Maximum workpiece weight for a 1960s Deckel FP2 ?

I need to do some machining work on the underside of the table from a cylindrical grinder (mounting an encoder spar) and want to use my 1960s Deckel FP2 for this. But the part is heavy and I am concerned that it might overload Z or even tip over the mill (which is not bolted down). I am sure that I have seen maximum workpiece weights for the machine listed somewhere but can't find those. Does anyone here have that information? This would go on top of the large fixed horizontal table which weighs about 50kg.

Here's a first idea (from the manual for a later aktiv FP2)...




And here's the answer : 300kg

Hey Bruce,

What TNB said stands for your large angular table as well, as may be found in an brochure I checked (Deckel FP2 Brochure May 1969 - Small). Can't post image at this moment, but it's 300 kgr.

(if the thing is very large and protrudes from the table, place a jack or a support of some kind just to be on the safe side)

Dear Tien, Dear Thanos,

Thank you both! This is good, because the part is probably about 100kg and the horizontal table adds another 50kg. So the total of 150kg is well below the 300kg limit.

Thanos, yes, it will stick out on the left and right ends. If it's not well balanced I'll rig up a support.

Cheers, Bruce

ballen said:

Dear Tien, Dear Thanos

Thank you both! This is good, because the part is probably about 100kg and the horizontal table adds another 50kg. So the total of 150kg is well below the 300kg limit.

Thanos, yes, it will stick out on the left and right ends. If it's not well balanced I'll rig up a support.

Cheers, Bruce

Click to expand...

Hey Bruce,

not that it matters at the point but I think the 300 kgr limit is not total plus the table, it's load FOR the table itself.
I still cannot post pictures but I checked that brochure again:

-swivelling table:
weight: 60 kgr
load: 200 kgr
-full range swivelling table:
weight: 130 kgr
load: 300 kgr

no need to go on, I think the load weight limit of the saddle itself is much higher than 300 kgr!!

The machine can take a lot of weight on the table until something breaks.

The problem is more with the torque and weight shift that happens when the table moves left and right, as the whole carriage moves along. More weight creates more weight shitft torque and more table drop at the ends of travel, especially if the machine is worn or the X-axis gib isn't properly adjusted, as the gib is essentially all that prevents the table from rocking/tilting.

Thereby the heavier the part, the more convex the cut along the x-axis.

The table carriage used on larger Mahos, FP-CC, and FP-50/60/80 are much better in this aspect.

I got my part (upside down table from my cylindrical grinder) on the FP2 and realised that I have additional complications. I need to mill about 0.7m (28") at the end, and the part is 1.7 meters (68") long. The X travel of my FP2 is 500mm (20") and the mill table is 0.8m long (32").

The good news in this is that all I am doing is simple 12mm (1/2") wide 3mm (1/8") deep slot plus some small threaded screw holes, and my tolerance is 0.1mm ( 0.004"). The part has precise ground surfaces that I can reference and index from. So I can clamp a pair of 123 blocks to the mill table which ride against the ground front edge of the part. That will allow me to mill 350mm then slide the part along 350mm and do the remaining 350mm.

To solve the nasty balance problem of having more than half the part hanging over the edge of the mill table I'll set up a support table to the side leveled to the mill table. But this means that I need to work without using Z. I can use the vertical quill for the 3mm of Z-direction travel that are needed, BUT I don't have a way to index the quill accurately. The small indicator dial has 0.5mm (0.020") markings and I need something that is a factor of ten more precise.

So a further question for this group: is there a decent way to index the quill on a standard FP2 long reach vertical head that will get me within 0.02mm (0.001")? If I can't figure something out I can swap in the vertical boring head, which has a holder for a dial indicator to index the quill. But I don't like to use that for milling, the bearings are wrong.

Cheers,
Bruce


PS: hmmm perhaps I should do this in horizontal mode. Issue then is to keep the part balanced on its edge.

You just need to adjust the vertical quill 3mm once or multiple times? Adjustment while the spindle is running or stationary? If adjusted while spindle is stopped can't you use a magnetic base indicator holder mounted on the head and indicate on the top of the drawbar? Remembering to remove the set-up before starting the spindle!

sneebot said:

You just need to adjust the vertical quill 3mm once or multiple times?

