Messages

46

CamBam help (General usage) / Re: Machining Polycarbonate

« on: December 02, 2022, 12:38:26 pm »

That's interesting Ralf,

I've seen conflicting information on chemical compatability of both PC and PMMA. I originally selected PC (perhaps 20 years ago) because of what was reported to be superior chemical resistance, primarily to gasoline and oils, and stablility at higher operating temperatures.

If you search the subject "Chemical Compatabilty of Polycarbonate", specifically with respect to gasoline/petroleum, the vast majority of references classify it as good to excellent. A few say unacceptable but referrence no standard or source for the rating. The source I buy my PC from rates it as "good" but not excellent.

If I do the same search for PMMA, most will say moderate to poor, and many (more than PC) will say not suitable. The same source I buy the PC stock from rates it as moderate to poor.

As far as operating temperature, PC has a glass transition temp of 147C while PMMA is 105C so I think that pretty clearly favors PC.

As far as aging and optical clarity, I think Ultraviolet is the primary culprit of diminished optical clarity for PC. Under the bonnet/hood, it's well shielded from sunlight.

Use and practice on actual operating engines over the years seems to bare out PC is indeed resistant to attack from gasoline, however they tend to get foggy deposits on the inside (oil vapor) of the filter and dust on the outside, both of which can be wiped off and cleaned with mild detergent, but it takes great care because the PC scratches so easily. I dont have the same history/experience with PMMA so can't comment other than I'm confident it would be much more scratch resistant.

I did buy some PMMA to compare machinability on the same part and MOPs but haven't done so yet.

Best,
Kelly

47

CamBam help (General usage) / Re: Machining Polycarbonate

« on: December 01, 2022, 21:38:04 pm »

I'm gonna call this one complete.

I made the second PC lid and I'd say it's improved over the previous but the perimeter cut although better is still poorer than it should be even though I reduced the full hieght finish cuts from .5" to .25" by cutting the chamfer before the finish cuts. I don't have more PC machining in the immediate future so maybe I can make some machine upgrades that add some rigidty and broader/better router speed control before the next go. Thanks for all the helpful suggestions fellas.

Best,
Kelly

48

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 01, 2022, 21:22:33 pm »

Some great points Dave. Thank you very much for that. Last night I took some measurements to see the art of the possible with my existing hardware.

The sketches below use 20mm HGR/HGH style linear rail and bearings. 2 bearings per rail. One rail for each Y-Beam, and two for the X. I call the traveling beam the X. It uses my existing machine's beams, steppers, and rack & pinion drive. I'd need to make the mounting hardware, but it would be very inexpensive easy fab for me with materials I have on hand. This could all be reversed but can't see why I'd ever revert.

I could also very easily convert the X & Y rack and pinion to ball screw actuation too.

For the Z, I'd use the existing stepper but I'd build the rest from scratch using the same 20mm HGR/HGH linear rail with a pair of bearings on each and a ball screw actuator.

But, the weight increase for the traveling X-axis will be about 18lbs, 11lb of it due to the linear rail and bearings. The extra Z axis travel desire and larger router will also add some weight, but I'm guessing <5lb. The Y is powered by two steppers (one on each beam) but the X only one. I dont know the total weight of the existing traveling beam assembly or what percent invrease that is but the majority of the weight increase would at least be borne by the two-stepper driven Y-axis.

Looks like ~$250 for as shown which seems like good value for money to me and another $150 to add 16mm ball screws on X&Y. Not sure about that. What do you think, BallScrews or R&P? I see a rack beside your rail.

Best,
Kelly

49

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: November 30, 2022, 15:05:12 pm »

To simplify this (Maybe

I scrapped the idea of a spindle in lieu of using Super PiD and Router to get more speed range and CAM control of speed. I’ll start a thread on that when I get to installing the hardware.

I still like the idea of linear rail and ball screw conversion of my machine, but what I really need is a better Z-axis with more useable z envelop and travel.

The advertised travel for my machine was 3.7” but there was no way to achieve anywhere near that as received because of the height of the MDF bed and the router ran into the Z-stepper motor when retracted. After I dropped the MDF bed and router in the mounting clamp and can realize about 3.5”. I need to be able to machine stock at least 4” thick and preferably 6”. Right now there is 6.75” under the gantry rail, 5.75” under the stationary Z-Plate and wheels. I think with a properly designed Z-axis, I could get nearly all that 5.75” as available travel and Z work envelop.

