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View Full Version : Spoilboard to support board insallation..."down" to how thin?



paco
07-07-2004, 09:34 PM
I have this idea to use wood glue "spot" around each screws that I'll use to install spoilboard to support board... my idea is to use the spoilboard to, maybe, pretty thin (economical aspect)... and at around 1/2" (from 1"), I could remove screws to prevent bit collision/breakage... screws would be 0.625" to 0.750" deep in spoilbard...

So... what do you SB'ers think about that?

Should I glue or should I screw... (The Clash)


8-)

gerald_d
07-08-2004, 01:09 AM
Only glue - no screws. Then you do not have to remove the old spoilboard before you glue the new one over the top. We just keep on adding boards on top. Normally it is a Friday afternoon job to put the board on, glue sets over the weekend, Monday morning a half-hour on surfacing and then it is good for a couple of weeks.

elcruisr
07-08-2004, 06:29 AM
Most people in the CNC industry put their spoilboards down with a bead of silicone. It's easy to pull the old board and prevents vacuum leaks out the side of the seam. Make sure you surface the back side of the board before you install it. Most MDF has a surface treatment you want to remove to improve flow through the board.

ron brown
07-08-2004, 08:14 AM
This shows two of several attitudes in "How". Eric uses a large vacuum pump and pulls vacuum through the spoil board. Gerald uses more clamps and screws to hold his parts. A third method is to use low-power vacuum pumps and ports in the table/jig.

Which is better? The big vacuum pump costs several hundred dollars or more. Plumbing and piping add to that. A spoil board one screws to or uses screws and a low-power vacuum is considerably less expensive. Both have strong and weak areas in what they can do more efficiently.

"Most people in the CNC industry".... I haven't seen that study and have some doubts as to the accuracy of it. I will say MANY do as Eric states. I will also contend that is in the routing end of the industry. Many also use "pods" and/or dedicated vacuum fixtures. It all depends on what one is attempting to achieve and the number, size and shape of parts one has to produce.

Ron

elcruisr
07-08-2004, 10:36 AM
OK, let me rephrase that. Most people I have known who do production panel routing......

Pod machines mostly do solid wood components or customised small part runs. The guys I know running pod machines for panel routing seem to have routine problems with their operators running through pods.

I do tend to look at things from a large volume production standpoint as that is "my world". I could never run the numbers I do with a low powered pump and/or screws!

Eric

paco
07-08-2004, 10:59 AM
Interesting...

Gerald

"Down" to how thin do you use your spoilboard?
Do you use screws to fix it, then remove later, or clampS?
Do you use more or less glue than I suggest (spots around screws holes)?

Thanks for sharing!

8-)

gerald_d
07-08-2004, 11:51 AM
Our table is MDF and our spoilboards are also MDF. We nomally add a 18mm (approx 3/4") sheet when the table and old board is down to 25 - 30mm (1" - 1.25"). (We can't go thinner than 20mm, because then we will find the heads of the carriage bolts that hold the table to the cross-members) At the moment we have a glue-line about 22mm from the bottom and another at 28mm with total thickness of 42mm.

We use "cold glue" (the white general purpose stuff - looks like thick milk and is water soluble). 2 liters (4.4 pints) spread all over with a finely notched trowel - like carpet layers use.

Drop the new board on. "Hovercraft" it around a bit to settle the high glue spots. Clamp around the edges. Pack heavy stuff on top and leave to stand for the weekend. That's a good time to sweep out the shop because all the junk is loaded on the SB.

sagreen83
07-22-2004, 08:51 PM
My ShopBot Alpha shipped today, and I am anxiously waiting its arival.

I have a couple of questions related to this thread.

1) I have had one of my local machine shops construct the table according to the plans provided by ShopBot. Based on what I am reading here, and in the assembly manual. I believe that the proper way to put down the support board is with bolts through the crossmembers of the table. So, my question is how do I go about alining this support board, and later the spoilboard to be absolutely square with the X and Y axis's of the tool. I.E. It would seem to me that you would want to be able to align these parts of the table in a way that when you align your 4x8 material (to be cut / carved) on the table, the factory edges of the material could be used as is for the outer parts milled from the 4x8 sheet. So if you were cutting a 2'x2' square from a 4'x8' sheet, you could cut it from one of the corners of the 4x8 sheet, and save waste and un-needed cuts. IMHO this would not be possible without perfect alignment of the support and spoilboard giving you something to align the material to. Bill P. has some tab supports that rotate into place displayed on his web site that accomplish the material to spoilboard alignment.

