12 Z flex issue. Should I buy the 96x48x12?

[bsouhlal]

Hi I am anew and planning to by a $x8 shopbot.
I thought of buyind the one with 12 inches for the Z but the sale person told me that there maybe a flex issue and when I cut panel boards, I should built a base table to raised it to 6 inches to avoid flex issues on the Y. HIs that a real issue and what people have been doing to avoid it? Is it better just to buy the normal shopbot without the increased Z. I am a retiree that want to suplement my income so money matters
Many thanks for the guidance
Bobby

[Brady Watson]

It is important to be clear. What do you want to do with the machine?

The only 2 things a 12" Z is good for is really thick 3D foam parts and if you want to run a 6" indexer the full 8 feet.

The reailty is that you are not really going to cut material thicker than 3 or 4" at a time max. Software will allow you to slice thick 3D parts, which brings down the Z height requirement. Large turnings (over 6") are few & far between, and if you wanted to do longer turnings, you would just piece shorter lengths together.

At the end of the day, the money is in 2D parts, by the way.

-B

[bsouhlal]

In fact I am not sure of what I want to do ...
I love woodworking and maybe think that i can supplement my income by building furnitures/ signs etc, using wood I am cutting from my farm. Basically Cherry, poplar and Maple.
I do not want to do that on full time basis and becoming back slave of fix hours etc. I paid my share of slavery in the coorporate world... for too long.
I may do name plate for boats and carving ( 3D). I am quite open to any suggestion.
I live close to Metro DC so maybe a nice potential market. The reality is I am a new retiree that needs to use my brain if any and quite naive. You can give me some gudance before I commit a large chunk of cash.
Many thanks,
Bobby

[dana_swift]

I agree with Brady (most of the time ;) ) and he is spot on with "what are you going to do with the machine? That determines how much Z you need.

I like a lot of Z and have mangled my BT-32 to provide something like 12 inches of Z. Those 12 inches are then lost to the spoilboard thickness (and or vacuum table) and the bit length with any collet extender you might be using. So if the bot has 12 inches of Z and you make your spoil board 3 inches thick. That leaves you with 9 inches. Then if you mount a 4 inch bit with 3 inches protruding below the collet you get 6 inches of Z. Then if your material is 3 inches thick you can pull clear of it by 3 inches when you are all done.

Extra Z does allow more flex, then so does longer bits. It all adds up, but IMHO extra Z is really nice to have.

Hope that made sense.

Also I love the $x8 Amen on the $$$.

D

[steve_g]

I have a 4'X4'X12" (06' PRT Alpha) no matter what size you buy, eventually you'll wish it was bigger. Flex? Yes some... enough that I'm disappointed in my ability to reliability to use my dual Z as a defacto tool changer. Sometimes I notice a small variance in distance between Zs after tugging on the collet to change the bit. Would I have a machine with less Z? NO! Seldom do I need the height to carve into... but I can easily engrave a pre-made box or other object others would have to dissemble or turn down.

SG

[kg4mon]

I'm with Brady and Dana on this one. I thought about a 12"Z but got the regular and have NEVER needed 12". I do lots of 3d HDU signs and when I need a really deep sign, I slice the reliefs. 99% of the stuff you'll probably do is between 3/4 - 4-1/2 inches thickness. I say save your money and get a regular shopbot. It all comes down to what you see yourself doing with it.

[garyc]

Bobby...
Heed the advice of the guys above and the salesperson that you talked to. The 12" Z is akin to you you working off a step ladder. You have less rigidity and power due to the added reach required. This is due to the extra height of the gantry off the frame. Raising the table will only reduce the amount the Z extrusion is boomed out. Doesn't change the rest.

The ShopBot sales staff would love to sell you a machine. They do not, however, wish to sell you one that is not the proper tool for the job. The 12" Z model is NOT made for cutting sheetgoods.

[jerry_stanek]

Save your money and get an indexer.

[crash5050]

just so I understand in my head? an Indexer is basiucally a CNC Lathe?

[bobmoore]

I say get a good hold down system and dust collector with your standard 6 inch. You can always sell a 6 inch and trade up if you get so good as to need a 12 inch z or even an indexer imho.
Bob

[Brady Watson]

just so I understand in my head? an Indexer is basiucally a CNC Lathe?

No. The only thing it shares in common with a CNC lathe is the fact that it turns on axis and has a headstock and tailstock.

A 4th axis indexer, indexes in degrees and is essentially keyed up with the other 3 axes so that you can have synchronous movement between the indexer and the router. A standard 2-axis CNC lathe just spins & X and Z axes do the work with a knife.

Everybody is so quick to push the indexer, however in the real world if I took a poll, I would guesstimate that 90% or more of the indexers ever sold are still sitting in their little mini crate. Very few know how to use them, and even less know how to use them well.

Spend your money on a larger tool, like a 5x10 and get a spindle. You can always do 'the indexer thing' later after you make some money.

-B

[dana_swift]

David- Again Brady's point is very valid. Most people dont use an indexer much, however: if you have work that needs to be rotated in controlled amounts they are the perfect tool.

I have found the indexer to be a very handy tool, and I have only done a little "lathe" type cutting on my shopbot. There are times when I want my part to rotate to a new position so I can do regular XYZ operations on it and the indexer is just way cool.

