Consistant cutting depth problem

[mjkirby795]

I am trying to cut a pattern into a 4" x 16" x 3/8" piece of manufactured flooring. I have set the cutting depth to 0.050. The bit is a 60 degree v bit. The problem appears to be variations in cutting depth throughout the process. Some areas cut and in other areas the bit does not penetrate the surface. Any suggestions as to what is causing this and more importantly - what's the fix?

[jeb2cav]

The very first thing I would check is can the z axis travel down far enough to enable the cut. I learned to think about this early on, and there are some other posts on this forum that talk about "light" lettering, or lettering that seems to fade away.

What is happening in this case is that the z axis can't travel far enough to reach the cut depth set in the toolpath, but it can get part way there. So, the initial cut may even look reasonable to the eyeball, but not to a depth gauge. Then, it starts reaching the z travel limit, but as there are no limit switches, the rod turns, it typically is a short distance so you may not notice any abnormal noises, but it didn't really travel that distance. Then it picks up to move the the next one. So, now it is 'higher' than it really should be had it been able to travel 'down' all the way. This process repeats until it gets to a point where it can travel all the way 'down', but of course, that is now higher than desired in reality.

In my case, using a Shark ProPlus, if I'm using any of the v-bits I purchased from Rockler for example (a "normal" router shaft length), I have to have at least a 1/2" scrap underneath a 3/4" board for a typical v-carve.

Some folks may not notice this as they're using a scarf table, and that is usually 1/2 or more. But, if it 'looks right' in vcarve, but the lettering or cut is too shallow on the shark, the first thing to look at is the z travel. Other things would include a slipping z coupler (motor/screw rod), loose bit in the router, loose router collar, probably some others I haven't thought about off the top of my head.

Let us know if this solved it for you or not. Lots of good ideas out there.

[Bob]

If you would be willing to export your file in .eps format, I would be willing to try it. I have several ideas, but would like to try your file first to see if I can replicate your problem.
Bob

[DRMRDR]

I am having a similar problem. When carving a design in a 3/4" oak board 7" x 12" inches the cutter cut about .030 deep on one side of the board and across 7" to the oter side of the board it did'nt touch the board. In the 6 months I have owned my shark pro I never get a even cut. I always set the cut rate very slow and a cut path .004 deep with a final pass at .001. I now thinh the machine just flexes to much and is not built strong enough. I think it would help if the table was solid and the steel shaft was larger.

[Bob]

Drmrdr, Mjkirby,
Is the same area of the table always the lighter area on other projects too? And, is it always when you are making a light surface cut?
Bob

[bollenbacherjj]

Is the table level? I found that the bottom half of my table is lower than the top half. I have learned to shave off about an 1/8" of the material before I cut with my v-bits. You can try to use a mdf board as the first layer and level it with a 1/2" end mill bit and then make your v-cut on your project piece on top of the mdf. It's extremely frustrating I know but to have a perfect cut path on large pieces requires the top surface piece to be perfectly level with the gantry. You might also was to make sure your chrome rods and gears are lubed enough so the router does not loose it's zero during the cut. I read that DuPont Silicon Teflon Spray is something that you can apply.

[historybuff]

I think I may be seeing a depth variance in my project too. It is a "printing plate" for an old-fashioned wood engraving. The white areas are what are to be cut down from the surface. Black areas are NOT routered or cut. The preview image was generated by VCarve. I have circled in red what appears to be problem areas. I have not tried to produce the plate in wood yet. Just want to make sure my finished product won't appear the same as the VCarve preview image. Any ideas?

Also, I may need to resurface my wood prior to cutting/routing to make sure it is perfectly even. How do I do this? e.g. produce a blank image of the size I want, load the "tool path" in the CNC control panel, set to 0, then start the router?

How do I add difference router bits into the Vcarve database?

Thanks in advance for your time and consideration.

Original

VCarve Preview

[Bob]

I have two quick fixes for you to try:

1. In the toolpath menu on the right side of the screen in VCarve set the flat depth a lot shallower. For example, try .005, or .01, or something like that. It will limit the maximum depth you can go.

If that doesn't do it, then go to step two:

2. Draw a rectangular border around the outside of the whole picture. Select the border and the picture and calculate a new VCarve tool path. This will create a negative image of your first attempt.
Bob

[Bob]

OK two things:
1. Go here to see how to add tools: http://www.cncsharktalk.com/viewtopic.p ... base#p1284

2. When I need to flatten a board prior to engraving, I do the following:

In VCarve draw a rectangle around the outside of the whole area to be engraved
Select pocket cut from the toolpath menu
Set an appropriate depth to cut in the flat depth .... like .001, or whatever you need.
I like to use a 3/8" straight bit for flattening.
Calculate the toolpath
Flatten that board.


Bob

[historybuff]

Thanks Bob for your kind assistance. I tried both of your methods to correct the "gauging" in those few areas without much improvement. Here are the settings I used:

Machine Vectors = Inside/Left

Cut Depth (Start) = 0.0
Cut Depth (C) = 0.0469
Start Depth = 0.0
Flat Depth = 0.0469
Pass Depth = 0.0469
Pass Stepover = 0.01
Clearance Pass Stepover = 0.1
Clearance (Z1) = 0.0469
Plunge (Z2) = 0.0469
Outside/Right

I can't activate anything on the Tabs/Leads/Ramps, etc. section.

This is the result of the preview image:

Its better, but to make a more-accurate representation I should probably use a smaller bit. This was done with a 1/2 inch 90 Degree bit. What bit do you recommend?

Thanks for your kind help.

Rick Brown