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frank134
04-16-2009, 08:17 PM
I have a PRS Alpha 5x10 with the 4hp spindle. My son and i set it up and got to the point of surfacing the table. The table is composed of 3/4" birch plywood and two sheets of 3/4 MDF. We leveled the table using a transit and it is within a few thousands. We are using a 2.5" Amana tool spoilboard bit for this and the surfacing program that comes with the SB software. Now i know that larger bits can leave tool path marks but what it is leaving seems to be more than just tool path marks. At first we thought the table was not level or out of square. When we rechecked them they were all OK. What is happening is that when the machine is surfacing the table, the outside edges are higher than the inside edges by about .015 with it slightly decreasing as it moves towards the center of the table. This is the case as it travels across the X axis and the Y axis leaving a picture frame effect on the table. I could figure this out if all cuts had a higher edge in the same direction but this is not the case.

rb99
04-16-2009, 08:46 PM
It sounds like the Y is sagging with the weight of the router. 5' gantry...

RB

Gary Campbell
04-16-2009, 09:23 PM
Frank...
First let me say that the 2.5" bits are very unforgiving. I surface my table only in the X direction for this reason.

It sounds as tho something is loose in either your Spindle mounting, Z extrusion rollers or the lower rollers on your YZ car. If anything is even slightly out of adjustment in any of these areas, you will have a few thousandths movement. This movement will show up on a large bit more than any other.

Start by giving the spindle some pressure in both the X and Y directions and look for something obvious. Take care of the obvious first, then following the instruction manual, adjust/tighten all of the points I listed above. Let us know the results.
Gary

thewoodcrafter
04-16-2009, 09:54 PM
Make sure the Z is trammeled accurately.

wberminio
04-16-2009, 10:23 PM
Frank
Gary is correct.Follow his suggestions.

BTW-I don't believe there can be any sagging in your Y axis

Erminio

frank134
04-16-2009, 11:01 PM
One mistake that i think we may have made when attaching the motors on the xy car, is that i just held the motors up hand tight without clamping the xy car to the x rail. Should I clamp the xy car to the x rail to try to get it seated on the x rail better. Or what is the best way to align the rollers to the table? These do seem out of alignment when rolling down the table. I thought that the weight of the spindle running across the xy car was supposed to make it shift a little.

frank134
04-20-2009, 08:46 PM
Thank Gary for all the help. 2-1/2" cutter and 30% over path and it look like glass.I'am just jumping up and down, I didn't think it would cut so clean. I got my vacuum board (stay up till 2:30 am just to watch it cut) cut and already to seal. BY the way I used that plastic nails and glue and it look like it going to work out. you can't even find the nails.
again
thank you
frank.

frank134
04-20-2009, 08:51 PM
sorry resetting the Z fix it. As soon as I loosen the both I felt the z drop to the x rail.
thank you all
frank

pappybaynes
04-21-2009, 12:37 PM
Gary,
How do you surface you table in JUST the X direction?? Did you write a specific surfacing program to do that??
thanks as always for sharing your expertise!
Dick

wberminio
04-21-2009, 01:07 PM
Dick

Try Paco's Surfacing Routine
http://pacosarea.blogspot.com/2007/02/surfacing-along-axis-shopbot-routine.html

Erminio

tmerrill
04-21-2009, 01:22 PM
Dick,

You can prepare your own surfacing routine using the design software you have.

Define your material size as your table size and draw a rectangle the same size or a little larger. Define your tool, the speed and stepover you want (keep them both large) and perform a pocket cut, selecting raster as the cutting strategy.

Tim


3794

wberminio
04-21-2009, 01:38 PM
Paco has already done the work for you.
It also works well for surfacing warped lumber.
I say give it a try!

Gary Campbell
04-21-2009, 03:58 PM
Dick...
Erminio is right... I actually got a copy from David Buchsbaum. Its the same program. I added my own variations to it, and David added a climb mill version that works well on large slabs with bark edges.
Gary