[peteeng]

Hi Mr-MaW - Your intent maybe good but you are breaking forum rules by "seeking or advertising" business on the threads. Every entry so far has been "business" so you could be banned or removed by a moderator at any time. Just want to let you know. Peter

[suspension]

Any one having any opinions about clear epoxy resins available at alibaba.com for cheap prices?

[pippin88]

Any one having any opinions about clear epoxy resins available at alibaba.com for cheap prices?

For what purpose?

Link?

[suspension]

For what purpose?

Link?

https://m.alibaba.com/product/1600220040089/Epoxy-Resin-Art-Resin-Crystal-Clear.html?__sceneInfo=%7B%22cacheTime%22%3A%22180 0000%22%2C%22type%22%3A%22appDetailShare%22%7D&fro m=share&ckvia=share_8e0760390bf141088c4c3dd1bf6ca2 81

For epoxy granite base of the CNC machine.

[ardenum2]

getting epoxy from china is a huge gamble.

[Mr-MaW]

I was attending a very important exhibition recently and saw a lot of new things, linear motors, cradle turntables, mineral castings, carbon fiber and so on.
There are so many types of resin glues that only a small fraction can be used to produce mineral castings. Otherwise he will creep/creep.
What I understand is that Alibaba does not currently have a type of resin glue specifically for mineral castings, and you need to communicate separately to deploy the products you need.

[suspension]

I was attending a very important exhibition recently and saw a lot of new things, linear motors, cradle turntables, mineral castings, carbon fiber and so on.
There are so many types of resin glues that only a small fraction can be used to produce mineral castings. Otherwise he will creep/creep.
What I understand is that Alibaba does not currently have a type of resin glue specifically for mineral castings, and you need to communicate separately to deploy the products you need.

Do you know any chinese suppliers who can provide epoxy for mineral casting?

[suspension]

I have started the CAD. With the given travels, the depth of the machine is around 1300mm which is too much. One thing I can do to reduce it a bit more is to fix the Y axis's ball nut bracket to saddle towards the edge of the saddle rather than middle. This way I will be able to shift the whole Y ball screw + assembly toward the red arrow as shown. Any issues with that?

[peteeng]

Hello Sus - I doubt you will find any supplier that produces an epoxy specifically for mineral casting. In broad terms any 100% solids epoxy is suitable if you use it as per its technical application. The best epoxies for EG are the slow curing, river casting types or infusion types... Peter

[suspension]

Hello Sus - I doubt you will find any supplier that produces an epoxy specifically for mineral casting. In broad terms any 100% solids epoxy is suitable if you use it as per its technical application. The best epoxies for EG are the slow curing, river casting types or infusion types... Peter

Thanks Pete. I feel like finding a supplier from alibaba who has epoxy with these properties. Is there any way I can verify the suitability of a particular epoxy? For example, is there a test that can be done to check properties of epoxy granite made out of a particular epoxy?

[suspension]

Need some advice on the saddle (base for X axis) build.
In stef's machi9ne, he uses steel plates to come up with a complex structure. I am not sure if it need to be that complex. Any issue in building it with EG?
What would be the minimum thickness that is recommended. I see that Stef's X axis base is around 144mm. Would a similar sized thickness EG built base strong enough?

Thanks
Sus

[ardenum2]

If you don't want to weld it I'd use xometry to have it machined from a solid piece, around $500. Making it from eg will be problematic due to geometry issues but if you include holes for carriage bolts and length of anchors a good size would be 60mm pockets, 60mm for anchors and 60mm for rail anchors. 180mm height would be appropriate.

for epoxy look at viscosity and pot life, low viscosity <500 and long pot life, the longer it is the more time it will have to cure which means low thermals over time, less chance to fail when curing.

[peteeng]

Hello Sus - Depends on what you want to know ie what test do you do?? The most important value to know is the composites young's modulus - E. This enables you to design parts accurately. To test for E you need to make a coupon suitable for a flexure test (that's what I have been doing) Many companies quote compression test E and this seems to be biased to the high side. My flexure test result have been much lower than expected even with very high modulus minerals like ALOX. Since machine structures are being "bent" or flexed the flexural modulus seems to me to be the most important. In an isotropic material the tensile. compressive and flexural modulus are the same eg metals. Since the epoxies modulus is around 3GPa for all epoxies its pointless testing the epoxy only. The minerals modulus are well documented. Its the combination of the two or more that is in dispute. Lots of people build from sand and epoxy and the resulting machine is good. But my tests show the modulus is much lower than these people would expect.... If I was building a bespoke machine I would make the parts in steel, have them laser cut with tabs and slots so they are self assembling and then I would braze the structures together. I have done this on my small routers. The result is accurate via FEA and working with steel is the cheapest stiffest pathway to a good machine....The EG pathway is fraught with issues... if I were to build many machines I would look at using engineering grout so I can make moulds and cast the parts. Grout or UHPC is a known commercial product out of a bag (I use sika3350). Insensitive to water as it is a water based product (EG has many issues eg if you do not dry your filler; epoxy does not like water, if the filler and epoxy do not bond, then you have a very inefficient structure) so keep at it.... Peter

