« on: December 22, 2015, 02:16:45 PM »

Hello, after many months of mechanical problems with my new lathe I'm now facing a software related problem...

Long story short: lathe had both Z and X axis compromised, ball nuts where pushing the saddle up and down, left and right, so the finish was MECHANICALLY wavy.
Leadscrews have been fixed, sliding surfaces grinded and so on.
When I now cut a straight line (be is only on Z, only on X or any angle) the surface is silk smooth.
So any G1 movement is perfect.

When I make any arc (G02 or G03) I get a rippled finish.
Like here:

I tried J/K, absolute or relative parameters with no luck.

I use servo motors, if this can make any difference.

Controller is a Ethernet kind.

Does Constant Velocity or Exact Stop have any influence with that?

Thanks a lot!


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15

General Mach Discussion / Taper correction

« on: December 18, 2015, 12:57:52 PM »

Hello???


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16

General Mach Discussion / Taper correction

« on: December 15, 2015, 09:55:17 AM »

Hello!
The lathe I have cuts a bit tapered when moving in the Z axis only. It's less then 1 degree and it's annoying...
Is there a way Mach 3 can compensate this error in some way?
Thanks!


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17

Video P*r*o*b*i*n*g / Best setup for probing a trumpet mouthpiece

« on: November 20, 2015, 04:07:50 AM »

Eheh, unfortunately i need to use a 0.2 or 0.4mm radius tip for cutting.


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18

Video P*r*o*b*i*n*g / Best setup for probing a trumpet mouthpiece

« on: November 19, 2015, 03:59:55 AM »

Thanks Eric! I think I might achieve even better results with the mill version of your wizard. Mill unfortunately is out of order at the moment so that's why I've resorted to the lathe.
Gary: in my. Business the amount of material you take away during the final polishing is more than the precision I get while making the measure so there is no big concern. But yes, the better the measure the better the result.


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19

Video P*r*o*b*i*n*g / Best setup for probing a trumpet mouthpiece

« on: November 18, 2015, 11:22:08 AM »

Regarding precision: a trumpet mouthpiece is between 5 and 15 arcs depending on complexity so, in the end, you don't need so many points to infer what's the shape you are copying. What's more important is the offset derived by how much the stylus bends before you have a contact.
This, as you wrote, takes a bit of calculation but it's not that hard.
Let's meet on skype, thanks!

Mouthpiece: I had it, then I exchanged it for a new lathe from Germany that is still not working... I'm am pissed of, badly.


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20

Video P*r*o*b*i*n*g / Best setup for probing a trumpet mouthpiece

« on: November 17, 2015, 10:41:10 AM »

Update: probe arrived, connection made, stylus installed (Renishaw, 15mm long, 1.5mm ball).
I had to install ProbeIt Turn (30 dollars VERY well spent!).

Here are the problems I had to solve: the software can't handle both big diameter ruby tips. 3mm with a step over of 0.5mm won't happen.
If you need a small step over like 0.2 or 0.3mm you need a 1.5 or 1.0 ruby tip.
The software is very easy to use but it needs many points and very close together to behave in a reliable way.
Export is both points and lines Ina DXF file, easily imported into any cad program.

Installation is very easy if you know how to solder two wires and how electricity works... I don't so I asked a friend and watched him doing it. It was easy...

You have to map one of the input channels to Digitize. The probe is always short circuited unless you open it by pressing the probe. This is for safety, makes sense...

The logic of the ProbeIt Turn is simple and clever: you first touch off the piece telling the wizard how big is the radius it's touching. Then you tell it how to move (clock or counter-clock wise) and then it will start probing. Every touch it makes it will move further on the side. If it senses the surface is curving it will try to guess the corner radius and thus it will make a "side step" that will follow the surface to be always square to it.

Problems: the stylus is always prone to some bending when it touches the surface, this depends on the stylus length, thickness, probing feed and probe sensitivity.

All of this can be solved by a little bit of math: you prove an external diameter, then an internal diameter. You calculate how smaller the distance is and this is the error. Divide it by two and make an offset of the scanned profile. Then simply translate the profile towards the center by that amount.

If you have backlash just enable the correction under Mach3, it will be cured properly.

The final test was to cut a mouthpiece with my lathe and then immediately scanning it.
I made a few cross checks and the measures are off by less than 1/100th of a mm!

There won't be many trumpet players here but this procedure can be useful for other purposes as well.

Have a good day!


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