A few days ago, I received a requirement from Ayman from Iran regarding ZAMAK (zinc polish) sanitary parts smoothing and polishing. There are many accessories such as faucet handles, taps and valve bodies, etc. Ayman told me that he will be in China for 2 weeks to discuss how we can help him to improve surface and reduce labor work.
Ayman has hot die casting machines but he is not happy about the performance. Because the machine does not always make the same casting quality. I ask him if he can send me few sample to check the surface and then I can do some trial in our laboratory. At the same time, I will take some video and photo to show how we do the process step by step.
Ayman is happy about the idea. And in 2 days I get the sample.
1. Surface inspection of sample
As we check through the sample, the surface is rough with big flash need to remove. The parts size is medium with big production volume (3000 pcs per day). Therefore, the vibratory finishing process is a good choice.
Also, I can see clearly that Ayman have parts with good molding and bad molding. With good molding quality, vibratory finishing time can largely reduce and product output with much better quality.
2. Burr removal
General burr removal with ceramic media is done in the first stage process. Firstly, we do the process in our vibratory finishing machine with media of various size to check the performance. Firstly we do deburring with ceramic media for 1.5 hours. Bellow, you can see parts surface condition:
However, those very large scales and flash hard to remove even we tried later with extending 4 hours in ceramic media. Moreover, the whole parts shape deformed.
3. Surface smoothing of zamak3 sanitary parts
After burr removal is smoothing process. The smoothing process carried out in plastic media for 1.5 hours to reduce surface roughness and Ra value. Therefore surface is preferable for electroplating and nickel plating.
Bellow you can see the surface after plastic smoothing process:
4. Sanitary parts zinc polish
The polishing process takes only 30 minutes. This step is not necessary for every zinc parts manufacturer. Because the final product needs nickel plating so polishing with vibratory finishing is not so important.
However, if polishing with vibratory finishing is required, we need to make high media to part ratio, preferably 8:1 to prevent parts on parts hit and damage.
5. Tip for Ayman: big casting flashes need to remove with grinding wheel
The deburring process takes about 1.5 hours. However, only loose burr and thin burr are removed. Those thick flashes are hard to remove. Even those big flashes removed with longer tumbling time, the whole material shape will deform. Of course, this is not what we want.
I suggest Ayman do wheel grinding before vibratory finishing process. Not all surface need grinding, but the only edge with big burr and flash need remove. So we can save time and energy in the vibratory finishing process.
6. Important: prevent lodging
The media lodging is really a painful issue for workshop owner. It takes time and labor work to recover the parts. Therefore, the right selection of media size and shape is very important.
In this case, we would see that:
- The handles and taps don’t have a special surface (only 15 mm hole).
- Valves we have 4 mm hole for water running through, 30 mm opening at the bottom. 10 mm hole at the top.
- For washer parts, we can basically use any angle cut ceramic media with a smaller size.
In the first place, cone shape ceramic media and plastic media is preferred because of no lodging. However, cone shape media with special shaping process, so it has higher cost than other shapes of media.
If the customer is cost sensitive, we can suggest T/P shape media (a mixture of TET tetrahedron shape media and pyramid shape media). Besides, cylinder wedge shape media also suggest because of less possibility of lodging than T/P shape media. 25 mm or 20 mm ceramic media is suggested for long service life.
Cone shape plastic media is the most common shape and cheap to make. So we can use 20 mm or 25 mm cone shape.
7. Media recycle and reuse
Prevent lodging is an important issue as we discussed. So we need to remove undersize media after some time of using. If an opening size 30 mm, when media size reduces down to 15 mm, is have the possibility to lodge in. At this time we have to remove those undersize media with vibratory separation sieve.
However, those media is just smaller size, they are in good condition. Simply throw them away is a waste of resource. If we check carefully, we will find that washer parts without any hole or cavity. Therefore those undersize media can use in this parts without any loss.
8. The right selection of machine
The right selection of machine to achieve finishing requirement is very important. The reason I get from this case as follow:
- Get required surface finishing result in a certain time period
- We can do the work (in this case 3000 pcs per day)
- We can greatly reduce labor work (the most time-consuming job)
In this case, we suggest a 600L round vibratory finishing machine instead of vibratory finishing machine with separation deck. Because in the machine with separation deck (internal separation) parts and parts will hit and scratch. Especially zinc or zamak3 alloy is a soft material.
This will finally affect nickel plating performance after smoothing step.
To make manual collection process easier, we suggest Ayman install a speed converter (Variable Frequency Drive). So he can make stronger vibration in the deburring process while making a slower movement in the separation process. Therefore this will be easier and faster for the worker to do the job.
The vibratory dryer is another machine that we recommend. Because zinc material is easy to rust when exposing to air environmental. As a result, it needs immediate drying after smoothing and polishing. Later, it can move to nickel plating step to get long lasting mirror shining surface.
9. Automatic solution
Ayman later ask me the possibility of automation. He wants to reduce possible error from labor worker. Therefore I show him our recent development of automation drawing and design for a zamak door handle factory.
Ayman is delighted about the design and idea because only one worker can operate the whole system. Besides, media can be returned to loading hopper and recycle to use. Furthermore, undersize media is removed by the double-layer vibratory separator to save labor work.
We have more automatic surface finishing solutions that you can check. All those solutions are customized and according to practical requirement.