Looking for suggestions and help in NE area

[ShopKat]

I'm a relatively new user to ShopBot/CNC machines and have had a difficult time since the machine was new with the Z axis and my depth of cut. I just manually Z zero all the time (using feeler gauge) but the machine is very erratic and despite what I enter for the toolpath my cuts are frequently too shallow. I go back and recalculate the toolpath to cut deeper but it does not cut what I have entered. I've gone through my procedure and various possibilites with ShopBot IT but still not getting good results. I just tried a different font that was better - could my font (Times Roman) be corrupt? I'm essentially cutting very simple sign lettering. Any suggestions? Or I'd also appreciate any help with using this machine if someone in the area (NE?!) is able to do so.
Thanks.

[donek]

without photos, it's tough to know exactly what is going on, but if you're not getting deep enough cuts, just manually set your z deeper. The VA command will enable you to reassign the z-axis height to whatever you need.

[bob_reda]

There could be alot of issues at play here and it still is best to work it through with shopbot IT. Does your z pionion gear tight or worn? is the axis screwed in or taped? if taped it will have a tendencay to slide a little. Are your unit values correct? Is it a consistent depth or is it different every time? Shopbot IT won't give up, just be at the machine when you call them.

Bob

[ShopKat]

that's a great work-around idea for mid project. Thanks! The depth problem is strangely erratic and sometimes works fine so I'd have to see that it was doing the lite groove first but very helpful, thanks again.

[adrianm]

What type of toolpath are you creating with the fonts? Is it a VCarve toolpath or a profile toolpath?

If it's a VCarve toolpath how are you "recalculating the toolpath to cut deeper" as you describe?

If you're entering larger numbers for the flat depth option (presuming you're using Partworks) that won't do anything if the VCarve isn't cutting that deep to start with. You would need to make the text larger or use a v-bit with a sharper angle to get more depth.

[ShopKat]

Sorry, just getting used to how to post and reply. Last message to Sean but also partially answers Bob. Bob, machine has always had problems but very little use so I doubt that the z pinion is worn. Tight? How do I tell? Axis is as it arrived! It is not a consistent depth problem every time and sometimes is just right??!! I set the depth of cut for the toolpath to 0.14 to 0.16 every time and then see what happens! ShopBot IT - those guys are great and very patient but I'm wondering if there is an out-of-the-box thought. Also, I'm hoping to find someone close by that can either run my machine or that I can watch theirs run through a program and see if mine has a problem or if it's the operator. (Can't find the winking face here so ;) ). Thank for all replies.

[paul_z]

You have a PM.

Paul Z

[donek]

that's a great work-around idea for mid project. Thanks! The depth problem is strangely erratic and sometimes works fine so I'd have to see that it was doing the lite groove first but very helpful, thanks again.

What machine are you using? Even on my 7 month old PRS, it's important to be very conscious of my plunge speeds. Movement in the z is typically minimal, so it's not really important to keep it high. On my old PR the maximium z-move speed I ever use is 0.3ips. On my PRS, I keep it at 1ips. in most materials, but set it at 0.2ips in aluminum. If you are loosing steps in the middle of your parts, but not loosing communication, your most probable problem is too rapid a movement in the z direction. Bits are rarely designed to plunge and even ones that are, don't do it well at a high rate of speed. Watch those values, and you are likely to fix the issue.

[ShopKat]

Hi Adrian and Sean,
Adrian, I just had a long discussion with Ryan in IT about fonts, size of font, and what the Partworks software will cut with a particular tool, in this case a 90 V bit. It does make sense and I'll be trying out setting the z axis at just below zero to see how that works.
Some of the work is a profile but still cut with the same 90 V bit so probably limited - however this cut sometimes starts with a too deep plunge (!) that leaves me with a fat part of line and then the rest is smooth. (fortunately I'm a good sander!) Sean, I need to read through and check on the plunge speeds and do some tests there too so thanks for the tips there.
I did recalculate and resave the file per ShopBot instructions and have had success with small lettering actually cutting deeper when I do this - sometimes! Apparently I'm asking a lot if I'm using a wood surface that it be consistently flat enough to do a fine detail carving of lettering given various font/software/bit limitations so I'm also rethinking my whole approach to this.
Enjoy the weekend.
Ktenia
P.S. How's things in Surrey Adrian? I grew up in SE London.

[feinddj]

You can use your Shopbot to mill the wood surface flat before you cut your detail. With V carving, a small difference will show up more than you thought it could. I mill one side flat and then flip it and mill the second side flat as well, mainly to avoid shifting or rocking. You can fool the bot into a hogging pass with the vbit by telling it the material is thicker. Then go back at the actual thickness for the finish cut if you are having chattering issues.

David

[gene]

Is there any chance that the bit could have slipped? I did that once:)

[ShopKat]

Hi David, I usually sand (large machine not by hand) the material just before I work on it but perhaps that is still not enough. I have had problems getting the Z axis to move in the right direction, move what I tell it to, and also having it be too deep. You mentioned the material thickness which is interesting as I didn't understand why you bother to enter that if then it is so important to Z zero. Thanks for the idea of milling with the Shopbot first as that certainly should leave it flat to Shopbot levels.

[jerry_stanek]

If you enter the material as .75 and the material is .78 and you zero to the table then you would be cutting .03 deeper than you wanted and if you wanted to cut trough and zeroed to the top you would not cut deep enough.

[feinddj]

Jerry has it right. The benefit of using the bot is that it will be flat to the bed of the machine. A thickness sander or a planer makes two sides parallel. Very different than flat. Even though, for the purposes of most woodworkers, it would be flat enough.

Checking that you, as a matter of habit or need, always zero to the top of the material or the table is crucial. Most of my "lost" bits and or projects were because I zeroed to the wrong surface and the machine did what I asked it to do and dove an inch and three eighths on a single pass.

D