Tombstone Selection

[DTHOMSON]

We are receiving a new Okuma MB-4000H in about a month. This is our first horizontal and need to select a few tombstones. We will start off with just 2 pallets and an additional 4 pallet pool will show up in about 4-5 months. Almost all our work will be aluminum on this machine and planning to build replaceable fixture plates to mount on each face located on common tooling pin locations and bolted to the face of the tombstone. So questions:

Is it a "best practice" to buy tombstones without holes and plan to add the tool pins and tapped holes on the machine?

Is it best to stay with cast iron for something like this or go with the aluminum to save wear and tear on the machine?

Tombstone supplier recommendations?

Initially I'm looking at a 4 sided pallet for mid sized parts and a 6 sided pallet for our smaller parts.

Thanks for any and all input!

[crazy^millman]

Tombstone City in one if you are not making them yourself. Kurt, Carr Lane, and many many others make tombstones. I always tell someone new to anything bring in an consultant or the OEM and have someone from their application staff help you. Going at something blindly will get the job done as a broken clock is right 2 times a day, but gleaming knowledge from someone who has done it before is invaluable and worth every penny spent.

 

Here is a link: http://cnctombstones.com/

[Sticky]

If you can use an off the shelf tombstone I like KURT, they are made in the USA and have great prices on a reasonable amount of sizes. Tombstone city are Taiwan MFG iirc.

In certain cases rolling your own can be a good option too. Really just comes down to what you need. I have about 20 tombstones in my own fms, and have made another 10 for other people, and they are all a bit different. You need to get all your parts together, figure your cycle times, fixturing costs etc and go from there.

 

It is best practice to put all your locating and tapped holes in yourself. I would make absolute sure you do have the machine square though. One thing I have learned about HMC's is that techs always do a xxxxty job on YZ squareness. Level and square are completely different.

 

For most things Aluminum does fine tombstone material. I have about 6 tombstones in my FMS that have 1-1.25' thick walls, 356 aluminum, and they do fine drilling 2" diameter holes in 304ss 26" off the pallet face. If you are utilizing all your Y travel, cast steel or iron adds up fast in the weight dept.

 

6 sided pallets RARELY offer an advantage on smaller parts, unless you need to hit more then 3 sides per op.

[Guest]

...One thing I have learned about HMC's is that techs always do a xxxxty job on YZ squareness. Level and square are completely different....

You sure they ALWAYS do a $#!++Y job? It can't be that $#!++Y floor people put their HMC's on can it? Or the 3 separate concrete pads the machine sits on, or the single pad with 5 cracks running through it now can it? Nahhhhhhh. Can't be. EVERYONE pours the recommended foundation so everything stays square and parallel.

[DTHOMSON]

Thanks for the input everyone. The goal is to get a steady stream of complete assemblies each week rather than a large number of parts for a few part numbers. So it is planned that each tombstone face will likely have a different part number. Some faces will actually have multiple part numbers.

Sticky - Could you elaborate on your experience with 6 sided tombstones? I also appreciate your comment on the aluminum tombstone.

Crazy - I have spent some time with the applications dept but there seemed to be a lack of familiarity with these types of questions. They know the machine, but I believe there is a greater breadth and depth on this forum for practical, real world considerations. It also gives me additional questions to ask them as well.

Foghorn - I have followed the advice of you (and others) on this forum and we did pop for a 30" pad for this machine. It's our first horizontal and I wanted do it right. We are transitioning from Haas VMC's....and it will be interesting I'm sure.

[Sticky]

You sure they ALWAYS do a $#!++Y job? It can't be that $#!++Y floor people put their HMC's on can it? Or the 3 separate concrete pads the machine sits on, or the single pad with 5 cracks running through it now can it? Nahhhhhhh. Can't be. EVERYONE pours the recommended foundation so everything stays square and parallel.

 

Of course not having a proper foundation is a problem, albeit a different problem then what I was talking about. Sorry I said always?

