Need Help! Cutting Quality 3/4 MDF


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Thread: Cutting Quality 3/4 MDF

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    Default Cutting Quality 3/4 MDF

    Hey all,
    So i am still trying to get this 4896 Zenbot CNC figured out to produce good quality cuts, i am currently using a Yonico 33210-sc 2 Flute Compression bit, i was using Amana 2 flute compression bit but was still getting same results and i am only getting 8-10 sheets of 3/4 melamine cut before it seems the bits go dull. Currently im running a Hitachi M12vc 2 1/4 Hp router and running at 100IPM at 11k rpm, a few questions i would to get help answered:

    1. Since Compression bits are made to cut 3 directions should i be cutting the 3/4 MDF in one pass? Reason i ask is if i make three passes no matter what i only using the first 1/4in of the compression bit which would dull it very fast i'm guessing?

    2. When cutting im getting rough cuts in certain areas, mostly corners are not rounded it leaves hump before curve? Possible something to do with where the cut starts and stops? I noticed there very small wavyness to the cuts if you look close there not smooth
    Inside Cutout as well leaving hump.

    3. When i make my dado cut on the line it starts and makes a little swerve before starting?


    4. I am not familiar with doing the ramp cuts and things, i currently have it plunge and start?

    5. Circles are more oblonged than circle? Any advice on that?

    I have been trying different things for a few months now to get it running smooth, time to try and seek advice from everyone. I have been looking around the DesMoines Iowa area to find assistance to pay someone to help but not much luck on the wood cnc machines.

    Thanks

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    Default Re: Cutting Quality 3/4 MDF

    First, that's not MDF, it's particle board.

    One problem, is that you have a lot of flex in the machine, or something is loose.

    1) I don't think you have the rigidity to cut in one pass. But what you might want to try is to make two roughing passes, each about .35" deep, and leave about .05" for a finish pass, then make a full depth finish pass, removing the last .05". This will lighten the load on the tool, but I'm not sure it will help. Also try climb cutting on the roughing passes, and conventional cut on the finish pass.

    2&3) Again, rigidity, or mechanical issue.

    4) You should always ramp in, but it won't help your problems. It will make the bit last longer, though.

    5) Need to see a pic. Could be backlash, but is probably the same issue as the other cuts.

    With no tool in the router, grab the collet, and push and pull on it. If it's visibly moving, you're going to struggle getting good cuts.

    Gerry

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    Default Re: Cutting Quality 3/4 MDF

    One of these:zenbot 4896 4x8 cnc router ? The photos provided on that site are murky, and don't show much of the mechanical details, so it's hard to say where the weak points are. Which parts are made from plastic - the gantry sides? If so, replacing them with aluminum parts would increase rigidity. They talk about belt drive - is that a long belt, used instead of a ball screw or rack-and-pinion drive? That works for low-end 3D printers, which don't have cutting counter-forces to contend with (the better ones use ball screws). It's not so good for routers. Replacing that stuff with racks and pinions would help the thing cut more consistently. They talk about using their own proprietary slide system, but don't give any details about it. Is that a series of wheels running on rails? Is any of it plastic? That might be another thing you could replace with something else, like real profile rails and ball-bearing trucks, and see improved performance.

    I don't think the problem is with your tooling or electronics; I'd agree with Ger in attributing it to lack of rigidity. It might be that something can be adjusted to be tighter, but it looks like that machine was basically engineered to hit a price point, more than a performance point. Rebuilding it might be worthwhile, but selling it and using the money to build something else could be your best bet.

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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by awerby View Post
    One of these:zenbot 4896 4x8 cnc router ? The photos provided on that site are murky, and don't show much of the mechanical details, so it's hard to say where the weak points are. Which parts are made from plastic - the gantry sides? If so, replacing them with aluminum parts would increase rigidity. They talk about belt drive - is that a long belt, used instead of a ball screw or rack-and-pinion drive? That works for low-end 3D printers, which don't have cutting counter-forces to contend with (the better ones use ball screws). It's not so good for routers. Replacing that stuff with racks and pinions would help the thing cut more consistently. They talk about using their own proprietary slide system, but don't give any details about it. Is that a series of wheels running on rails? Is any of it plastic? That might be another thing you could replace with something else, like real profile rails and ball-bearing trucks, and see improved performance.

    I don't think the problem is with your tooling or electronics; I'd agree with Ger in attributing it to lack of rigidity. It might be that something can be adjusted to be tighter, but it looks like that machine was basically engineered to hit a price point, more than a performance point. Rebuilding it might be worthwhile, but selling it and using the money to build something else could be your best bet.
    thanks for correction, i was thinking of MDF for a different project im working on when posted intial. Here some info.

