last cut....help

[framingengineer]

Ok
This has probably come up in so many threads but it is still relevant.

For those that don't know me I am one of a few engineers/technicians out there servicing and repairing your picture framing machinery.

I have been seeing an increasing problem on Morsos of all ages and all conditions............namely the inability to make the last cut without breaking off the final tiny piece of Gesso/finish on the bottom back edge of the moulding.
Normally I would suspect that the blade is not sharp, incorrectly set, not travelling far enough into the fence, bottom set incorrectly alligned, damaged blades or the moulding not being totally square on the back edge.

However even with all aspects being correct I am still finding a problem on a whole range of moulding from different suppliers and manufacturers. I have been suspecting for a while that the high mineral content in the coatings is so hard, brittle and thick that it is virtually impossible to make this last cut without it snapping off the final 2mm.
I see more and more framers having to adjust their stock to accommodate this problem.

It is not often in my line of work that I ask the customer for help but I would like to throw this one open to you.
If you have found a fix I would love to hear about it...... as would a large number of my customers.

I would also be interested in any comments from moulding suppliers/manufacturers (not plastic) as to why this phenomena is on the increase.

note : this is not the snap off and tail problem caused by bad blades or the dodgy balsa wood moulding syndrome..

Look forward to your thoughts.

Neil Stout
framingengineer.com

[stcstc]

one issue with a lot of chinese mouldings is the back edge is slightly round or trimmed, ie not quite square all the way to the bottom

this does mean as you cut that last cut near the bottom there is no support for the finish etc

could this be the cause neil?

[framingengineer]

On some yes....but not all.
I wish it was that simple........
thanks for the response..............give my love to 'the Storeroom'
Neil

[stcstc]

the storeroom?

[framingengineer]

ooopps
'Storehouse'

[Roboframer]

I've bought chevron sets which are perfect, but when I try to cut the same mouldings I get results like your photo - and far far worse, so I assume the chevrons were cut on a good mitre saw; not a morso, and I don't have a good mitre saw, or any mitre saw and nor do I want one, so the chevrons go in the bin.

[Roboframer]

This moulding is gessoed and it's not cut as it was intended to be, it's cut on it's side - asking for it, but it was fine - therefore so's my morso - it's some mouldings that can't 'cut it' and they get one or two chances before they are history to my walls.

outer.jpg

[framingengineer]

And yet a few years ago you would have cut these finishes on a Morso.......are we to assume that moulding manufacturers aren't aware of the fact that 90% of their customers have guillotines? or do they just not give a t--s.
Silly me I thought they actually wanted to sell these mouldings...........!!

[prospero]

I think this isn't just an issue with hard and brittle compo. I think it is mostly down to the thickness of the coating. This combined with a rounded off base makes chipping off the bottom edge almost inevitable. Hard, thick compo also compounds the issue by dulling the blades a whole lot quicker.
If you look at Neil's photo, even the cut higher along the back is a tad ragged. Half cut and half broken.

I don't worry too much about this nowadays as most of the my frames are hand-finished so I can make good any chips. But in the past I have tried various things. Whacking the blade though on the last cut as fast as possible sometimes works. Another way I have used is to use plasticine or similar modelling clay . You have to roll a couple of 'sausages' down to around 2mm diameter, and jam them in the back corner between the bed and fence on either side. It's a PITA and takes time to get a snug fit. Then you have to scrape it out again to cut dead square moulding. It's worth doing if you are cutting a lot of the same moulding at a time.

[pixnut83]

L&G,
I used to have problems with spalling of the lower corner. I use a lot of unfinished plainwood and the lighter woods like Obeche would really lose great chips off the corners. I've lost count of the number of black-finished frames I had to write off due to lumps falling off.
Until a hint from a friendly supplier led me to adjust the throw of the knife block. The lever pivot is an eccentric which can be adjusted using two spanners.
The aim is to get as small a gap to the inner corners of the fences as you can get without the blades touching the fences (else the blades get nicked). Don't even leave a gap of 1/4 mm for the wood to distort into.
See Page 39 of your Morso manual 'Adjustment of Forward Travel' Fig F-4-2
Since doing this I've had much better, cleaner cuts.
Hope that helps,
John.

[Graysalchemy]

Neil its not just morso users yes I have this problem on one particular matt white arqadia moulding



I believe our good friend Paul has the same problem with this moulding using a 939. I always assumed it was because the gesso was to brittle and too thick.