2) Gerald, you speak of something different than what the assembly manual talks about for attaching the spoilboard to the support board. What I am understanding here is that you have a 3/4 (18mm) board as your support board bolted to the table through the cross members. And you are somehow glueing your 3/4" (18mm) spoilboard to the support board, and not using any screws to hold it. So, if this is the case, why do you have to stop at 20mm, if you have countersunk your bolts in the support board. I would have thought you could go all the way to 18mm if the bolts were countersunk. So after you get to your 20mm, you are still above the support board, and I assume you just glue on another spoil board. Nit picking here, but I just want to understand. Also, is your White Glue just Elmers? Why not use a yellow glue? The 2nd part of the question, is can you explain what you are meaning by the following ... "At the moment we have a glue-line about 22mm from the bottom and another at 28mm with total thickness of 42mm"

Thanx in advance for the help!

Scott...

paco
07-22-2004, 10:16 PM
Spoiled board is ON support board (3/4" plywood)... So one could use his tool (PRT) to make his edge refered to linear guide (rails); be cautious at close height to "cross members", clean in between to installed your "tab supports that rotate into place" ... My 1" MDF sheet is 97" X 49"...

ron brown
07-22-2004, 10:42 PM
Strictly personal preferences here. I prefer plywood. For the last table I built 5' X 5' baltic birch was the least expensive. I bond "sleepers" to the cross supports of my custom built tables - the last one had 2" square members on 12" centers - let the adhesive cure, remove any temporary fasners and "true" them with the router.

The first layer of spoilboard is then placed, clamped, bonded or countersunk and screwed in place. That is then "trued" and a second layer is bonded in place. The "top" is now ready for transforming into whatever one desires to have as a "top".

The life of the "tops" I have installed depend on the uses I have and the accuracy needed for projects. I'd guess I go through an inch of spoil-board a year and cut about 20 hours a week. I have found the better quality base I use on my machine the less time I take truing the surface.

A lot depends on the accuracy you want and how much time you are willing to spend to achieve it. In my own aspirations, I tend to look at and analyze each part run off my machine and strive to impove each run. A proper table is the start of that attitude,

Ron

beacon14
07-23-2004, 12:32 AM
Scott,

Don't worry too much about absolute square, except aim to put the bottom left corner of your support board as close to where you want the 0,0 (origin) to be as you can. Even better, move the sheet 1/4" or so to the left and down from 0,0. Then use the ShopBot to machine the left and bottom edges of the spoilboard (I do all 4 edges). If you have a 1/2" bit, then move the machine to mx,-.25 to cut the left edge, and my,-.25 to cut the bottom edge, so you end up with machined edges at exactly the machine's 0 points. Leave 1/8" in thickness of the support board so you don't get too close to the steel crossmembers. Then use the machined edges as your reference surfaces.

Good luck with your new machine,
David B.

gerald_d
07-23-2004, 02:14 AM
Scott asked me "why do you have to stop at 20mm, if you have countersunk your bolts in the support board. I would have thought you could go all the way to 18mm if the bolts were countersunk". We are only talking of a 2mm difference, and that is a safe distance to keep the surfacing cutter away from the heads of the bolts. Don't be tempted to countersink the bolts deeper in - there is a danger that they can tear the bottom out of your support board, something that is difficult to detect and to repair. The support board takes a lot of strain when you try and clamp down twisted railway sleepers......

