[hoss2006]

A new PDB version is printing right now that addresses the possible binding lacl brought up, this one is much more on center so should lift straight up like the PDB 2, about as tall as the first one but doesn't angle so far forward and has a different lever and cylinder mount, same ratio but needs 4+ stroke.
Hoss

[mhackney]

Hoss, it seems once you get into the 4" stroke range that this could be used manually with a lever too. Perhaps a phase 1 manual and Phase 2 pneumatic drawbar?

cheers,
Michael

[hoss2006]

Hoss, it seems once you get into the 4" stroke range that this could be used manually with a lever too. Perhaps a phase 1 manual and Phase 2 pneumatic drawbar?

cheers,
Michael

Hmmm, something to think about.
There have been a couple manual leverage ones done on the Tormach.
This is using 5-600 lbs from the air cylinder with the lever now but maybe make a version that uses a cheater bar of sorts the user can make as long as they'd need and so it's removable and out of the way.
The MAD on steroids.
We're on it, something to do tomorrow while parts are printing, thanks Michael!
Hoss

[mhackney]

I'm already thinking this would be nice scaled down for my X2. I don't want to make the investment for a full PDB but something like this would be just the ticket.

cheers,
Michael

[hoss2006]

Yeah what would concern me is the force on the head pulling down on the lever, I think the g0704 could handle 50 lbs or so but that might yank an X2 head off.
But of course the X2 doesn't need as much belleville tension either, like half of what I was planning here.
Hoss

Edit: as I think about it I think that using just a lever by hand we'd lose the floating aspect of the scissor action of the floating design and the full force of compressing the bellevilles would be transmitted onto the spindle.

[mhackney]

Good point, I hadn't thought of that.

cheers
Michael

[Kibo]

Hoss, the design you have there looks like it's going to put a lot of side load on the cylinder rod. It would be better if you replace the slot on the lever arm with a pivot and hinge the cylinder mounting plate centrally so it self-aligns with the force on the lever arm through the range of motion. Just a thought.

[hoss2006]

Hoss, the design you have there looks like it's going to put a lot of side load on the cylinder rod. It would be better if you replace the slot on the lever arm with a pivot and hinge the cylinder mounting plate centrally so it self-aligns with the force on the lever arm through the range of motion. Just a thought.

That is exactly what the new version does.
I didn't care for the friction of the lever slot so the new one has oillite bearings for the cam lever ends and the cylinder mount pivots.
Should have the mockup finished printing today.
Hoss

edit: The side load wasn't of much concern as the stroke was 2 inches or less, the angle of the lever slot and the cylinder rod only varied 10 degrees and the cylinder rod is very stout. Made much more of a difference with the new long stroke version so the pivots cured that.

[hoss2006]

Here's a quick vid of PDB 3 version 2 and a mount I made for my new P1AS.
Hoss

https://www.youtube.com/watch?v=mUky5Yqz86k

[Zenji]

Hoss, I'm a big fan of your work, only one critique though.
Could you start a new thread please? 480 pages, too much!

[hoss2006]

Can't break records that way. oh I find searching 2 threads easier than 20 spread out all over anyway.
Hoss

[Analias]

Can't break records that way. oh I find searching 2 threads easier than 20 spread out all over anyway.
Hoss

Not to mention the countless number of folks who have marked the thread as one of their favorites and have monitoring enabled.

-Freeman

[AlanB243]

Hi Folks. I've been away awhile, and I see I've some catching up to do. I'm re-starting my stalled CNC project, and need to decide which mill to get.

I've been planning on getting the G0704 version of this mill, but I see the PM BF25 has a BLDC motor and belt drive standard. I presume the Grizzly still has the plastic gears. How is that new BLDC motor working out and is it worth the extra cost (1600 vs 1300)?

Are there any other differences that I should be concerned about??

Thanks to Hoss and everyone else here who have made a community for this CNC project, it is a great help.

Thanks, Alan

[hoss2006]

Welcome back Alan,
The pm25 with the bldc is a relatively new offering, haven't read anyone here yet with a review of one, don't know if they've shipped any yet, last word was PM was changing suppliers for the third time.
Best bet would be to contact them directly for news.
Hoss

[AlanB243]

OK, Thanks Hoss. And thanks for the Phase 3 updates to the DVD set I purchased awhile back, very nice!!

I'm not quite ready for the mill purchase yet so I'll watch awhile. I prefer a really good motor, had bad motor problems on the G0516 lathe, ended up using a monster DC treadmill motor and SCR driver there. Still have the last new Grizzly motor in the box, had refitted it by the time it arrived. Have been reading through the G0516 motor problems on here from the early days. I also want to do synchronized tapping eventually and the BLDC might make that easier, one less encoder to add. So buying a better motor from the start is appealing, though buying it cheaper and upgrading with 1100W BLDC has some appeal as well, though it is yet another project.

Looking forward to hearing from those with the new PM25. Especially those putting phase 3 dual-nut ballscrews on them.

[hoss2006]

The PDB 3 ver.2 fits nicely on the mill, very happy with the balance with the air cylinder on the mockup even as huge as it is.
Going shopping again for a 2.5 inch bore cylinder, this one is a tad on the overkill side now that it's seen in person.
Time to start making some chips.
Hoss

https://www.youtube.com/watch?v=j9-W_IsQwAc

[Fastest1]

Hoss, @ 80psi, if you are generating 3300lbs of force, is the arm or additional leverage necessary? I wouldnt think so.

[hoss2006]

Hoss, @ 80psi, if you are generating 3300lbs of force, is the arm or additional leverage necessary? I wouldnt think so.

3300 lbs is with the leverage, the 80mm cylinder puts out about 600 lbs (@80psi) x 5.5:1 leverage ratio = 3300, on paper anyway.
Hoss

[hoss2006]

Snagged a Fabco air cylinder on Ebay for $25, it's a 2.5 in. bore, 4 in. stroke pancake type (G-521-X)
This is what I'd use as the minimum for the PDB which should be good for what I used before successfully with no pullout on the 0704, about 1500-1800 lbs holding force.
I can however run at much higher minimum pressure with the compressor I have but I'll test at 80-90 psi first to see if this works as expected.
Don't go rushing to buy cylinders just yet, you might wind up with extras like me.
Cylinders of this size aren't that expensive even new so be patient.
Hoss

[gcofieldd]

Hey Hoss, have you seen the lever drawbar on the Novakon Pulsar? That seems like a good solution for people with no interest in an ATC. I have been thinking about something like that for my BF20. I would be curious to see you design a version of that...you are faster than me