On a personal note Neil I am not a happy man just found out the stout is off, turned to vinagar.

[Framerpicture]

Not only is the compo/ gesso very thick but seems very hard and brittle on certain far eastern mouldings and can take the edge of the blades quite quickly.
Our solution with these difficult mouldings is to put a 5mm x 20mm wooden spacer against the fence and along the measuring arm so you cut the back edge without using the tip of the blades - Although this is a bit of a fiddle, and remember to read the moulding width with spacer in place, this causes far less break out.

[Ken]

cheers to all

Sorry for long techy first post...

I've just setup a Jyden electric guillotine after converting it to single phase and the test pieces I used for first cutting were Chinese 20mm stretcher bar. It is a type of cedar (though the seller called it pine) with practically zero cross grain strength, so the back, back bottom edge and rebate all exhibited breakout - very similar to the framingengineer picture. My Schleicher manual guillotine cutting result on this stretcher bar was the same.
My take on this corner breakout issue is that the gesso is over-extended in its composition, so the end result is a very brittle product with little tensile strength - the binding resin has become so low in the (over-filled) mix that there is literally nothing holding it together. This is very similar to a super-fast growing tree wood, the fibre ratio is very low and the air content is high, like an over proved loaf of bread. So the bread will cave in, even under the slight pressure of a sharp knife, rather than cut.
To cut 'these weak materials,' via a knife and anvil the stress placed on the 'media' by the knives must obviously be less than the media's tensile strength, or breakout will occurr.
In framingengineer's classic picture, the fact the corner is not square is a primary issue, as it leaves the weak tensile gesso with no connection to the lower guillotine (or fence) anvil plates.
So primarily the bottom corner needs anvil support in the way of a shaped hard form that will connect to the media radius and provide support against the blade pressure. Like a female mould - that fills the unsupported gap.
Ideally there should also be minimal pressure from the blades, so a false fence may help, by moving the cut from the blade tip. Also the final cut should be reduced in size. Reducing the 'final' cut size will reduce the blade pressure against the gesso. This partial solution is easy to test by cutting the moulding over length and then cutting in to the final length with extremely light 'whisker' shaves (by moving the moulding towards the blades - not via head ratchet). Taking a whisker at a time off the moulding will likely allow the weak gesso to survive - even though corner is unsupported. Unfortunately most if not all guillotines have their head ratchets fixed, but if the ratchet could be modified to take 3 or four final whisker shaves instead of one final shave this might well work.
So in summary,
1. The blades should be very sharp. 2. The 'missing corner' needs support, on its gesso, from a matching custom made (car auto repair bog with plastic overlay should form and work fine) female 'anvil filler' strip. 3. The final cut (or cuts) need to be whisker thin for minimal blade to gesso tensile pressure. 4. Reinforced racing tape placed over the final cut area (to support the 'missing' corner) prior to cutting may also help for low volume work. Peeling it off after cutting may need due care - with pulling from the 'furthest from cut side' first. Finally, for rebate rag reduction, roughing the rebate supports and epoxy gluing false 'shoes' of 1mm alluminium strip to them, then filing it to match the bed anvils, before trimming it with a 'hisker' shave from the knives, is a great solution which eliminates rebate rag from poor distant rebate support anvils.
The above post suggests a false fence to move the cut from the tip of the blades, this is a possible solution. Ideally though the false fence should incorporate the bottom female 'missing corner' support. If there is a lot of moulding to be cut, or just a few lengths, it is not hard to make a custom 'false fence form' - via car bog in a supermarket plastic bag.... then trim it after setting.
I imagine the problem is easily solved on a saw (like Alfamacchine M400/T400) by reducing the cut speed (with the feed rams outgoing air throttle valve). This allows the 120 blade teeth (336,000 per minute) to whisker cut, though this may need some balance if the moulding is urethane and melts under even low heat of blade friction - then it needs cooling water/mist spray! Like the 'Alloy' versions of these saws have for the window industry.
I hope this post helps members find their own successful outcome.

[Graysalchemy]

I think the real solution to the problem is for Moulding suppliers to address the problem and for us to complain and do something about it. However I fear that it will fall on deaf ears.