    Here is what the Zenbot 4896 looks like before placing the bed on it, the gantry sides are a hard plastic material but is supported with a brace across the back that ties them together. The system rolls on the galvanized rails using internal sealed bearings, i did reach out to Zenbot and got a replacement gantry after learning the load specs on the bearings were off but havent tested it yet. Yes, it is driven by kevlar belts, two on each side and two motors run the X axis and one runs the y and one runs Z. Maybe im wrong but kevlar belts are used in motors for timing im guessing they not strong enough for a cnc? there pretty thick and wide.

    Was hoping to get by learning as a new CNC'r then buying a better unit, gotta start somewhere. I use a 2 1/4hp Hitachi router, would it help to change it out for a spindle? and if so any recommendations?

    Thanks for the responses, hoping others that have or buy a Zenbot will have some info, don't see much on them.
    P.S I did go around and tighten and checked all bolts and checked the collet which had no slack or play to it.

    Attached Thumbnails Attached Thumbnails Cutting Quality 3/4 MDF-20170113_182747-jpg   Cutting Quality 3/4 MDF-20170502_162038-jpg   Cutting Quality 3/4 MDF-20170104_175923-jpg  


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    Default Re: Cutting Quality 3/4 MDF

    Maybe im wrong but kevlar belts are used in motors for timing im guessing they not strong enough for a cnc?
    The pictures of your cuts would indicate that they are no where near strong enough.
    About all you can do is get the belts as tight as you possibly can.
    You just don't have a very rigid machine, and the lack of rigidity is the problem.

    Gerry

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    Default Re: Cutting Quality 3/4 MDF

    Try taking lighter cuts and slow the feed down. That will reduce the cutting forces, might help. Your tool bit life may suffer from slowing the feed down. Maybe try an upcut bit rather than a down cut. Try the bits from Home Depot or Lowes, about $20. Changing out the Hitachi router won't help unless the spindle bearings are very loose.



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by Jim Dawson View Post
    Try taking lighter cuts and slow the feed down. That will reduce the cutting forces, might help. Your tool bit life may suffer from slowing the feed down. Maybe try an upcut bit rather than a down cut. Try the bits from Home Depot or Lowes, about $20. Changing out the Hitachi router won't help unless the spindle bearings are very loose.
    On figuring the Feed/speed would this be correct:

    Particle/Melamine .019 Chipload at 1xD
    IPM200 divided by (.019x2)=.038 RPM 5,263

    Specs say 3x D reduce chipload by 50% (What does this mean? 3 passes?)

    IPM200 divided by (.010x2)=.020 RPM 10,000

    I contacted Amana tools and got the chipload from them for the bit i use. They recommended 200IPM 15k RPM and to cut first pass at 3/8th and complete cut 2nd pass, also they said ramp should always be set at half on IPM speed?

    Trying to learn and figure things out, i would think by cutting in three passes i would be ok but i need a good feed/speed starting point and could i get help with the ramp feature i have never used it in Aspire.Theres smooth and zigzag settings and a choice of Angle or Distance, not sure what does what and what i should be using for the settings there,

    Thanks again



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by Wisker View Post
    On figuring the Feed/speed would this be correct:

    Particle/Melamine .019 Chipload at 1xD
    IPM200 divided by (.019x2)=.038 RPM 5,263

    Specs say 3x D reduce chipload by 50% (What does this mean? 3 passes?)

    IPM200 divided by (.010x2)=.020 RPM 10,000

    I contacted Amana tools and got the chipload from them for the bit i use. They recommended 200IPM 15k RPM and to cut first pass at 3/8th and complete cut 2nd pass, also they said ramp should always be set at half on IPM speed?

    Trying to learn and figure things out, i would think by cutting in three passes i would be ok but i need a good feed/speed starting point and could i get help with the ramp feature i have never used it in Aspire.Theres smooth and zigzag settings and a choice of Angle or Distance, not sure what does what and what i should be using for the settings there,

    Thanks again
    3x D means depth of cut is 3 times the tool diameter, or in this case 0.750 inch for a 0.250 tool.

    Gerry is correct, your machine is not very stiff so you are not going to be able to get maximum performance from your tool bits.

    I could run with the Amana recommended feeds and speeds on my machine, but my machine weighs over 5000 lbs and is solid. Just my X axis (cross axis) carriage, at about 300 lbs, weighs more than your whole machine. I'm not bragging here, this is just to illustrate the differences in machines.

