Extra Z axis

[benchmark]

Hi

Can anyone tell me what is the difference between the additional Tandem Z axis ($1995) and the additional independent YZ axis ($2995)

Thank you



Paul

[henrik_o]

Paul, the tandem Z cuts in tandem with the main Z. It is used for producing two parts simultaneously, and only that (it "copies" the main Z).

The independent Z is another Z axis besides the main. It is used for having another bit in that Z and thus effectively making your bot a two-tool machine.

At least this is how it was explained to me by Shopbot.

If you are thinking of buying a machine with an additional independent Z, please observe that the mounting of this added z steals some space so you need extra space on the table for both Z axises to be able to reach the whole sheet.

[benchmark]

Thanks Henrik,

I will be going for the independant Z which will be a loss of 355mm on the Y axis.
If I need to machine 3050 x 1525 sheets I will have to remove the independant Z.





Paul

[henrik_o]

Paul,

You can see a picture of a PRS with an independent Z in this (http://www.talkshopbot.com/forum/show.cgi?tpc=312&post=55163#POST55163) post.

Please note that it is not possible to win any travel by removing the tool from the independent Z: it is the gantry that limits travel and you can not do anything about that.

Maximum Y travel on the main Z of our PRS Alpha is approximately 1495mm. If this is unacceptable to you, I am afraid there is no solution but to skip the independent Z or live with the consequences of being forced to process the non-covered space with the independent Z.

If you intended it mainly for drilling, you could buy the air drill unit instead.

[benchmark]

Henrik,

Is the blue back plate all one piece with the two Z axis mounted on the one plate or are they seperate back plates. My plan was a 120 x 60 with one Z axis mounted and then mount the complete second Z for machining 96 x 48 sheets with two spindles.

I will be mounting a drill in front of the main Z axis.



Paul

[benchmark]

Henrik,

This is what I am looking for but closer together.
457

Many thanks to Bill Young for the Sketchup file.


Paul

[henrik_o]

Paul,

The gantry ('back plate') is in one piece.

Exchanging a double-gantry model as per your illustration would be a serious hassle, if it was even available (which it is not, afaik).

I think the main issue here is the frequency of machining panels that have a width exceeding the max travel of the main Z. You can machine them with a main and independent Z installed, but you would need to use both the main Z and the independent Z, which would be a hassle to program if the cuts overlap, not to mention accuracy issues.

If machining panels exceeding ~1495mm, where the whole width needs to be machinable, is going to be a common occurence, then I quite honestly do not see an elegant solution to that with two Z's.

If, on the other hand, it will be relatively infrequent, you could perhaps live with some workarounds.

What are you going to cut with it? Do you really need to do 120x60 sheets? Etc.

[benchmark]

Henrik,

I need to look at a machine close up to see what is possible. I will speak to Shopbot to see if there is a PRSalpha in the UK.

I have some large components in plywood to machine from 120x60 sheets.

Thanks for your help


Paul

[henrik_o]

Paul,

You should definetly talk to shopbot. If there's no PRS Alpha in the UK, however, I'd be glad to measure and photograph any particular parts you are interested in since my PRS Alpha is of the 120-60 variant with an independent z. Just let me know.

Regarding larger sheets, do they need to be machined across the entire width? As stated previously, you have a max of about 1495mm on the main Z afaict -- this should normally cover almost all machining on 1525/1530mm wide panels, except for those cases where you absolutely must get from end to end.

[harryball]

For the occasional times when full width panels need to be cut rather than removing the 2nd Z couldn't you load the same bit in both spindles and share the work? Let the left spindle cut parts over to the left and the right over to the right?

I know toolpathing would become more difficult and you would need your alignment dead on... but it's a thought.

Robert

[benchmark]

Henrik,

Thank you for the offer of pictures and measuring, but I have found a PRSAlpha less than 1 hour away.

I have spoken at length with Chris at Shopbot and it seems the way to go is an independent Z with its own Y motor fitted with a reversed back plate so the two Y motors are opposed to each other. This will give me the option to drop the bottom V rollers and lift off the Z-axis when I need to machine 10 x 5 sheets.

Robert,
As you suggested in splitting the cutting file between the two spindles ….. I think there might be too many “user” errors that way.


Thanks

Paul

[henrik_o]

Sounds good Paul, Chris knows his stuff, he (et al) was very helpful in getting me up and running.

The suggested solution sounds very interesting, had no idea that was offered. Be sure to post pics and a good description when/if you get that far!

[benchmark]

Henrik,

I have just placed my order, I will keep you informed.


Paul

[henrik_o]

Great!

There's so many interesting things happening regarding extra axises right now, this one adds to the merry mix.

Now, Paul, get ready for anticipation-of-delivery stress

[benchmark]

I still have my trusty old Shobot, but I am looking forward to the new arrival as I am moving into a new workshop...Once the builders have finished !!!!

[henrik_o]

Aha, I see. Expanding the business and doing some upgrading, are we? Sounds great, Paul.

I have ~12,000 sq feet (in 2 floors, bummer), but desperately need a new attached machine hall. Must coax the neighbour to give up some horse grazing ground, but with my luck he'll have to think about that for, oh, I don't know, a year or two.

In any case, good luck with this and keep us updated.

[bill.young]

Hi Paul,

Glad you could get some use out of the benchtop model...I'll try to do models of the various Z options when I get some time.

FYI, I've just posted a preliminary version of a PRS4896 in the 3d warehouse that may be helpful for shop layout, etc. As with the benchtop model there have been some modifications to make the models smaller and easier to do, but they are pretty close to the current shipping model.

http://sketchup.google.com/3dwarehouse/search?uq=11727467109187197754

Bill

[benchmark]

Hi Bill,

Thanks again, I will stretch the 9648 to 12060.


Paul

[bill.young]

Hey Paul,

I've updated the PRS96 model in the 3d warehouse with one that's a little more accurate and better oriented with the X and Y axis in Sketchup. I'll try to get models of the rest of the standard sizes uploaded soon.

Bill

[benchmark]

Thanks Bill,

Don't you just love Sketchup.

Paul

[tradition_wood]

So what if you wanted to mount the airdrill attachment, do you need a 2nd Z or an independant Z, one of the jobs that i want to run on the bot when we get one has a series of holes in each part so it would be easier on the drill than the spindle.

[bill.young]

Hey Geoff,

With the PRS tools you can put a single air drill on a single Z, or mount two air drills on that Z if you want. You can also do the same thing on a second Z, giving you the ability to have up to 4 air drills on a single tool.

Bill