Strength - The strength of materials needed in machines is quite low as the machine is designed to be very stiff (or it should be) EG and UHPC are suitable for all machine parts. You can observe this via FEA in your CAD system. Stefs saddle was not complex and all parts there are needed. You can make simpler saddles but you may then have access issues with carriage bolts and bearing bolts. You need to develop a CAD model to visualise your concept and work through the issues. If you are good with oxy/acetylene or oxy/propane you can braze together steel parts and they will not need stress relief. This is because you have not melted any parent metal. Its the shrinkage of the parent metal and the weld metal that is the roof=[t cause of the problem. Brazing metal has a bigger plastic liquidus range then steel so introduces very little stress into the structure as it solidifies.... Even soft solders can be used to create strong enough parts. A couple of my small routers use soldered assemblies for the Z axis bits...

I have been working with a local epoxy manufacturer for over 30 years. They have several epoxies that will do the job. Look up ATL Composites they would be helpful.

I have also heard the discussion about creep and this is unlikely to occur in correctly post cured epoxies or very active ambient curing epoxies. I have been involved in creep testing of fibreglass parts in the insulated crane industry. Creep in cnc machine parts is unlikely to happen for various reasons. Lay people get creep and relaxation mixed up. Relaxation can occur in partially cured epoxy. This is when the polymer chains start sliding past each other in a process called orientation. But in a large machine part casting with a filler this is very unlikely.... Plus epoxy is a twisted horseshoe shape molecule so its mechanically locked vs some other polymers which are linear and can slide past each other very easily like polyester and polyethylene, that's why you can stretch your shopping bag quite easily...

[ardenum2]

I only read this one about creep.

[peteeng]

Hi Ard et al - Thanks for the article. I Have read it before. The only "force" on a machine that induces "creep" is gravity. It's a constant load with no restraint. The article has done this correctly by using weights and cantilevers. The test is run over 66 days on beams with a "constant" global max stress of 5MPa. Taking the test on face value shows that the epoxy performs the worse in this test. The usual sizes of columns and parts in machine tools would have a gravity stress of less then 5MPa I'd expect but someone can correct me on that. Next time I'm running a machine model I'll have a look at that. Granite and concrete don't relax. They do not state how or if the epoxy was correctly post cured plus the measurement position is too close to the application of the load. They should have had the sensors at the bottom of the beam (look up Saint Vernants principle and Hertian stresses), But the trend is clear. ie they could be measuring a local relaxation or permanent deformation due to the local stress condition vs the global beam stress. Lets just say that it works if the epoxy is correctly cured and the machine parts are correctly sized. A couple of years ago I was excited for epoxy mineral solutions but I have gone over to grout for various reasons. Still waiting on Sika to deliver some 3350 so I can test it!! Peter

[ardenum2]

what do you think about forcer-stator attraction in this regard? table below from hiwin shows a range from 80kg to 570kg, that's a lot and it's constant. I fear leaving a column in one resting spot would spell trouble over time.

[suspension]

Hello Sus - Depends on what you want to know ie what test do you do?? The most important value to know is the composites young's modulus - E. This enables you to design parts accurately. To test for E you need to make a coupon suitable for a flexure test (that's what I have been doing) Many companies quote compression test E and this seems to be biased to the high side. My flexure test result have been much lower than expected even with very high modulus minerals like ALOX. Since machine structures are being "bent" or flexed the flexural modulus seems to me to be the most important. In an isotropic material the tensile. compressive and flexural modulus are the same eg metals. Since the epoxies modulus is around 3GPa for all epoxies its pointless testing the epoxy only. The minerals modulus are well documented. Its the combination of the two or more that is in dispute. Lots of people build from sand and epoxy and the resulting machine is good. But my tests show the modulus is much lower than these people would expect.... If I was building a bespoke machine I would make the parts in steel, have them laser cut with tabs and slots so they are self assembling and then I would braze the structures together. I have done this on my small routers. The result is accurate via FEA and working with steel is the cheapest stiffest pathway to a good machine....The EG pathway is fraught with issues... if I were to build many machines I would look at using engineering grout so I can make moulds and cast the parts. Grout or UHPC is a known commercial product out of a bag (I use sika3350). Insensitive to water as it is a water based product (EG has many issues eg if you do not dry your filler; epoxy does not like water, if the filler and epoxy do not bond, then you have a very inefficient structure) so keep at it.... Peter

Strength - The strength of materials needed in machines is quite low as the machine is designed to be very stiff (or it should be) EG and UHPC are suitable for all machine parts. You can observe this via FEA in your CAD system. Stefs saddle was not complex and all parts there are needed. You can make simpler saddles but you may then have access issues with carriage bolts and bearing bolts. You need to develop a CAD model to visualise your concept and work through the issues. If you are good with oxy/acetylene or oxy/propane you can braze together steel parts and they will not need stress relief. This is because you have not melted any parent metal. Its the shrinkage of the parent metal and the weld metal that is the roof=[t cause of the problem. Brazing metal has a bigger plastic liquidus range then steel so introduces very little stress into the structure as it solidifies.... Even soft solders can be used to create strong enough parts. A couple of my small routers use soldered assemblies for the Z axis bits...