 

What I am talking about is most hmc installs I see the techs are often not even bringing a square to the job, and if they do, its a 200mm. Which is a problem when most 300mm hmc's need at least a 500mm square to get YZ done properly.

 

Thanks for the input everyone. The goal is to get a steady stream of complete assemblies each week rather than a large number of parts for a few part numbers. So it is planned that each tombstone face will likely have a different part number. Some faces will actually have multiple part numbers.

Sticky - Could you elaborate on your experience with 6 sided tombstones? I also appreciate your comment on the aluminum tombstone.

Crazy - I have spent some time with the applications dept but there seemed to be a lack of familiarity with these types of questions. They know the machine, but I believe there is a greater breadth and depth on this forum for practical, real world considerations. It also gives me additional questions to ask them as well.

Foghorn - I have followed the advice of you (and others) on this forum and we did pop for a 30" pad for this machine. It's our first horizontal and I wanted do it right. We are transitioning from Haas VMC's....and it will be interesting I'm sure.

 

For lots of parts without 90* side features you can get more parts on a wide 4 sided tombstone (column being as wide as the pallet).

 

This can push you close to your swing limit for the machine, and if the parts have a lot of Z thickness, you might exceed the swing. This is where a 6 sided tombstone can shine, because with 6 smaller sides you can sit closer to your center of rotation and fit inside the swing.

[RaiderX]

I would consider drawing max work piece diam. and place some of your most common parts up to see what configuration tomb works best for your average work. you can run out of envelope very quick with pallet, fixture and stock stack. putting hole pattern in on machine has always worked best in my experience (standardize between tombs) this will let you know at all times where you are within the envelope and be able to easily use either or tombs.

 

Doug

[Matthew Hajicek - Singularity]

We're using cast iron, faced and holed on the machine. But then again we're doing large steel blocks, not a bunch of bitty bits of aluminum.

[Guest]

Of course not having a proper foundation is a problem, albeit a different problem then what I was talking about. Sorry I said always?

 

What I am talking about is most hmc installs I see the techs are often not even bringing a square to the job, and if they do, its a 200mm. Which is a problem when most 300mm hmc's need at least a 500mm square to get YZ done properly.

Wow. New machines getting installed without a square? That's pretty uhhhhh, messed up I guess you could say. Our guys use 300mm squares. The 500's are almost 200lbs. That's too much to ask for a guy to lug that thing around. We had a ceramic square that was 36" but ceramic just isn't durable enough for everyday field use. Even when you're extremely careful.

 

IIRC most of the squareness checks I see in the machine accuracy reports from the factories state a value in 300mm.

[betts]

I will only buy another tombstone from "Tombstone City" if I am the most desperate man on earth. I can't find huge fault with their product, though it is low end. I will not tolerate crappy service and rude people. I don't mean average rude, I mean flaming hole out of control.

 

As for shape my recommendation would be plan by the jobs you intend to run. If they are sharing many jobs then you can make a good case for going with a simple design and some will benefit, some will not. I have some real odd designs that work wonderful, but they were for specific reasons.

 

As for where to purchase we use a lot of Amrok from AME. They do custom if you want, and we have on some. We normally put grid holes and such in ourselves though. They are not cheap but you can expect excellent workmanship. Like most custom builders I pad their quote time by at least two weeks if my production dates are counting on it being there.

[MIL-TFP-41]

Weight, as mention before, is a huge issue. Our matsuura 405 is rated at 880lbs. A cast iron T column weighs almost that much alone. These are very rigid and MUCH lighter. (no particular brand loyalty to Kurt...just an example)

[dstryr]

Abbott workholding is where I got my 2 aluminum ones. Next time I'll just build my own.

[Sticky]

We're using cast iron, faced and holed on the machine. But then again we're doing large steel blocks, not a bunch of bitty bits of aluminum.