    As a starting point, take less depth of cut, maybe 0.060, and slow the IPM down to about 50 IPM If that works OK, then increase the IPM and/or depth of cut and see what happens. You have to make allowances for the machine that you are using.

    Upcut bits require less cutting force, and are more appropriate for your machine. I rarely use downcut bits. Also down cut bits do not plunge well, and you have to ramp into the cut when using them. I have never used Aspire, but I'm going to guess that Smooth and Angle might be the best settings. Maybe try an angle of 2° to start.

    The bottom line is you just have to experiment to figure out what will work best for your machine and materials.



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by Jim Dawson View Post
    3x D means depth of cut is 3 times the tool diameter, or in this case 0.750 inch for a 0.250 tool.

    Gerry is correct, your machine is not very stiff so you are not going to be able to get maximum performance from your tool bits.

    I could run with the Amana recommended feeds and speeds on my machine, but my machine weighs over 5000 lbs and is solid. Just my X axis (cross axis) carriage, at about 300 lbs, weighs more than your whole machine. I'm not bragging here, this is just to illustrate the differences in machines.

    As a starting point, take less depth of cut, maybe 0.060, and slow the IPM down to about 50 IPM If that works OK, then increase the IPM and/or depth of cut and see what happens. You have to make allowances for the machine that you are using.

    Upcut bits require less cutting force, and are more appropriate for your machine. I rarely use downcut bits. Also down cut bits do not plunge well, and you have to ramp into the cut when using them. I have never used Aspire, but I'm going to guess that Smooth and Angle might be the best settings. Maybe try an angle of 2° to start.

    The bottom line is you just have to experiment to figure out what will work best for your machine and materials.
    Ok, i will try to lower the IPM and try using a upcut bit and currently im doing 1/4 passes, if i slow the feedrate down should i speedup the router RPM or would it be lowered too.



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    Default Re: Cutting Quality 3/4 MDF

    I would think around 10,000 rpm would be about right.



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    Default Re: Cutting Quality 3/4 MDF

    An upcut bit will chip the melamine badly. A downcut may be your best option.

    Gerry

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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by ger21 View Post
    An up cut bit will chip the melamine badly. A down cut may be your best option.
    Thanks, i bought one of each to try. Will post results this weekend!

    I do plan on buying a better cnc in the future, for 4k i have learned allot about the software and the operations of a cnc, pretty cheap knowledge before jumping into a 15k+ machine.



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by Wisker View Post
    Hey all,
    So i am still trying to get this 4896 Zenbot CNC figured out to produce good quality cuts, i am currently using a Yonico 33210-sc 2 Flute Compression bit, i was using Amana 2 flute compression bit but was still getting same results and i am only getting 8-10 sheets of 3/4 melamine cut before it seems the bits go dull. Currently im running a Hitachi M12vc 2 1/4 Hp router and running at 100IPM at 11k rpm, a few questions i would to get help answered:

    1. Since Compression bits are made to cut 3 directions should i be cutting the 3/4 MDF in one pass? Reason i ask is if i make three passes no matter what i only using the first 1/4in of the compression bit which would dull it very fast i'm guessing?

    2. When cutting im getting rough cuts in certain areas, mostly corners are not rounded it leaves hump before curve? Possible something to do with where the cut starts and stops? I noticed there very small wavyness to the cuts if you look close there not smooth
    Inside Cutout as well leaving hump.

    3. When i make my dado cut on the line it starts and makes a little swerve before starting?


    4. I am not familiar with doing the ramp cuts and things, i currently have it plunge and start?

    5. Circles are more oblonged than circle? Any advice on that?

    I have been trying different things for a few months now to get it running smooth, time to try and seek advice from everyone. I have been looking around the DesMoines Iowa area to find assistance to pay someone to help but not much luck on the wood cnc machines.

    Thanks
    If you use a mortise compression bit, the upcut section is smaller, about .100-.125". I would use a 1/4" or 3/8" tool to put less stress on your spindle. This would allow you to take a shallower first pass, then use the second pass to cut through. Better yet would be to program a leave of .01", and do a finish pass only on the bottom (single pass).

    If you're using a router for a spindle, I find it better to use single-edge tools, which will allow you to run a higher spindle speed, which is better for routers.



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by louieatienza View Post
    If you use a mortise compression bit, the upcut section is smaller, about .100-.125". I would use a 1/4" or 3/8" tool to put less stress on your spindle. This would allow you to take a shallower first pass, then use the second pass to cut through. Better yet would be to program a leave of .01", and do a finish pass only on the bottom (single pass).