Explaining the gluelines....
-At first (end of year 2000) we put only one sheet of MDF on our table, probably 32mm thick (our support board was never 18mm thick as you assumed above), and countersunk that board quite deep so that the top of the bolt heads were less than 18mm from the top of the steel bearers.
-Then, over the course of some months, that first sheet got worked down to around 24mm thick and we glued an 18mm sheet over that, hiding all the bolt heads.
- For the next spoilboard, we surfaced through the old glue-line (not nice for the cutter), exposed the bolt heads less than 1/4" away from the expensive cutter, and said to ourselves that we don't want to do that too often. So we created that glueline at 22mm that was mentioned earlier.
- For the next spoilboards, we left that 22mm glue line intact and added sheets somewhere above that - hence the second glue line. We don't make a distinction between support board and spoilboard, life is too short for that.


On the name of the glue, please realise that I am from a foreign culture to you, and that our terminologies and brand names are quite different to yours. You will not find anyone in South Africa who stocks MDF, or Elmers, or white or yellow glue. Here we have Supawood (Superwood), cold glue and Balcotan. On this Forum I often give a long silly description of a product because I don't know what most of you guys call it.

This (http://www.alcolin.com/product/wood/coldgb.htm) is the cold glue that is most popular over here.

sagreen83
07-23-2004, 10:36 AM
Thanx for all of the info and help...

Based on what you guys are saying it seems to me that the best way to accomplish this is to purchase "oversized" support and spoil boards and machine them to size (48"x96") to get a square combination. I'm sure this is not scarry to you guys, but for me not having my machine yet, its a little scarry to machine the support board getting close to the cross members... I will have to be carefull!

So, for me, it seems that both the spoil and support boards will have to be made from MDF because my local suppliers do not carry any plywood that is larger than 48"x96".

Once again, thanx for all of your prompt help. I'm sure I will have more questions as I assemble this thing!

Thanx,
Scott...

beacon14
07-23-2004, 11:10 AM
Scott,

In real life, it's unlikely that you need the spoilboard to be exactly 48 x 96 - your workpiece can go over the right and top edges a little without hurting anything, and 99 times out of 100 you will use the left and bottom edges as your reference surfaces, so if you really want to use plywood I wouldn't worry too much about it. Personally I like MDF because of its uniformity and the fact that is doesn't splinter as the surface gets all cut up. The bonus is that it comes 49 x 97, making it easy to trim to an exact 48 x 96 with the 'Bot.

gerald_d
07-23-2004, 12:19 PM
A nominal 96" SB actually cuts a lot bigger than 96" if it has a single z-axis installed. Why cut the table back to 96"?

fleinbach
07-23-2004, 02:55 PM
Why not??

gerald_d
07-23-2004, 03:39 PM
I am only trying to encourage some lateral thinking. For example, if your main work is going to be on 49 x 97 MDF, then 48 x 96 is not relevant. We work metric, and the table of our PRT96 is 2620mm long - again, 96" means nothing to us. A good y=0 line/edge/upstand/gutter/whatever, cut by the SB parallel to its own x-rails, is much more important than a table size. There is no need to cut this reference edge all the way down to the steel bearers.

Plus I would recommend that the table top does not fill the whole space between the x-rails - leave space for clamps and sweeping off sawdust.

kerrazy
07-23-2004, 03:52 PM
I'm with Gerald, on that... Holy **** Did I just agree with Gerald...Just Kidding

It is good to have clearance for dust/debris removal, clamping and I installed a couple L-Brackets on the edge of my spoilboard to use when registering material. I simply turn them down when cutting.
I know a fellow here in Ottawa who has his whole table covered, and he really only uses a 2 ft square area on any given day so it makes no sense.
Of course everyones need are different.

Dale

beacon14
07-23-2004, 04:39 PM
"In real life, it's unlikely that you need the spoilboard to be exactly 48 x 96"

isn't that exactly what I said?

Trimming two spoilboard edges to 0 makes it quick & easy to align a panel with the 0,0. Some of my patterns have parts within 1/4" (6mm, Gerald!) of both sheet edges, so accurate registration is a must. And I do sometimes have a use for registering off of the far end or edge of the spoilboard, to make sure a workpiece is parallel to the x axis, but in those cases I am probably going to register the machine starting point from the workpiece itself, so the actual position of the spoilboard edge isn't important.
I think Scott was just thinking 48x96 because that is what we are used to here in the good old USA. As he gets more familiar with his new machine, he'll have a better understanding of what's important (like not cutting clamps in half).

