Images of my new pcb milling machine

[rbasniak]

Hi everyone...

After lots os reading and research, I finally almost finish my pcb milling machine.

I would like to share with you and hear about bad things or possible improvements...

Best regards,
Rodrigo Basniak

[mcphill]

Put another shaft support on the main spindle, as low on it as you can. You will get much flex with only one support so high up.

[rbasniak]

Oh... I didn't notice it was hidden. Actually there are two welded supports on the spindle body, one on each end of it =) Thanks for noticing...

[rot]

Hello,

very nice machine that you are planning. Can you give ous more information to the spindle design? Which type of motor are you planning to use?

greetings Rene

[rbasniak]

Hello...

Sure Rene, anything you wanna know just ask.

I'm planning to start manufacturing it in 1 or 2 weeks... I'll post the results as soon as I have some.

The motor I'm planning is a small DC motor, 24V, 27W at 23400rpm. To be true I'm choose it almost in the dark. Someone here told me he sucessfully milled pcb's with 30W motors. So I picked up this cheap one that I think has good rpm and almost 30W. If I'm now very wrong on my cutting force estimations it should be ok.

Best regards...
Rodrigo Basniak

[wildwestpat]

Hi Rodrigo

IMO the welding on the spindle housing should be avoided. You risk distortion of the spindle bearing case a better approach might be to use two split clamps and keep the bearing housing as a simple tubular construction. As the spindle speed increases so does the need to get the bearings into perfect alignment with each other and this would in your design have to be done after all welding and heat treatment to remove the stresses induced by the welding.


I also question the use of all the extrusions for the base of the machine. The copper on a PCB is very thin so you need to have the table flat. I suggest that a simple thick plate with a grid of tapped holes would be both easier to use when clamping the PCB blanks than 'T' slots which fill with crud and jam. I am assuming that the PCB blanks will tend to be similar in size one run to the next. Also a flat plate would provide better support IMO over say an A4 size PCB blank as the PCB has a flexible substrate. You could then machine the the solid alli plate using and end mill in your spindle where as the alloy extrusions would suffer as the sections are not very thick and the anodising would be removed and the base metal may not age as gracefully as standard alloy plate.

I assume the bellows are an artifact of your 3D rendering as they look as if they would not concertina properly. The PCB material produces some very abrasive dust so some form of sealing would be a good idea as well as a dust extraction hood for the spindle.

Looks good so far – have a nice build – regards Pat

[uvodee]

kind of cooling elements?

wow, I must be drunk right now, i just cannot figure it out...


Jean-Pierre

[rbasniak]

Pat,

I thought about this problem with the spindle, but since the housing was supposed to be made of aluminum I didn't see much problem since TIG welding shouldn't produce much distortion. Even though you're right, at my speeds even the slightest distortion could cause some problems. I'll review this, maybe make the housing of steel and support it with nylon supports.

The extrusions I used because I thought on them as a good and light way to ensure stiffness to the base. But now that you told, I really think it could cause issues with these thin layers. I really liked the idea of a base plate milled with the machine itself. I'm imagining a base plate fixed on the extrusions and the milled. I'll spend some thoughts on this.

I'll made a kind of a box around the machine, to protect the environment (it will be used on my apartment ), and also to help with the noise. I have thought about the extraction, but couldn't imagine something different from a vacuum cleaner. Wouldn't be much of a problem, since it'll be used just as a hobby...

Thank you so much for pointing those critical points....

Best regards...
Rodrigo Basniak

[rbasniak]

Jean... LOL.. =) They're just a representation for some flexible material that could be used to hide the inferior part of the base =)

[wildwestpat]

Hi Rodrigo

IMO the spindle is best treated as a cassette and the simple form is a tubular construction as this is easily turned on a lathe between centers. Any form of localised heating will cause distortion - even some bar materials will move when large amounts of the material are cut away and this is important when considering the small tolerances required for mounting high speed spindle bearings.

The dust that you will produce by machining PCBs is nasty and will contain some very small particles. I would suggest that you incorporate a telescopic shroud that encircles the cutter and lowers and retracts with the cutter so as to maintain a very small gap between the PCB being milled and the shroud when lowered for cutting. The shroud is then exhausted with a suitable vaccum source that has filters that capture the smallest particles. It would also be a good idea to exhaust the filtered air outside. There are some quiet dust extractors available that are reasonably low cost with the capability to attach an exhaust hose. The noise as well as the dust are problem areas which if solved at the design stage make for a first class user experience when the machine is completed.

Regards Pat