Tuesday, 22 January 2013

Cutting veneer substrate from plywood panels.

I order the birch plywood for the substrate a couple of days ago.

One problem the quoting that they gave me didnt add up to the prices I had to pay for.
Couldnt really say much since they were just scribbled down quotes. Next I think it will be best to request a printed out copy of the costings and get them to sign it.

I only need 2 sheets of 15mm plywood, one sheet of 12mm and 1 sheet of 9mm. And yes they told me it was going to be 7mm not 9mm. ARGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHH. Also they told me it was going to be 1200mm by 2400mm sheets not 1220mm by 2440mm sheets. All well.

Still is a bit of a pain when you work out all your sheet layouts than find out that everything is changed when you come to purchasing it.

so the new costs for the sheeting are here

Birch Ex plywood BB/BB 1220mm*2440mm

sheet no 1: 12mm 9 ply for a sheet costed $98.50 plus $9.85 GST which in total was $108.35
sheet no 2: 9mm 7 ply for a sheet costed $77.91 plus $7.79 GST which in total was $85.70
sheet no 3 15mm 11 ply for a sheet and need 2 sheets. A sheet costed $116.90. So times that by 2 which is $233.80 and plus $23.38 for GST which in total was $257.18.

So the grand total was $451.23 including GST. PRICYYYYYYYYYYYYYYYY.

yeah a bit expensive but like I said did not want movement and wanted good faces so I wouldnt have to do any repairs before veneering. Was a bit more expensive since they told me the wrong quoted prices.


Sheet 1 15mm birch plywood BB

Sheet 2 15mm birch plywood BB

Sheet 3 9mm birch plywood BB

Sheet 4 12mm birch plywood BB

These were the cutting layout drawings of the parts on the different thicknessed boards. This showed me what sizes the parts needed to be and the different process cuts that needed to be made before cutting down further for smaller parts. It was important to have these drawings since also the board was cross grain.

A bit of a poor photo (dam you sky lighting).

One thing to rem when cutting materials from plywood sheets. So its easier for you to move around and is at standing height try and keep your sheets on trolleys. I had one of my work mates help me so try to keep in mind having two people makes work a lot more easier as well, especially on the back. Normally I place my sheets on a folding trolley but at the time was being used for dining table tops at work.

When cutting out sheets have a layout plan as to how your going to cut it all out. Since these boards were in cross grain I had to work in the opposite way compared to what I'm used to which is cutting from long grain sheets.

Have a layout plan down in front of you also the cutting list so when you cut out a part you can mark it off so you don't accidentally cut another one by mistake. And rem to check twice and cut once. Unfortunately I failed this (had to be on the most expensive sheet). Guess that happens on a long day at work than after that doing your final piece. The mistake is fixable and I'll explain to you how to fix it just in case you make the same mistake as me one day.

As well have a tool trolley.  On this you will keep your layout sheet drawings, chalk, rulers, tape measure, calculator etc. Things get to messy and you find things become less productive when tools are spread on work parts and panel saw. Prep your area first before any job and clean the area before and after every job to help things run more smoothly.

Since the parts spread over 4 sheets I wanted to keep the sheet jobs separate so I decided on keeping all the parts of each sheet on separate pallets.

On the lay out plan I had stages in which broke down the sheets into smaller sections that would than further be broken down to the over sized panel parts for veneering. I numbered these according to the stage coding references so when it came to machining down to smaller parts I knew which parts had to be cut out of what stages. This just makes things easier to handle, plus afterwards you don't need another person to help anymore since these parts can be handled by one person.

If it wasn't for veneering and had to be finished size from sheet if you have material to play with try to oversize it. Its a lot easier to cut a panel to correct size when its in a smaller form. Usually when cutting sheets you need to square it. Its not 100 percent square from the supplier. Also you will find that edges may be damaged from when straps have been put on them or knocked against when in the racks at the suppliers. Usually this knocking happens from the fork lift when continuously been taken down from the storage racks when in pack piles.

I didn't bother with this since I had limited room to play with with certain sheets. Its not majorly out of square with the sheets but a little bit. I explain later down the track to get a 100 percent square panel before I transfer the over sized shape to certain sheets.

One little trick when getting a panel square you want to make a cut on the width edge and length edge so you have a reference point to rest up against the rip fence or docking stopper. Once this is done draw a square with chalk in the corner of your reference point. Now you will now which corner is at 90 deg that you can use as a starting reference.

Some times you will want to make a small panel purposely out of square. This will because you may have a framing that the panel needs to go into that is out of square. ( this only works if the framing is out of square inside not outside.) The inside may not even look out of square until you get out a ruler. To do this place packers( strips of timber or veneer) behind the boards edge that is resting up against the docking saw sliding fence. Draw a line that is to be your out of square reference so your following true with it.

