Dialing in my table

[WCSG (Unregistered Guest)]

Okay I think I've dialed my table to the best of my ability without taking it out of whack. My table is fine for what i mainly do, dimensional lettering and signs. Now I seem to be going into doing ADA Signs where I'm working with cutting out and away small lettering of a second surface, lettering as small as 5/8". Now with working so small I'm beginning to see how my table is not dialed in, working with small plaques the size of 6" x 8" and trying to do 20 at a time I begin to see where I'm either not cutting off enough or cutting into the 1st surface of the sign to much. So basicaly I have a 6"x8" sign and part aren't cut enough and some parts to much. This noramlly would'nt be a problem when working on bigger stuff but now it is. What kind of individual would I need to dial my router in, a machinest? Or some other sort? I'm just not to informed on calibrating my table with dials and guages. Maybe after watching someone do it I can learn.

[bleeth]

WCSG- Get a 1"-1 1/2" flat bottom bit and follow the instructions for flattening your table in your manual. This should alleviate your problem which sounds like the plane the router is running in is not parallel to the table surface. You also have to be sure your parts are being held evenly.
If you are concerned about the x rails themselves being out of level with each other a bubble level (clear tube with water in it) will help you dial it in like a pro.

Dave

[WCSG (Unregistered Guest)]

It planes down farely well with very small lines that my 1.25" bit leaves it's just trying to consistantly cut a depth and route out letters at .030 ". I have to use a engravig bit with a 30 Deg angle, so if the bit goes a little to high or to low it changes the stroke of the letter

Here's a pic of what I'm doing to give you an idea

http://www.thesignsyndicate.com/miscstuff/alum3.jpg

So with a table full of these consistancy has to be pretty true.

[paco]

Hi WCSG!

Did you re-zero different tool bits within thoses parts?... like using more than one tool bit?

Assuming so, one have to be VERY consistent in it's method when zeroing tools that SHOULD work accuratly in relation to a previous one; say pocketting with more than one tool bit and needing 'em to be at THE SAME depth/height.

I've check my tool with a dial gauge to troubleshoot a such problem recently and come to the conclusion that I was faulty (not being consistent when re-zeroing a next tool bit); the tool was accurate in it's positionning within 0.002"... and it have no free play.

[Brady Watson]

WCSG,
A couple things....with a $39 Harbor Freight digital caliper, measure the thickness of your Zzero plate. The value that is in the zzero file (the line says &ZBot = .131), tells the software how far from the spoilboard the bit is when the bit hits the plate. In many cases this value is incorrect. Mine was off by .01" in the Z (it was really .121, not .131 as the file was assigning). Measure, change the line in zzero.sbp and replace with your value if necessary.

The other thing is, I can see from your pics that the Z is way out. Here's how I would fix it...Observe the cut marks on the table left by the last surfacing. In your mind's eye, try to picture which way the router is tilted out of position by reading the cut marks and how they tilt. This will give you some feedback as to where the router needs to be. Loosten the Z-axis bolts a little bit & clamp a 2' level to the Z axis somewhere nice and flat. Clamp it as high as you can to get a good reading. Snug up the bolts when you are satisfied reading level one way, but don't tighten just yet. Put the level on the adjacent part of the Z to level it now the other way (you may have done the XZ plane 1st, but now have to do the YZ plane or vice versa). When you have checked both sides and all is dialed in, tighten the bolts up & re-check. When all is well, resurface your table. It should be dead on with no ridges, only slight stepover marks which knock right down with sandpaper.

If you are satisfied with this, then re-check your X and Y rails to make sure that they were properly setup from Day 1. This will involve shimming the rails to eliminate dips and straightening them if necessary. You may also find that the cam bolts on the v-roller bearings need a little adjustment after using the machine for a while.

Hope that helps!
-Brady

[gerald_d]

WCSG, has your material got a consistent thickness all over the sheet? Is your table made of temperature stable materials? When the tool cuts too shallow (or deep) is this in a recognizable area of the table - in the middle, at the edges, etc.? (I would suggest that you surface/skim/plane your table with the same cut "load" as you use when v-cutting - to get similar deflections).

Looking at your pics, I am actually surprised that you are getting results that good! (I don't see problem issues with your set-up or procedure). Your "30 degree cutter" is probably making slope angles of only 30 degrees and some of us would call that a 120 degree cutter. If a cutter like that gets blunt it tends to ride up the slope rather than cut (ie. it cuts shallower).

If my arm was really twisted to take on that job, I would ask the client if I can do the 120 deg. V-cutting a little shallow and then run a steeper bit around the outside edges for the final definition.

[WCSG (Unregistered Guest)]

I'm Zeroing everytime I change bits and I do know about the Zero PLate change and that's a change I haven't done yet in the file. But I still get a inconsistant depth and it doesn't seem to be in one particular spot of the table. Brady you said my Z is way out? I'm just visualizing in my head how accurately I can get both X rails perfectly parallel with one another and at the same perfect height with one another. The engraving bits I have are new and sharp, I've even traded them around. I'll have to play around somemore with it I guess expecially with the Z. But something I have set is not getting an accurate depth and making it float around

[fleinbach]

Wcsg

Have you checked the pinion gear on your Z-axis to make sure that it is tight? If it were loose it could easily cause your Z-axis to float.