I have been working with a local epoxy manufacturer for over 30 years. They have several epoxies that will do the job. Look up ATL Composites they would be helpful.

I have also heard the discussion about creep and this is unlikely to occur in correctly post cured epoxies or very active ambient curing epoxies. I have been involved in creep testing of fibreglass parts in the insulated crane industry. Creep in cnc machine parts is unlikely to happen for various reasons. Lay people get creep and relaxation mixed up. Relaxation can occur in partially cured epoxy. This is when the polymer chains start sliding past each other in a process called orientation. But in a large machine part casting with a filler this is very unlikely.... Plus epoxy is a twisted horseshoe shape molecule so its mechanically locked vs some other polymers which are linear and can slide past each other very easily like polyester and polyethylene, that's why you can stretch your shopping bag quite easily...

Very comprehension be I go.
Just to see f I understand you correctly following are the main points I extracted.

1. If I can get a local company to test Young's modulus of various combinations of epoxy/minerals this will give me a good indication if the mixture is appropriate.

2. For the saddle/X base more appropriate option would be to use steel plates as Stef s machine. In order to avoid heat treatment I can use blazing techniques with a steel structure that use slots and tabs. For blazing I can use oxy/propane etc. I am not sure if you are suggesting that this steel structure be filled with UHPC or engineering grout after?

3. Are you suggesting other parts also be made with steel as above? I mean the machine base and column?

4. Do you suggest engineering grout/UHPC is better suited than epoxy granite for machine base and column?

[peteeng]

Hi Sus:
1) I've done that and I'm happy to share the results. See the Milli thread or ask for specific info. All EG moduli will be low compared to metals. Typically quoted E=40GPa but my tests are <20GPa in flexure
2) I suggest you don't fill steel structures with anything, design it right from the start
3) If your going down this path make all your machine parts the same way
4) Yes I think grout or UHPC is better than epoxy/stuff. Do not make your own UHPC, then you are still in never know land. Buy a premixed material that has a specification

Re steel structures if you have a fabricator with a laser welder I'd be confident it could be laser welded then final machined with no TSR. or buy a laser welder for the workshop. If I was setting up a commercial workshop today I'd have laser welders....

For a one off garage built Mill my choices would be as follows:
1) laser cut steel tabs and slots - laser welded. If cost of stainless steel is less than mild steel plus painting then I'd use SS. I have done that in my small machines, painting is a pain & rust is even worse & the time $$$ spent on painting (chasing threads, change of fit or masking etc etc) often equalises the cost of the SS Steel E=200GPa
2) laser cut steel tabs and slots etc - tobin bronze brazing (SS or mild steel)
3) Thick plate edge bolted steel or aluminium construction. Need access to reasonable cost mill to achieve this Al E=70GPa

With all of the above you get what you designed....

If casting a machine and I would only do this if it is for multiple parts (or for fun):
1) Use carbon fibre E=80GPa via my tests
2) use grout E=40+ not sure yet as I have not had it tested but the data sheet says 58GPa in compression
3) Use glass fibre E=32GPa via my tests

With these I get what I designed as I have tested the materials and used correct FE to design machines. Others may not, as they do not do test programs but rely on data sheets or hope that the material is good.

Cheers Peter

[peteeng]

Hi Ard - Would the machine be left on for months at the same place? Need to do a FE and determine if the stress is say <5MPa. Are you chasing um's? Peter

[Mr-MaW]

Very comprehension be I go.
Just to see f I understand you correctly following are the main points I extracted.

1. If I can get a local company to test Young's modulus of various combinations of epoxy/minerals this will give me a good indication if the mixture is appropriate.

2. For the saddle/X base more appropriate option would be to use steel plates as Stef s machine. In order to avoid heat treatment I can use blazing techniques with a steel structure that use slots and tabs. For blazing I can use oxy/propane etc. I am not sure if you are suggesting that this steel structure be filled with UHPC or engineering grout after?

3. Are you suggesting other parts also be made with steel as above? I mean the machine base and column?

4. Do you suggest engineering grout/UHPC is better suited than epoxy granite for machine base and column?

According to our company's production experience, because there are many types of epoxy resins, and they are affected by ambient temperature and humidity, the stability of the products produced is different.So creep will take a long time, so what kind of precision do you need, design your product structure and materials according to this precision.

You can listen to his advice (peteeng), many of his points are correct.
Another very important point is the actual production experience, because in the actual operation process, the theory and practice may be somewhat different, so the product experience is also key. Have you seen my products and drawings? That has been mass-produced for 8 years（VMC855 、 VMC1160 ）.
Hi peteeng，If you can, you can upload the products you have made, as well as the actual application and analysis of the products, the accuracy records in the later stage, etc.

Hi SUSPEN，Your product should be similar to the product I have made, you can send me the drawings when you have time, and I will help you analyze it. Of course, the results of the analysis are designed according to the strength of our company's materials.

Finally, I wish you to complete your product as soon as possible. My product has been exhibited at the exhibition site in Shanghai, it is the base of a gantry machining center, the length is 8m, the weight is 19 tons.