Click to expand...

Multiple times.

Adjustment while the spindle is running or stationary?

Click to expand...

Stationary should be OK.

If adjusted while spindle is stopped can't you use a magnetic base indicator holder mounted on the head and indicate on the top of the drawbar?

Click to expand...

Yup, that would work, but it's fussy. Anyone have a better idea?

Hey Bruce,

I'd turn a collar with a set screw and put it on the top protruding part of the quill. You'll have to remove the cover for this. (I guess your taper pin in the nut at the end of the drawbar is in perfect condition, so easily removable. If not, make the collar split).

Then use the collar as a quill stop: measure once, set it up, use it many times.

Alternatively you can use the end if the quill travel as a stop! Fully extend your quill and lock it. Adjust your depth of cut with your Z and lock it. Then just release the quill, do your things and fully extend it again next time you need to cut!

(Or, if you have a reference somewhere, put together a spacer set at your doc. Do your setup, then lower quill till you hit that spacer plus a piece of shim (=you're at your desired doc), remove shim, slide spacer out of the way, start cutting)

PICTURES PLEASE!!

BR,
Thanos

Hello Bruce,

I set the quill in bottom position,
Then move the table up to Desired depth with quill retracted again so everytime i put the quill in bottom position the depth is the same.

Hope this helps

Peter


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Personally i would avoid running a milling job with the quill fully extended....Most machines in this vintage and years of use suffer from some wear at the quill/head interface and extending the quill
will only cause finish and accuracy problems.

I would either mount the boring head and use the indicator or gauge block to set depth, or make a split 2 piece collar to fit onto the quill extension on top of the vertical head as Thanos describes with some
additional cautions....(a two piece collar eliminates the need to remove the draw bar retaining collar).

Set your part load centered to start..Extend the quill slightly more than the depth you intend to cut.raise the table till you set off the tool you are going to use on the reference surface (the point from which you will gauge the depth)
Clamp the collar against the top of the vertical head on the spindle extension....Drop the "Z" slightly and using the quill hand lever bias the quill against the collar firm.
Now raise the table till you are just touching the reference surface. (paper feeler or shim stock or "zero setting gauge)....
Now raise the quill fully.
Raise the table the depth you need to cut....

Position the part supporting the end etc.....cut till the collar bottoms out....repeat for the next length needed...
If you require precise depth steps, use Feeler gauges between the collar and the vertical head (spindle stopped of course)


Nor sure which plane you need as a reference in your setup....Horizontal setup will have the advantage of eliminating errors in the table droop and your outboard support....
Would think you would want contact pads at the ends of the spar with relief in the center (sets the spar flat)....Further think pads at the ends to locate the spar as to being aligned to the movement axis as well would
be desirable...accurate enough that when fitted the spar is aligned in two planes by the locating pads....This is exactly how Deckel fitted the scales to their CNC machines in that when set against the 4 contact points
the scales require no indicating for proper alignment.

Cheers Ross

Here's a photo of the work in progress. This is the underside of the table from my cylindrical grinder. I am mounting a ground steel strip, 3mm x 12mm x 680mm, which will carry a Renishaw RGS-20s optical scale strip. The scale strip is 6mm x 0.2mm with a 20 micron grating and read by a separate optical read head. The distance from the read head is 0.8mm (0.032") and this spacing (ride height) should have less than 0.1mm (0.004") variation. Getting this to fit and avoid interference is quite a hassle. The machine is from a pre-DRO era, so it's hard to find space for even a scale strip and separate read head. No way to get a classic enclosed scale in there.

To do this with my undersized mill requires many steps:

(1) Get the strip in place with an accuracy of about 0.1-0.2mm. That's what I am doing now, indexing off some of the machined faces of the table (I have checked these already for truth before removing the table from the machine).

(2) Lay the table upside down (as you see it) on my surface plate, which is long enough to support the entire length. Run a dial indicator up and down the length of the strip and see if I got it level within 0.1mm.

