Registry and holddown dilemma

[andyb]

Please bear with me as I try to explain this. OK, here is my dilemma. I have to cut out some figures along existing lines with very little tolerate. The customer is going to drill two to four registry holes for me. I have vacuum on my table and do not want to drill registry pins into the table. This is my thought. To register the material and hold it down, I was thinking about using a ¼” or ½” sheet of MDF on top of my spoilage board, drill the registry pin holes into it. Then drill several holes where the figure cutout will be and use Allstar Adhesive gasketing material around them. Currently I’m just using a ShopVac for the vacuum holddown, that work great for my current cut jobs but will be upgrading to two Imperial motors when they are back in stock. Oh, the figures will be in three sizes 12x24 putting several on a sheet at once, 28x60 and 36x72.

Do you think that I can get enough suction to hold the material down through the extra board?

Do you have any other suggestions on holding it down? I may be able to use tabs if I have to but need to pop these out as fast as possible without any hand work.

Andy B.

[knight_toolworks]

How many are you doing? If more then a few it would not be a big deal to drill into the spoilboard. You can plug the holes up later. It won’t effect how well it works.
Myself I don’t think you will get the suction you need if you use more material on top. And how much are you saving even if you have to replace the spoilboard?
But here is a tool that I use for such jobs with it you can line up the drawing with the precut/marked parts. I have used it for that job quite a bit and it is great. It’s great for setting up the shopbot and drill presses and such too.
http://www.lasercenteredgefinder.com/main.html

[ed_lang]

Andy,

First, if you do not have the laser edge finder Steve posted above, get one. I have had mine for over a year and it is fantastic. Get spare batteries just in case you leave it on overnight. It will drain the cells.

I use a vacuum mask very much like you are talking about. I use 1/4" Baltic Birch and All Star. I cut the center of the ply under the parts out so I can expose as much of the spoilboard as possible allowing as much surface area to hold. I then use the AllStar around the cutout part but inside of the profile cut if I am cutting parts out of larger blanks. I can either glue registration pins or blocks onto the vacuum mask. When I put the vacuum mask on the table, I have points marked that I use the laser edge finder to align the mask. I do this by sending the router to some point like J2,24,4 and moving the mask to line up with the red dot. Then I can J2 48,4 and verify the mask is good to the X axis. Then I could and sometimes do a third point to make sure I have it all right. then I use small spring clamps or some type of clamp to hole the vacuum mask tight to the spoilboard. Then loading and unloading will not cause it to move.

I hate to change bits as much as the next guy so I have been thinking about mounting the laser onto the spindle and knowing how much the offset is from the center of the spindle to the red dot. So far, I just change the cutter and the laser in and out as needed.

Hope some of this helps

[andyb]

Thanks for the reply guys.

Steve, I'm hoping to be cutting a lot. Starting out I think there is about 100 of the small ones. Not sure on the larger two sizes. I'll have to order me one of the laser edge finders.

Ed, We're thinking along the same lines. I was thinking about it last night and thought about cutting larger holes in the second board when ribs between just to hold the board flat. Right now I have two sample pieces to cut. I'm going to cut them in the morning and meeting with the customer tomorrow afternoon. If the cuts work than I may be bringing back more work, I hope.

Andy B.

[Gary Campbell]

Andy...
If we were going to cut 100 parts, I wouldnt even question adding a few holes to the spoilboard to insure accurate registry. We even will cut a recess in the spoilboard for pieces that can use a little extra lateral hold.

Unless you remove the spoilboard and install a purpose built "pallet" with gaskets etc. the registry holes/dowels combo will give the best hold down and repeatability results. The lasers work well for what they are, but are just another version of "eyeballed".
Gary

[andyb]

Gary,
Your right about not thinking second on adding a few holes to the spoilage board. But, since this may be an ongoing job I don't want to have to drill into the spoilage board every time. That is why I was thinking about the second board laying on top and tryng to pull the vacuum past it. With the smaller pieces I can get several on a sheet/jig. This way I can throw the sheet/jig on, align the sheet and saving time I hope. The larger pieces I can only get one per sheet, so a couple holes I'm wouldn't worry about in the spoilage board.

Andy B.

[wberminio]

Why not use a Brady VAC Jig?

Erminio

[knight_toolworks]

are these still in the sheet or cutout?
I agree the laser is a eyeball thing but this one is very fine only a few thousandths. it is far more accurate then our cnc machine is.
for setting up a part that has to be lined up to your drawing it is unmatched I think. I have to cut this cardboard out thats preprinted. I make a toolpath on the line for a few of the pieces run it and move the cardboard till it matches the toolpath. turn on the vac and cut away.
use it to set my jigs up where they are very exact. or find an odd corner.

[sawdust535]

Steve,
Are you using the Original LC/EF (3-3/8" long) or the Mini Version (2-3/8" long).

[knight_toolworks]

I got the original. but I would go for the mini. the more headroom the better. I hit something once when I topped out on my z zero.