A few years ago i had a relatively inexpensive silver moulding which seamed to be dropping in quality in the years I used it. The main problem was the amount of gesso and the quality of the wood or lack of it. It was like balsa wood and didn't cut resulting in a bad joint. Also the underpinner had nothing to bight into.

I complained to the rep and was told that it was at the contract end of the market and he said he was sure the technical department would tell me to use a saw which is fair enough but didn't solve the problem of under pinning. As a result I stopped using it for two years and converted to plastic. Eventually I was forced back to using it and the new rep assured me that it was much better than it was to this day I have never had a problem with it.

So please moulding suppliers please have a look at this problem or if you are then let us know. We understand that there is obviously a trade off between cost and quality but this is getting beyond a joke.

[Ken]

Appealing to the molding manufacturers could only work with the ethical ones at best - if that!

I don't know anything about gesso mixtures, but all good resin binders (be they urea glues, epoxy, car bog etc) cost heaps and using fillers to extend them is the only salvation. If moulding manufacturers wish to skimp on their costs and make life difficult for their customer framers then the framers just have to get smart and counter the difficulties. Dollars tend to rule and all manufacturers pick away at their costs... endlessly... like a chook feeding!

This weak media/gesso is pretty easily sorted once the cause is realised. I just hope I can get my Alfa saws converted to single phase operation with VFD or even static converter, if not a 3 phase generator to solve all this style of issue real fast. My friendly local picture framer uses a carbide blade hand operated single mitre saw for difficult materials. I have pair of Alfa saws ready to take over from 2 guillotines when the dollars allow phase conversion.

'Make a game of the problem and then you can win it!'

:-0

[Graysalchemy]

'Make a game of the problem and then you can win it!

Sorry I haven't got time to play games I just want to put a length of moulding in the saw and cut frames, preferably a couple of hundred and make lots of money. This is a manufacture problem and not one that we should have to work around.

[kev@frames]

a bead of silicone down the "gap" will last day or two and support the bottom edge.
Or warm the moulding a lot with a heat gun.
Both a pain in the ass.

So my solution is to not use mouldings that do that.

interesting point being made about the suppliers wanting to sell mouldings, or whether they give a toss. Unless framers give their suppliers feedback they are often not aware of the problem, or it's extent.

When you get bothersome mouldings and you have staff, it is even worse. Often people with staff are using more mouldings, and from the people I know in the business who have staff (most of whom don't inhabit this forum) most will simply discontinue any moulding that gives any bother at all. Staff time is money, and fiddling round touching up stuff is something that should be the exception, not the rule.


After almost 18 years in the business, I have a feeling that these finishes are often more "brittle" than they used to be.

[Graysalchemy]

Unless framers give their suppliers feedback they are often not aware of the problem, or it's extent.

That is what I did but to no avail.

Sometimes we have to continue using a moulding in contract work as as the name implies it is contract work where they give you repeat business using the same format and same moulding so quite often you have no choice but to continue unless you can get the client to change.

The moulding in question I was using at the time probably 1000ft a month so they lost quite a bit when I changed to plastic. The other problem for them was once I used plastic for contract I began to switch over for others.

So really it is the interest of suppliers to take note.

[Ken]

Other ideas - Just before making cuts -

1. place moulding in guillotine and soft mark the cut region on the moulding (white board marker - or chalk/pencil) and remove from guillotine uncut -

2. then place framing tape placed tightly around the moulding at 90 degrees on the intended cut area -

3. then replace moulding in guillotine and cut through, minimise the final shaves if you can,

This works fine as the 'missing corner' support workaround! AND I only use the cheapest tape I can find...

So = use standard framing tape as a corner bandage and cut through it!!

Try it, you'll be laughing!

[kev@frames]

there are so many moulding choices available that you shouldn't need to "make do" and bodge up standard frame shop equipment to cut it. Most of the time you can find an alternative that will cut OK.

Its a good idea to shell out and buy a length or two rather than just scrounge chevron samples, and put a frame together from it and see how it is before offering it on your board to customers. I have had a few this year that looked really great by the stick, but turned into pretty second rate corners by the time they had been put together from the actual mouldings the suppliers sent.
You even get some where the finish cracks under the pressure of the underpinner clamp.
Perhaps manufacturers are using different solvents in the mix or something these days, for economy, environment, health and safety, and that might have a bearing on it? These cracking up mouldings seem more common than they used to.