It seems that most if not all cnc router Z-axis with linear rails are designed such that bearing blocks are on the traveling Z-plate and the linear rails are mounted to the stationary Z-plate. I was thinking of doing it the other way around with the rails mounted to the traveling plate so the traveling plate could extend below the fixed Z-plate and gantry to cut thinner stock with short cutters over the entire work envelop without inserting a platform, re-tramming that surface, etc. Obviously, the linear rails get stiffened by being attached to the stationary plate, but the same could be done by attaching them to a (stiff) traveling plate. It does potentially increase the weight of the traveling plate, which is of course undesirable but I think this could be minimized. Then it’s just a matter of where you attach the ball screw bearing and length of the screw to make it work at desired stroke range.

In theory, it could be designed such that you could extend the traveling Z plate or at least the collet all the way to bed, but in practice would only need to approach the height needed for the shortest cutter ever used.

The reason for the additional extension is to be able to machine very soft materials (polystyrene foam) across the entire work envelop without (a large) platform to the elevate the work, then I could use a smaller (than 35x35 which actually would need to be more like 44”x44” to use the work envelop) platform for machining hard materials with the machine in its most rigid position.
 
Do you follow? Anyone see anything fundamental wrong with this train of thought and approach?

Best,
Kelly

50

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 30, 2022, 03:30:41 am »

......Will also need to check the gecko controller in my machine.

I'm talking out my backside. My Mega V controller board has an Arduino mega2560.

https://store.arduino.cc/products/arduino-mega-2560-rev3?_gl=1*in7xq1*_ga*OTQxNzI0OTI1LjE2NDk2ODcxNDI.*_ga_NEXN8H46L5*MTY0OTY4NzE0Mi4xLjEuMTY0OTY4NzE0OC4w

The board is running grbl 1.1i or later, customized by MR for rotary axis enablement. I'll have to do some more investigation on router control and the pin outs. I did order the Super PiD and will start another thread when th etime comes to get it up and running.

Best,
Kelly

51

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 29, 2022, 23:17:29 pm »

Wonderful!  Thanks for checking in Airnocker.

That will add worlds of capabilities to your machine at not much cost.  You still must deal with the rigidity problems, but speed has been one of your major issues, and this will solve that.

Lloyd

As far as rigidity I actually think the gantry beams are ok, but the Z-axis definitely needs some attention. It's fairly stout for extruded aluminum rail. Here it is compared to open builds C-Channel.

Best,
Kelly

52

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 29, 2022, 23:05:33 pm »

I just updated my previous post regarding the Super-PID info.

Here's a link to a wealth of information on the CNCZone forum concerning this, I'm a contributor as well:

https://www.cnczone.com/forums/diy-cnc-router-table-machines/112658-cnc-manufacturing-forum.html

Wow, that thread is 101 pages back to 2010. CNC zone is where I discovered S-PiD but I didnt see that one. I started at the end and read a few pages back. I've also read the manual and instruction. Think I'm sold. I have several older 6902 Porter Cable routers.  Although the are older they are virtually brand new. 10 amp 120vac, 1/2" collet capable. Not variable speed. I dont recall if they are soft start but if so no biggie to mod for that and rpm sensor.

I'll get some additional wire/cable length, knob, 5v fan, some other odds and ends. Can package myself. no problem. I may come back to you when it gets time for the CB interface. Will also need to check the gecko controller in my machine. Am I forgetting anything before I order?

Best,
Kelly

53

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 29, 2022, 18:08:22 pm »

Of course, rigidity of the axes is the first thing you should 'fix', if they're repairable.

But then, as was mentioned earlier, consider adding a PID speed control.  They're not expensive, and you can get nearly full horsepower out of a brush motor, even at very low speeds.

Lloyd

Thanks for that suggestion Lloyd. I did some searching found this offering. I'm sure there are others but this may be a very sensible alternative to an import spindle and VFD for me for many reasons such as posted in my machine upgrade thread. I won't get spindle perofrmance but may get similar level of control and good/better performance for a niversal brush motor, and I have many routers. If anyone is ware how has a favorite please let me know.

https://www.vhipe.com/product-private/SuperPID.htm
https://www.vhipe.com/product-private/SuperPID-v2_Instructions.pdf

But, ships from Australia. No worries about that except time and cost being a US based guy.

Has anyone here actually used this product with CamBam?

Best,
Kelly

54

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 29, 2022, 17:21:02 pm »

.......One thing I forgot to mention earlier, was that the longitudinal slots (on close inspection) look a little wavy, you can improve on this by changing the machining strategy (toolpaths).

