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DIY Calibration panels for HP/David

Posted: 09 Oct 2018, 04:21
by Farquarl
Hello,

I would be really glad if some of you could share how they build their calibration panels.
I am not statisfied with mine, the scans get warped and are therfore hard to align.

Best regards,
Thore

Re: DIY Calibration panels for HP/David

Posted: 09 Oct 2018, 15:39
by Micr0
I've used a number of different methods to make panels ranging from 60mm to 1000mm. The best panels (the ones that produce the most accurate scans I made on one of my VMCs. The smaller ones I made by milling away white vinyl that was layered over 2 layers of black vinyl on glass plates. The larger ones were made from white Laminate Melamine and I milled the circles .1mm deep, then filled then with black paint. These were held by 3D printed holders for the small panels and CNC'd Aluminum holders for the larger ones. I''v tried printing patterns with a laser printer, Roland vinyl cutter and having anodized aluminum laser engraved. None were as accurate as the CNC'd parts.

Re: DIY Calibration panels for HP/David

Posted: 11 Oct 2018, 04:40
by Farquarl
Thank you for your input!
I don't own a vmc sadly but i'll buy a CNC router. Maybe i should go this route than. I want to scan really small items and therefore precision of the panels ist crucial.
Is there a list of sone sort that shows the important factors?
90° is important ofc and the distance between the dots as well. But what ist about the distance between the twp sides of the panel, their rotation and alignment?

Cheers

Re: DIY Calibration panels for HP/David

Posted: 01 Nov 2018, 02:58
by goldenfab
I just purchased the software (v5) and it did not come with the pdf file for the calibration panels. Does anyone know where I can download them?

[Edited: I just fond out they are in my program file directory C:\Program Files\HP 3D Scan 5\printout]

Re: DIY Calibration panels for HP/David

Posted: 05 Nov 2018, 14:22
by Micr0
goldenfab wrote: 01 Nov 2018, 02:58 I just purchased the software (v5) and it did not come with the pdf file for the calibration panels. Does anyone know where I can download them?

[Edited: I just fond out they are in my program file directory C:\Program Files\HP 3D Scan 5\printout]
They are also available on Davids old download site. Just google david laserscanner and it comes up.

Re: DIY Calibration panels for HP/David

Posted: 05 Nov 2018, 14:45
by Micr0
Farquarl wrote: 11 Oct 2018, 04:40 Thank you for your input!
I don't own a vmc sadly but i'll buy a CNC router. Maybe i should go this route than. I want to scan really small items and therefore precision of the panels ist crucial.
Is there a list of sone sort that shows the important factors?
90° is important ofc and the distance between the dots as well. But what ist about the distance between the twp sides of the panel, their rotation and alignment?

Cheers
My understanding, and big bomber understands this better than I is that the most crucial parameter is the positioning of the dots and the flatness of the panels. David can compensate for the panels not being perfectly normal to each other. And it has compensation for the panels being slightly rotated retaliative to each other. That said, it is always better to not have errors that to try to compensate for them.

As for the VMC slash Router. Most CNC routers use stepper motors without encoders. Even with encoders, steppers are not anywhere near as good as servos when it comes to positional accuracy. Not to mention the difference in the mechanism for translating the rotational force of the motor to linear motion of the machine. Linear rails with preloaded ball screws will be far more precise than V rail and rack and pinion or gear reduction to timing belt drive.

However, all this is really mostly academic. You can still get good calibration results with less than laboratory grade calibration panels. It will take a little bit of work to tweak it till you get it where you get acceptable results. Read some of the threads on the forum about RMS error and calibration to understand better what you are shooting for.

Re: DIY Calibration panels for HP/David

Posted: 06 Nov 2018, 05:53
by Farquarl
Good to know!
My router will have servos and preoloaded hiwin rails, so in that regard im set. Well at least i should have betrer precsion than my laserprinter.
Thanks for your input.
Cheers

Re: DIY Calibration panels for HP/David

Posted: 30 May 2022, 18:39
by Tyrone2022
Hello
As for the VMC slash Router. Most CNC routers use stepper motors without encoders. Even with encoders, steppers are not anywhere near as good as servos when it comes to positional accuracy.
This is not true, in general by nature stepper motors are much more precise than servo motors, encoders in fact are even not needed to obtain accurate positioning with stepper motors

Servo motors instead are quite imprecise and can be used with success for accurate positioning only using encoders and quite sophisticated electronics to monitor what they do and correct all errors on the fly.

Both type of motors can be used with success, with stepper motors it is possible to obtain excellent results at relatively low cost, this is true until the machine structure is lightweight, also with servo motors is possible to obtain excellent results, but at a much higher cost and using a much more sophisticated electronic system, servos are also capable to move with ease very heavy machines.

In other words, for what is concerning precision and accuracy stepper motors are excellent, but can not be used for heavy machines nor for high speed applications, servo motors are not as good, can give excellent results too but only if using encoders and good electronics, are necessary in order to move heavy structures and/or for high speed applications.

Of course accuracy, precision and repeatability also heavily depend on the mechanics used, so in general using the same good quality lightweight structure and mechanics it is possible to obtain excellent results using both kind of motors, but the cost with servo motors will be much higher.

Re: DIY Calibration panels for HP/David

Posted: 02 Jun 2022, 17:07
by Micr0
If your application is something like a laser or FDM 3D printer with virtually no lateral force on the head, then yes. However, if you are trying to push a cutting tool into a material like on a router, the structure needs to be far more rigid/massive, and stepper suffer proportionally.

We've used there on a number of projects of various sizes. Incredibly fast, accurate and powerful.

https://teknic.com/products/clearpath-b ... th-servos/