[bleeth]

You can check and adjust your z using a trammel rig chucked into your router. It can be more accurate than leaning a level against a router.
You can make a quick trammel by wrapping some stiff wire around the shaft of a bit, go out 8-12" and then bend it down to the table. By turning the router slowly with your hands you can see if your router is leaning and which way.

[bill.young]

Dave asked an important question...how are you holding the pieces down? Are they being held tightly to the table surface everywhere?

Bill

[WCSG (Unregistered Guest)]

Here's another quick question I've had in my head for a while now before I check the above (& thx a bunch guys) WOuld I have a almost perfect table having a machine shop weld up my table, would that insure that everything would be level and accurate, si that part of the process a machine shop would do? That way all I would have to worry about is the position of the Z and bearing seats?

[gerald_d]

IMHO, fiddling with the angle of the Z axis, or the zero plate thickness, is not relevant for this situation where different random parts of the table appear to give different z heights. I say "appear" because the material thickness may not be consistent, nor may the material be held down tight. The z-gear may be loose, or you may have the often reported z-axis creep, or the bit is slipping in the collet, or there is dirt buildup on the x&y rails, or the x&y rail pairs are not parallel to each other, or the sun shines on your table and material, or the heavy cat walks over the table while you are cutting, or, or, or ...........

ETA: I run a mechanical machine/welding shop and I wouldn't want my guys to build me a FLAT steel table. Flat in our language, for a table that size, (only welded and not stress-relieved & machined) would be about a tolerance of +/- 1/16".

[WCSG (Unregistered Guest)]

The materials used are 1/2" PVC with .032 Brushed Aluminum laminated on top. 2nd surface is 1/32" rowmark ADA applique. I'm holding down using a thin double sided tape.

Oh okay I thought there were advantages to having a welded up table.

[gerald_d]

A welded table sub-frame (or chassis) yes, but still covered with a softer material that is skimmed/planed/levelled by the ShopBot itself.

[Brady Watson]

I was looking at your spoilboard ridges...not the cut piece when I commented on your Z being 'way out'...

-Brady

[gerald_d]

...then it must be impossible to play on this soccer pitch:



3795
Our spoil board looks the same as WCSG's under certain lighting conditions although it is perfectly trammeled/plumb/perpendicular. The optical effect is given by the cutter direction causing the remaining surface fibres to lay in a certain direction.

[gerald_d]

How the lines are made on a pitch (http://bg.grounds-mag.com/ar/grounds_maintenance_establish_mowing_patterns/)

[rookie432]

WCSG,
I just went through this same problem doing a similar job as yours. 1/8" ada acrylic laminated material. Did about 75-100 wayfinding signs. After repeated attempts at zeroing to the material on my mdf spoil board I would still be off .01-.03 or more of humidity was high. I have noticed that temp and humidity will play a big part when working with such small tolerances.
Here was my cheap fix. I went down to the local lumber yard and bought a $20 hollow core Luan Door. I clamped the door to my table surface. Then I used spray adhesive for the back of the acrylic sheet and pressed it to the luan door. Since I was doing small parts and letters this seemed a better solution than vac due to the fact that all the signs were different and gasketing would have been a nightmare.
I think this worked because the luan door carried a flat plane over any slight discrepencies my spoilboard would have had and the fact that every square inch of the acrylic sheet was flat against the plane of the door due to the spray adhesive technique. This option was pretty low tech but fairly effective.
This being said this was a quick cheap fix for 50-100 signs. If ADA signs were my main product I would definitly invest in having an aluminum table w/ vac etc.

Hope this helps
Bill

[WCSG (Unregistered Guest)]

Would I buy a specialty Alum table surface made for CNC or is that something I would have to build? If I use an alum table do I still use a spoilboard? I've seen pics of engravers but not sure if those are made to cut thru or just made for surface engraving.

[rookie432]

WCSG,

I keep seeing some nice looking aluminum vac tables from a german co. on ebay they are different sizes and work from a venturi valve.
You wont need a full sized one due to the fact that Rowmak acrylic only comes in 24x48" sheets max.
I had the same question as you though when it comes to spoilboards. I wouldn't want to cut into the aluminum with a fine engraving blade. Maybe someone here can answer that quetion for both of us.

Bill

[rookie432]

Here is the one ive been considering,

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=25297&item=7522592 518&rd=1&ssPageName=WDVW

Bill

[bleeth]

Bill: debece(the manufacturer of the table you are looking at includes a "mill through mat" For use when you are cutting through parts. I assume it is a constant thickness membrane. Here is their site: http://www.debece.net/

Dave

[WCSC (Unregistered Guest)]

You know it would be a good idead to creat a bracket on both sides of the table to use this on and off the table when needed, Hmmmm

[rookie432]

Thanks Dave,

I was always curious about how that problem was solved.

Bill