You have a good eye. I had to go hold the part up and look down the grooves very closely and at first I thought it may have just been irregular deburring of the edge but looking closer, I think you are absolutely correct. Those are done with an engraving MOP. I don't get a lead in choice with that MOP but don't think that is the source.

Having watched the video, although the .188"D ball nose is 1" CL double spriral carbide, and BN isnt the best cutting profile, I don't think it's cutter flex based upon sound of cut. The cut depth is so light, it seems much more likely to be Z-axis flex. Having already tightened up the wheels, I just may need build a platform and reduce the router stick out as previously suggested, because if it's flexing that much on those light cuts, no wonder I get poor performance on those full (1/2") depth perimeter cuts, even shaving .005".

The acrylic machining video was eye opening. I did buy some acrylic to experiment with. We'll see how it goes with respect to blow outs and cratering.

Thanks for those vids.

Best,
Kelly

55

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: November 29, 2022, 16:23:31 pm »

With the spindle bigger is not always better, as if it’s a lot heavier than the old one it will affect the machine dynamics;

This is potentially a deal breaker for a spindle upgrade. I noticed immediately that they are listed as 10kg. I’ll weigh my little router and compare, and I could even weight my Z to observe the performance impact, but with NEMA 23s and weight added for additional travel, I doubt I’ll get that far. I’m waning a bit on enthusiasm for the spindle upgrade and may just use a slightly larger router I have with ½” collet and make/buy a controller for it, preferably one I could drive from CamBam…..seems easy enough to drive a Universal motor.

Make sure that the VFD has inputs compatible with the output from your controller.

$300 for a spindle and VFD sounds too good to be true and may very well be. The reason I added the VFD/Spindle upgrade to this thread was hope that someone that had done it and uses an import could point me to a reliable source and comment on reliability. Huang Yuang sells on eBay but there are many knock-off of the knock offs, and though they are inexpensive HY has been a round for a long time.

There’s 41 page thread over on cnczone about the HY VFD and spindles. Some complain of failures in a few weeks, others years of reliable service. The most common issue is poor documentation which leads to difficulties in properly configuring the unit…..like Chipowner’s thread below in this sub forum. The cnczone thread has a collection of English manuals and 41 pages of examples of issues and fixes. Though fighting through that isn’t particularly attractive, one thing that is a big concern to me is EMI from a cheap VFD.

I have a couple (KB Brand) VFDs in my shop, and even though they are filtered and isolated, they generate large amounts of EMI, both conducted and radiated. I solved most with additional filters for everything except the DRO scales on my lathe which were iGaging brand magnetic scales. The problem was lack of sufficient ground plane in the pcb on the controller and it just wasn’t fixable (without major pcb surgery) if it was plugged into any source with the VFD running (which ran the lathe!). So I run the DRO displays on batteries and they last a good long time.

Introducing a VFD to my CNC scares me to deat, let alone running power cables anywhere near my control cables or controller. I had horrible unexplained crashes and errors when I first started with my machine and it was all caused by static build/discharge from dust collection. Ground the piss out of everything solved that problem. Between that and the lathe experience I lost a large portion of my life I’ll never get back and don’t wish a recurrence! Oddly, I didn’t see one single complaint of such in the 41 page anaconda thread at cnczone on the HY VFDs.

I did go and have a look at the Millright machine and the linear bearings on the Y Axis are the type I would have chosen, and will give a trouble free service life and will probably outlast you if you can manage to cover them with a bellows like cover, and lubricate them on a regular schedule with a light lithium based grease, avoid using a graphite fortified grease.

I had to search the naming convention for the import stuff and found they're based upon the Taiwanese manufacturer standards.

https://circuitist.com/hiwin-linear-rails-guide/

Ya-know, set me straight if you think otherwise, but I was thinking HGH series linear rails are a better choice than the ones MR uses because they look identical to what they use on the Z-axis on my machine and those are or the equivalent of MGN series linear bearings. The latter are two-point contact and former four-point, which supposedly have both higher load and precision. They are only slightly larger for a given rail width and the cost difference on the imports is negligible for a comparable size. I’d bet the MillRight rails are 15mm. I could get HGH in either 15mm or 20mm for a slight price difference. With 8 linear bearings guiding each axis, I suspect load capability would be fine with smaller.

Thanks for all input and replies.