David B.

fleinbach
07-23-2004, 05:43 PM
I figured that question would get a response. I realy didn't have much time to type any more then 2 words. But now I have a little more time before the movie. My old PRT96 was setup with a 49 X 97 sheet of MDF and I always aligned my material on the 0,0 edge. Which of course should result in being able to align any edge since all 49 X 97 inch sheets are all the same size, or are they. No, I have found anywhere from 0 to 3/16" differance in size from sheet to sheet. Not to mention all sheets are not perfectly square. Though by chance some are. Any way back to why I will make my table a bit smaller then the largest sheets I intend to cut. Oh, did I mention I am in the fianal stages of setting up my Alphaprt 120. Everything is running smoothly at this point and it has a 61 X 121 MDF support board on it. The mechenical stops are 1" past the edge on the Y axis. I set the limit switches .625" from the mechenical stop to give the carrige at least some buffer in case a 30 in/sec jog hits a limit. I'm told it actualy takes 3 inches for the alpha motor to reverse from a stop at 30 in/sec. so at least it will be a little slower if it ever hits a mechenical stop. Now since I will proubably not be cutting 61 X 121" sheets most of the time I intend to move my Y axis 0 position in another inch hence I will trim another inch from the support and spoil board so most of my cutting will give me an additional inch of protection. Of course I will still be able to cut close to the edge of a 61 X 121 inch sheet when needed by simply overhanging.

bleeth
07-24-2004, 03:20 PM
The non-squareness of plywood and composites is becoming a much more serious difficulty as time goes on. The number of times I throw a sheet down on my machined vac/spoilboard and have alignment out on the y after aligning the 0,0 corner and the x axis is more often than expected. For critical squareness in parts I am taking to hanging off the y a bit and remachining. Therefore I strongly suggest you leave enough free travel distance to let a 1/2 inch bit travel in the negative area. Much more than that in the y and you can come close to limit if you are cutting 49" stock and want to pass clean through eg. -.65 to 49.65 in y.

Dave

(As a builder there is a lot of me more fascinated in the engineering of my bot than the actual cutting of parts-For those of you favoring post message quotes:

The only thing renarkable about flying is it isn't very remarkable. Amelia Earhart)

jdelongchamp@sterlingmillwork.com
01-05-2005, 09:36 AM
I recently became involved with CNC routers and need to tool up the new machine that is on its way. I am researching tooling requirements such as spoilboards, cutters,routers, tools, speeds and feeds for various materials such as solid woods hard and soft, MDF, Corian, etc. Is there anyone or anywhere someone can direct me to gather this information? Any help at all would be greatly appreciated.

Thank You,
Jonah DeLongchamp
jdelongchamp@sterlingmillwork.com (mailto:jdelongchamp@sterlingmillwork.com)

mikejohn
01-05-2005, 10:07 AM
Jonah
Search for each of those items on this forum.
There are hundreds of threads covering these subjects.
You may have to look around a bit, but its all there.
Any specific questions, just post them.
Someone is sure to have an answer.
.......Mike

toe_jam
01-14-2005, 11:44 AM
The way I do mine is I bought a 1" MDF as my support board and countersunk it in at all the points. I Surfaced that and then applied 2 rows of 24" transfere tape on top of the support board. I then applied 3M spray adhesive on top of the transfere tape. Then I throw on top a 1/4" spoil board and put a few heavy weights on top, or walk around the whole table top. I let it dry for 15 minutes and I'm good to go. Now all I have to do it remove the spoil board which is easy when ever needed and it's already leveled out and ready to go everytime.

gerald_d
01-26-2005, 01:52 AM
Erik, how do you fix things to that 1/4" spoilboard? And, how do you know that your fixing method (vac pucks, d/sided tape, whatever) is not pulling your spoilboard away from the thick MDF base? If you use screws through the spoilboard in to the MDF, you will probably get a lump developing in the joint between the two boards - unless you are very careful about drilling pilot and clearance holes for the screws.