Proxxon MF70 - USB to parallel adaptor

[atferrari]

I've found no better forum to post this question. Sorry if wrong!

Almost a year ago I decided to get a Proxxon MF70 for milling PCBs. (Even asked "how to start" here).

Something that helped in delay the buying was the eventual difficulty to be confined to control that machine via parallel port.

To my question on controlling the Proxxon MF 70 via USB, Peter Urban from www.usovo.de who does the modification for CNC, said:

No, maybe there comes an adapter from USB to parallel. But the machine is almost parallel. So you can update it later to USB.

Does any owner of that machine solved the conversion USB to parallel in a reliable way?

I am interested in starting milling PCBs as soon as I can. It will be good if I can buy the adaptor in Europe (UK or Germany) when I pick up the machine.

PLease help me with just proven solutions, no guessing. Spent too much time / $ in non working solutions along life.

Definitely I will appreciate any concrete suggestion coming from hands on experience.

Gracias.

[TarHeelTom]

Using USB to drive a machine contains many problems.

The machine controll engineers understand that it's getting harder to buy a computer with a parallel port, and are working on making this work in USB in the distant future.

The controller software needs to send movement signals to the cnc drivers at precise timing intervals.

USB prohibits that, as it contains its own timing information. But it's very easy with a parallel port.

Your computer is basically a parallel device.

You can buy a parallel port card to plug into one of the expansion slots inside your computer for about $30 US. If you've already got the PC, you need to take a picture of the inside of the computer, showing the expansion slots.

Keep in mind that for $30 you can frequently buy an older computer which already contains a parallel port. For this type of work, older computers often work better.

Tom

[joshua.robot]

As Tom mentioned, you can not use USB for applications with hard timing requirements.

Writing as an engineer who has developed X86 (32 bit PC architecture) based real-time instrumentation let me personally assure you that there USB is incapable of meeting the hard timing requirements needed for many CNC machines. Any engineer worth his / her salt would not specify USB for use with any time critical application.

USB is not a robust communication protocol. It was designed for peripheral communication only. Unfortunately, USB has caught on in the market place, and is being used in all sorts of inappropriate ways.

If a CNC system were designed to work with USB, it would have to use buffering and it's own controller to pre-load and buffer move instructions prior to execution.

While not discussed in detail, this project utilizes a very cool RS-485 network / node based communication control protocol for CNC. Fab-In-A-Box is essentially a robust operating system that can be readily adapted to different machines, axis and is computer platform independent. Check it out, it's quite impressive.

Anyway, I'm sorry that I don't have a solution to offer you!