I bought the indexer without any specific need. Then found a zillion little things like cutting threads (and rethreading):

http://www.youtube.com/watch?v=M1_xu9MQ_cw

I have cut new threads using both taps and dies using the indexer also.

There are just tasks that need SLOW turning of the tool, and the indexer does just that.

I was just posting to the thread on winding field coils with magnet wire using the indexer. Yet another application that is not in the textbooks.

Brady is right.. most of the indexers just sit idle if they ever get hooked up at all. Its a real shame tho..

D

[kg4mon]

There is some good advice here. I have a indexer and I have used it maybe 8-10 times in 5 years. But I do cut 40-60 sheets of plywood a week building commerical and residental cabinetry, countertops and signs.

[steve_g]

In defense of the 12" Z...

Mr. Souhlal

You have been given very good advice by very knowledgeable people... And I agree with them somewhat. Brady's very first comment was "What do you want to do with the machine?" and that remains the elephant in the room... If you're going to be making cabinets and cutting sheet goods all day, the 12" Z is a poor choice. However Since you stated you are retired I doubt that's the case! Custom furniture a retiree is likely to make will often require jigs and fixtures that eat up the Z. I've attached some photos of a project that was brought to me earlier this week... It' a gage pod mockup for a sports car. because I have 12" of Z I was able to make the part.

SG

[bsouhlal]

Thank you for all your comments!I have learned a lot and will decide this WE.
Enjoy ths WE
Bobby

[hespj]

I have a 12" Z. Whilst it's probably true that most of the time I'm cutting sheet goods the real money (and for me the interest) has been in the occasional 3D jobs. Some of these have been foam, some MDF (never again) and some timber. The "slop" is partly eradicated by firstly rough cutting, and then finishing the part.

When cutting sheet goods or other thin stuff I have a 5" temporary "spoil board" in place. I do some 3D stuff with this in place and you could cut boat name boards with a 6" Z.

It's worth mentioning that cutting 3D stuff requires 3D CAD and CAM software which is more expensive and more difficult to learn than 2D software. You've probably really got to want a 12" Z to justify the extra cost and potential hassle. Some of us do.

I also have an indexer which I've used a few times in seven years, but I don't think it's ever earned me any money.

John

[rb99]

I am waiting for a 12" Z to arrive. Now I read this thread...

I have an old PR and I would like to figure out a way to raise the Y carriage when I want to cut extra thick materials. I am thinking of aluminum blocks I would be able to insert that will raise up the Y rails by 5" or so.

Anyone think this might work? Other suggestion? Sarcastic remarks?

[Brady Watson]

Richard,
If I were doing this to a PR, I would use some 4x4 or unequal leg steel angle iron. You could also use AL, just make sure it is stiff enough with twice the wall thickness of the steel you would use (say no less than 3/8" thick in AL). Be sure to really gusset that riser piece in the Y direction or it will be too sloppy. You want to put the longer leg of the angle underneath or on top of the Y utilistrut and bolt it up with at least 3 bolts per member (6 per side).

-B

[rb99]

I can get Boche extrusion that is about 4" square and really solid. I was going to use it as a spacer.

You think it needs bracing to work though...

The extra Z height will be good to have when raising the router I guess...

[danhamm]

Why not just build a single piece gantry, it removes a whole bunch of the problems..

[Brady Watson]

Dan - I agree 100%, but the problem with a PR is, once you do one thing, you have to do another in order for it to work...and then something else to get that thing to work. I bought a PR a while back with the intention of giving it to my dad...and what I wound up doing is just keeping the upgraded PRT control box and motors that was on it, and building a PRT style machine from scratch. It took me a little while to do, but in the end he has a machine that he can use reliably without me needing to go fix it or put it back on the tracks again. For around $1200 in steel, racks and new pinions, and a whole lot of 'sweat equity' and time, he's got a brand new PRT with used motors.

If you went to a PRT style "1 piece' X car, then you have to do something about the X rails. Since the PR rolls on the corners of a piece of utility strut, it gets dicey trying to keep that 45 deg wheel orientation when you goto a PRT style gantry...which means that you would have to come up with a vertical rail for the new X-car to ride on...and then you would probably want to switch over to a PRT style motor mount, which means you'd need to move the gear rack underneath - and then you need angle iron rails for that to work and while you're there you'd probably want to move up to 1/2" rack...Where does it end!!!???

My advice would be keep the upgrades simple. The PR isn't exactly a pillar of strength structurally - especially when you start adding more speed to it. If you are going vertical - either lower the table, raise the X car or raise the Y car. Just make sure it is well gusseted/triangulated to reduce the wobblies...It may sound hokey, but another pair of Y rails (utility strut) with a piece of wood in the middle, sandwiched between the original Y rails and the new ones, may be an easy option. You can roll down to Fastenal and Depot or Lowes to get everything you need and raise it up in just a couple of hours.

Food for thought....

-B

[rb99]

I have learned from experience to really over think any change as the domino effect kicks in and a simple thing turns into days and days of work.

I would love to build a machine more like a PRS with the nice single Y. Ain't gonna happen...