Best,
Kelly

56

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: November 29, 2022, 16:21:56 pm »

The newer of my two 4' x 8' bed routers has an HSD brand 3-phase spindle, model AT/MT1073-140.  It's air-cooled, whisper-quiet, and has been perfectly reliable for over five years.  I periodically check its runout, and it's still within factory tolerance. Lloyd

Thanks Lloyd. Looks like a really nice spindle but at $1750, a bit out of my league, especially for a guy that mostly machines Styrafoam……LoL!

Kelly I don’t have the link at hand, But here is a snap of the front page, ……..If you struggle to find it in the MIT library, shoot me a PM with a link to sent it to.

Will do.

The Masso controller is good, a little spendy though.

Definitely a big improvement over my machine, but like all things, performance at price point.

If you plan to let the jobs run for many hours and live in either a very hot (cooling) or cold place (heaters in the tank) then water cooled spindle bearings last longer, If you live in a temperate climate (and all else is equal) it doesn’t matter that much.

My machine lives in climate controlled shop…..no problem there.

Best,
Kelly

57

Members Machines / Contemplating some upgrades to my CNC Router

« on: November 28, 2022, 17:06:08 pm »

I’ve been kicking around some machine upgrades. All comments and input are welcome.

90% of what I do with it is machine polystyrene foam patterns for lost foam casting, so the machining loads are light and desired feed rates high. The machine is fairly lightweight so the smaller steppers do ok. It’s a relatively large work envelop but I need more Z travel (more on the z-design later) for pattern work and will be modifying that  to 8”+ under spindle. To get the additional height I plan to just raise the entire gantry system and for work where I need more rigidity I’ll build a platform that minimizes Z extension and may build wet cutting fluid retention/return features into the platform for harder materials.

Here’s the machine as it stands. There are of course likes and dislikes about the machine but all things at a price point. IMO, It’s a decent hobby grade machine and at the time I bought I have about $2000 into it. It’s the larger XL model. There’s pictures at the link and you can take in whatever you have the appetite for.

https://millrightcnc.com/product/millright-cnc-mega-v-router-bundle/

Some of my future pattern work may have very long run times. I need to get the machine to the point where it can reliably and at relatively low risk run unattended. I’m looking at replacing the POM rolling wheels with HGH linear track and SFU ball screws on all axis. Although I’ll likely pick up some accuracy, another major reason is debris tolerance. The v-grooves gather statically charged foam which can accumulate to the point to cause loss of steps. The rack and pinion has a similar issue to a lesser extent with foam but worse when collecting hard materials. The wipers on the linear rails and screws seem to do a good job, and as they collect a little foam dust even better. It may also reduce rolling and actuation friction a bit which can’t hurt with my smallish NEMA 23 steppers but may actually be needed with the increase Z-axis travel and weight due to not only the larger travel but also the possible addition of a spindle instead of the router.

The manufacturer of my machine more recently has offered what they call a “pro-version” that has similar linear rail approach but retains the rack and pinion drive. I’d replace the R&P with ball screws. Here is a link to that machine.

https://millrightcnc.com/product/mega-v-pro/

I can buy import versions linear rail and ball screw the such to do the entire machine for about $350.
I’m also looking at upgrading from the smallish DeWalt 611 VS Router to a spindle. I don’t think I need a lot of power, but I do want the ability to handle ½” shank bits and ER20 collet spindles seem to be minimum 2.2kw or better and quieter running would certainly be welcome. There’s also the matter of air vs water cooled. Of course, I’m looking at the 4-bearing Chinese imports which can be had with VFD for under $300. I’m very leery of purchasing the Chinese sourced VFD without first seeing a manual first to make sure I can understand it. I seem to recall a thread somewhere (cnczone maybe?) that covers this very well. Any reference sources would be appreciated. Any opinion on water versus air cooled?  Water is just more overhead but not that big of a deal to engineer.

While I had everything apart, for added rigidity I’d fill the gantry aluminum extrusions, at least the stationary two, and maybe the traveling one, I’d use the existing extrusions because they are very easy to retrofit. I could replace them with steel but at that point about the only thing I’m using from the original machine are the steppers and controller, which also could be better. I know the extrusions are not as straight/true as you’d want for linear rail but I see it done all over the place with apparent success.
On the z-axis, it seems the practice is to mount the rails on the stationary Z-plate and bearings on the travel portion. To get the under gantry clearance the router would have to be mounted significantly below the lower linear bearing packs. I was going to mount the rails on the traveling plate and make the traveling plate a stiff as possible, that way it would remain quite stiffer in the retracted position where heavier cutting could be done on platform. When extended, I’d probably only be cutting foam so the loads would be very low and inconsequential. Any other pros/cons to the two approaches?

