[Jalex]

Hi all:

I have done a slightly reduced machine ( Joe2006 at 80 % ) myself and I´m testing different materials and speeds.

Trying to do a v carved letter got what is shown on the pic.
Left side is somehow scalloped , right sides are not showing this problem.

Can any of you tell me what may the cause be ?
Have tested several tool speeds, feed speeds and tool shapes , all with this nasty effect.

Thanks for your help.

[acondit]

Hi all:

I have done a slightly reduced machine ( Joe2006 at 80 % ) myself and I´m testing different materials and speeds.

Trying to do a v carved letter got what is shown on the pic.
Left side is somehow scalloped , right sides are not showing this problem.

Can any of you tell me what may the cause be ?
Have tested several tool speeds, feed speeds and tool shapes , all with this nasty effect.

Thanks for your help.

Jalex,

I don't know for sure, but my initial guess would be backlash. As the machine cuts up one side it is pushing with the screw keeping out any backlash effect but as it cuts down the other side it is retracting with the screw and thus allowing the cutter to push back to the extent of the backlash (thus creating the scallop).

Alan

[bp092]

Looks like chatter, poor chip too. I've only cut plastics esp plexi with an oflute. What kind of plexi is it?

[Jalex]

Looks like chatter, poor chip too. I've only cut plastics esp plexi with an oflute. What kind of plexi is it?

Hi bp092:
i don´t know exactly the type. It is called acrilic locally by the sign makers. This is a scrap piece i got from them ( transparent, with a plastic film on both sides ) use by them for several jobs in signs.

Jalex

[SCRAPWOTSCRAP]

Looks like multiple issues, might be extruded acrylic versus cast. The melt on extruded acrylic will weld to your bit and make quite a mess. Cast acrylic is a must for engraving. Also, you're quite deep, I might make several passes at that , last one being a cleanup pass. Might want to lower your RPM's a bit.
I've had some good luck with some Amana bits made for acrylic, here is a link .

http://routerbitworld.com/Amana_4573...37;2045731.htm

[Jalex]

Hi Alan:

I thought it was backlash too, and made 2 new nuts ( x and y ) with delrin and a very tight fit. Now i can say there is no backlash on both axis. But the pic was taken after the change... and the problem is still there.

May be the tool support is flexing ( on the x direction ) while it moves Y ...
All the machine is made in MDF. Really dont know what to do !

Thanks for your answers.
Jalex

I don't know for sure, but my initial guess would be backlash. As the machine cuts up one side it is pushing with the screw keeping out any backlash effect but as it cuts down the other side it is retracting with the screw and thus allowing the cutter to push back to the extent of the backlash (thus creating the scallop).

Alan

[Jalex]

Hi :

This is a 3/16 inch acrylic and that was carved about 1/8 or a little more by 4 passes. I made also a speed control unit and am pretty shure it is not melting the material. And the problem is on one side and not in the other one.
Backlash, vibration, flexing tool support... but cant find it.

Thanks for your help.
Jalex

Looks like multiple issues, might be extruded acrylic versus cast. The melt on extruded acrylic will weld to your bit and make quite a mess. Cast acrylic is a must for engraving. Also, you're quite deep, I might make several passes at that , last one being a cleanup pass. Might want to lower your RPM's a bit.
I've had some good luck with some Amana bits made for acrylic, here is a link .

http://routerbitworld.com/Amana_4573...na%2045731.htm

[beone]

this is almost undoubtedly tool (holder) flex. try a light finishing pass

[acondit]

Hi Alan:

I thought it was backlash too, and made 2 new nuts ( x and y ) with delrin and a very tight fit. Now i can say there is no backlash on both axis. But the pic was taken after the change... and the problem is still there.

May be the tool support is flexing ( on the x direction ) while it moves Y ...
All the machine is made in MDF. Really dont know what to do !

Thanks for your answers.
Jalex

Jalex,

The nuts are not the only places where you can have backlash. You can also have backlash where the screw passes through the bearings.

If you have a dial indicator, you might put a piece of 1/4" rod in the router chuck, and set up the dial indicator aligned with the x axis against the rod. Then grab a hold of the bottom of the router, then push and pull in alignment with the dial indicator and see how much movement you get. Then move the setup 90° (aligned with the y axis) and try the same thing in those directions. Once you see how much flex or movement you are getting, you can begin to try and find where the flexing or movement is taking place.