With todays technology to getting maximum usage out of sheets and limiting wastage they can be run on Nesting machines. A nesting machine is one type of CNC. We have one at work but it plays up from time to time and I didn't have the time to do the programing. Plus didn't want to damage a $116 sheet. Don't really have the time to explain why it plays up but  one of the main responses is that the sheets we use for this certain one are too thick to cut through. To much strain on the gears of the machine.

Place the process layout sheet sheets with the boards that they refer to and when you have cut the boards down to its stage parts place the layout sheet with them as well. This is so you don't get confused. Keep sheets separate from one another again to limit the confusion.

Not the best picture but this is one of the sheets at its 3 section broken down stage. Another note as to why to have a process sheet layout drawing as it will show you when you need to use the score blade. What a score blade is is a small blade that is placed in front of the large cutting blade. This is used for cross grain cutting on panels. What the score blade is doing is just finally scoring the material before the major cut is made. What this does is stops tare out from the material. You only need to really do this with material that involves a grain. So with MDF it is not needed since there is no grain. Different materials will use different blades. This is case to get a finer cut you would use a blade that has thiner spacing of teeth. Also the blade will have smaller teeth and more of them. 

This is the small panel saw I used which is a small Altendorf panel saw, a very older version. If your ever wanting to get second hand machines look for the old green cast iron ones. Cast iron has very good vibrations properties. A lot of the new machines theses days are made up of lower grade metals and plastics.

Another one of the panel sheets cut into 4 section cutting stage. Again keeping it separate from the other sheets.

Me on the panel saw. Always remember to ware eye and ear protection. Also steal cap boots for feet protection. If your using machines use a dust extractor. This is not to just protect your lungs from the fine dust particles but also to prevent dust from clogging up your machine. Remember to have to saw guard as low as you can. In this case this is as low as I can go because of the docking fence. It can go a lot lower when ripping. Usually the rule of thumb with how low to place guards is the half point thickness of you finger.

If you have the space use part trolleys. In this case its just a pallet on a trolley frame. This will be good for your back since you wont have to keep bending down all the time and will keep your finished sized cut parts in one area. Each pallet holds the parts and offcuts for a sheet. Try to also invest in a jack trolley thats if you have the space. This will make things a lot easier to move around also jack trolleys these days can jack up to the height that the trolley above is at. As well they will lock into place when they go this high preventing movement. 

When you have cut the parts mark it with the chalk. When I do projects I tend to have my parts under codings. Codings will usually be the first letter of the part, a number if it refers to another part ie (laminating) and a qty number.

Keep the offcuts even if its small bits that cant be used. Ill be keeping these smaller offcuts since ill be able to use them for glue tests. Always important to do glue tests. Every material will be different especially different types of timbers so its always important to choose the correct glue for the specific job your doing. Would be a bit of a bummer that you used the wrong glue to everything and nothing bonded properly. Waste of time and a waste of money. Plus keeping offcuts you can use them as test pieces for other machining stages ie spindal molding. Also you can use them for staining and oiling test pieces.

Also mark your parts in the direction your wanting the grain to go if your using veneers. This will make things a lot easier down the track, limit the mistakes and speed up productivity. In this case it is very important since I need to keep the alternating grain direction with the veneers to the plywood panels.

Parts and offcuts are kept in storage for the next break down stage which ill explain later on. Place a blanket or weighted waist board to prevent warping/ protection if not being used for a while. I only used a blanket to avoid things like glue falling on it or being knock ( you can never be too careful when final piece is left at work.)

This is the mistake I was talking about earlier. There is also another one that is this size as well. Just one little mistake can cause so much further work to be done to bring it back to square one.

This is easily fixable and no one will notice when it is veneered over. Ill explain the process more in depth in future photos but ill briefly explain how I'm going to fix it.

  • First I needed to get the size back to its over sized length. Well in fact this is over sized over sized since it will be machined a little bit for repair. 

When ever your having parts connecting like this draw a triangle like this and number it. This while show you where the parts need to go for specific joints. Perfect for when machining up boards for table tops.

Lucky since I know that this part is for one of the parts that will be the diamond arrow shape so most of this will be machined away. But still needs to be a strong repair joint.

  • After this I will make the jointed edges as straight was possible. I'll be doing this on the jointer. In some cases this is not best since its ply and there is a combination of end and long grain. Don t tend to run end grain on jointer's will get a lot of break out. Another way is to re-cut these on the saw and obtain a more straighter cut. Another alternative is doing this on the spindle moulder with a straight edge or with a router straight edge with a ball bearing, but having the ball bearing running under a jig edge.

You can also do this on a linasure which is a horizontal free standing sander. But you need to make sure in this case that your work plate is as long as the piece.