    If you're using a router for a spindle, I find it better to use single-edge tools, which will allow you to run a higher spindle speed, which is better for routers.
    Some good news, i reached out to Shaun the owner of Zenbot and he sent me a new Gantry assembly and new rails after we realized the one i was using had the bearing preloads off which lagged down the motor and was causing grooves in the rails.

    Got the new Gantry and rails and a BIGGER motor to drive the Gantry. Old one.
    New one!

    Went around and checked all belts and bolts to make sure they were tight. Set my IPM to 80 from 100IPM and started out 10k RPM then raised to 12k to get it to ride smoothly through the cuts making 3 passes using a 1/4 compression bit since i still had one left.
    The bump that was being left i thought maybe was due to the start of the cut was right before curve, so i set the starting point after the curve on the straight away and got perfect inside curves.

    To cut my holes i set the IPM to 50 and they turned out very nice.
    So i made a few more.

    Took a mic to the parts and they were all within .01-.02 of what was set in the Vectric.

    Corners seem to be nicely cut.

    I made so many changes i'm not sure what corrected the issues, but it is like a new machine know, hopefully it stays that way. I will upload a video to post on it cutting.

    On to the next venture! Zero Probe Tool


    Attached Thumbnails Attached Thumbnails Cutting Quality 3/4 MDF-20170502_162038-jpg   Cutting Quality 3/4 MDF-20170203_105304-jpg   Cutting Quality 3/4 MDF-20170507_174659-jpg   Cutting Quality 3/4 MDF-20170507_151008-jpg  

    Cutting Quality 3/4 MDF-20170507_170041-jpg   Cutting Quality 3/4 MDF-20170507_173233-jpg   Cutting Quality 3/4 MDF-20170507_175826-jpg   Cutting Quality 3/4 MDF-20170507_151155-jpg  

    Cutting Quality 3/4 MDF-20170507_163843-jpg  


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    Default Re: Cutting Quality 3/4 MDF

    Cutting Quality 3/4 MDF-51ldev-dqll-_sl1001_-jpgCutting Quality 3/4 MDF-61cnkklbgal-_sl1001_-jpg


    CurrentFeed = GetOemDRO(818) 'Get the current feedrate to return to later
    CurrentAbsInc = GetOemLED(48) 'Get the current G90/G91 state
    CurrentGmode = GetOemDRO(819) 'Get the current G0/G1 state

    If GetOemLed (825)=0 Then 'Check to see if the probe is already grounded or faulty
    DoOEMButton (1010) 'zero the Z axis so the probe move will start from here
    Code "G4 P3" ' this delay gives me time to get from computer to hold probe in place
    Code "G90 G31Z-4. F4" 'probing move, can set the feed rate here as well as how far to move
    While IsMoving() 'wait while it happens
    Wend
    ZProbePos = GetVar(2002) 'get the exact point the probe was hit
    Code "G0 Z" &ZProbePos 'go back to that point, always a very small amount of overrun
    While IsMoving ()
    Wend
    Call SetDro (2, .760) ' change .060 to your plate thickness and then adjust for final accuracy
    Sleep 200 'Pause for Dro to update.
    Code "G1 Z1. F50" 'put the Z retract height you want here, must be greater than the touch plate thickness
    While IsMoving ()
    Wend
    Code "(Z axis is now zeroed)" 'puts this message in the status bar
    Code "F" &CurrentFeed 'Returns to prior feed rate
    Else
    Code "(Z-Plate is grounded, check connection and try again)" 'this goes in the status bar if applicable
    End If
    If CurrentAbsInc = 0 Then 'if G91 was in effect before then return to it
    Code "G91"
    End If
    If CurrentGMode = 0 Then 'if G0 was in effect before then return to it
    Code "G0"
    End If

    Simple Z axis zero code i found on a video online, works great except for one thing, my probe is exactly mic at .760 thickness so i input that into the code, when i zero out the x,y and hit the go to z button in Mach it goes to zero on the Z axis but the mill is always exactly a piece of paper folder over 4 times above the top of the surface? I tried to adjust the height in the code but didn't seem to make a difference, something im doing wrong?



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    Default Re: Cutting Quality 3/4 MDF

    Try probing slower

    Gerry

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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting Quality 3/4 MDF

    Happy to hear you have your cut problem solved. Sounds like there were a lot of mechanical problems.



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    Default Re: Cutting Quality 3/4 MDF

    Quote Originally Posted by Jim Dawson View Post
    Happy to hear you have your cut problem solved. Sounds like there were a lot of mechanical problems.




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