(3) If not, either add shims to or scrape the mounting pockets to get strip level to better than 0.1mm. (I could also selectively grind away the back of the strip where it rests on the mounting pockets but am not sure if that will telegraph to the other side of the strip. Does anyone know?)

(4) Test in place on the grinder (with an indicator tip running on the strip) to make sure it's parallel to the travel to better than 0.1mm

(5) Finally mount the 6mm x 0.2mm optical strip scale onto the 12 x 3mm ground strip shown in the photo. I'll have to make an application jig for this that references the scale position from the side of the table, because it needs to be laid straight within 0.1mm and it's self-adhesive so I only have one shot at it.

The ground metal strip will be held in place with epoxy in the pockets and epoxy and M5 screws on the two ends. I'll mount it (and eventually the scale) when the table is upside down on the surface plate and equalised in temperature. The steel has a coefficient of thermal expansion that's very close to cast iron so they should move together. After carrying out single point calibration (also called "slope correction") the scale/head combination should be accurate to within 3 microns (0.00012") over the entire travel and better than 1 micron (0.00004") over travels less than a few inches. Just for comparison, a five Celsius (nine Farenheit) increase in temperature will cause the scale assembly to increase in length by 30 microns (0.0012").

Here are a few more photos of the setup for working on the end of the part. In this first photo you can see the setup for controlling the quill. I first move the quill down to a reference point on the part, then lay a gage block (typically 1.5mm) on the drawbar and zero the test indicator. To move the quill down (say 6.5mm) I move the quill down farther than needed, put an 8mm gage block on top of the drawbar, and then slowly bring the quill back up until the test indicator reads zero again. Then I lock the quill. It's fussy but it works.



Here is the setup from the other end. I have clamped a rectangular aluminium extrusion to the bottom of the part. That rides on a ball-bearing roller (normally used at the outfeed of my woodworking table saw).



A final view showing the aluminium extrusion clamped on the "bottom" of the part. I put the word in quotes because it is actually the upper side of the grinder slide. It is clamped against ground flat surfaces so establishes a support plane which is parallel to the axis of the part.

I am paranoid about this kind of rigging: just below the level of the roller is a wood block and plastic spacer intended to "catch" the part if the roller fails and the unbalanced part starts to topple the mill.

This is working out well. I've got the scale mounting strip (3 x 12 x 700mm, 1/8" x 1/2" x 28") fitted but not yet screwed/epoxied in place. Without any touch-up work it's level to 0.05mm = 0.002", which is well within the Renishaw RGH24 head specs, which require ride-height variations to be less than 0.1mm = 0.004". Tomorrow I'll spend a half hour to cut that error in half (deepening the high pockets by hand) before permanently fastening the mounting strip into place.

OK, the scale mounting strip is now fixed into place with epoxy. The variation in the vertical position is 0.02mm = 0.0008" over the 700mm = 28" range. That's a factor of five better than the scale specifications require. In Connelly's book, "Machine Tool Reconditioning", he explains (Section 16.13) the importance of having a small and simple indicator jig that can be slid along surfaces. Getting this strip parallel to the axis motion is a good example of that. Once I had an indicating jig that worked well, it became easy to tune the surface.


I was concerned about whether the epoxy (JB Weld) was strong enough, but should not have worried. Here is why. Consider thermal stress. Say the scale is 5C (9 Farenheit) cooler than the rest of the machine. In this case the scale will shrink by thermal contraction, compared with the body of the machine. Since the coefficient of thermal expansion of steel is about 10^-5/Celsius, this will shrink the length of the scale by 10^-5 x 5 x 700mm = 0.035mm = 35 microns. On the other hand the scale is constrained (with epoxy) at the two ends and at regular intervals in between. Since the elastic modulus is about 200 Newtons/mm^2 the force required to stretch the scale mounting strip (cross section 3 x 12mm = 36mm^2) by 35 microns is 200 N/mm^2 x 36mm^2 x 35um/700mm = 0.36 N. This is the gravitational force produced by a 36 gram mass (a bit more than one ounce!). The epoxy bonds are 10,000 times stronger than this, because they would require at least a few hundred kg of mass to break them.