Ill use the jointer first and if this doesn't work ill use the saw. It should be ok will just have to be very careful, taking the least amount off as possible in one pass.

  • Once I have a clean joint will make a grove on the joint edge with a two part saw blade on the spindle moulder. The grove only needs to be about 6mm wide. I will be making the grove 20mm deep and will run the entire length of the board edge. 

  • Do not use timber as a loose tongue connection for the groves since this will expand and making the two parts move. I can not afford this especially since I'm veneering over this. Don t want a step seen in the veneer. 

I plan on using a strip of plywood, a scrap section from the offcuts. Will just have to sand it down to the thickness I need. But will need to make sure that I sand on each face evenly (what you do to one face do to the other) This is so the floating tongue will be structurally balanced. Will be using calipers to make sure im taking off the right amounts. The grain of the tongue will need to be running in the opposite grain direction to its top ply layer that is above it.

I decided on using a slotted loose tongue since it will create even more of a long grain bonded surface. Now you want a tight grove for the tongue to sit in but not too tight. Just a nice snug tight fit that you can still move around without too much effort. You don't really want too much movement since this will create more bowing to happen within joint when clamped up.

The groves in the two parts must be in the exact placements so there will be no step created. I can not afford to sand off too much. I have about .2mm to play with after that I start to go down from my finished size. Its ok if I go down past .7mm but no more than this. Going past .7mm will bring the finished size of panel including veneer to 15.5mm. I need to try and keep in the + /- of 1mm.

  • Once I'm happy with the jointing ill do a dry run. Always do a dry run to see whether parts go together properly. A dry run is just putting everything together without any glue but clamping up to see whether everything is going to assemble properly. 
Ill be running a clamp on each end and one in the middle of the bottom face. Use sache clamps that are the right sizes. Between the sache clamp and board use timber strips to avoid metal touching the timber. This can leave rust marks on timber if not done so (i find using timber biscuits works a treat). Normally you place a sache clamp on the top face in the middle not the bottom to avoid bowing up and even out the structural clamping pressure. But if I added a sache clamp in the middle on the top face the below secondary clamping procedure would not work.

  • On the glue joint ill be placing glad rap over it, both on top and bottom and masking taping it to the panel faces. This is going to prevent the clamping strip from sticking to the plywood material after excess glue is released from the joint. Now clamped to the clamping strip is going to be another piece of timber that is slightly curved. This piece of timber will slightly curve out wards from the middle creating a very small convex curve. This piece of timber will only be placed on the top face. At the ends of the piece of timber will be G-clamps. 
What this piece of timber does is when clamped out at the ends creates evenly spaced pressure that spans across to the middle point keeping even pressure across the whole board towards the ends. This is a great trick to use if your wanting the exact even clamped pressure on the sides and in the middle as well. This is an old technique used before hydraulic presses and vacuum bag clamps were invented for laminating.

This technique will also press down any lipping that may be caused by warping in the joint between the two parts. Again need to make sure that both joints have the correct spacing for the grove.

  • Once I'm happy with the dry run ill begin gluing. Ill be using tight bond glue 2 since I know this works well with plywood bonding. Before the glue up and during will check that the board is running flat when clamped up there are no high spots at the joint section. Clean up any excess glue that has come in contact with other sections of board with damp rag. 
  • Once left for 2 hours or more. I usually like leaving things for over 24 hours if I have time up my sleeve. Now cure times will vary with different glues you use so keep that in mind. Will take out of clamps and run through veneer sander if needed. Will be sanding off light amounts about .2mm on each face evenly. If I don't need to run through veneer sander will clean up sections with cabinet scraper.
  • After this cut to over sized measurement for veneering. 
now we are back to square one again. YAY!!!!!!

Started to wrap up parts with plastic wrap to transport back to my work shop on ute. Will load smaller pieces into cab and load and strap down larger pieces onto a pallet onto back tray of ute. Parts will be stacked up on a separate work bench and weight will be placed on it to prevent bowing. Also will have a blanket over it for extra protection. It will only be like this for a couple of weeks until I get enough funding for extra machines and materials to continue onto the next process.

Went over process layout sheet pages and marked the parts in which direction the grain of the veneer was going.

Double checking over parts to see whether they are square. Some are only a little bit out. The panel saw at work is slightly out. This doesnt mater so much since all my parts are over size for veneering. I'll be using the panel saw at tafe for final cutting or I might use the CNC at tafe to do the final sizing when veneering is done.


I found another mistake. I must have been tired that day. Same mistake as the other part I stuffed up. Looks like I really failed in the measure twice cut once. Again this will be easy to fix up and most of it will be cut out. This part that stuffed up is the substrate for the lids for the drawer boxes. Only two were stuffed up unfortunately. Will be fixing this up the same time as I fix up the other parts.

No comments:

Post a Comment