Jog Speeds

[nat_wheatley]

I'm curious what others are using as a jog speed when they're machining cabinet parts. I've always had mine set around 18"/second, but as with anything, am wondering if I could be going faster.

I'm generally cutting at 8"/second with good results, the exception of the occasional small piece lifting off of the table. My dadoes still aren't as sharp as I'd like them to be, but are within reason for what I use them for, mainly capturing 1/4" backs and locating drawer stetchers.

[Gary Campbell]

Nat...
I have my jog set at 25ips. I tried the 8ips on the cutting, but wasnt able to get the ramp settings to work well with both the faster speeds and not be too soft on the slower speeds when cutting the smaller parts. I settled on 400 ipm (6.66 ips) and it has only added a few seconds to a sheet file.

Getting the plunge speed on the drill over 100 ipm was a bit factor in shortening sheet times (along with the jog speed) as I have a lot of drills on the cases we are doing currently.

Did you move to America yet?

Gary

[bill_lumley]

Hi Nat , I am in the process up upgrading to an Alpha machine and I only dream of speeds like those
What are you using for vacuum and how often do you surface the spoil board. I always notice when I resurface that it 'feels' like I get better hold down.I am thinking I put off surfacing maybe more than I should for several reasons.

For the new machine I am taking a serious look at a PVC plenum to hopefully beaf up vacuum performance .I just started using blind dadoes mostly for positioning parts such as stretchers as you mentioned . They are a bit tight at times but mostly OK .

Maybe I am wrong but I am thinking that there is a direct relationship betwen how fast you can cut and the effectiveness of your vacuum hold down .

Bill

[Gary Campbell]

Bill, Nat...
One of the things that you can do to increase vacuum and help reduce the number of times you have to resurface is add 1/2" collar. This helps keep the sheet "sealed" around the perimeter which, on our machine, keeps vacuum over 9 inHg until we cut thru.

We usually surface .030 every 30-35 sheets. We used to have to do it about every 20.
Gary

[bill_lumley]

Wow , sometimes I think I barely know anything about this machine when Professor Campbell speaks

Gary , I am not sure what you are saying about keeping the 1/2 collar sealed ? Are you saying that if you don't leave a collar that there is no kerf to hold chips to keep vacuum in ? Currently I have a kerf between parts of about 1/2" total and about 1/2" empty at the edge of the board when a board is finished. When I am on the cleanup pass I notice that the the kerf is 'clean' with no chips . I have part clearance and collar set to .2" and 'nest to edge of sheet' selected .

Bill

[nat_wheatley]

Gary,

Still living in metric land but getting closer to making the switch. I've started to change some of my libraries so that the metric sizes will switch easily over to imperial sizes (6" drawer fronts etc.) I still do like the metric for figuring reveals, hardware placement etc. Creature of habit, I know.

Bill,

I have the 4 Amtek vacuum motors mounted directly beneath my plenum (thanks Gary). I think I have the smaller Amteks and may swap them out for larger ones, at some point. Lightwight MDF for the spoilboard, sealed on the edges. I would guess that I surface it every 40 sheets or so. The current set up works fine for just about everything, but if I do have sheets of just smaller parts, I do increase the part spacing to leave a 'web' between parts. I do keep an eye on things, and assist with a 'manual' (read: hand) holdown on small parts that end up on the outside of a sheet.

I do like the idea of the outer collar, the only drawback being that with the collar I can't get 2 base cabinet sides/decks, (or 4 wall cabinet sides/tops/bottoms) across a sheet. Seems like an ideal idea for other parts, though.

[Gary Campbell]

Bill...
What the 1/2" collar does in my case is leave border completely around the table that never gets a slot cut in it. THis adds around 1.5 inHg to my gauges in most conditions. It is especially helpful 30 sheets into a cutting job.

Nat...
I agree. I have seen some nests that dont like the collar as it sometimes adds sheets. I reduce or eliminate it and cut those parts last.
Gary

[erniek]

With my PRT non-alpha machine I jog at 10 ips. Cutting is at 5 - 6 ips with a 1/4" single flute bit. I tried a double fluted cutter and it overloaded the machine and it started losing position at that speed. So would a double fluted cutter cause more flexing in the machine as well?

For how often I re-surface, another problem is the MDF swelling un-evenliy under humid conditions. It can get to the point where it doesn't cut thru in places and that's when I re-surface.

[bill_lumley]

Nat , I noticed your comment about larger motors so took a look at the lighthouse vac motor page and noticed they have a new motor recommended for CNC use http://www.centralvacuummotor.com/shopbot.htm Has anyone tried this motor and have they noticed/measured any difference in vacuum performance. I had not noticed previously that they require leakage to cool the motor and I expect that because I do not have sealed edges on my spoilboard that is not an issue for me at the moment but my next spoilboard/plenum was going to be sealed in all possible places . Ward thinks the 3/16" number quoted for the new motor should really be 3/8" leakage required for cooling .