 

I think the needing steel/cast iron etc for tombstone for "heavy" work is a common misconception. It certainly isn't going to harm anything, so if you have the weight capacity then its not too big of a deal, although it does accelerate wear on the machine. I wouldn't have the slightest reservation about setting up a 200lb block of steel that needed heavy hogging on a 1.5" thick aluminum angle plate or tombstone.

 

Wow. New machines getting installed without a square? That's pretty uhhhhh, messed up I guess you could say. Our guys use 300mm squares. The 500's are almost 200lbs. That's too much to ask for a guy to lug that thing around. We had a ceramic square that was 36" but ceramic just isn't durable enough for everyday field use. Even when you're extremely careful.

 

IIRC most of the squareness checks I see in the machine accuracy reports from the factories state a value in 300mm.

 

Yeah I know, its crazy. It actually seems to be getting more common. So many techs just level it and leave. And that might be a good thing, because they probably couldn't square it anyways.

 

The 500mm granite 5 sided squares are heavy, I wish I could have afforded a Ceramic one, those are actually pretty light. I think Ceramic are the best for service work because they are so thermally stable. But you do need a good Pelican case and you have to handle them carefully. The granite ones really need to sit in the environment they are used in for a while to stabilize.

 

Over 300mm is a common squareness value, but is a REALLY poor indicator of squareness particularly on these newer hmc's with big Y travel. its pretty easy to get .under 5 microns YZ squareness over 300mm when you put the square on the pallet, throw a 500-600mm square on the pallet and trying to get under 5 microns over 600mm is another story.

 

 

Weight, as mention before, is a huge issue. Our matsuura 405 is rated at 880lbs. A cast iron T column weighs almost that much alone. These are very rigid and MUCH lighter. (no particular brand loyalty to Kurt...just an example)

 

This is why I mostly have aluminum tombstones, and then add steel wear surfaces to them.

[Pilot Plant Supervisor]

I've been using Jergens for my vise column and angle plates. Recently, I needed a tombstone in a hurry but the lead time from Jergens wasn't going to work for me. My tooling vender put me in touch with Stevens Engineering and they bailed me out and delivered a very nice tombstone made to the Jergens specs so it would fit the rest of my tooling. That said, I recommend either company, as the products I have recieved have been first rate and the engineers from both are easy to work with.

[Charlie Pierson]

I would consider using a Chick 4-sided double vise tstone to start with, cuz' it just comes in too handy for all sorts of work.

Next I would make your own 4 sided tstones w/ a common bolt-pin pattern. Make them out of aluminum and do your fixturing w/ steel sub-plate mounted to the aforementioned aluminum tstones.

A square configuration is OK if you only need to get at two faces of your parts, unless the part is large enough that you can reach 3 faces.

My favorite config looks like a + sign when viewed down the centerline of the B-axis. There is plenty of clearance to get to 3 sides of your part + some non-90 degree features as well without the previous part getting in the way of the part you are working on.

I find that the more sides you have, the less room and feature reach you have you have. (Tstone sides + feature faces = extended tooling (at best).

Consider attempting to finish the part w/ multi-ops on the same tstone, instead of fitting as many parts as you can (1-op) on the tstone.

Instant feedback and faster throughput can be gained this way (though a bit longer setup and more available tools are required)

 

my 2 cents,

[FROZEN]

I have had great luck using http://www.abbottworkholding.com/. I also would look into chick vise with machinable jaws. Vise is the fast fixturing.

[RaiderX]

just ran accross this in my journey of searching up 800mm tombs

http://www.omlusa.com/pdf/CATALOG_USA_Tomb_01.pdf

know nothing about them but would love any input anyone has

[crazy^millman]

just ran accross this in my journey of searching up 800mm tombs

http://www.omlusa.co...USA_Tomb_01.pdf

know nothing about them but would love any input anyone has

 

Crankwebs that is a new word for me. Sorry I know nothing about them, but picked up a new word.

[GoetzInd]

Haha never heard of either. Interesting.

 

Mike