In addition to my original purchase price, +$650 for ball screw and linear rail along with a spindle seems like good value for money, compared to $7.5-$15k to buy another more rigid machine with similar features……and yah I suppose the upper end of that could potentially buy a used (up?) real cnc machine, but I don’t have the space or appetite for that.

Best,
Kelly

58

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 28, 2022, 14:23:48 pm »

……..One thing I forgot to mention earlier, was that the longitudinal slots (on close inspection)
look a little wavy, you can improve on this by changing the machining strategy (toolpaths).
Joe Pie has an excellent video on the causes of this and the solution.

Thanks Dave I'll have a look at those.

With the upgrades for your machine, the priority concern would be the Y axis, the present carriage mechanism is wanting in many ways.

Completely agree. I’ll take in those videos too. Is there a way you can PM me a link so I can download the larger pdf document? For my machine I was thinking HGH style rails and SFU series ball screws to replace the wrack and pinion. You can probably tell I’m talking Taiwanese/Chinese stuff. Not real CNC grade stuff but the machine will never be that standard nor does it need to be. Though I’d likely pick up some positional accuracy, the other big motivation was debris tolerance and reduced maintenance/recalibrating. My future projects will have long run times and my machine needs to be able to run reliably unattended. The vast majority of use will be polystyrene lost foam casting patterns. I think it may be best for me to start a different thread on the machine upgrades in the machine section of the forum. As an odd coincidence, the manufacturer of my machine recently offered what they are calling the “pro” version of my machine. My linear rail strategy would be similar but with slightly better rails than they chose. They stuck with the rack and pinion drive but I’m eyeing ball screws. Here’s their link.

https://millrightcnc.com/product/mega-v-pro/

Upgrades can be a rabbit hole, you upgrade one aspect of the router and this points out another weak point.

You sure got that right. I’m looking at 2.2kw spindles as well. At some point there’s a decision to be taken on whether to upgrade or buy up.

Best,
Kelly

59

CamBam help (General usage) / Re: Machining Polycarbonate - Progress

« on: November 28, 2022, 14:21:39 pm »

.........I'm in the school that with the right feeds & speeds and the right bit, fluid isn't needed. Having the same problem as you with the MDF bed and also not wanting anything else added to the atmosphere or my shop, it's used for other commercial activity........There are videos on YT of people cutting PC, 6mm depth of cut, 5m per minute speed with 6mm bits on machines not disimilar to yours, getting nice clean cuts........I would seriously look at the bits you use first and this may cure all your problems without you needing to create other solutions & solve the problems it may create. I appreciate not as cheap as a bit of washing up liquid or WD40 but will allow you to carry on cutting dry.

Good points. Given the improvement I saw with the O-Flute cutters, I'm certainly interested in gains available with other cutters as well, but I can say having observed and experimented my machine, it's hard for me to see getting anywhere near the recommended feeds/speeds from the cutter manufacturer on my machine or those in that video. I need to assess/address the (prone) aspects of my Z axis as to how much contribution is there. Just keep in mind this is a relatively large work envelop machine  that is supported by an aluminum extrusion gantry........it has it's limitations in riigity but was still probably good value for money, is very light and works well for cutting foam at high speed. I just need to decide how much Polycarbonate (and/or hard material) machining I want to do in the future.

I just wanted to machine two PC air filter lids, but didn't appreciate it may present the need to reconfigure the machine, build a platform, add a fluid dispensing and collection system, and buy a set of dedicated cutting bits. 

However, I may be willing to account for such things if I decide to do future machine upgrades. It's a ball rolling down hill.

Best,
Kelly

60

CamBam help (General usage) / Re: Machining Polycarbonate

« on: November 28, 2022, 02:08:00 am »

"... bumping into the limits of my machine rigidity greatly aggravated by my having the router fully extended and all things biased for maximum stroke and height under gantry."
--------------
So. elevate the work with some plates beneath it.  Get it up closer to the gantry, so that the rigidity is not so challanged.

Lloyd

Yes, I'm actually going to raise the gantry further becasue I need more z travel for pattern work and a removable platform was the plan. I just havent been cutting much but foam so wasn't as obvious until I started cutting on the pc recently.

Best,
Kelly