Alan

[joecnc2006]

Yes, my guess is your Z-Axis is Flexing, try adding some angle on the outside of the Z-Axis back plats and wrap the other infront of the plate, meaning one angle will be on side bolted and the other will make a 90deg. and be infront of the plate, make holes to rebolt tool holder side brackets back on.

Joe

[lovebugjunkie]

I had the same thing happen to me but on a much smaller scale. I was using a 1/8 bit.

I thought my feed rate might be to fast for my router (Ryobi trim) so I slowed it down which seemed to clear up the problem. Still don’t understand why in one direction it was ok and the other not.

[joecnc2006]

I had the same thing happen to me but on a much smaller scale. I was using a 1/8 bit.

I thought my feed rate might be to fast for my router (Ryobi trim) so I slowed it down which seemed to clear up the problem. Still don’t understand why in one direction it was ok and the other not.

maybe conventional cutting versus climb cutting.

[Jalex]

maybe conventional cutting versus climb cutting.

Hi Joecnc2006 !

This is a V bit . What is the difference when running along same Z ??
Sorry this may be a too newbie question, but the hole thing is new for me.!

And talking about flexing Z... May be I have to remake my Z cart. I do not have the lateral plates on. Some pics later...

Jalex

[Jalex]

Jalex,

The nuts are not the only places where you can have backlash. You can also have backlash where the screw passes through the bearings.

If you have a dial indicator, you might put a piece of 1/4" rod in the router chuck, and set up the dial indicator aligned with the x axis against the rod. Then grab a hold of the bottom of the router, then push and pull in alignment with the dial indicator and see how much movement you get. Then move the setup 90° (aligned with the y axis) and try the same thing in those directions. Once you see how much flex or movement you are getting, you can begin to try and find where the flexing or movement is taking place.

Alan

Thanks Alan for the info.
Both X and Y axis were moving a little back and forth. Added some pretension and a second nut to thight them against bearings.
But still showing some movement in the X direction ( looks like somehing flexing rather than moving ) . And the problem appears while cutting in the Y direction. It is not shown on the X cut. Perhaps the tool or holder is flexing in X.

Jalex

[Jalex]

Hi Joecnc2006 !

This is a V bit . What is the difference when running along same Z ??
Sorry this may be a too newbie question, but the hole thing is new for me.!

And talking about flexing Z... May be I have to remake my Z cart. I do not have the lateral plates on. Some pics later...

Jalex

Hi Joecnc :

Here is the pic showing present tool holder.
The paralelogram holding the bearings may be distorting a little and allowing tool movement in x direction.

Jalex

[BobF]

The steps look pretty regular. Look at the G-code and see if it is running a bunch of small steps on that side. It could be the font, or whatever generated the code if you have a lot of small stair steps.

[diecutter]

I read recently in an article on routing letters that if the g-code was generated from a scanned bitmap rather than being a pure vector such as a truetype font, then the angle it was scanned at can cause a ragged edge, often only on one side. Try cutting an "A" from a simple vector rather than a scanned "A". Also, you can slightly rotate the image before scanning which often helps. I believe they call this deskewing.

[DistortedDesign]

The buckling on the left side can happen when there is an extra couple of pixels on that side. When a lot of people use programs like photoshop to make them look 3d or have those nifty edges those extra pixels get blown up. The edge of the letter has to be clean and also has to be the EXACT same color. Sometimes if the color in the letter is off by just a couple of #'s it can have that effect when you 3d it. I would do as diecutter says and try and stick to vector graphics (stuff you can type out in photoshop or something like it). If you don't have that option then you can clean up the letter by using photoshop or something like it. If you need help with the process just ask and I can tell you how to clean it.

[Jalex]

Hi: BobF and others:

G code checked. Nope , its a 2 points straight line. Must be a mechanical thing. The original drawing ( and the code ) are just a few lines from a to b, c,d,e,.etc.
And the path is just following the line.

Jalex

The steps look pretty regular. Look at the G-code and see if it is running a bunch of small steps on that side. It could be the font, or whatever generated the code if you have a lot of small stair steps.

[joecnc2006]

Looking at your Z-Axis, my bet would be your tool has some play in it, looks like it is held into place with a strap clamp, If you look at all my mounts i have two holders so there is no movement of the tool at all.

I would add another clamp about where the label is on the trim router.

Joe